Retire Remap: a translation shifts, and only a stretch needs a fraction

`Remap` existed to invert a composition, and a translation never needed
one: shifting a box shifts everything composed into it by the same
amount, because `lerp(s + d, e + d, t) == lerp(s, e, t) + d` on both
channels. That holds whether or not the box has a relative extent, so
the carry branch was answering a question it did not have to ask.

So the decision is made once, before the walk, and neither relocation
method branches. A translation is already one slot write. A change of
length calls `UiRegion::stretch`, which re-expresses each part at its
own fraction of the new box and needs `stretchable` -- a fixed length
holds its parts as offsets from its start and keeps no fraction to
stretch by.

`Remap`, `UiScalar::outside`, `UiSpan::outside` and `LerpUtil::lerp_inv`
are all gone with it. Nothing inverts a lerp any more: the one division
is done against a denominator `stretchable` already established is not
zero.

What it gives up is the per-axis carry, so a box that changed length on
one axis and not the other is redrawn where it used to be remapped.
Counted: six of `tabs`'s fourteen relocations and five of `text`'s
sixteen, and one extra redraw per frame on `replace_cost`'s 200 rows --
354,310,889 instructions against 354,272,387, which is noise.

Checked: fmt, clippy and 42 tests. `tabs` (with the image replay),
`view`, `minimal` and `text` all still render byte-identical to
`upstream/main`.

Cargo.toml

@@ -1,19 +1,44 @@
 [package]
 name = "iris"
-version = "0.1.0"
-edition = "2024"
-default-run = "test"
+version.workspace = true
+edition.workspace = true
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+iris-core = { workspace = true }
+iris-macro = { workspace = true }
+parley = { workspace = true }
+winit = { workspace = true }
+arboard = { workspace = true, features = ["wayland-data-control"] }
+pollster = { workspace = true }
+wgpu = { workspace = true }
+image = { workspace = true }
+tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread"] }
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread", "time"] }
+
+[workspace]
+members = ["core", "macro", "rig-input"]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2024"
+
+[workspace.dependencies]
 pollster = "0.4.0"
 winit = "0.30.12"
-wgpu = "27.0.1"
+wgpu = "30.0.1"
 bytemuck = "1.23.1"
-image = "0.25.6"
-cosmic-text = "0.15.0"
-unicode-segmentation = "1.12.0"
+image = "0.25.10"
+parley = "0.11.1"
+swash = "0.2.10"
 fxhash = "0.2.1"
-arboard = { version = "3.6.1", features = ["wayland-data-control"] }
-
+log = "0.4.29"
+arboard = "3.6.1"
+iris-core = { path = "core" }
+iris-macro = { path = "macro" }
+tokio = "1.49.0"
+wayland-client = "0.31.15"
+wayland-protocols-wlr = { version = "0.3.12", features = ["client"] }

TODO

@@ -1,19 +1,6 @@
 images
     settings (sampler)
-
-text
-    figure out ways to speed up / what costs the most
-    resizing (per frame) is really slow (assuming painter isn't griefing)
-    j is weird / fix x offset
-
-masks r just made to bare minimum work
-
-scaling
-    could be just a simple scaling factor that multiplies abs
-    and need to ensure text uses raw abs and not scaled abs
-    naming? (pt, px)
-    want to keep (drawn) regions using px? or should I add another field to UiScalar/Vec
-    field could be best solution so redrawing stuff isn't needed & you can specify both as user
+    consider typed TextureHandle<T> variants for distinct texture uses
 
 WidgetRef<W> or smth instead of Id
     enum that's either an Id or an actual concrete instance of W
@@ -24,17 +11,6 @@ WidgetRef<W> or smth instead of Id
     maybe introduce InnerWidget trait to allow for editors to expose & modify inner type
     maybe could also store a parent widget and keep using InnerWidget trait? unsure if possible
 
-really weird limitation:
-    I don't think you can currently remove an element from a parent and put it in a child of the same parent
-    because it removes the unused children after the entire parent redraw
-    but the child gets drawn during that, so it will think the child is still active !!!
-    or something like that idk, maybe I need a special enum for parent that includes a undecided state where it may or may not get redrawn by the parent
-    or just do ref counting and ensure all drawn things == 1 afterwards (seems like best way)
-    ok so I'm removing the limit for now
-
-don't forget I'm streaming
-
-tags
 vecs for each widget type?
 
 POTENTIAL BUG: closures that store IDs will not decrement the id!!! need to not increment id if moved into closure somehow??? wait no, need to decrement ID every time an event fn is added...... only if the id is used in it..??

core/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "iris-core"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+wgpu = { workspace = true }
+bytemuck ={ workspace = true }
+image = { workspace = true }
+parley = { workspace = true }
+swash = { workspace = true }
+fxhash = { workspace = true }
+log = { workspace = true }

core/src/attr.rs

@@ -0,0 +1,23 @@
+use crate::{UiRsc, WeakWidget, WidgetIdFn, WidgetLike};
+
+pub trait WidgetAttr<Rsc, W: ?Sized> {
+    type Input;
+    fn run(rsc: &mut Rsc, id: WeakWidget<W>, input: Self::Input);
+}
+
+pub trait Attrable<Rsc, W: ?Sized, Tag> {
+    fn attr<A: WidgetAttr<Rsc, W>>(self, input: A::Input) -> impl WidgetIdFn<Rsc, W>;
+}
+
+impl<Rsc: UiRsc, WL: WidgetLike<Rsc, Tag>, Tag> Attrable<Rsc, WL::Widget, Tag> for WL {
+    fn attr<A: WidgetAttr<Rsc, WL::Widget>>(
+        self,
+        input: A::Input,
+    ) -> impl WidgetIdFn<Rsc, WL::Widget> {
+        |rsc| {
+            let id = self.add(rsc);
+            A::run(rsc, id, input);
+            id
+        }
+    }
+}

core/src/event/ctx.rs

@@ -0,0 +1,18 @@
+use crate::{HasEvents, WeakWidget, Widget};
+
+pub struct EventCtx<'a, Rsc: HasEvents, Data> {
+    pub state: &'a mut Rsc::State,
+    pub data: Data,
+}
+
+pub struct EventIdCtx<'a, Rsc: HasEvents, Data, W: ?Sized> {
+    pub widget: WeakWidget<W>,
+    pub state: &'a mut Rsc::State,
+    pub data: Data,
+}
+
+impl<Rsc: HasEvents, Data, W: Widget> EventIdCtx<'_, Rsc, Data, W> {
+    pub fn widget<'a>(&self, rsc: &'a mut Rsc) -> &'a mut W {
+        &mut rsc.ui_mut().widgets[self.widget]
+    }
+}

core/src/event/manager.rs

@@ -0,0 +1,162 @@
+use crate::{
+    ActiveData, Event, EventCtx, EventFn, EventIdCtx, EventLike, HasEvents, IdLike, LayerId,
+    WeakWidget, WidgetEventFn, WidgetId,
+    util::{HashMap, HashSet, TypeMap},
+};
+use std::{any::TypeId, rc::Rc};
+
+pub struct EventManager<Rsc> {
+    widget_to_types: HashMap<WidgetId, HashSet<TypeId>>,
+    types: TypeMap<dyn EventManagerLike<Rsc>>,
+}
+
+impl<Rsc> Default for EventManager<Rsc> {
+    fn default() -> Self {
+        Self {
+            widget_to_types: Default::default(),
+            types: Default::default(),
+        }
+    }
+}
+
+impl<Rsc: HasEvents + 'static> EventManager<Rsc> {
+    pub fn get_type<E: EventLike>(&mut self) -> &mut TypeEventManager<Rsc, E::Event> {
+        self.types.type_or_default()
+    }
+
+    pub fn register<I: IdLike + 'static, E: EventLike>(
+        &mut self,
+        id: I,
+        event: E,
+        f: impl for<'a> WidgetEventFn<Rsc, <E::Event as Event>::Data<'a>, I::Widget>,
+    ) {
+        let i = id.id();
+        self.get_type::<E>().register(id, event, f);
+        self.widget_to_types
+            .entry(i)
+            .or_default()
+            .insert(Self::type_key::<E>());
+    }
+
+    pub fn type_key<E: EventLike>() -> TypeId {
+        TypeId::of::<TypeEventManager<Rsc, E::Event>>()
+    }
+}
+
+pub trait EventsLike {
+    fn remove(&mut self, id: WidgetId);
+    fn draw(&mut self, active: &ActiveData);
+    fn undraw(&mut self, active: &ActiveData);
+}
+
+impl<Rsc: HasEvents + 'static> EventsLike for EventManager<Rsc> {
+    fn remove(&mut self, id: WidgetId) {
+        for t in self.widget_to_types.get(&id).into_flat_iter() {
+            self.types.get_mut(t).unwrap().remove(id);
+        }
+    }
+
+    fn draw(&mut self, active: &ActiveData) {
+        for t in self.widget_to_types.get(&active.id).into_flat_iter() {
+            self.types.get_mut(t).unwrap().draw(active);
+        }
+    }
+
+    fn undraw(&mut self, active: &ActiveData) {
+        for t in self.widget_to_types.get(&active.id).into_flat_iter() {
+            self.types.get_mut(t).unwrap().undraw(active);
+        }
+    }
+}
+
+pub trait EventManagerLike<State> {
+    fn remove(&mut self, id: WidgetId);
+    fn draw(&mut self, data: &ActiveData);
+    fn undraw(&mut self, data: &ActiveData);
+}
+
+type EventData<Rsc, E> = (E, Rc<dyn for<'a> EventFn<Rsc, <E as Event>::Data<'a>>>);
+pub struct TypeEventManager<Rsc: HasEvents, E: Event> {
+    // TODO: reduce visiblity!!
+    pub active: HashMap<LayerId, HashMap<WidgetId, E::State>>,
+    pub global: E::Global,
+    map: HashMap<WidgetId, Vec<EventData<Rsc, E>>>,
+}
+
+impl<Rsc: HasEvents, E: Event> EventManagerLike<Rsc> for TypeEventManager<Rsc, E> {
+    fn remove(&mut self, id: WidgetId) {
+        self.map.remove(&id);
+        for layer in self.active.values_mut() {
+            layer.remove(&id);
+        }
+    }
+    fn draw(&mut self, data: &ActiveData) {
+        self.active
+            .entry(data.layer)
+            .or_default()
+            .entry(data.id)
+            .or_default();
+    }
+    fn undraw(&mut self, data: &ActiveData) {
+        if let Some(layer) = self.active.get_mut(&data.layer) {
+            layer.remove(&data.id);
+        }
+    }
+}
+
+impl<Rsc: HasEvents, E: Event> Default for TypeEventManager<Rsc, E> {
+    fn default() -> Self {
+        Self {
+            active: Default::default(),
+            global: Default::default(),
+            map: Default::default(),
+        }
+    }
+}
+
+impl<Rsc: HasEvents + 'static, E: Event> TypeEventManager<Rsc, E> {
+    fn register<I: IdLike + 'static>(
+        &mut self,
+        widget: I,
+        event: impl EventLike<Event = E>,
+        f: impl for<'a> WidgetEventFn<Rsc, E::Data<'a>, I::Widget>,
+    ) {
+        let event = event.into_event();
+        self.map.entry(widget.id()).or_default().push((
+            event,
+            Rc::new(move |ctx, rsc| {
+                f(
+                    EventIdCtx {
+                        widget: WeakWidget::new(widget.id()),
+                        state: ctx.state,
+                        data: ctx.data,
+                    },
+                    rsc,
+                );
+            }),
+        ));
+    }
+
+    pub fn run_fn<'a>(
+        &mut self,
+        id: impl IdLike,
+    ) -> impl for<'b> FnOnce(EventCtx<'_, Rsc, E::Data<'b>>, &mut Rsc) -> bool + 'a {
+        let fs = self.map.get(&id.id()).cloned().unwrap_or_default();
+        move |ctx, rsc| {
+            let mut consumed = false;
+            for (e, f) in fs {
+                if let Some(data) = e.should_run(&ctx.data) {
+                    consumed |= e.consumes(&data);
+                    f(
+                        EventCtx {
+                            state: ctx.state,
+                            data,
+                        },
+                        rsc,
+                    )
+                }
+            }
+            consumed
+        }
+    }
+}

core/src/event/mod.rs

@@ -0,0 +1,53 @@
+mod ctx;
+mod manager;
+mod rsc;
+
+pub use ctx::*;
+pub use manager::*;
+pub use rsc::*;
+
+pub trait Event: Sized + 'static + Clone {
+    type Data<'a>: Clone = ();
+    type State: Default = ();
+    /// State the whole event type keeps, rather than one copy per widget.
+    type Global: Default = ();
+    #[allow(unused_variables)]
+    fn should_run<'a>(&self, data: &Self::Data<'a>) -> Option<Self::Data<'a>> {
+        Some(data.clone())
+    }
+
+    /// Whether having run on this data uses up whatever triggered it, so
+    /// nothing further should see it.
+    #[allow(unused_variables)]
+    fn consumes(&self, data: &Self::Data<'_>) -> bool {
+        false
+    }
+}
+
+pub trait EventLike {
+    type Event: Event;
+    fn into_event(self) -> Self::Event;
+}
+
+impl<E: Event> EventLike for E {
+    type Event = Self;
+
+    fn into_event(self) -> Self::Event {
+        self
+    }
+}
+
+pub trait EventFn<Rsc: HasEvents, Data>: Fn(EventCtx<Rsc, Data>, &mut Rsc) + 'static {}
+impl<Rsc: HasEvents, F: Fn(EventCtx<Rsc, Data>, &mut Rsc) + 'static, Data> EventFn<Rsc, Data>
+    for F
+{
+}
+
+pub trait WidgetEventFn<Rsc: HasEvents, Data, W: ?Sized>:
+    Fn(EventIdCtx<Rsc, Data, W>, &mut Rsc) + 'static
+{
+}
+impl<Rsc: HasEvents, F: Fn(EventIdCtx<Rsc, Data, W>, &mut Rsc) + 'static, Data, W: ?Sized>
+    WidgetEventFn<Rsc, Data, W> for F
+{
+}

core/src/event/rsc.rs

@@ -0,0 +1,35 @@
+use crate::{
+    Event, EventCtx, EventLike, EventManager, IdLike, UiRsc, WeakWidget, Widget, WidgetEventFn,
+};
+
+pub trait HasState: 'static {
+    type State;
+}
+
+pub trait HasEvents: Sized + UiRsc + HasState {
+    fn events(&self) -> &EventManager<Self>;
+    fn events_mut(&mut self) -> &mut EventManager<Self>;
+
+    fn register_event<W: Widget + ?Sized, E: EventLike>(
+        &mut self,
+        id: WeakWidget<W>,
+        event: E,
+        f: impl for<'a> WidgetEventFn<Self, <E::Event as Event>::Data<'a>, W>,
+    ) {
+        self.events_mut().register(id, event, f);
+    }
+}
+
+pub trait RunEvents: HasEvents {
+    /// Whether anything that ran used up what triggered it.
+    fn run_event<E: EventLike>(
+        &mut self,
+        id: impl IdLike,
+        data: <E::Event as Event>::Data<'_>,
+        state: &mut Self::State,
+    ) -> bool {
+        let f = self.events_mut().get_type::<E>().run_fn(id);
+        f(EventCtx { state, data }, self)
+    }
+}
+impl<T: HasEvents> RunEvents for T {}

core/src/lib.rs

@@ -0,0 +1,33 @@
+#![feature(macro_metavar_expr_concat)]
+#![feature(const_ops)]
+#![feature(const_trait_impl)]
+#![feature(const_convert)]
+#![feature(unboxed_closures)]
+#![feature(fn_traits)]
+#![feature(const_destruct)]
+#![feature(associated_type_defaults)]
+#![feature(unsize)]
+#![feature(coerce_unsized)]
+#![feature(option_into_flat_iter)]
+
+mod attr;
+mod event;
+mod num;
+mod orientation;
+mod primitive;
+mod render;
+mod ui;
+mod widget;
+
+pub mod util;
+
+pub use attr::*;
+pub use event::*;
+pub use num::*;
+pub use orientation::*;
+pub use primitive::*;
+pub use render::*;
+pub use ui::*;
+pub use widget::*;
+
+pub type UiColor = primitive::Color<u8>;

core/src/num.rs

@@ -0,0 +1,49 @@
+use crate::util::Vec2;
+use std::marker::Destruct;
+
+pub const trait UiNum {
+    fn to_f32(self) -> f32;
+}
+
+const impl UiNum for f32 {
+    fn to_f32(self) -> f32 {
+        self
+    }
+}
+
+const impl UiNum for u32 {
+    fn to_f32(self) -> f32 {
+        self as f32
+    }
+}
+
+const impl UiNum for i32 {
+    fn to_f32(self) -> f32 {
+        self as f32
+    }
+}
+
+pub const fn vec2(x: impl const UiNum, y: impl const UiNum) -> Vec2 {
+    Vec2::new(x.to_f32(), y.to_f32())
+}
+
+const impl<T: const UiNum + Copy> From<T> for Vec2 {
+    fn from(v: T) -> Self {
+        Self {
+            x: v.to_f32(),
+            y: v.to_f32(),
+        }
+    }
+}
+
+const impl<T: const UiNum, U: const UiNum> From<(T, U)> for Vec2
+where
+    (T, U): const Destruct,
+{
+    fn from((x, y): (T, U)) -> Self {
+        Self {
+            x: x.to_f32(),
+            y: y.to_f32(),
+        }
+    }
+}

core/src/orientation/align.rs

@@ -1,4 +1,4 @@
-use crate::layout::vec2;
+use crate::vec2;
 
 use super::*;
 
@@ -187,7 +187,7 @@ impl From<CardinalAlign> for Align {
     }
 }
 
-impl const From<RegionAlign> for UiVec2 {
+const impl From<RegionAlign> for UiVec2 {
     fn from(align: RegionAlign) -> Self {
         Self::rel(align.rel())
     }

core/src/orientation/axis.rs

@@ -68,3 +68,48 @@ impl Vec2 {
         }
     }
 }
+
+pub const trait AxisT {
+    fn get() -> Axis;
+}
+
+pub struct XAxis;
+const impl AxisT for XAxis {
+    fn get() -> Axis {
+        Axis::X
+    }
+}
+
+pub struct YAxis;
+const impl AxisT for YAxis {
+    fn get() -> Axis {
+        Axis::Y
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+pub struct BothAxis<T> {
+    pub x: T,
+    pub y: T,
+}
+
+impl<T> BothAxis<T> {
+    pub const fn axis<A: const AxisT>(&mut self) -> &mut T {
+        match A::get() {
+            Axis::X => &mut self.x,
+            Axis::Y => &mut self.y,
+        }
+    }
+    pub fn take_axis<A: const AxisT>(self) -> T {
+        match A::get() {
+            Axis::X => self.x,
+            Axis::Y => self.y,
+        }
+    }
+    pub fn axis_dyn(&mut self, axis: Axis) -> &mut T {
+        match axis {
+            Axis::X => &mut self.x,
+            Axis::Y => &mut self.y,
+        }
+    }
+}

core/src/orientation/len.rs

@@ -1,5 +1,5 @@
 use super::*;
-use crate::{layout::UiNum, util::impl_op};
+use crate::{UiNum, util::impl_op};
 
 #[derive(Debug, Default, Clone, Copy, PartialEq)]
 pub struct Size {

core/src/orientation/mod.rs

@@ -3,7 +3,7 @@ mod axis;
 mod len;
 mod pos;
 
-use super::vec2::*;
+use crate::util::Vec2;
 
 pub use align::*;
 pub use axis::*;

core/src/orientation/pos.rs

@@ -2,7 +2,7 @@ use std::{fmt::Display, hash::Hash, marker::Destruct};
 
 use super::*;
 use crate::{
-    layout::UiNum,
+    UiNum,
     util::{LerpUtil, impl_op},
 };
 
@@ -56,13 +56,6 @@ impl UiVec2 {
         }
     }
 
-    pub const fn outside(&self, region: &UiRegion) -> UiVec2 {
-        UiVec2 {
-            x: self.x.outside(&region.x),
-            y: self.y.outside(&region.y),
-        }
-    }
-
     pub fn axis_mut(&mut self, axis: Axis) -> &mut UiScalar {
         match axis {
             Axis::X => &mut self.x,
@@ -124,13 +117,13 @@ impl Display for UiVec2 {
 impl_op!(UiVec2 Add add; x y);
 impl_op!(UiVec2 Sub sub; x y);
 
-impl const From<Vec2> for UiVec2 {
+const impl From<Vec2> for UiVec2 {
     fn from(abs: Vec2) -> Self {
         Self::abs(abs)
     }
 }
 
-impl<T: const UiNum, U: const UiNum> const From<(T, U)> for UiVec2
+const impl<T: const UiNum, U: const UiNum> From<(T, U)> for UiVec2
 where
     (T, U): const Destruct,
 {
@@ -209,10 +202,15 @@ impl UiScalar {
         }
     }
 
-    pub const fn outside(&self, span: &UiSpan) -> Self {
-        let rel = self.rel.lerp_inv(span.start.rel, span.end.rel);
-        let abs = self.abs - rel.lerp(span.start.abs, span.end.abs);
-        Self { rel, abs }
+    /// `within` undone against `from` and redone against `to`, for one axis.
+    /// `from`'s relative extent is the denominator, so it must not be zero.
+    fn stretch(&self, from: &UiSpan, to: &UiSpan) -> Self {
+        let frac = (self.rel - from.start.rel) / (from.end.rel - from.start.rel);
+        Self {
+            rel: frac.lerp(to.start.rel, to.end.rel),
+            abs: self.abs - frac.lerp(from.start.abs, from.end.abs)
+                + frac.lerp(to.start.abs, to.end.abs),
+        }
     }
 
     pub fn within_len(&self, len: UiScalar) -> Self {
@@ -283,13 +281,6 @@ impl UiSpan {
         }
     }
 
-    pub const fn outside(&self, parent: &Self) -> Self {
-        Self {
-            start: self.start.outside(parent),
-            end: self.end.outside(parent),
-        }
-    }
-
     pub const fn len(&self) -> UiScalar {
         self.end - self.start
     }
@@ -324,14 +315,7 @@ impl UiRegion {
             y: self.y.within(&parent.y),
         }
     }
-    pub const fn outside(&self, parent: &Self) -> Self {
-        Self {
-            x: self.x.outside(&parent.x),
-            y: self.y.outside(&parent.y),
-        }
-    }
-
-    pub const fn axis(&mut self, axis: Axis) -> &UiSpan {
+    pub const fn axis(&self, axis: Axis) -> &UiSpan {
         match axis {
             Axis::X => &self.x,
             Axis::Y => &self.y,
@@ -407,6 +391,30 @@ impl UiRegion {
             },
         }
     }
+
+    /// Whether a stretch out of this box can be expressed. Each part inside a
+    /// box is held as a fraction of it, and a fixed length has no fraction to
+    /// hold one by -- every part of it is just an offset from its start.
+    pub fn stretchable(&self) -> bool {
+        self.x.start.rel != self.x.end.rel && self.y.start.rel != self.y.end.rel
+    }
+
+    /// Re-expresses a region inside `from` as the same fractions of `to`.
+    /// `from` must be `stretchable`; a translation is `shift` instead, which
+    /// needs no fractions and works out of any box.
+    pub fn stretch(&self, from: &UiRegion, to: &UiRegion) -> UiRegion {
+        debug_assert!(from.stretchable(), "a fixed length has no fraction");
+        UiRegion {
+            x: UiSpan {
+                start: self.x.start.stretch(&from.x, &to.x),
+                end: self.x.end.stretch(&from.x, &to.x),
+            },
+            y: UiSpan {
+                start: self.y.start.stretch(&from.y, &to.y),
+                end: self.y.end.stretch(&from.y, &to.y),
+            },
+        }
+    }
 }
 
 impl Display for UiRegion {
@@ -421,7 +429,7 @@ impl Display for UiRegion {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub struct PixelRegion {
     pub top_left: Vec2,
     pub bot_right: Vec2,

core/src/primitive/color.rs

@@ -1,15 +1,21 @@
-#![allow(clippy::multiple_bound_locations)]
+use std::marker::Destruct;
 
 /// stored in linear for sane manipulation
 #[repr(C)]
 #[derive(Clone, Copy, Hash, PartialEq, Eq, bytemuck::Zeroable, Debug)]
-pub struct Color<T: ColorNum> {
+pub struct Color<T> {
     pub r: T,
     pub g: T,
     pub b: T,
     pub a: T,
 }
 
+impl<T: ColorNum> Default for Color<T> {
+    fn default() -> Self {
+        Self::BLACK
+    }
+}
+
 impl<T: ColorNum> Color<T> {
     pub const BLACK: Self = Self::rgb(T::MIN, T::MIN, T::MIN);
     pub const WHITE: Self = Self::rgb(T::MAX, T::MAX, T::MAX);
@@ -56,23 +62,47 @@ pub trait ColorNum {
     const MAX: Self;
 }
 
-impl<T: ColorNum + F32Conversion> Color<T> {
-    pub fn mul_rgb(self, amt: impl F32Conversion) -> Self {
+macro_rules! map_rgb {
+    ($x:ident,$self:ident, $e:tt) => {
+        #[allow(unused_braces)]
+        Self {
+            r: {
+                let $x = $self.r;
+                $e
+            },
+            g: {
+                let $x = $self.g;
+                $e
+            },
+            b: {
+                let $x = $self.b;
+                $e
+            },
+            a: $self.a,
+        }
+    };
+}
+
+impl<T: ColorNum + const F32Conversion> Color<T>
+where
+    Self: const Destruct,
+{
+    pub const fn mul_rgb(self, amt: impl const F32Conversion) -> Self {
         let amt = amt.to();
-        self.map_rgb(|x| T::from(x.to() * amt))
+        map_rgb!(x, self, { T::from(x.to() * amt) })
     }
 
-    pub fn add_rgb(self, amt: impl F32Conversion) -> Self {
+    pub const fn add_rgb(self, amt: impl const F32Conversion) -> Self {
         let amt = amt.to();
-        self.map_rgb(|x| T::from(x.to() + amt))
+        map_rgb!(x, self, { T::from(x.to() + amt) })
     }
 
-    pub fn darker(self, amt: f32) -> Self {
+    pub const fn darker(self, amt: f32) -> Self {
         self.mul_rgb(1.0 - amt)
     }
 
-    pub fn brighter(self, amt: f32) -> Self {
-        self.map_rgb(|x| {
+    pub const fn brighter(self, amt: f32) -> Self {
+        map_rgb!(x, self, {
             let x = x.to();
             T::from(x + (1.0 - x) * amt)
         })
@@ -120,7 +150,7 @@ impl ColorNum for f32 {
 
 unsafe impl bytemuck::Pod for Color<u8> {}
 
-impl const F32Conversion for f32 {
+const impl F32Conversion for f32 {
     fn to(self) -> f32 {
         self
     }
@@ -129,7 +159,7 @@ impl const F32Conversion for f32 {
     }
 }
 
-impl const F32Conversion for u8 {
+const impl F32Conversion for u8 {
     fn to(self) -> f32 {
         self as f32 / 255.0
     }

core/src/primitive/layer.rs

@@ -1,6 +1,11 @@
 use std::ops::{Index, IndexMut};
 
-use crate::render::{MaskIdx, Primitive, PrimitiveHandle, PrimitiveInst, Primitives};
+use crate::{
+    render::{LayerDraws, MaskIdx, Primitive, PrimitiveHandle, PrimitiveInst},
+    util::to_mut,
+};
+
+pub type LayerId = usize;
 
 struct LayerNode<T> {
     next: Ptr,
@@ -34,7 +39,7 @@ struct Child {
     tail: usize,
 }
 
-pub type PrimitiveLayers = Layers<Primitives>;
+pub type DrawLayers = Layers<LayerDraws>;
 
 impl<T: Default> Layers<T> {
     pub fn new() -> Layers<T> {
@@ -49,13 +54,13 @@ impl<T: Default> Layers<T> {
         self.vec.push(LayerNode::head());
     }
 
-    fn push(&mut self, node: LayerNode<T>) -> usize {
+    fn push(&mut self, node: LayerNode<T>) -> LayerId {
         let i = self.vec.len();
         self.vec.push(node);
         i
     }
 
-    pub fn next(&mut self, i: usize) -> usize {
+    pub fn next(&mut self, i: LayerId) -> LayerId {
         if let Ptr::Next(i) = self.vec[i].next {
             return i;
         }
@@ -75,7 +80,7 @@ impl<T: Default> Layers<T> {
         i_new
     }
 
-    pub fn child(&mut self, i: usize) -> usize {
+    pub fn child(&mut self, i: LayerId) -> LayerId {
         if let Some(c) = self.vec[i].child {
             return c.head;
         }
@@ -100,11 +105,11 @@ impl<T: Default> Layers<T> {
         self.vec.iter_mut().map(|n| &mut n.data).enumerate()
     }
 
-    pub fn iter(&self) -> impl Iterator<Item = (usize, &T)> {
+    pub fn iter(&self) -> impl Iterator<Item = (LayerId, &T)> {
         self.indices().map(|i| (i, &self.vec[i].data))
     }
 
-    pub fn iter_depth(&self) -> impl Iterator<Item = ((usize, usize), &T)> {
+    pub fn iter_depth(&self) -> impl Iterator<Item = ((LayerId, usize), &T)> {
         self.indices()
             .map(|i| ((i, self.vec[i].depth), &self.vec[i].data))
     }
@@ -114,8 +119,12 @@ impl<T: Default> Layers<T> {
     }
 }
 
-impl PrimitiveLayers {
-    pub fn write<P: Primitive>(&mut self, layer: usize, info: PrimitiveInst<P>) -> PrimitiveHandle {
+impl DrawLayers {
+    pub fn write<P: Primitive>(
+        &mut self,
+        layer: LayerId,
+        info: PrimitiveInst<P>,
+    ) -> PrimitiveHandle {
         self[layer].write(layer, info)
     }
 
@@ -130,16 +139,16 @@ impl<T: Default> Default for Layers<T> {
     }
 }
 
-impl<T> Index<usize> for Layers<T> {
+impl<T> Index<LayerId> for Layers<T> {
     type Output = T;
 
-    fn index(&self, index: usize) -> &Self::Output {
+    fn index(&self, index: LayerId) -> &Self::Output {
         &self.vec[index].data
     }
 }
 
-impl<T> IndexMut<usize> for Layers<T> {
-    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+impl<T> IndexMut<LayerId> for Layers<T> {
+    fn index_mut(&mut self, index: LayerId) -> &mut Self::Output {
         &mut self.vec[index].data
     }
 }
@@ -170,8 +179,7 @@ impl<'a, T> Iterator for LayerIteratorMut<'a, T> {
     fn next(&mut self) -> Option<Self::Item> {
         let i = self.inner.next()?;
         // SAFETY: requires index iterator to work properly
-        #[allow(mutable_transmutes)]
-        let layer = unsafe { std::mem::transmute::<&T, &mut T>(&self.inner.vec[i].data) };
+        let layer = unsafe { to_mut(&self.inner.vec[i].data) };
         Some((i, layer))
     }
 }
@@ -180,8 +188,7 @@ impl<'a, T> DoubleEndedIterator for LayerIteratorMut<'a, T> {
     fn next_back(&mut self) -> Option<Self::Item> {
         let i = self.inner.next_back()?;
         // SAFETY: requires index iterator to work properly
-        #[allow(mutable_transmutes)]
-        let layer = unsafe { std::mem::transmute::<&T, &mut T>(&self.inner.vec[i].data) };
+        let layer = unsafe { to_mut(&self.inner.vec[i].data) };
         Some((i, layer))
     }
 }

core/src/primitive/mod.rs

@@ -0,0 +1,9 @@
+mod color;
+mod layer;
+mod text;
+mod texture;
+
+pub use color::*;
+pub use layer::*;
+pub use text::*;
+pub use texture::*;

core/src/primitive/text.rs

@@ -0,0 +1,282 @@
+use crate::{
+    Align, GlyphAtlas, GlyphEntry, GlyphKey, PlacedGlyph, RegionAlign, UiColor, util::Vec2,
+};
+use parley::{
+    Alignment, AlignmentOptions, FontContext, FontFamily, FontFamilyName, GenericFamily, Layout,
+    LayoutContext, LineHeight, PositionedLayoutItem, StyleProperty,
+};
+use std::hash::{DefaultHasher, Hash, Hasher};
+use swash::{
+    FontRef,
+    scale::{Render, ScaleContext, Source, StrikeWith},
+    zeno::{Format, Vector},
+};
+
+pub struct TextData {
+    pub font_ctx: FontContext,
+    pub layout_ctx: LayoutContext<UiColor>,
+    scale_ctx: ScaleContext,
+    pub atlas: GlyphAtlas,
+}
+
+impl Default for TextData {
+    fn default() -> Self {
+        Self {
+            font_ctx: FontContext::new(),
+            layout_ctx: LayoutContext::new(),
+            scale_ctx: ScaleContext::new(),
+            atlas: GlyphAtlas::default(),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq)]
+pub enum Family {
+    SansSerif,
+    Serif,
+    Monospace,
+    Named(String),
+}
+
+impl Family {
+    fn family(&self) -> FontFamily<'_> {
+        let name = match self {
+            Self::SansSerif => FontFamilyName::Generic(GenericFamily::SansSerif),
+            Self::Serif => FontFamilyName::Generic(GenericFamily::Serif),
+            Self::Monospace => FontFamilyName::Generic(GenericFamily::Monospace),
+            Self::Named(name) => FontFamilyName::Named(name.as_str().into()),
+        };
+        FontFamily::Single(name)
+    }
+}
+
+#[derive(Clone, PartialEq)]
+pub struct TextAttrs {
+    pub color: UiColor,
+    pub font_size: f32,
+    pub line_height: f32,
+    pub family: Family,
+    pub wrap: bool,
+    pub align: RegionAlign,
+}
+
+pub const LINE_HEIGHT_MULT: f32 = 1.1;
+
+impl Default for TextAttrs {
+    fn default() -> Self {
+        let size = 16.0;
+        Self {
+            color: UiColor::WHITE,
+            font_size: size,
+            line_height: size * LINE_HEIGHT_MULT,
+            family: Family::SansSerif,
+            wrap: false,
+            align: Align::CENTER_LEFT,
+        }
+    }
+}
+
+/// Keeps text and its corresponding layout from getting out of sync.
+pub struct TextBuffer {
+    text: String,
+    layout: Layout<UiColor>,
+    layout_key: Option<LayoutKey>,
+}
+
+#[derive(PartialEq)]
+struct LayoutKey {
+    attrs: TextAttrs,
+    max_width: Option<f32>,
+}
+
+impl TextBuffer {
+    pub fn new(text: impl Into<String>) -> Self {
+        Self {
+            text: text.into(),
+            layout: Layout::new(),
+            layout_key: None,
+        }
+    }
+
+    pub fn new_empty() -> Self {
+        Self::new("")
+    }
+
+    pub fn text(&self) -> &str {
+        &self.text
+    }
+
+    pub fn layout(&self) -> &Layout<UiColor> {
+        &self.layout
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.text.is_empty()
+    }
+
+    pub fn set_text(&mut self, text: impl Into<String>) {
+        let text = text.into();
+        if text != self.text {
+            self.text = text;
+            self.layout_key = None;
+        }
+    }
+
+    /// Invalidates the layout and returns the underlying string for editing.
+    pub fn edit(&mut self) -> &mut String {
+        self.layout_key = None;
+        &mut self.text
+    }
+
+    pub fn size(&self) -> Vec2 {
+        Vec2::new(self.layout.width(), self.layout.height())
+    }
+
+    pub fn shape(&mut self, data: &mut TextData, attrs: &TextAttrs, width: Option<f32>) {
+        let layout_key = LayoutKey {
+            attrs: attrs.clone(),
+            max_width: width,
+        };
+        if self.layout_key.as_ref() == Some(&layout_key) {
+            return;
+        }
+        let mut builder = data
+            .layout_ctx
+            .ranged_builder(&mut data.font_ctx, &self.text, 1.0, true);
+        builder.push_default(StyleProperty::FontFamily(attrs.family.family()));
+        builder.push_default(StyleProperty::FontSize(attrs.font_size));
+        builder.push_default(StyleProperty::LineHeight(LineHeight::Absolute(
+            attrs.line_height,
+        )));
+        builder.push_default(StyleProperty::Brush(attrs.color));
+        builder.build_into(&mut self.layout, &self.text);
+        self.layout.break_all_lines(width);
+        self.layout
+            .align(Alignment::Start, AlignmentOptions::default());
+        self.layout_key = Some(layout_key);
+    }
+}
+
+impl TextData {
+    pub fn place(&mut self, buffer: &TextBuffer) -> Vec<PlacedGlyph> {
+        let mut placed = Vec::new();
+        for line in buffer.layout.lines() {
+            for item in line.items() {
+                let PositionedLayoutItem::GlyphRun(run) = item else {
+                    continue;
+                };
+                let font = run.run().font();
+                let font_size = run.run().font_size();
+                let coords = run.run().normalized_coords();
+                let Some(font_ref) = FontRef::from_index(font.data.as_ref(), font.index as usize)
+                else {
+                    continue;
+                };
+                let coords_hash = hash_coords(coords);
+                let font_id = font.data.id();
+
+                for glyph in run.positioned_glyphs() {
+                    let subpixel = ((glyph.x.fract() * 4.0).round() as i32).rem_euclid(4) as u8;
+                    let key = GlyphKey {
+                        font: font_id,
+                        glyph: glyph.id,
+                        size: glyph_size_key(font_size),
+                        subpixel,
+                        coords: coords_hash,
+                    };
+                    let Some(entry) = self.glyph_entry(GlyphRaster {
+                        key,
+                        font: font_ref,
+                        font_size,
+                        coords,
+                        subpixel,
+                        glyph_id: glyph.id,
+                    }) else {
+                        continue;
+                    };
+                    placed.push(PlacedGlyph {
+                        entry,
+                        offset: Vec2::new(
+                            glyph.x.floor() + entry.left as f32,
+                            glyph.y.floor() - entry.top as f32,
+                        ),
+                    });
+                }
+            }
+        }
+        placed
+    }
+
+    fn glyph_entry(&mut self, glyph: GlyphRaster<'_>) -> Option<GlyphEntry> {
+        if let Some(entry) = self.atlas.get(&glyph.key) {
+            return entry;
+        }
+
+        let mut scaler = self
+            .scale_ctx
+            .builder(glyph.font)
+            .size(glyph.font_size)
+            .hint(true)
+            .normalized_coords(glyph.coords)
+            .build();
+        let image = Render::new(&[
+            Source::ColorOutline(0),
+            Source::ColorBitmap(StrikeWith::BestFit),
+            Source::Outline,
+        ])
+        .format(Format::Alpha)
+        .offset(Vector::new(glyph.subpixel as f32 / 4.0, 0.0))
+        .render(&mut scaler, glyph.glyph_id as u16);
+
+        if let Some(image) = image {
+            self.atlas.insert(glyph.key, &image)
+        } else {
+            self.atlas.insert_empty(glyph.key);
+            None
+        }
+    }
+}
+
+struct GlyphRaster<'a> {
+    key: GlyphKey,
+    font: FontRef<'a>,
+    font_size: f32,
+    coords: &'a [i16],
+    subpixel: u8,
+    glyph_id: u32,
+}
+
+fn hash_coords(coords: &[i16]) -> u64 {
+    let mut hasher = DefaultHasher::new();
+    coords.hash(&mut hasher);
+    hasher.finish()
+}
+
+const GLYPH_SIZE_STEPS_PER_PIXEL: f32 = 16.0;
+
+fn glyph_size_key(font_size: f32) -> u32 {
+    (font_size * GLYPH_SIZE_STEPS_PER_PIXEL).round() as u32
+}
+
+pub struct RenderedText {
+    pub glyphs: Vec<PlacedGlyph>,
+    pub size: Vec2,
+    pub color: UiColor,
+}
+
+impl TextData {
+    pub fn render(
+        &mut self,
+        buffer: &mut TextBuffer,
+        attrs: &TextAttrs,
+        width: Option<f32>,
+    ) -> RenderedText {
+        buffer.shape(self, attrs, width);
+        let glyphs = self.place(buffer);
+        RenderedText {
+            glyphs,
+            size: buffer.size(),
+            color: attrs.color,
+        }
+    }
+}

core/src/primitive/texture.rs

@@ -1,15 +1,13 @@
+use crate::util::{RefCounter, Vec2};
+use image::{DynamicImage, GenericImageView};
 use std::{
     ops::Index,
     sync::mpsc::{Receiver, Sender, channel},
 };
 
-use image::{DynamicImage, GenericImageView};
-
-use crate::{layout::Vec2, render::TexturePrimitive, util::RefCounter};
-
 #[derive(Debug, Clone)]
 pub struct TextureHandle {
-    inner: TexturePrimitive,
+    slot: u32,
     size: Vec2,
     counter: RefCounter,
     send: Sender<u32>,
@@ -28,14 +26,26 @@ pub struct Textures {
 pub enum TextureUpdate<'a> {
     Push(&'a DynamicImage),
     Set(u32, &'a DynamicImage),
+    Patch(u32, PatchRect, &'a DynamicImage),
     Free(u32),
+    /// Added and freed before the renderer drained either update. It still has
+    /// to push a slot to stay lined up with `images`; `Free` then empties it.
     PushFree,
     SetFree,
 }
 
+#[derive(Debug, Clone, Copy)]
+pub struct PatchRect {
+    pub x: u32,
+    pub y: u32,
+    pub width: u32,
+    pub height: u32,
+}
+
 enum Update {
     Push(u32),
     Set(u32),
+    Patch(u32, PatchRect),
     Free(u32),
 }
 
@@ -53,14 +63,8 @@ impl Textures {
     pub fn add(&mut self, image: impl Into<DynamicImage>) -> TextureHandle {
         let image = image.into();
         let size = image.dimensions().into();
-        let view_idx = self.push(image);
-        // 0 == default in renderer; TODO: actually create samplers here
-        let sampler_idx = 0;
         TextureHandle {
-            inner: TexturePrimitive {
-                view_idx,
-                sampler_idx,
-            },
+            slot: self.push(image),
             size,
             counter: RefCounter::new(),
             send: self.send.clone(),
@@ -80,6 +84,23 @@ impl Textures {
         }
     }
 
+    pub fn image_mut(&mut self, handle: &TextureHandle) -> &mut DynamicImage {
+        self.images[handle.slot as usize]
+            .as_mut()
+            .expect("texture was freed while still held")
+    }
+
+    /// Queue an upload of just `rect`, after writing it with `image_mut`.
+    pub fn patch(&mut self, handle: &TextureHandle, rect: PatchRect) {
+        self.updates.push(Update::Patch(handle.slot, rect));
+    }
+
+    /// How many textures are live, which is what a ui can ask; the renderer's
+    /// copies follow from the updates it drains.
+    pub fn count(&self) -> usize {
+        self.images.iter().flatten().count()
+    }
+
     pub fn free(&mut self) {
         for idx in self.recv.try_iter() {
             self.images[idx as usize] = None;
@@ -98,14 +119,19 @@ impl Textures {
                 .as_ref()
                 .map(|img| TextureUpdate::Set(i, img))
                 .unwrap_or(TextureUpdate::SetFree),
+            Update::Patch(i, rect) => self.images[i as usize]
+                .as_ref()
+                .map(|img| TextureUpdate::Patch(i, rect, img))
+                .unwrap_or(TextureUpdate::SetFree),
             Update::Free(i) => TextureUpdate::Free(i),
         })
     }
 }
 
 impl TextureHandle {
-    pub fn primitive(&self) -> TexturePrimitive {
-        self.inner
+    /// Index into `Textures`, and into the renderer's parallel slots.
+    pub fn slot(&self) -> u32 {
+        self.slot
     }
     pub fn size(&self) -> Vec2 {
         self.size
@@ -115,7 +141,7 @@ impl TextureHandle {
 impl Drop for TextureHandle {
     fn drop(&mut self) {
         if self.counter.drop() {
-            let _ = self.send.send(self.inner.view_idx);
+            let _ = self.send.send(self.slot);
         }
     }
 }
@@ -124,7 +150,7 @@ impl Index<&TextureHandle> for Textures {
     type Output = DynamicImage;
 
     fn index(&self, index: &TextureHandle) -> &Self::Output {
-        self.images[index.inner.view_idx as usize].as_ref().unwrap()
+        self.images[index.slot as usize].as_ref().unwrap()
     }
 }
 

core/src/render/atlas.rs

@@ -0,0 +1,245 @@
+use crate::{
+    PatchRect,
+    util::{HashMap, Vec2},
+};
+use image::RgbaImage;
+use swash::scale::image::{Content, Image};
+
+/// Side of one page, and so of every layer of `render::page`'s array texture.
+pub(crate) const PAGE: u32 = 1024;
+
+/// Transparent margin kept around every glyph, so that sampling one cannot
+/// pick up its neighbour along a shared edge.
+const PAD: u32 = 1;
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct GlyphKey {
+    pub font: u64,
+    pub glyph: u32,
+    /// Font size in 1/16 px, so sizes that round to the same pixels share a
+    /// raster instead of filling the atlas with near-duplicates.
+    pub size: u32,
+    /// Horizontal subpixel phase, in 1/4 px.
+    pub subpixel: u8,
+    /// Hash of the variation coordinates; a variable font at two weights is two
+    /// different sets of pixels from one glyph id.
+    pub coords: u64,
+}
+
+#[derive(Clone, Copy)]
+pub struct GlyphEntry {
+    pub uv_min: Vec2,
+    pub uv_max: Vec2,
+    /// Offset from the glyph's pen position to the top-left of its pixels.
+    pub left: i32,
+    pub top: i32,
+    pub width: u32,
+    pub height: u32,
+    pub is_colored: bool,
+    /// Which atlas array layer this glyph is on.
+    pub layer: u32,
+}
+
+impl GlyphEntry {
+    const IS_COLORED: u32 = 1;
+
+    pub(crate) fn flags(&self) -> u32 {
+        if self.is_colored { Self::IS_COLORED } else { 0 }
+    }
+}
+
+struct Page {
+    image: RgbaImage,
+    x: u32,
+    y: u32,
+    shelf_height: u32,
+}
+
+/// A rectangle of one page the renderer has not uploaded yet.
+#[derive(Clone, Copy)]
+pub struct PageUpload {
+    pub layer: u32,
+    pub rect: PatchRect,
+}
+
+#[derive(Default)]
+pub struct GlyphAtlas {
+    pages: Vec<Page>,
+    /// `None` for a glyph that rasterised to nothing -- a space, say. Cached
+    /// too, so it is not re-rasterised on every layout.
+    entries: HashMap<GlyphKey, Option<GlyphEntry>>,
+    uploads: Vec<PageUpload>,
+}
+
+impl GlyphAtlas {
+    pub fn get(&self, key: &GlyphKey) -> Option<Option<GlyphEntry>> {
+        self.entries.get(key).copied()
+    }
+
+    pub fn insert(&mut self, key: GlyphKey, image: &Image) -> Option<GlyphEntry> {
+        let w = image.placement.width;
+        let h = image.placement.height;
+        if w == 0 || h == 0 {
+            log::warn!(
+                "glyph {} in font {} rasterized at {w}x{h}; skipping it",
+                key.glyph,
+                key.font,
+            );
+            self.entries.insert(key, None);
+            return None;
+        }
+        if w > PAGE - PAD * 2 || h > PAGE - PAD * 2 {
+            log::warn!(
+                "glyph {} in font {} rasterized at {w}x{h}, too large for the {PAGE}x{PAGE} atlas; skipping it",
+                key.glyph,
+                key.font,
+            );
+            self.entries.insert(key, None);
+            return None;
+        }
+
+        let upload = self.allocate(w, h);
+        let PatchRect { x, y, .. } = upload.rect;
+        write_glyph(&mut self.pages[upload.layer as usize].image, image, x, y);
+        self.uploads.push(upload);
+
+        let scale = 1.0 / PAGE as f32;
+        let entry = GlyphEntry {
+            uv_min: Vec2::new(x as f32 * scale, y as f32 * scale),
+            uv_max: Vec2::new((x + w) as f32 * scale, (y + h) as f32 * scale),
+            left: image.placement.left,
+            top: image.placement.top,
+            width: w,
+            height: h,
+            is_colored: matches!(image.content, Content::Color),
+            layer: upload.layer,
+        };
+        self.entries.insert(key, Some(entry));
+        Some(entry)
+    }
+
+    /// Reserves room for a `w` by `h` glyph, adding a page if none has it.
+    fn allocate(&mut self, w: u32, h: u32) -> PageUpload {
+        let rect = |x, y| PatchRect {
+            x,
+            y,
+            width: w,
+            height: h,
+        };
+        if let Some((i, (x, y))) = self
+            .pages
+            .iter_mut()
+            .enumerate()
+            .find_map(|(i, page)| page.allocate(w, h).map(|position| (i, position)))
+        {
+            return PageUpload {
+                layer: i as u32,
+                rect: rect(x, y),
+            };
+        }
+
+        self.pages.push(Page {
+            image: RgbaImage::new(PAGE, PAGE),
+            x: PAD + w + PAD,
+            y: PAD,
+            shelf_height: h + PAD,
+        });
+        PageUpload {
+            layer: self.pages.len() as u32 - 1,
+            rect: rect(PAD, PAD),
+        }
+    }
+
+    /// Drains what has been written since the last call, for the renderer to
+    /// upload. A new page needs nothing more: wgpu leaves the rest of a fresh
+    /// layer transparent, which is what an atlas wants.
+    pub fn uploads(&mut self) -> impl Iterator<Item = (PageUpload, &RgbaImage)> {
+        let pages = &self.pages;
+        self.uploads
+            .drain(..)
+            .map(|upload| (upload, &pages[upload.layer as usize].image))
+    }
+
+    pub fn insert_empty(&mut self, key: GlyphKey) {
+        self.entries.insert(key, None);
+    }
+
+    pub fn page_count(&self) -> u32 {
+        self.pages.len() as u32
+    }
+
+    pub fn glyph_count(&self) -> usize {
+        self.entries.len()
+    }
+}
+
+impl Page {
+    fn allocate(&mut self, w: u32, h: u32) -> Option<(u32, u32)> {
+        let need_w = w + PAD;
+        let need_h = h + PAD;
+        if self.x + need_w > PAGE {
+            if need_w + PAD > PAGE || self.y + self.shelf_height + need_h > PAGE {
+                return None;
+            }
+            self.y += self.shelf_height;
+            self.x = PAD;
+            self.shelf_height = 0;
+        } else if self.y + need_h > PAGE {
+            return None;
+        }
+
+        let position = (self.x, self.y);
+        self.x += need_w;
+        self.shelf_height = self.shelf_height.max(need_h);
+        Some(position)
+    }
+}
+
+/// Mask glyphs keep coverage in alpha so their raster can be tinted at draw time.
+fn write_glyph(page: &mut RgbaImage, image: &Image, x: u32, y: u32) {
+    let width = image.placement.width as usize;
+    let height = image.placement.height as usize;
+    let page_stride = page.width() as usize * 4;
+    let x = x as usize * 4;
+    let y = y as usize;
+    let page = page.as_mut();
+
+    for row in 0..height {
+        let start = (y + row) * page_stride + x;
+        let target = &mut page[start..start + width * 4];
+        match image.content {
+            Content::Color => {
+                let start = row * width * 4;
+                target.copy_from_slice(&image.data[start..start + width * 4]);
+            }
+            Content::Mask => {
+                let start = row * width;
+                for (target, &alpha) in target
+                    .as_chunks_mut::<4>()
+                    .0
+                    .iter_mut()
+                    .zip(&image.data[start..start + width])
+                {
+                    target.copy_from_slice(&[255, 255, 255, alpha]);
+                }
+            }
+            Content::SubpixelMask => {
+                let start = row * width * 4;
+                for (target, source) in target
+                    .as_chunks_mut::<4>()
+                    .0
+                    .iter_mut()
+                    .zip(image.data[start..start + width * 4].as_chunks::<4>().0)
+                {
+                    target.copy_from_slice(&[255, 255, 255, source[1]]);
+                }
+            }
+        }
+    }
+}
+
+#[derive(Clone, Copy)]
+pub struct PlacedGlyph {
+    pub entry: GlyphEntry,
+    pub offset: Vec2,
+}

core/src/render/data.rs

@@ -0,0 +1,88 @@
+use crate::{UiRegion, util::Id, util::Vec2};
+use wgpu::*;
+
+#[repr(C)]
+#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable, Default)]
+pub struct WindowUniform {
+    pub dim: Vec2,
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct PrimitiveInstance {
+    pub region: UiRegion,
+    pub mask_idx: MaskIdx,
+    pub move_idx: MoveIdx,
+}
+
+impl PrimitiveInstance {
+    const ATTRIBS: [VertexAttribute; 6] = vertex_attr_array![
+        0 => Float32x2,
+        1 => Float32x2,
+        2 => Float32x2,
+        3 => Float32x2,
+        4 => Uint32,
+        5 => Uint32,
+    ];
+
+    pub fn desc() -> VertexBufferLayout<'static> {
+        VertexBufferLayout {
+            array_stride: std::mem::size_of::<Self>() as BufferAddress,
+            step_mode: VertexStepMode::Instance,
+            attributes: &Self::ATTRIBS,
+        }
+    }
+}
+
+pub type MaskIdx = Id<u32>;
+
+impl MaskIdx {
+    pub const NONE: Self = Self::preset(u32::MAX);
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct Mask {
+    pub region: UiRegion,
+    pub move_idx: MoveIdx,
+}
+
+/// Its own type rather than another `Id<u32>`, because it sits beside
+/// `MaskIdx` in an instance and the two must not be swappable.
+#[repr(transparent)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct MoveIdx(u32);
+
+impl MoveIdx {
+    pub const NONE: Self = Self(u32::MAX);
+
+    pub(crate) fn slot(idx: usize) -> Self {
+        Self(idx as u32)
+    }
+
+    pub(crate) fn idx(self) -> usize {
+        self.0 as usize
+    }
+}
+
+/// One link of the chain a primitive's position is resolved through: a
+/// translation in physical pixels, and the slot it is relative to. Moving a
+/// subtree writes its own slot and nothing else.
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct MoveOffset {
+    pub delta: Vec2,
+    pub parent: MoveIdx,
+}
+
+unsafe impl bytemuck::Pod for MoveOffset {}
+unsafe impl bytemuck::Zeroable for MoveOffset {}
+
+impl MoveOffset {
+    pub fn root(parent: MoveIdx) -> Self {
+        Self {
+            delta: Vec2::ZERO,
+            parent,
+        }
+    }
+}

core/src/render/mod.rs

@@ -0,0 +1,403 @@
+use crate::{
+    UiData, UiRenderState,
+    render::{data::PrimitiveInstance, util::ArrBuf},
+    util::{HashMap, Vec2},
+};
+use data::WindowUniform;
+use wgpu::{
+    util::{BufferInitDescriptor, DeviceExt},
+    *,
+};
+
+mod atlas;
+mod data;
+mod page;
+mod primitive;
+mod texture;
+mod util;
+
+pub use atlas::*;
+pub use data::{Mask, MaskIdx, MoveIdx, MoveOffset};
+pub use primitive::*;
+
+const PRELUDE: &str = include_str!("./shader/prelude.wgsl");
+
+pub struct UiRenderNode {
+    shared_layout: BindGroupLayout,
+    shared_group: BindGroup,
+    format: TextureFormat,
+
+    /// One per registered primitive, in id order.
+    primitives: Vec<PrimitivePipeline>,
+
+    layers: HashMap<usize, RenderLayer>,
+    active: Vec<usize>,
+    window_buffer: Buffer,
+    masks: ArrBuf<Mask>,
+    moves: ArrBuf<MoveOffset>,
+}
+
+struct RenderLayer {
+    /// One per registered primitive, `None` where this layer draws none.
+    primitives: Vec<Option<ListBuffers>>,
+}
+
+/// What draws one registered primitive.
+struct PrimitivePipeline {
+    data_layout: BindGroupLayout,
+    pipeline: RenderPipeline,
+    render: Box<dyn PrimitiveRender>,
+}
+
+/// One list's vertex buffer and the data its shader reads.
+struct ListBuffers {
+    instance: ArrBuf<PrimitiveInstance>,
+    data: ArrBuf<u8>,
+    group: Option<BindGroup>,
+    /// What the primitive asked to keep per instance, if anything.
+    bindings: Vec<u32>,
+}
+
+impl UiRenderNode {
+    pub fn draw<'a>(&'a self, pass: &mut RenderPass<'a>) {
+        pass.set_bind_group(0, &self.shared_group, &[]);
+        for i in &self.active {
+            let layer = &self.layers[i];
+            for (id, list) in layer.primitives.iter().enumerate() {
+                let Some(list) = list else { continue };
+                let Some(group) = &list.group else { continue };
+                let primitive = &self.primitives[id];
+                pass.set_pipeline(&primitive.pipeline);
+                pass.set_bind_group(1, group, &[]);
+                pass.set_vertex_buffer(0, list.instance.buffer.slice(..));
+                primitive.render.draw(
+                    pass,
+                    ListDraw {
+                        instances: list.instance.len() as u32,
+                        bindings: &list.bindings,
+                    },
+                );
+            }
+        }
+    }
+
+    pub fn update(
+        &mut self,
+        device: &Device,
+        queue: &Queue,
+        ui: &mut UiData,
+        ui_render: &mut UiRenderState,
+    ) {
+        // Before the layers: each list is given its pipeline's data layout.
+        self.build_pipelines(device, queue, &ui.primitives);
+        self.active.clear();
+        for (i, draws) in ui_render.layers.iter_mut() {
+            self.active.push(i);
+            for change in draws.apply_free() {
+                if let Some(inst) = ui_render.active.get_mut(&change.id) {
+                    for h in &mut inst.primitives {
+                        if h.layer == i && h.kind == change.kind && h.inst_idx == change.old {
+                            h.inst_idx = change.new;
+                            break;
+                        }
+                    }
+                }
+            }
+            let rlayer = self.layers.entry(i).or_insert_with(RenderLayer::new);
+            if draws.updated {
+                let lists = draws.primitives();
+                // The zip would otherwise skip a list with no pipeline.
+                assert!(lists.len() <= self.primitives.len());
+                rlayer.primitives.resize_with(lists.len(), || None);
+                for ((buffers, list), primitive) in rlayer
+                    .primitives
+                    .iter_mut()
+                    .zip(lists)
+                    .zip(&self.primitives)
+                {
+                    let Some(list) = list else {
+                        continue;
+                    };
+                    buffers
+                        .get_or_insert_with(|| ListBuffers::new(device))
+                        .update(device, queue, primitive, list);
+                }
+                draws.updated = false;
+            }
+        }
+        for primitive in &mut self.primitives {
+            primitive.render.update(ui);
+        }
+        let mut regroup = false;
+        if ui.masks.changed {
+            ui.masks.changed = false;
+            regroup |= self.masks.update(device, queue, &ui.masks[..]);
+        }
+        if ui_render.moves.changed {
+            ui_render.moves.changed = false;
+            regroup |= self.moves.update(device, queue, ui_render.moves.entries());
+        }
+        if regroup {
+            self.shared_group = Self::shared_group(
+                device,
+                &self.shared_layout,
+                &self.window_buffer,
+                &self.masks,
+                &self.moves,
+            );
+        }
+    }
+
+    pub fn resize(&mut self, size: impl Into<Vec2>, queue: &Queue) {
+        let size = size.into();
+        let slice = &[WindowUniform { dim: size }];
+        queue.write_buffer(&self.window_buffer, 0, bytemuck::cast_slice(slice));
+    }
+
+    pub fn new(device: &Device, config: &SurfaceConfiguration) -> Self {
+        let window_uniform = WindowUniform {
+            dim: Vec2::new(config.width as f32, config.height as f32),
+        };
+        let window_buffer = device.create_buffer_init(&BufferInitDescriptor {
+            label: Some("window"),
+            contents: bytemuck::cast_slice(&[window_uniform]),
+            usage: BufferUsages::UNIFORM | BufferUsages::COPY_DST,
+        });
+
+        let shared_layout = Self::shared_layout(device);
+        let masks = ArrBuf::new(
+            device,
+            BufferUsages::STORAGE | BufferUsages::COPY_DST,
+            "ui masks",
+        );
+        let moves = ArrBuf::new(
+            device,
+            BufferUsages::STORAGE | BufferUsages::COPY_DST,
+            "ui move offsets",
+        );
+        let shared_group =
+            Self::shared_group(device, &shared_layout, &window_buffer, &masks, &moves);
+
+        Self {
+            shared_layout,
+            shared_group,
+            format: config.format,
+            primitives: Vec::new(),
+            window_buffer,
+            layers: HashMap::default(),
+            active: Vec::new(),
+            masks,
+            moves,
+        }
+    }
+
+    /// Compiles a pipeline for every primitive registered since the last call.
+    /// Sources only ever arrive at the end, so an id keeps its pipeline.
+    fn build_pipelines(&mut self, device: &Device, queue: &Queue, registry: &PrimitiveRegistry) {
+        for source in &registry.sources()[self.primitives.len()..] {
+            let render = (source.render)(device, queue);
+            let data_layout = Self::data_layout(device, source.stride);
+            let mut groups = vec![Some(&self.shared_layout), Some(&data_layout)];
+            groups.extend(render.layout().map(Some));
+            let layout = device.create_pipeline_layout(&PipelineLayoutDescriptor {
+                label: Some(source.label),
+                bind_group_layouts: &groups,
+                immediate_size: 0,
+            });
+            let pipeline = Self::pipeline(device, &layout, self.format, source.wgsl, source.label);
+            self.primitives.push(PrimitivePipeline {
+                data_layout,
+                pipeline,
+                render,
+            });
+        }
+    }
+
+    fn pipeline(
+        device: &Device,
+        layout: &PipelineLayout,
+        format: TextureFormat,
+        wgsl: &str,
+        label: &str,
+    ) -> RenderPipeline {
+        let module = device.create_shader_module(ShaderModuleDescriptor {
+            label: Some(label),
+            source: ShaderSource::Wgsl(format!("{PRELUDE}\n{wgsl}").into()),
+        });
+        device.create_render_pipeline(&RenderPipelineDescriptor {
+            label: Some(label),
+            layout: Some(layout),
+            vertex: VertexState {
+                module: &module,
+                entry_point: Some("vs_main"),
+                buffers: &[Some(PrimitiveInstance::desc())],
+                compilation_options: Default::default(),
+            },
+            fragment: Some(FragmentState {
+                module: &module,
+                entry_point: Some("fs_main"),
+                targets: &[Some(ColorTargetState {
+                    format,
+                    blend: Some(BlendState::ALPHA_BLENDING),
+                    write_mask: ColorWrites::ALL,
+                })],
+                compilation_options: Default::default(),
+            }),
+            primitive: PrimitiveState {
+                topology: PrimitiveTopology::TriangleStrip,
+                strip_index_format: None,
+                front_face: FrontFace::Cw,
+                cull_mode: Some(Face::Back),
+                polygon_mode: PolygonMode::Fill,
+                unclipped_depth: false,
+                conservative: false,
+            },
+            depth_stencil: None,
+            multisample: MultisampleState {
+                count: 1,
+                mask: !0,
+                alpha_to_coverage_enabled: false,
+            },
+            multiview_mask: None,
+            cache: None,
+        })
+    }
+
+    /// What every draw in the ui is given: the window, the masks and the
+    /// move chain every position is resolved through.
+    fn shared_layout(device: &Device) -> BindGroupLayout {
+        device.create_bind_group_layout(&BindGroupLayoutDescriptor {
+            entries: &[
+                BindGroupLayoutEntry {
+                    binding: 0,
+                    visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
+                    ty: BindingType::Buffer {
+                        ty: BufferBindingType::Uniform,
+                        has_dynamic_offset: false,
+                        min_binding_size: BufferSize::new(size_of::<WindowUniform>() as u64),
+                    },
+                    count: None,
+                },
+                BindGroupLayoutEntry {
+                    binding: 1,
+                    visibility: ShaderStages::FRAGMENT,
+                    ty: BindingType::Buffer {
+                        ty: BufferBindingType::Storage { read_only: true },
+                        has_dynamic_offset: false,
+                        min_binding_size: BufferSize::new(size_of::<Mask>() as u64),
+                    },
+                    count: None,
+                },
+                BindGroupLayoutEntry {
+                    binding: 2,
+                    visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
+                    ty: BindingType::Buffer {
+                        ty: BufferBindingType::Storage { read_only: true },
+                        has_dynamic_offset: false,
+                        min_binding_size: BufferSize::new(size_of::<MoveOffset>() as u64),
+                    },
+                    count: None,
+                },
+            ],
+            label: Some("ui shared"),
+        })
+    }
+
+    fn shared_group(
+        device: &Device,
+        layout: &BindGroupLayout,
+        window: &Buffer,
+        masks: &ArrBuf<Mask>,
+        moves: &ArrBuf<MoveOffset>,
+    ) -> BindGroup {
+        device.create_bind_group(&BindGroupDescriptor {
+            layout,
+            entries: &[
+                BindGroupEntry {
+                    binding: 0,
+                    resource: window.as_entire_binding(),
+                },
+                BindGroupEntry {
+                    binding: 1,
+                    resource: masks.buffer.as_entire_binding(),
+                },
+                BindGroupEntry {
+                    binding: 2,
+                    resource: moves.buffer.as_entire_binding(),
+                },
+            ],
+            label: Some("ui shared"),
+        })
+    }
+
+    /// Layout for a list of one primitive's data. Every size in the ui is
+    /// stated, so "is the buffer big enough for one entry?" is answered when
+    /// the bind group is made; a `None` size is wgpu's to check on every draw.
+    fn data_layout(device: &Device, stride: u64) -> BindGroupLayout {
+        device.create_bind_group_layout(&BindGroupLayoutDescriptor {
+            entries: &[BindGroupLayoutEntry {
+                binding: 0,
+                visibility: ShaderStages::FRAGMENT,
+                ty: BindingType::Buffer {
+                    ty: BufferBindingType::Storage { read_only: true },
+                    has_dynamic_offset: false,
+                    min_binding_size: BufferSize::new(stride),
+                },
+                count: None,
+            }],
+            label: Some("ui primitive data"),
+        })
+    }
+}
+
+impl RenderLayer {
+    fn new() -> Self {
+        Self {
+            primitives: Vec::new(),
+        }
+    }
+}
+
+impl ListBuffers {
+    fn new(device: &Device) -> Self {
+        Self {
+            instance: ArrBuf::new(
+                device,
+                BufferUsages::VERTEX | BufferUsages::COPY_DST,
+                "instance",
+            ),
+            data: ArrBuf::new(
+                device,
+                BufferUsages::STORAGE | BufferUsages::COPY_DST,
+                "primitive data",
+            ),
+            group: None,
+            bindings: Vec::new(),
+        }
+    }
+
+    fn update(
+        &mut self,
+        device: &Device,
+        queue: &Queue,
+        primitive: &PrimitivePipeline,
+        list: &InstanceList,
+    ) {
+        self.bindings.clear();
+        primitive.render.instance_bindings(list, &mut self.bindings);
+        self.instance.update(device, queue, list.instances());
+        let resized = self.data.update(device, queue, list.data());
+        if list.instances().is_empty() {
+            self.group = None;
+        } else if resized || self.group.is_none() {
+            self.group = Some(device.create_bind_group(&BindGroupDescriptor {
+                layout: &primitive.data_layout,
+                entries: &[BindGroupEntry {
+                    binding: 0,
+                    resource: self.data.buffer.as_entire_binding(),
+                }],
+                label: Some("ui primitive data"),
+            }));
+        }
+    }
+}

core/src/render/page.rs

@@ -0,0 +1,156 @@
+use wgpu::*;
+
+use crate::{GlyphAtlas, UiData};
+
+use super::{
+    atlas::PAGE,
+    primitive::{ListDraw, PrimitiveRender},
+    texture::{default_sampler, sampled_group, sampled_layout, write_region},
+};
+
+/// Draws glyphs from the atlas, which it owns: one array texture bound once
+/// for a whole list, since every glyph in it reads the same pages.
+pub struct GlyphRender {
+    pages: GpuPages,
+    layout: BindGroupLayout,
+    sampler: Sampler,
+}
+
+impl GlyphRender {
+    pub fn new(device: &Device, queue: &Queue) -> Self {
+        let layout = sampled_layout(device, TextureViewDimension::D2Array, "ui atlas");
+        let sampler = default_sampler(device);
+        Self {
+            pages: GpuPages::new(device, queue, &layout, &sampler),
+            layout,
+            sampler,
+        }
+    }
+}
+
+impl PrimitiveRender for GlyphRender {
+    fn layout(&self) -> Option<&BindGroupLayout> {
+        Some(&self.layout)
+    }
+
+    fn update(&mut self, ui: &mut UiData) {
+        self.pages
+            .update(&mut ui.text.atlas, &self.layout, &self.sampler);
+    }
+
+    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>) {
+        pass.set_bind_group(2, self.pages.group(), &[]);
+        pass.draw(0..4, 0..list.instances);
+    }
+}
+
+/// The glyph atlas on the GPU: one array texture whose layers are the pages
+/// `GlyphAtlas` packs.
+///
+/// One array rather than a texture per page because a layer index is ordinary
+/// Vulkan 1.0 / GLES sampling, where a `binding_array` would need
+/// `VK_EXT_descriptor_indexing`, which a real share of Android GPUs lack.
+pub struct GpuPages {
+    device: Device,
+    queue: Queue,
+    texture: Texture,
+    group: BindGroup,
+}
+
+impl GpuPages {
+    pub fn new(
+        device: &Device,
+        queue: &Queue,
+        layout: &BindGroupLayout,
+        sampler: &Sampler,
+    ) -> Self {
+        let texture = create_array(device, 1);
+        Self {
+            device: device.clone(),
+            queue: queue.clone(),
+            group: atlas_group(device, layout, &texture, sampler),
+            texture,
+        }
+    }
+
+    pub fn update(&mut self, atlas: &mut GlyphAtlas, layout: &BindGroupLayout, sampler: &Sampler) {
+        if atlas.page_count() > self.texture.depth_or_array_layers() {
+            self.grow(atlas.page_count(), layout, sampler);
+        }
+        for (upload, page) in atlas.uploads() {
+            let dst = TexelCopyTextureInfo {
+                texture: &self.texture,
+                mip_level: 0,
+                origin: Origin3d {
+                    x: upload.rect.x,
+                    y: upload.rect.y,
+                    z: upload.layer,
+                },
+                aspect: TextureAspect::All,
+            };
+            write_region(&self.queue, dst, page, upload.rect);
+        }
+    }
+
+    pub fn group(&self) -> &BindGroup {
+        &self.group
+    }
+
+    /// Doubles until `needed` fits and copies the old layers across GPU side.
+    /// The new texture stales the group, so that is rebuilt here.
+    fn grow(&mut self, needed: u32, layout: &BindGroupLayout, sampler: &Sampler) {
+        let old = self.texture.depth_or_array_layers();
+        let mut layers = old;
+        while layers < needed {
+            layers *= 2;
+        }
+        let texture = create_array(&self.device, layers);
+        let mut encoder = self
+            .device
+            .create_command_encoder(&CommandEncoderDescriptor {
+                label: Some("atlas grow"),
+            });
+        encoder.copy_texture_to_texture(
+            self.texture.as_image_copy(),
+            texture.as_image_copy(),
+            Extent3d {
+                width: PAGE,
+                height: PAGE,
+                depth_or_array_layers: old,
+            },
+        );
+        self.queue.submit(std::iter::once(encoder.finish()));
+        self.group = atlas_group(&self.device, layout, &texture, sampler);
+        self.texture = texture;
+    }
+}
+
+fn atlas_group(
+    device: &Device,
+    layout: &BindGroupLayout,
+    texture: &Texture,
+    sampler: &Sampler,
+) -> BindGroup {
+    let view = texture.create_view(&TextureViewDescriptor {
+        dimension: Some(TextureViewDimension::D2Array),
+        ..Default::default()
+    });
+    sampled_group(device, layout, &view, sampler, "ui atlas")
+}
+
+fn create_array(device: &Device, layers: u32) -> Texture {
+    device.create_texture(&TextureDescriptor {
+        label: Some("glyph atlas"),
+        size: Extent3d {
+            width: PAGE,
+            height: PAGE,
+            depth_or_array_layers: layers,
+        },
+        mip_level_count: 1,
+        sample_count: 1,
+        dimension: TextureDimension::D2,
+        format: TextureFormat::Rgba8Unorm,
+        usage: TextureUsages::TEXTURE_BINDING | TextureUsages::COPY_DST | TextureUsages::COPY_SRC,
+        view_formats: &[],
+    })
+}

core/src/render/primitive.rs

@@ -0,0 +1,401 @@
+use std::{any::TypeId, marker::PhantomData};
+
+use crate::{
+    Color, TextureHandle, UiData, UiRegion, WidgetId,
+    render::{
+        data::{MaskIdx, MoveIdx, PrimitiveInstance},
+        page::GlyphRender,
+        texture::ImageRender,
+    },
+    util::{HashMap, Vec2},
+};
+use bytemuck::Pod;
+use wgpu::{BindGroupLayout, Device, Queue, RenderPass};
+
+/// One instance of a primitive, laid out as the struct its shader reads.
+///
+/// The type carries its own shader, so drawing one is all the wiring it needs:
+/// its list, free list, buffers and pipeline follow from being registered.
+pub trait Primitive: Pod + 'static {
+    /// Compiled after `prelude.wgsl`, which states what it declares and what
+    /// it is given.
+    const WGSL: &'static str;
+
+    /// Made once, the first time the renderer sees this primitive. It owns
+    /// whatever the shader samples and records the primitive's own draws; the
+    /// default owns nothing and draws every instance in one call.
+    fn render(device: &Device, queue: &Queue) -> Box<dyn PrimitiveRender>
+    where
+        Self: Sized,
+    {
+        let _ = (device, queue);
+        Box::new(Instanced)
+    }
+}
+
+/// The renderer's half of a primitive: what it samples, what it uploads, and
+/// what draws it records.
+///
+/// Everything a draw shares -- the pipeline, the window and masks, the list's
+/// own data and instance buffer -- is set before this is called. What is left
+/// is what only this primitive knows: its group 2, and how many draws its
+/// instances are.
+pub trait PrimitiveRender {
+    /// The layout its shader reads at group 2. `None` for a primitive whose
+    /// shader samples nothing, whose pipeline then has no group 2 at all.
+    fn layout(&self) -> Option<&BindGroupLayout> {
+        None
+    }
+
+    /// Uploads whatever this primitive owns, once a frame, before any draw.
+    fn update(&mut self, ui: &mut UiData) {
+        let _ = ui;
+    }
+
+    /// Keeps what the primitive needs per instance at draw time, read from
+    /// the list's own data. A primitive that binds nothing per instance --
+    /// most of them -- leaves this empty and draws in one call.
+    fn instance_bindings(&self, list: &InstanceList, out: &mut Vec<u32>) {
+        let _ = (list, out);
+    }
+
+    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>);
+}
+
+/// What a `PrimitiveRender` draws: this list's instances, and whatever
+/// `instance_bindings` kept for them.
+pub struct ListDraw<'a> {
+    pub instances: u32,
+    pub bindings: &'a [u32],
+}
+
+/// The default: nothing sampled, every instance in one call.
+pub struct Instanced;
+
+impl PrimitiveRender for Instanced {
+    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>) {
+        pass.draw(0..4, 0..list.instances);
+    }
+}
+
+/// Which registered primitive an instance is.
+pub struct PrimitiveKind<P> {
+    id: u32,
+    _p: PhantomData<fn(P)>,
+}
+
+impl<P> PrimitiveKind<P> {
+    fn new(id: u32) -> Self {
+        Self {
+            id,
+            _p: PhantomData,
+        }
+    }
+}
+
+impl<P> Clone for PrimitiveKind<P> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<P> Copy for PrimitiveKind<P> {}
+
+/// Every primitive a ui can draw, in the order they were first drawn.
+#[derive(Default)]
+pub struct PrimitiveRegistry {
+    kinds: Vec<PrimitiveSource>,
+    ids: HashMap<TypeId, u32>,
+}
+
+pub struct PrimitiveSource {
+    pub wgsl: &'static str,
+    pub label: &'static str,
+    /// Size of one instance's entry, stated as the data binding's minimum.
+    pub stride: u64,
+    pub render: fn(&Device, &Queue) -> Box<dyn PrimitiveRender>,
+}
+
+impl PrimitiveRegistry {
+    /// Registers `P` if this is the first time it has been drawn.
+    pub fn kind<P: Primitive>(&mut self) -> PrimitiveKind<P> {
+        let Self { kinds, ids } = self;
+        let id = *ids.entry(TypeId::of::<P>()).or_insert_with(|| {
+            kinds.push(PrimitiveSource {
+                wgsl: P::WGSL,
+                label: std::any::type_name::<P>(),
+                stride: size_of::<P>() as u64,
+                render: P::render,
+            });
+            kinds.len() as u32 - 1
+        });
+        PrimitiveKind::new(id)
+    }
+
+    pub fn sources(&self) -> &[PrimitiveSource] {
+        &self.kinds
+    }
+}
+
+/// One registered primitive's instances in one layer. Everything per-instance
+/// rides here, so it stays in step through a `swap_remove`.
+pub struct InstanceList {
+    instances: Vec<PrimitiveInstance>,
+    /// The widget each instance belongs to, for renumbering its handles.
+    assoc: Vec<WidgetId>,
+    free: Vec<usize>,
+    /// `stride` bytes of the primitive's own data per instance.
+    data: Vec<u8>,
+    /// From the type the list was made for, so a write is never checked.
+    stride: usize,
+}
+
+impl InstanceList {
+    fn new<P: Primitive>() -> Self {
+        Self {
+            instances: Vec::new(),
+            assoc: Vec::new(),
+            free: Vec::new(),
+            data: Vec::new(),
+            stride: size_of::<P>(),
+        }
+    }
+
+    pub fn instances(&self) -> &[PrimitiveInstance] {
+        &self.instances
+    }
+
+    pub fn data(&self) -> &[u8] {
+        &self.data
+    }
+
+    pub fn stride(&self) -> usize {
+        self.stride
+    }
+
+    fn push(&mut self, id: WidgetId, inst: PrimitiveInstance, data: &[u8]) -> usize {
+        if let Some(i) = self.free.pop() {
+            self.instances[i] = inst;
+            self.assoc[i] = id;
+            self.data[i * self.stride..][..self.stride].copy_from_slice(data);
+            i
+        } else {
+            let i = self.instances.len();
+            self.instances.push(inst);
+            self.assoc.push(id);
+            self.data.extend_from_slice(data);
+            i
+        }
+    }
+
+    fn free(&mut self, i: usize) -> MaskIdx {
+        self.free.push(i);
+        self.instances[i].mask_idx
+    }
+
+    fn apply_free(&mut self, kind: u32) -> impl Iterator<Item = PrimitiveChange> {
+        self.free.sort_by(|a, b| b.cmp(a));
+        let instances = &mut self.instances;
+        let assoc = &mut self.assoc;
+        let data = &mut self.data;
+        let stride = self.stride;
+        self.free.drain(..).filter_map(move |i| {
+            instances.swap_remove(i);
+            assoc.swap_remove(i);
+            let last = instances.len();
+            data.copy_within(last * stride..(last + 1) * stride, i * stride);
+            data.truncate(last * stride);
+            if i == last {
+                return None;
+            }
+            let id = assoc[i];
+            Some(PrimitiveChange {
+                id,
+                kind,
+                old: last,
+                new: i,
+            })
+        })
+    }
+}
+
+/// Everything one layer draws, one list per registered primitive.
+pub struct LayerDraws {
+    /// `None` until this layer draws that primitive, because only the write
+    /// knows the type the list is for.
+    primitives: Vec<Option<InstanceList>>,
+    pub updated: bool,
+}
+
+impl Default for LayerDraws {
+    fn default() -> Self {
+        Self {
+            primitives: Vec::new(),
+            updated: true,
+        }
+    }
+}
+
+impl LayerDraws {
+    pub fn write<P: Primitive>(
+        &mut self,
+        layer: usize,
+        PrimitiveInst {
+            kind,
+            id,
+            primitive,
+            region,
+            mask_idx,
+            move_idx,
+        }: PrimitiveInst<P>,
+    ) -> PrimitiveHandle {
+        self.updated = true;
+        // Grown on first use rather than sized from the registry, which a
+        // layer cannot see.
+        if self.primitives.len() <= kind.id as usize {
+            self.primitives.resize_with(kind.id as usize + 1, || None);
+        }
+        let inst_idx = self.primitives[kind.id as usize]
+            .get_or_insert_with(InstanceList::new::<P>)
+            .push(
+                id,
+                PrimitiveInstance {
+                    region,
+                    mask_idx,
+                    move_idx,
+                },
+                bytemuck::bytes_of(&primitive),
+            );
+        PrimitiveHandle {
+            layer,
+            kind: kind.id,
+            inst_idx,
+        }
+    }
+
+    pub fn primitives(&self) -> &[Option<InstanceList>] {
+        &self.primitives
+    }
+
+    pub fn apply_free(&mut self) -> impl Iterator<Item = PrimitiveChange> {
+        self.primitives
+            .iter_mut()
+            .enumerate()
+            .filter_map(|(kind, list)| Some((kind as u32, list.as_mut()?)))
+            .flat_map(|(kind, list)| list.apply_free(kind))
+    }
+
+    pub fn free(&mut self, h: &PrimitiveHandle) -> MaskIdx {
+        self.updated = true;
+        self.list(h).free(h.inst_idx)
+    }
+
+    pub fn region_mut(&mut self, h: &PrimitiveHandle) -> &mut UiRegion {
+        self.updated = true;
+        &mut self.list(h).instances[h.inst_idx].region
+    }
+
+    /// A handle is only ever made by `write`, which is what created the list.
+    fn list(&mut self, h: &PrimitiveHandle) -> &mut InstanceList {
+        self.primitives[h.kind as usize]
+            .as_mut()
+            .expect("handle names a primitive this layer never drew")
+    }
+}
+
+pub struct PrimitiveInst<P> {
+    pub kind: PrimitiveKind<P>,
+    pub id: WidgetId,
+    pub primitive: P,
+    pub region: UiRegion,
+    pub mask_idx: MaskIdx,
+    pub move_idx: MoveIdx,
+}
+
+pub struct PrimitiveChange {
+    pub id: WidgetId,
+    /// Which registered primitive's list moved, since they index separately.
+    pub kind: u32,
+    pub old: usize,
+    pub new: usize,
+}
+
+#[derive(Debug)]
+pub struct PrimitiveHandle {
+    pub layer: usize,
+    pub kind: u32,
+    pub inst_idx: usize,
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct RectPrimitive {
+    pub color: Color<u8>,
+    pub radius: f32,
+    pub thickness: f32,
+    pub inner_radius: f32,
+}
+
+impl Primitive for RectPrimitive {
+    const WGSL: &'static str = include_str!("shader/rect.wgsl");
+}
+
+impl RectPrimitive {
+    pub fn color(color: Color<u8>) -> Self {
+        Self {
+            color,
+            radius: 0.0,
+            thickness: 0.0,
+            inner_radius: 0.0,
+        }
+    }
+}
+
+/// `color` is multiplied by the atlas alpha for a mask glyph; a colour glyph
+/// takes the texel unchanged, which `GlyphEntry::IS_COLORED` selects.
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct GlyphPrimitive {
+    pub uv_min: Vec2,
+    pub uv_max: Vec2,
+    /// Which atlas array layer this glyph is on.
+    pub layer: u32,
+    pub color: Color<u8>,
+    pub flags: u32,
+}
+
+// Manual rather than derived: `Vec2`'s alignment leaves four bytes of padding
+// here, which is how WGSL lays the struct out.
+unsafe impl bytemuck::Pod for GlyphPrimitive {}
+unsafe impl bytemuck::Zeroable for GlyphPrimitive {}
+impl Primitive for GlyphPrimitive {
+    const WGSL: &'static str = include_str!("shader/glyph.wgsl");
+
+    fn render(device: &Device, queue: &Queue) -> Box<dyn PrimitiveRender> {
+        Box::new(GlyphRender::new(device, queue))
+    }
+}
+
+/// One drawn image. Its shader reads nothing per instance; the slot names the
+/// texture to bind for it.
+#[repr(C)]
+#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct TexturePrimitive {
+    pub slot: u32,
+}
+
+impl Primitive for TexturePrimitive {
+    const WGSL: &'static str = include_str!("shader/texture.wgsl");
+
+    fn render(device: &Device, queue: &Queue) -> Box<dyn PrimitiveRender> {
+        Box::new(ImageRender::new(device, queue))
+    }
+}
+
+impl From<&TextureHandle> for TexturePrimitive {
+    fn from(handle: &TextureHandle) -> Self {
+        Self {
+            slot: handle.slot(),
+        }
+    }
+}

core/src/render/shader/glyph.wgsl

@@ -0,0 +1,33 @@
+// Matches `GlyphEntry::IS_COLORED`.
+const COLORED: u32 = 1u;
+
+// The glyph atlas, whose array layers are its pages.
+@group(2) @binding(0)
+var atlas: texture_2d_array<f32>;
+@group(2) @binding(1)
+var samp: sampler;
+
+struct GlyphInfo {
+    uv_min: vec2<f32>,
+    uv_max: vec2<f32>,
+    // Which layer of the atlas array this glyph's page is.
+    layer: u32,
+    color: u32,
+    flags: u32,
+}
+
+@group(1) @binding(0)
+var<storage> glyphs: array<GlyphInfo>;
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
+    let g = glyphs[in.idx];
+    let uv = mix(g.uv_min, g.uv_max, in.uv);
+    let texel = textureSample(atlas, samp, uv, i32(g.layer));
+    if (g.flags & COLORED) != 0u {
+        return masked(in, texel);
+    }
+    var color = unpack4x8unorm(g.color);
+    color.a *= texel.a;
+    return masked(in, color);
+}

core/src/render/shader/prelude.wgsl

@@ -0,0 +1,129 @@
+// Prepended to every primitive's shader, which declares its own instance data
+// as `var<storage> <name>: array<T>` at group 1 binding 0, and an `fs_main`
+// shading one instance of it. What it samples, if anything, is bound at group
+// 2: the texture at binding 0 and the sampler at binding 1.
+
+@group(0) @binding(0)
+var<uniform> window: WindowUniform;
+@group(0) @binding(1)
+var<storage> masks: array<Mask>;
+@group(0) @binding(2)
+var<storage> move_offsets: array<MoveOffset>;
+
+struct WindowUniform {
+    dim: vec2<f32>,
+};
+
+struct Mask {
+    x: UiSpan,
+    y: UiSpan,
+    move_idx: u32,
+}
+
+struct MoveOffset {
+    delta: vec2<f32>,
+    parent: u32,
+}
+
+const MOVE_NONE: u32 = 4294967295u;
+// Keep in step with `iris_core::CHAIN_LIMIT`. It bounds a malformed cycle
+// rather than any real tree, and the CPU walk uses the same number so both
+// resolve a deep one the same way.
+const CHAIN_LIMIT: u32 = 64u;
+
+fn resolve_move(idx: u32) -> vec2<f32> {
+    var total = vec2<f32>(0.0, 0.0);
+    var at = idx;
+    for (var step = 0u; step < CHAIN_LIMIT; step++) {
+        if at == MOVE_NONE {
+            break;
+        }
+        let entry = move_offsets[at];
+        total += entry.delta;
+        at = entry.parent;
+    }
+    return total;
+}
+
+struct UiSpan {
+    start: UiScalar,
+    end: UiScalar,
+}
+
+struct UiScalar {
+    rel: f32,
+    abs: f32,
+}
+
+struct InstanceInput {
+    @location(0) x_start: vec2<f32>,
+    @location(1) x_end: vec2<f32>,
+    @location(2) y_start: vec2<f32>,
+    @location(3) y_end: vec2<f32>,
+    @location(4) mask_idx: u32,
+    @location(5) move_idx: u32,
+}
+
+struct VertexOutput {
+    @location(0) top_left: vec2<f32>,
+    @location(1) bot_right: vec2<f32>,
+    @location(2) uv: vec2<f32>,
+    @location(3) @interpolate(flat) mask_idx: u32,
+    @location(4) @interpolate(flat) idx: u32,
+    @builtin(position) clip_position: vec4<f32>,
+};
+
+@vertex
+fn vs_main(
+    @builtin(vertex_index) vi: u32,
+    @builtin(instance_index) ii: u32,
+    in: InstanceInput,
+) -> VertexOutput {
+    var out: VertexOutput;
+
+    let top_left_rel = vec2(in.x_start.x, in.y_start.x);
+    let top_left_abs = vec2(in.x_start.y, in.y_start.y);
+    let bot_right_rel = vec2(in.x_end.x, in.y_end.x);
+    let bot_right_abs = vec2(in.x_end.y, in.y_end.y);
+
+    let moved = resolve_move(in.move_idx);
+    let top_left = floor(top_left_rel * window.dim) + floor(top_left_abs + moved);
+    let bot_right = floor(bot_right_rel * window.dim) + floor(bot_right_abs + moved);
+    let size = bot_right - top_left;
+
+    let uv = vec2<f32>(
+        f32(vi % 2u),
+        f32(vi / 2u)
+    );
+    let pos = (top_left + uv * size) / window.dim * 2.0 - 1.0;
+    out.clip_position = vec4<f32>(pos.x, -pos.y, 0.0, 1.0);
+    out.uv = uv;
+    out.top_left = top_left;
+    out.bot_right = bot_right;
+    out.mask_idx = in.mask_idx;
+    out.idx = ii;
+
+    return out;
+}
+
+fn masked(in: VertexOutput, color: vec4<f32>) -> vec4<f32> {
+    if in.mask_idx == 4294967295u {
+        return color;
+    }
+    let mask = masks[in.mask_idx];
+    let tl = vec2(mask.x.start.rel, mask.y.start.rel);
+    let tl_abs = vec2(mask.x.start.abs, mask.y.start.abs);
+    let br = vec2(mask.x.end.rel, mask.y.end.rel);
+    let br_abs = vec2(mask.x.end.abs, mask.y.end.abs);
+
+    // Its own chain, not the drawn primitive's, so a stationary viewport
+    // clips content that moves inside it.
+    let moved = resolve_move(mask.move_idx);
+    let top_left = floor(tl * window.dim) + floor(tl_abs + moved);
+    let bot_right = floor(br * window.dim) + floor(br_abs + moved);
+    let pos = in.clip_position.xy;
+    if pos.x < top_left.x || pos.x > bot_right.x || pos.y < top_left.y || pos.y > bot_right.y {
+        return color * 0.0;
+    }
+    return color;
+}

core/src/render/shader/rect.wgsl

@@ -0,0 +1,39 @@
+struct Rect {
+    color: u32,
+    radius: f32,
+    thickness: f32,
+    inner_radius: f32,
+}
+
+@group(1) @binding(0)
+var<storage> rects: array<Rect>;
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
+    let rect = rects[in.idx];
+    var color = unpack4x8unorm(rect.color);
+
+    let edge = 0.5;
+    let size = in.bot_right - in.top_left;
+    let corner = size / 2.0;
+    let center = in.top_left + corner;
+    let pos = in.clip_position.xy;
+
+    let dist = distance_from_rect(pos, center, corner, rect.radius);
+    color.a *= 1.0 - smoothstep(-min(edge, rect.radius), edge, dist);
+
+    if rect.thickness > 0.0 {
+        let dist2 = distance_from_rect(pos, center, corner - rect.thickness, rect.inner_radius);
+        color.a *= smoothstep(-min(edge, rect.inner_radius), edge, dist2);
+    }
+
+    return masked(in, color);
+}
+
+fn distance_from_rect(pixel_pos: vec2<f32>, rect_center: vec2<f32>, rect_corner: vec2<f32>, radius: f32) -> f32 {
+    // vec from center to pixel
+    let p = pixel_pos - rect_center;
+    // vec from inner rect corner to pixel
+    let q = abs(p) - (rect_corner - radius);
+    return length(max(q, vec2(0.0))) - radius;
+}

core/src/render/shader/texture.wgsl

@@ -0,0 +1,10 @@
+// The image this instance draws, bound for it alone.
+@group(2) @binding(0)
+var image: texture_2d<f32>;
+@group(2) @binding(1)
+var samp: sampler;
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
+    return masked(in, textureSample(image, samp, in.uv));
+}

core/src/render/texture.rs

@@ -0,0 +1,243 @@
+use image::{DynamicImage, EncodableLayout, GenericImageView, RgbaImage};
+use wgpu::{util::DeviceExt, *};
+
+use crate::{
+    PatchRect, TextureUpdate, Textures, UiData,
+    render::{
+        TexturePrimitive,
+        primitive::{ListDraw, PrimitiveRender},
+    },
+};
+
+/// Draws standalone images, which it owns. Each is its own texture, so each
+/// instance binds its own and is a draw of its own.
+pub struct ImageRender {
+    textures: GpuTextures,
+    layout: BindGroupLayout,
+    sampler: Sampler,
+}
+
+impl ImageRender {
+    pub fn new(device: &Device, queue: &Queue) -> Self {
+        Self {
+            textures: GpuTextures::new(device, queue),
+            layout: sampled_layout(device, TextureViewDimension::D2, "ui image"),
+            sampler: default_sampler(device),
+        }
+    }
+}
+
+impl PrimitiveRender for ImageRender {
+    fn layout(&self) -> Option<&BindGroupLayout> {
+        Some(&self.layout)
+    }
+
+    fn update(&mut self, ui: &mut UiData) {
+        self.textures
+            .update(&mut ui.textures, &self.layout, &self.sampler);
+    }
+
+    fn instance_bindings(&self, list: &super::InstanceList, out: &mut Vec<u32>) {
+        let slots = list
+            .data()
+            .chunks_exact(list.stride())
+            .map(|data| bytemuck::pod_read_unaligned::<TexturePrimitive>(data).slot);
+        out.extend(slots);
+    }
+
+    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>) {
+        for (i, &slot) in list.bindings.iter().enumerate() {
+            let Some(image) = self.textures.group(slot) else {
+                continue;
+            };
+            pass.set_bind_group(2, image, &[]);
+            pass.draw(0..4, i as u32..i as u32 + 1);
+        }
+    }
+}
+
+/// The standalone images a ui draws, each its own texture and bind group --
+/// unlike the glyph atlas in `super::page`, which is one array they share.
+pub struct GpuTextures {
+    device: Device,
+    queue: Queue,
+    slots: Vec<Option<ImageGpu>>,
+}
+
+struct ImageGpu {
+    /// Kept for `patch`, which needs the texture rather than the view.
+    texture: Texture,
+    group: BindGroup,
+}
+
+impl GpuTextures {
+    pub fn new(device: &Device, queue: &Queue) -> Self {
+        Self {
+            device: device.clone(),
+            queue: queue.clone(),
+            slots: Vec::new(),
+        }
+    }
+
+    pub fn update(&mut self, textures: &mut Textures, layout: &BindGroupLayout, sampler: &Sampler) {
+        for update in textures.updates() {
+            match update {
+                TextureUpdate::Push(image) => {
+                    let image = self.create(image, layout, sampler);
+                    self.slots.push(Some(image));
+                }
+                TextureUpdate::Set(i, image) => {
+                    let image = self.create(image, layout, sampler);
+                    self.slots[i as usize] = Some(image);
+                }
+                TextureUpdate::Patch(i, rect, image) => self.patch(i, rect, image),
+                TextureUpdate::PushFree => self.slots.push(None),
+                TextureUpdate::SetFree => {}
+                TextureUpdate::Free(i) => self.slots[i as usize] = None,
+            }
+        }
+    }
+
+    pub fn group(&self, slot: u32) -> Option<&BindGroup> {
+        self.slots.get(slot as usize)?.as_ref().map(|i| &i.group)
+    }
+
+    fn create(
+        &self,
+        image: &DynamicImage,
+        layout: &BindGroupLayout,
+        sampler: &Sampler,
+    ) -> ImageGpu {
+        let rgba = image.to_rgba8();
+        let (width, height) = rgba.dimensions();
+        let texture = self.device.create_texture_with_data(
+            &self.queue,
+            &TextureDescriptor {
+                label: Some("image"),
+                size: Extent3d {
+                    width,
+                    height,
+                    depth_or_array_layers: 1,
+                },
+                mip_level_count: 1,
+                sample_count: 1,
+                dimension: TextureDimension::D2,
+                format: TextureFormat::Rgba8Unorm,
+                usage: TextureUsages::TEXTURE_BINDING | TextureUsages::COPY_DST,
+                view_formats: &[],
+            },
+            wgt::TextureDataOrder::MipMajor,
+            rgba.as_bytes(),
+        );
+        let view = texture.create_view(&TextureViewDescriptor::default());
+        let group = sampled_group(&self.device, layout, &view, sampler, "ui image");
+        ImageGpu { texture, group }
+    }
+
+    fn patch(&mut self, i: u32, rect: PatchRect, image: &DynamicImage) {
+        let Some(Some(slot)) = self.slots.get(i as usize) else {
+            return;
+        };
+        let dst = TexelCopyTextureInfo {
+            texture: &slot.texture,
+            mip_level: 0,
+            origin: Origin3d {
+                x: rect.x,
+                y: rect.y,
+                z: 0,
+            },
+            aspect: TextureAspect::All,
+        };
+        match image.as_rgba8() {
+            Some(rgba) => write_region(&self.queue, dst, rgba, rect),
+            // The texture is rgba8, so any other layout has to be converted --
+            // and converting the rectangle is cheaper than the whole image.
+            None => {
+                let sub = image
+                    .view(rect.x, rect.y, rect.width, rect.height)
+                    .to_image();
+                write_region(&self.queue, dst, &sub, PatchRect { x: 0, y: 0, ..rect });
+            }
+        }
+    }
+}
+
+pub fn write_region(queue: &Queue, dst: TexelCopyTextureInfo, src: &RgbaImage, rect: PatchRect) {
+    if rect.width == 0 || rect.height == 0 {
+        return;
+    }
+    let stride = src.width() * 4;
+    queue.write_texture(
+        dst,
+        src.as_bytes(),
+        TexelCopyBufferLayout {
+            offset: (rect.y * stride + rect.x * 4) as u64,
+            bytes_per_row: Some(stride),
+            rows_per_image: Some(rect.height),
+        },
+        Extent3d {
+            width: rect.width,
+            height: rect.height,
+            depth_or_array_layers: 1,
+        },
+    );
+}
+
+/// What a primitive that samples binds: a texture, and the sampler that reads
+/// it.
+pub fn sampled_group(
+    device: &Device,
+    layout: &BindGroupLayout,
+    view: &TextureView,
+    sampler: &Sampler,
+    label: &'static str,
+) -> BindGroup {
+    device.create_bind_group(&BindGroupDescriptor {
+        layout,
+        entries: &[
+            BindGroupEntry {
+                binding: 0,
+                resource: BindingResource::TextureView(view),
+            },
+            BindGroupEntry {
+                binding: 1,
+                resource: BindingResource::Sampler(sampler),
+            },
+        ],
+        label: Some(label),
+    })
+}
+
+/// The layout for one of those. The dimension differs -- the atlas is an
+/// array of pages and an image is not -- and nothing else does.
+pub fn sampled_layout(
+    device: &Device,
+    dimension: TextureViewDimension,
+    label: &'static str,
+) -> BindGroupLayout {
+    device.create_bind_group_layout(&BindGroupLayoutDescriptor {
+        entries: &[
+            BindGroupLayoutEntry {
+                binding: 0,
+                visibility: ShaderStages::FRAGMENT,
+                ty: BindingType::Texture {
+                    sample_type: TextureSampleType::Float { filterable: false },
+                    view_dimension: dimension,
+                    multisampled: false,
+                },
+                count: None,
+            },
+            BindGroupLayoutEntry {
+                binding: 1,
+                visibility: ShaderStages::FRAGMENT,
+                ty: BindingType::Sampler(SamplerBindingType::NonFiltering),
+                count: None,
+            },
+        ],
+        label: Some(label),
+    })
+}
+
+pub fn default_sampler(device: &Device) -> Sampler {
+    device.create_sampler(&SamplerDescriptor::default())
+}

core/src/render/util/mod.rs

@@ -21,17 +21,25 @@ impl<T: Pod> ArrBuf<T> {
             _pd: PhantomData,
         }
     }
-    pub fn update(&mut self, device: &Device, queue: &Queue, data: &[T]) {
-        if self.len != data.len() {
+    /// Returns whether the `Buffer` was recreated, which stales any cached
+    /// `BindGroup` holding it.
+    pub fn update(&mut self, device: &Device, queue: &Queue, data: &[T]) -> bool {
+        let resized = self.len != data.len();
+        if resized {
             self.len = data.len();
             self.buffer =
                 Self::init_buf(device, std::mem::size_of_val(data), self.usage, self.label);
         }
         queue.write_buffer(&self.buffer, 0, bytemuck::cast_slice(data));
+        resized
+    }
+    pub fn len(&self) -> usize {
+        self.len
     }
     fn init_buf(device: &Device, size: usize, usage: BufferUsages, label: &'static str) -> Buffer {
         let mut size = size as u64;
         if usage.contains(BufferUsages::STORAGE) {
+            // A binding cannot be empty or under the layout's minimum.
             size = size.max(std::mem::size_of::<T>() as u64);
         }
         device.create_buffer(&BufferDescriptor {
@@ -41,8 +49,4 @@ impl<T: Pod> ArrBuf<T> {
             usage,
         })
     }
-    #[allow(clippy::len_without_is_empty)]
-    pub fn len(&self) -> usize {
-        self.len
-    }
 }

core/src/ui/active.rs

@@ -0,0 +1,22 @@
+use crate::{LayerId, MaskIdx, MoveIdx, PrimitiveHandle, Size, TextureHandle, UiRegion, WidgetId};
+
+/// important non rendering data for retained drawing
+#[derive(Debug)]
+pub struct ActiveData {
+    pub id: WidgetId,
+    pub region: UiRegion,
+    /// What the widget said it used of `region`, the last time it drew.
+    pub size: Size,
+    pub parent: Option<WidgetId>,
+    pub textures: Vec<TextureHandle>,
+    pub primitives: Vec<PrimitiveHandle>,
+    pub children: Vec<WidgetId>,
+    /// The children whose size this widget read while drawing.
+    pub size_deps: Vec<WidgetId>,
+    /// Whether it read the output's size, and so is wrong when that changes.
+    pub reads_output: bool,
+    /// The move slot its primitives are positioned through.
+    pub move_idx: MoveIdx,
+    pub mask: MaskIdx,
+    pub layer: LayerId,
+}

core/src/ui/mod.rs

@@ -0,0 +1,114 @@
+use crate::{
+    Mask, MoveIdx, MoveOffset, PrimitiveRegistry, TextData, Textures, WeakWidget, WidgetId,
+    Widgets,
+    util::{Arena, Id, TrackedArena, Vec2},
+};
+
+/// How far the shader will walk a move chain. It bounds a malformed cycle
+/// rather than any real tree; `Moves::resolve` uses the same number so the
+/// two agree on what a deep tree resolves to.
+pub const CHAIN_LIMIT: u32 = 64;
+
+mod active;
+mod painter;
+mod render_state;
+
+pub use active::*;
+pub use painter::{Painter, PrimitiveLike};
+pub use render_state::*;
+
+#[derive(Default)]
+pub struct UiData {
+    pub widgets: Widgets,
+    /// Every primitive this ui can draw.
+    pub primitives: PrimitiveRegistry,
+    pub textures: Textures,
+    pub text: TextData,
+    pub masks: TrackedArena<Mask, u32>,
+}
+
+/// Where each widget's drawing sits relative to its parent's slot, so moving
+/// a subtree writes one entry rather than every descendant's primitives.
+#[derive(Default)]
+pub struct Moves {
+    arena: Arena<MoveOffset, u32>,
+    pub changed: bool,
+}
+
+impl Moves {
+    pub fn push(&mut self, parent: MoveIdx) -> MoveIdx {
+        self.changed = true;
+        MoveIdx::slot(self.arena.push(MoveOffset::root(parent)).idx())
+    }
+
+    pub fn remove(&mut self, idx: MoveIdx) {
+        self.changed = true;
+        self.arena.remove(Id::preset(idx.idx() as u32));
+    }
+
+    /// Sets a slot's translation, in physical pixels, relative to its parent.
+    pub fn set(&mut self, idx: MoveIdx, delta: Vec2) {
+        let entry = self.arena.get_mut(Id::preset(idx.idx() as u32));
+        if entry.delta != delta {
+            entry.delta = delta;
+            self.changed = true;
+        }
+    }
+
+    /// The translation a primitive in `idx` has accumulated, which is the
+    /// same walk the vertex shader does.
+    pub fn resolve(&self, idx: MoveIdx) -> Vec2 {
+        let mut total = Vec2::ZERO;
+        let mut at = idx;
+        for _ in 0..CHAIN_LIMIT {
+            if at == MoveIdx::NONE {
+                return total;
+            }
+            let entry = self.arena[at.idx()];
+            total += entry.delta;
+            at = entry.parent;
+        }
+        debug_assert!(
+            at == MoveIdx::NONE,
+            "a move chain longer than {CHAIN_LIMIT} resolves to the wrong place, \
+             and the shader stops at the same depth"
+        );
+        total
+    }
+
+    pub fn entries(&self) -> &[MoveOffset] {
+        &self.arena
+    }
+
+    pub fn clear(&mut self) {
+        self.changed = true;
+        self.arena = Arena::default();
+    }
+}
+
+pub trait UiRsc {
+    fn ui(&self) -> &UiData;
+    fn ui_mut(&mut self) -> &mut UiData;
+
+    #[allow(unused_variables)]
+    fn on_add(&mut self, id: WeakWidget) {}
+    #[allow(unused_variables)]
+    fn on_remove(&mut self, id: WidgetId) {}
+    #[allow(unused_variables)]
+    fn on_draw(&mut self, active: &ActiveData) {}
+    #[allow(unused_variables)]
+    fn on_undraw(&mut self, active: &ActiveData) {}
+
+    fn widgets(&self) -> &Widgets {
+        &self.ui().widgets
+    }
+    fn widgets_mut(&mut self) -> &mut Widgets {
+        &mut self.ui_mut().widgets
+    }
+    fn free(&mut self) {
+        while let Some(id) = self.widgets_mut().free_next() {
+            self.on_remove(id);
+        }
+        self.ui_mut().textures.free();
+    }
+}

core/src/ui/painter.rs

@@ -0,0 +1,250 @@
+use crate::{
+    Axis, Len, RenderedText, Size, StrongWidget, TextAttrs, TextBuffer, TextData, TextureHandle,
+    UiRegion, UiRenderState, UiRsc, UiScalar, UiVec2, WidgetId,
+    render::{
+        GlyphPrimitive, Mask, MaskIdx, MoveIdx, Primitive, PrimitiveHandle, PrimitiveInst,
+        PrimitiveKind, TexturePrimitive,
+    },
+    util::Vec2,
+};
+
+/// makes your surfaces look pretty
+pub struct Painter<'a> {
+    pub(super) state: &'a mut UiRenderState,
+    pub(super) rsc: &'a mut dyn UiRsc,
+
+    pub(super) region: UiRegion,
+    pub(super) mask: MaskIdx,
+    pub(super) textures: Vec<TextureHandle>,
+    pub(super) primitives: Vec<PrimitiveHandle>,
+    pub(super) children: Vec<WidgetId>,
+    /// The children whose size this widget read while drawing.
+    pub(super) size_deps: Vec<WidgetId>,
+    pub(super) reads_output: bool,
+    /// The move slot this widget's primitives are positioned through.
+    pub(super) move_idx: MoveIdx,
+    pub layer: usize,
+    pub(super) id: WidgetId,
+}
+
+impl<'a> Painter<'a> {
+    fn primitive_at<P: Primitive>(&mut self, primitive: P, region: UiRegion) {
+        let kind = self.rsc.ui_mut().primitives.kind::<P>();
+        self.write(kind, primitive, region);
+    }
+
+    /// Takes the kind, for a caller writing many of one primitive.
+    fn write<P: Primitive>(&mut self, kind: PrimitiveKind<P>, primitive: P, region: UiRegion) {
+        let h = self.state.layers.write(
+            self.layer,
+            PrimitiveInst {
+                kind,
+                id: self.id,
+                primitive,
+                region,
+                mask_idx: self.mask,
+                move_idx: self.move_idx,
+            },
+        );
+        self.push_primitive(h);
+    }
+
+    fn push_primitive(&mut self, h: PrimitiveHandle) {
+        if self.mask != MaskIdx::NONE {
+            // TODO: I have no clue if this works at all :joy:
+            self.rsc.ui_mut().masks.push_ref(self.mask);
+        }
+        self.primitives.push(h);
+    }
+
+    /// Writes a primitive to be rendered
+    pub fn primitive(&mut self, primitive: impl PrimitiveLike) {
+        let primitive = primitive.into_primitive(self);
+        self.primitive_at(primitive, self.region)
+    }
+
+    pub fn primitive_within(&mut self, primitive: impl PrimitiveLike, region: UiRegion) {
+        let primitive = primitive.into_primitive(self);
+        self.primitive_at(primitive, region.within(&self.region));
+    }
+
+    pub fn set_mask(&mut self, region: UiRegion) {
+        assert!(self.mask == MaskIdx::NONE);
+        self.mask = self.rsc.ui_mut().masks.push(Mask {
+            region,
+            move_idx: self.move_idx,
+        });
+    }
+
+    /// Draws a widget within this widget's region.
+    pub fn widget<'s, W: ?Sized>(&'s mut self, id: &'s StrongWidget<W>) -> DrawResult<'s, 'a, W> {
+        self.widget_at(id, self.region)
+    }
+
+    /// Draws a widget somewhere within this one. Drawing one a second time
+    /// gives it a new box, keeping the drawing it already has where it can.
+    pub fn widget_within<'s, W: ?Sized>(
+        &'s mut self,
+        id: &'s StrongWidget<W>,
+        region: UiRegion,
+    ) -> DrawResult<'s, 'a, W> {
+        let region = region.within(&self.region);
+        self.widget_at(id, region)
+    }
+
+    fn widget_at<'s, W: ?Sized>(
+        &'s mut self,
+        id: &'s StrongWidget<W>,
+        region: UiRegion,
+    ) -> DrawResult<'s, 'a, W> {
+        // A child listed twice would be moved twice.
+        if !self.children.contains(&id.id()) {
+            self.children.push(id.id());
+        }
+        let size = self.state.draw_inner(
+            self.layer,
+            id.id(),
+            region,
+            Some(self.id),
+            self.mask,
+            None,
+            self.rsc,
+        );
+        DrawResult {
+            child: id,
+            painter: self,
+            size,
+        }
+    }
+
+    /// What a child says its length is without being drawn, if it can say.
+    /// Asking counts as reading its size.
+    pub fn size_hint<W: ?Sized>(&mut self, id: &StrongWidget<W>, axis: Axis) -> Option<Len> {
+        let hint = self.rsc.widgets().get_dyn(id.id())?.size_hint(axis)?;
+        self.depend_on_size(id);
+        Some(hint)
+    }
+
+    fn depend_on_size<W: ?Sized>(&mut self, child: &StrongWidget<W>) {
+        if !self.size_deps.contains(&child.id()) {
+            self.size_deps.push(child.id());
+        }
+    }
+
+    pub fn render_text(
+        &mut self,
+        buffer: &mut TextBuffer,
+        attrs: &TextAttrs,
+        width: Option<f32>,
+    ) -> RenderedText {
+        let ui = self.rsc.ui_mut();
+        ui.text.render(buffer, attrs, width)
+    }
+
+    // TODO: merge the text methods into the primitive ones.
+    pub fn glyphs(&mut self, text: &RenderedText, origin: UiRegion) {
+        let kind = self.rsc.ui_mut().primitives.kind::<GlyphPrimitive>();
+        for glyph in text.glyphs.iter() {
+            let mut region = origin;
+            region.x.end = region.x.start;
+            region.y.end = region.y.start;
+            let mut region = region.offset(UiVec2::abs(glyph.offset));
+            region.x.end = region.x.start + UiScalar::abs(glyph.entry.width as f32);
+            region.y.end = region.y.start + UiScalar::abs(glyph.entry.height as f32);
+            self.write(
+                kind,
+                GlyphPrimitive {
+                    uv_min: glyph.entry.uv_min,
+                    uv_max: glyph.entry.uv_max,
+                    layer: glyph.entry.layer,
+                    color: text.color,
+                    flags: glyph.entry.flags(),
+                },
+                region,
+            );
+        }
+    }
+
+    pub fn region(&self) -> UiRegion {
+        self.region
+    }
+
+    /// The output's size in pixels. A widget that reads it draws again when
+    /// the output changes, since nothing else can put that right.
+    pub fn output_size(&mut self) -> Vec2 {
+        self.reads_output = true;
+        self.state.output_size
+    }
+
+    /// This widget's box in pixels. Resolved against the output's size, so a
+    /// widget that reads it draws again when the output changes.
+    pub fn px_size(&mut self) -> Vec2 {
+        self.reads_output = true;
+        self.region.size().to_abs(self.state.output_size)
+    }
+
+    pub fn text_data(&mut self) -> &mut TextData {
+        &mut self.rsc.ui_mut().text
+    }
+
+    pub fn child_layer(&mut self) {
+        self.layer = self.state.layers.child(self.layer);
+    }
+
+    pub fn next_layer(&mut self) {
+        self.layer = self.state.layers.next(self.layer);
+    }
+
+    pub fn label(&self) -> &str {
+        &self.rsc.widgets().data(self.id).unwrap().label
+    }
+
+    pub fn id(&self) -> &WidgetId {
+        &self.id
+    }
+}
+
+/// A child that has just been drawn. Reading its size records that this
+/// widget's own size depends on it; dropping it without reading draws the
+/// child and leaves the parent independent of what it came to.
+pub struct DrawResult<'p, 'a, W: ?Sized> {
+    painter: &'p mut Painter<'a>,
+    child: &'p StrongWidget<W>,
+    size: Size,
+}
+
+impl<W: ?Sized> DrawResult<'_, '_, W> {
+    pub fn size(self) -> Size {
+        self.painter.depend_on_size(self.child);
+        self.size
+    }
+
+    pub fn len(self, axis: Axis) -> Len {
+        self.size().axis(axis)
+    }
+}
+
+/// What `Painter::primitive` takes: a primitive, or something that yields one
+/// and does whatever else drawing it needs.
+pub trait PrimitiveLike {
+    type Primitive: Primitive;
+    fn into_primitive(self, painter: &mut Painter) -> Self::Primitive;
+}
+
+impl<P: Primitive> PrimitiveLike for P {
+    type Primitive = P;
+    fn into_primitive(self, _: &mut Painter) -> P {
+        self
+    }
+}
+
+impl PrimitiveLike for &TextureHandle {
+    type Primitive = TexturePrimitive;
+
+    /// Retains a share of the handle, so the slot the primitive names cannot
+    /// be freed and reused while it is still drawn.
+    fn into_primitive(self, painter: &mut Painter) -> TexturePrimitive {
+        painter.textures.push(self.clone());
+        self.into()
+    }
+}

core/src/ui/render_state.rs

@@ -0,0 +1,437 @@
+use crate::{
+    ActiveData, Axis, DrawLayers, IdLike, MaskIdx, MoveIdx, Moves, OnResize, Painter, PixelRegion,
+    Size, StrongWidget, UiRegion, UiRsc, WidgetId, Widgets,
+    util::{HashMap, HashSet, Vec2, forget_ref},
+};
+
+pub struct UiRenderState {
+    pub active: HashMap<WidgetId, ActiveData>,
+    pub layers: DrawLayers,
+    pub(super) output_size: Vec2,
+
+    old_root: Option<WidgetId>,
+    resized: bool,
+    draw_started: HashSet<WidgetId>,
+    /// A widget's move slot, which outlives any one `ActiveData`: a redraw
+    /// replaces that while its children go on pointing at the slot.
+    slots: HashMap<WidgetId, MoveIdx>,
+    pub moves: Moves,
+}
+
+impl UiRenderState {
+    pub fn new() -> Self {
+        Self {
+            active: Default::default(),
+            layers: Default::default(),
+            output_size: Vec2::ZERO,
+            old_root: None,
+            resized: false,
+            draw_started: Default::default(),
+            slots: Default::default(),
+            moves: Default::default(),
+        }
+    }
+
+    pub fn resize(&mut self, size: impl Into<Vec2>) {
+        self.output_size = size.into();
+        self.resized = true;
+    }
+
+    pub fn output_size(&self) -> Vec2 {
+        self.output_size
+    }
+
+    pub fn update<'a>(&mut self, root: impl Into<Option<&'a StrongWidget>>, rsc: &mut dyn UiRsc) {
+        // safety mechanism for memory leaks; might wanna return a result instead so user can
+        // decide whether to panic or not
+        if !rsc.widgets().waiting.is_empty() {
+            let widgets = rsc.widgets();
+            let len = widgets.waiting.len();
+            let all: Vec<_> = widgets
+                .waiting
+                .iter()
+                .map(|&w| format!("'{}' ({w:?})", widgets.label(w)))
+                .collect();
+            panic!(
+                "{len} widget(s) were never upgraded\n\
+                this is likely a memory leak; consider upgrading to strong if you plan on using it later\n\
+                weak widgets: {all:#?}"
+            );
+        }
+        let root = root.into();
+        if self.root_changed(root) {
+            self.redraw_all(root, rsc);
+            self.old_root = root.map(|r| r.id());
+        } else if self.resized {
+            // A region is a fraction of the output plus an offset, resolved
+            // against the window in the shader, so a resize moves the whole
+            // drawing on its own. Only a widget that read pixels can be wrong.
+            for (&id, active) in &self.active {
+                if active.reads_output {
+                    rsc.widgets_mut().needs_redraw.insert(id);
+                }
+            }
+        }
+        self.resized = false;
+        if rsc.widgets().has_updates() {
+            self.redraw_updates(rsc);
+        }
+    }
+
+    fn redraw_all(&mut self, root: Option<&StrongWidget>, rsc: &mut dyn UiRsc) {
+        self.clear(rsc);
+        // free all resources & cache
+        if let Some(id) = root {
+            self.draw_inner(0, id.id(), UiRegion::FULL, None, MaskIdx::NONE, None, rsc);
+        }
+    }
+
+    // TODO: should prolly make a DrawInfo struct or smth for everything other than rsc
+    #[allow(clippy::too_many_arguments)]
+    pub(super) fn draw_inner(
+        &mut self,
+        layer: usize,
+        id: WidgetId,
+        region: UiRegion,
+        parent: Option<WidgetId>,
+        mask: MaskIdx,
+        old_children: Option<Vec<WidgetId>>,
+        rsc: &mut dyn UiRsc,
+    ) -> Size {
+        let mut old_children = old_children.unwrap_or_default();
+        if self.active.contains_key(&id) {
+            if let Some(size) = self.try_reuse(id, region, rsc) {
+                return size;
+            }
+            // if not, then maintain resize and track old children to remove unneeded
+            let active = self.remove(id, false, rsc).unwrap();
+            old_children = active.children;
+        }
+
+        // draw widget
+        let move_idx = self.move_slot(id, parent);
+        self.moves.set(move_idx, Vec2::ZERO);
+        rsc.widgets_mut().needs_redraw.remove(&id);
+        self.draw_started.insert(id);
+
+        let mut painter = Painter {
+            state: self,
+            region,
+            mask,
+            layer,
+            id,
+            textures: Vec::new(),
+            primitives: Vec::new(),
+            children: Vec::new(),
+            size_deps: Vec::new(),
+            reads_output: false,
+            move_idx,
+            rsc,
+        };
+
+        let mut widget = painter.rsc.widgets().get_dyn_dynamic(id);
+        let size = widget.draw(&mut painter);
+        drop(widget);
+
+        let Painter {
+            state: _,
+            rsc: _,
+            region,
+            mask,
+            textures,
+            primitives,
+            children,
+            size_deps,
+            reads_output,
+            move_idx,
+            layer,
+            id,
+        } = painter;
+
+        debug_assert!(
+            Self::hints_agree(id, size, rsc),
+            "'{}' ({id:?}) drew a size its size_hint disagrees with",
+            rsc.widgets().label(id)
+        );
+
+        // add to active
+        let active = ActiveData {
+            id,
+            region,
+            size,
+            parent,
+            textures,
+            primitives,
+            children,
+            size_deps,
+            reads_output,
+            move_idx,
+            mask,
+            layer,
+        };
+
+        // remove old children that weren't kept
+        for c in &old_children {
+            if !active.children.contains(c) {
+                self.remove_rec(*c, rsc);
+            }
+        }
+
+        rsc.on_draw(&active);
+        self.active.insert(id, active);
+        size
+    }
+
+    /// The slot a widget's drawing is positioned through, made on its first
+    /// draw and kept until it stops being drawn.
+    fn move_slot(&mut self, id: WidgetId, parent: Option<WidgetId>) -> MoveIdx {
+        if let Some(&idx) = self.slots.get(&id) {
+            return idx;
+        }
+        let parent = parent
+            .and_then(|p| self.slots.get(&p).copied())
+            .unwrap_or(MoveIdx::NONE);
+        let idx = self.moves.push(parent);
+        self.slots.insert(id, idx);
+        idx
+    }
+
+    /// The drawing a widget already has, kept for a new box if the box has not
+    /// changed in a way it depends on.
+    fn try_reuse(&mut self, id: WidgetId, region: UiRegion, rsc: &dyn UiRsc) -> Option<Size> {
+        if rsc.widgets().needs_redraw.contains(&id) {
+            return None;
+        }
+        let active = self.active.get(&id)?;
+        let (size, old, slot) = (active.size, active.region, active.move_idx);
+        // TODO: epsilon?
+        if old.size() == region.size() {
+            // The right shape and only somewhere else, which is one slot to
+            // write however much is under it. Both boxes are in the
+            // coordinates its parent drew, so the chain above applies alike.
+            let moved =
+                region.to_px(self.output_size).top_left - old.to_px(self.output_size).top_left;
+            self.moves.set(slot, moved);
+            return Some(size);
+        }
+        if !self.reusable(id, region, rsc) || !old.stretchable() {
+            return None;
+        }
+        // Its drawing stands, re-expressed as the same fractions of the box.
+        self.stretch(id, old, region);
+        Some(size)
+    }
+
+    /// Whether the widget can keep the drawing it has and be given `region`
+    /// instead, asked one axis at a time: a change on an axis it does not
+    /// depend on costs nothing, whatever it depends on elsewhere.
+    fn reusable(&self, id: WidgetId, region: UiRegion, rsc: &dyn UiRsc) -> bool {
+        let Some(active) = self.active.get(&id) else {
+            return false;
+        };
+        let Some(widget) = rsc.widgets().get_dyn(id) else {
+            return false;
+        };
+        [Axis::X, Axis::Y].into_iter().all(|axis| {
+            let offered = region.axis(axis).len();
+            let had = active.region.axis(axis).len();
+            match widget.on_resize(axis) {
+                OnResize::Scale => true,
+                // `Translate` is not acted on yet, and cannot be until a
+                // drawing can sit somewhere other than its box. `region` is
+                // both the box a widget was given and the box its primitives
+                // are in, and `mov` remaps from it -- so carrying a drawing at
+                // its old size while the box grows makes the next move stretch
+                // it. The offset chain is what separates the two.
+                OnResize::Translate | OnResize::Redraw => offered == had,
+            }
+        })
+    }
+
+    fn hints_agree(id: WidgetId, size: Size, rsc: &dyn UiRsc) -> bool {
+        let Some(widget) = rsc.widgets().get_dyn(id) else {
+            return true;
+        };
+        [Axis::X, Axis::Y].into_iter().all(|axis| {
+            widget
+                .size_hint(axis)
+                .is_none_or(|hint| hint == size.axis(axis))
+        })
+    }
+
+    /// Rewrites a subtree's regions as the same fractions of a new box, for a
+    /// change of length that a slot cannot express. Every region it rewrites
+    /// is a region some slot was a delta from, so those go back to zero.
+    fn stretch(&mut self, id: WidgetId, from: UiRegion, to: UiRegion) {
+        let active = self.active.get_mut(&id).unwrap();
+        for h in &active.primitives {
+            let region = self.layers[h.layer].region_mut(h);
+            *region = region.stretch(&from, &to);
+        }
+        active.region = active.region.stretch(&from, &to);
+        self.moves.set(active.move_idx, Vec2::ZERO);
+        // SAFETY: children cannot be recursive
+        let children = unsafe { forget_ref(&active.children) };
+        for child in children {
+            self.stretch(*child, from, to);
+        }
+    }
+
+    /// NOTE: instance textures are cleared and self.textures freed
+    fn remove(&mut self, id: WidgetId, undraw: bool, rsc: &mut dyn UiRsc) -> Option<ActiveData> {
+        let mut active = self.active.remove(&id);
+        if let Some(active) = &mut active {
+            for h in &active.primitives {
+                let mask = self.layers.free(h);
+                if mask != MaskIdx::NONE {
+                    rsc.ui_mut().masks.remove(mask);
+                }
+            }
+            active.textures.clear();
+            rsc.ui_mut().textures.free();
+            if undraw {
+                rsc.on_undraw(active);
+            }
+        }
+        active
+    }
+
+    fn remove_rec(&mut self, id: WidgetId, rsc: &mut dyn UiRsc) -> Option<ActiveData> {
+        let inst = self.remove(id, true, rsc);
+        if let Some(inst) = &inst {
+            for c in &inst.children {
+                self.remove_rec(*c, rsc);
+            }
+        }
+        // After the descendants, whose slots name this one as their parent.
+        if let Some(idx) = self.slots.remove(&id) {
+            self.moves.remove(idx);
+        }
+        inst
+    }
+
+    fn clear(&mut self, rsc: &mut dyn UiRsc) {
+        for (_, active) in self.active.drain() {
+            rsc.on_undraw(&active);
+        }
+        self.slots.clear();
+        self.moves.clear();
+        self.layers.clear();
+        rsc.widgets_mut().needs_redraw.clear();
+        rsc.free();
+    }
+
+    pub fn redraw_updates(&mut self, rsc: &mut dyn UiRsc) {
+        while let Some(&id) = rsc.widgets().needs_redraw.iter().next() {
+            self.redraw(id, rsc);
+        }
+        rsc.free();
+    }
+
+    pub fn root_changed<'a>(&self, root: impl Into<Option<&'a StrongWidget>>) -> bool {
+        root.into().map(|r| r.id()) != self.old_root
+    }
+
+    pub fn needs_redraw<'a>(
+        &self,
+        root: impl Into<Option<&'a StrongWidget>>,
+        widgets: &Widgets,
+    ) -> bool {
+        self.root_changed(root) || self.resized || widgets.has_updates()
+    }
+
+    pub fn active_widgets(&self) -> usize {
+        self.active.len()
+    }
+
+    pub fn debug(&self, widgets: &Widgets, label: &str) -> impl Iterator<Item = &ActiveData> {
+        self.active.iter().filter_map(move |(&id, inst)| {
+            let l = widgets.label(id);
+            if l == label { Some(inst) } else { None }
+        })
+    }
+
+    pub fn debug_layers(&self) {
+        for ((idx, depth), draws) in self.layers.iter_depth() {
+            let indent = " ".repeat(depth * 2);
+            let counts: Vec<String> = draws
+                .primitives()
+                .iter()
+                .map(|l| l.as_ref().map_or(0, |l| l.instances().len()).to_string())
+                .collect();
+            println!("{indent}{idx}: [{}]", counts.join(", "));
+        }
+    }
+
+    /// Where a widget is on screen: the box it drew against plus whatever the
+    /// chain above has moved since, which is the walk the vertex shader does.
+    pub fn window_region(&self, id: &impl IdLike) -> Option<PixelRegion> {
+        let active = self.active.get(&id.id())?;
+        let moved = self.moves.resolve(active.move_idx);
+        let region = active.region.to_px(self.output_size);
+        Some(PixelRegion {
+            top_left: region.top_left + moved,
+            bot_right: region.bot_right + moved,
+        })
+    }
+
+    /// redraws a widget that's currently active (drawn)
+    pub fn redraw(&mut self, id: WidgetId, rsc: &mut dyn UiRsc) {
+        self.draw_started.remove(&id);
+        // Whoever read this widget's size may be a different size now, so the
+        // highest reader is what draws. Everything between the two is marked
+        // as well: their own boxes have not changed, so the mark is the only
+        // thing stopping the draw reusing its way past this widget.
+        if let Some(top) = self.mark_readers(id, rsc) {
+            self.redraw(top, rsc);
+            // Cleared by that draw if it reached here; if it did not, this is
+            // no longer drawn and asking again would not end.
+            rsc.widgets_mut().needs_redraw.remove(&id);
+            return;
+        }
+        rsc.widgets_mut().needs_redraw.remove(&id);
+
+        if self.draw_started.contains(&id) {
+            return;
+        }
+
+        let Some(active) = self.remove(id, false, rsc) else {
+            return;
+        };
+
+        self.draw_inner(
+            active.layer,
+            id,
+            active.region,
+            active.parent,
+            active.mask,
+            Some(active.children),
+            rsc,
+        );
+    }
+
+    /// The furthest ancestor that read this widget's size, directly or through
+    /// widgets that did the same, marking everything below it on the way.
+    fn mark_readers(&self, id: WidgetId, rsc: &mut dyn UiRsc) -> Option<WidgetId> {
+        let mut top = None;
+        let mut at = id;
+        while let Some(active) = self.active.get(&at)
+            && let Some(parent) = active.parent
+            && self
+                .active
+                .get(&parent)
+                .is_some_and(|p| p.size_deps.contains(&at))
+        {
+            rsc.widgets_mut().needs_redraw.insert(at);
+            top = Some(parent);
+            at = parent;
+        }
+        top
+    }
+}
+
+impl Default for UiRenderState {
+    fn default() -> Self {
+        Self::new()
+    }
+}

core/src/util/arena.rs

@@ -34,6 +34,10 @@ impl<T, I: IdNum> Arena<T, I> {
         self.tracker.free(id);
         self.data[i]
     }
+
+    pub fn get_mut(&mut self, id: Id<I>) -> &mut T {
+        &mut self.data[id.idx()]
+    }
 }
 
 impl<T, I: IdNum> Default for Arena<T, I> {

core/src/util/math.rs

@@ -1,33 +1,13 @@
-use std::ops::*;
-
 pub const trait LerpUtil {
     fn lerp(self, from: Self, to: Self) -> Self;
-    fn lerp_inv(self, from: Self, to: Self) -> Self;
 }
 
-pub const trait DivOr {
-    fn div_or(self, rhs: Self, other: Self) -> Self;
-}
-
-impl const DivOr for f32 {
-    fn div_or(self, rhs: Self, other: Self) -> Self {
-        let res = self / rhs;
-        if res.is_nan() { other } else { res }
-    }
-}
-
-impl<T: const Add<Output = T> + const Sub<Output = T> + const Mul<Output = T> + const DivOr + Copy> const
-    LerpUtil for T
-{
+const impl LerpUtil for f32 {
     /// linear interpolation
     /// from * (1.0 - self) + to * self
     fn lerp(self, from: Self, to: Self) -> Self {
         from + (to - from) * self
     }
-    /// inverse of lerp
-    fn lerp_inv(self, from: Self, to: Self) -> Self {
-        (self - from).div_or(to - from, from)
-    }
 }
 
 macro_rules! impl_op {
@@ -37,7 +17,7 @@ macro_rules! impl_op {
             use super::*;
             #[allow(unused_imports)]
             use std::ops::*;
-            impl const $op for $T {
+            const impl $op for $T {
                 type Output = Self;
 
                 fn $fn(self, rhs: Self) -> Self::Output {
@@ -46,12 +26,12 @@ macro_rules! impl_op {
                     }
                 }
             }
-            impl const $opa for $T {
+            const impl $opa for $T {
                 fn $fna(&mut self, rhs: Self) {
                     *self = self.$fn(rhs);
                 }
             }
-            impl const $op<f32> for $T {
+            const impl $op<f32> for $T {
                 type Output = Self;
 
                 fn $fn(self, rhs: f32) -> Self::Output {
@@ -60,7 +40,7 @@ macro_rules! impl_op {
                     }
                 }
             }
-            impl const $op<$T> for f32 {
+            const impl $op<$T> for f32 {
                 type Output = $T;
 
                 fn $fn(self, rhs: $T) -> Self::Output {
@@ -69,7 +49,7 @@ macro_rules! impl_op {
                     }
                 }
             }
-            impl const $opa<f32> for $T {
+            const impl $opa<f32> for $T {
                 fn $fna(&mut self, rhs: f32) {
                     *self = self.$fn(rhs);
                 }

core/src/util/mod.rs

@@ -0,0 +1,24 @@
+mod arena;
+mod borrow;
+mod change;
+mod id;
+mod math;
+mod refcount;
+mod slot;
+mod trust;
+mod typemap;
+mod vec2;
+
+pub use arena::*;
+pub use borrow::*;
+pub use change::*;
+pub use id::*;
+pub use math::*;
+pub use refcount::*;
+pub use slot::*;
+pub(crate) use trust::*;
+pub use typemap::*;
+pub use vec2::*;
+
+pub type HashMap<K, V> = fxhash::FxHashMap<K, V>;
+pub type HashSet<K> = fxhash::FxHashSet<K>;

core/src/util/refcount.rs

@@ -22,6 +22,12 @@ impl RefCounter {
     }
 }
 
+impl Default for RefCounter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl Clone for RefCounter {
     fn clone(&self) -> Self {
         self.0.fetch_add(1, Ordering::Release);

core/src/util/slot.rs

@@ -0,0 +1,69 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct SlotId {
+    idx: u32,
+    genr: u32,
+}
+
+pub struct SlotVec<T> {
+    data: Vec<(u32, Option<T>)>,
+    free: Vec<u32>,
+}
+
+impl<T> SlotVec<T> {
+    pub fn new() -> Self {
+        Self {
+            data: Default::default(),
+            free: Default::default(),
+        }
+    }
+
+    pub fn add(&mut self, x: T) -> SlotId {
+        if let Some(idx) = self.free.pop() {
+            let (genr, data) = &mut self.data[idx as usize];
+            *data = Some(x);
+            SlotId { idx, genr: *genr }
+        } else {
+            let idx = self.data.len() as u32;
+            let genr = 0;
+            self.data.push((genr, Some(x)));
+            SlotId { idx, genr }
+        }
+    }
+
+    pub fn free(&mut self, id: SlotId) {
+        let (genr, data) = &mut self.data[id.idx as usize];
+        *genr += 1;
+        *data = None;
+        self.free.push(id.idx);
+    }
+
+    pub fn get(&self, id: SlotId) -> Option<&T> {
+        let slot = &self.data[id.idx as usize];
+        if slot.0 != id.genr {
+            return None;
+        }
+        slot.1.as_ref()
+    }
+
+    pub fn get_mut(&mut self, id: SlotId) -> Option<&mut T> {
+        let slot = &mut self.data[id.idx as usize];
+        if slot.0 != id.genr {
+            return None;
+        }
+        slot.1.as_mut()
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.len() - self.free.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+
+impl<T> Default for SlotVec<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}

core/src/util/trust.rs

@@ -0,0 +1,17 @@
+#[allow(clippy::missing_safety_doc)]
+pub(crate) unsafe fn forget_ref<'a, T>(x: &T) -> &'a T {
+    unsafe { std::mem::transmute::<&T, &T>(x) }
+}
+
+#[allow(clippy::missing_safety_doc)]
+pub(crate) unsafe fn forget_mut<'a, T>(x: &mut T) -> &'a mut T {
+    unsafe { std::mem::transmute::<&mut T, &mut T>(x) }
+}
+
+#[allow(clippy::mut_from_ref, clippy::missing_safety_doc)]
+pub(crate) unsafe fn to_mut<T>(x: &T) -> &mut T {
+    #[allow(mutable_transmutes)]
+    unsafe {
+        std::mem::transmute::<&T, &mut T>(x)
+    }
+}

core/src/util/typemap.rs

@@ -0,0 +1,56 @@
+use crate::util::HashMap;
+use std::{
+    any::TypeId,
+    marker::Unsize,
+    ops::{Deref, DerefMut},
+};
+
+pub struct TypeMap<Trait: ?Sized> {
+    map: HashMap<TypeId, Box<Trait>>,
+}
+
+impl<Trait: ?Sized> TypeMap<Trait> {
+    pub fn set_type<T: Unsize<Trait> + 'static>(&mut self, val: T) {
+        self.map
+            .insert(TypeId::of::<T>(), Box::new(val) as Box<Trait>);
+    }
+
+    pub fn type_mut<T: Unsize<Trait> + 'static>(&mut self) -> Option<&mut T> {
+        Some(Self::convert_mut(self.map.get_mut(&TypeId::of::<T>())?))
+    }
+
+    pub fn type_or_default<T: Default + Unsize<Trait> + 'static>(&mut self) -> &mut T {
+        Self::convert_mut(
+            self.map
+                .entry(TypeId::of::<T>())
+                .or_insert(Box::new(T::default()) as Box<Trait>),
+        )
+    }
+
+    fn convert_mut<T: Unsize<Trait>>(entry: &mut Box<Trait>) -> &mut T {
+        // allegedly this is just what Any does...
+        unsafe { &mut *(entry.as_mut() as *mut Trait as *mut T) }
+    }
+}
+
+impl<T: ?Sized> Deref for TypeMap<T> {
+    type Target = HashMap<TypeId, Box<T>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.map
+    }
+}
+
+impl<T: ?Sized> DerefMut for TypeMap<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.map
+    }
+}
+
+impl<T: ?Sized> Default for TypeMap<T> {
+    fn default() -> Self {
+        Self {
+            map: Default::default(),
+        }
+    }
+}

core/src/util/vec2.rs

@@ -1,10 +1,11 @@
-use crate::{
-    layout::UiNum,
-    util::{DivOr, impl_op},
-};
-use std::{hash::Hash, marker::Destruct, ops::*};
+use crate::util::impl_op;
+use std::{hash::Hash, ops::*};
 
-#[repr(C)]
+/// `align(8)` because that is WGSL's alignment for a `vec2<f32>`, so any GPU
+/// struct holding one is laid out the way its shader reads it without having
+/// to say so itself. Those structs still need a manual `unsafe impl Pod`,
+/// since the trailing padding this introduces is what `derive(Pod)` refuses.
+#[repr(C, align(8))]
 #[derive(Clone, Copy, PartialEq, Default, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct Vec2 {
     pub x: f32,
@@ -20,10 +21,6 @@ impl Hash for Vec2 {
     }
 }
 
-pub const fn vec2(x: impl const UiNum, y: impl const UiNum) -> Vec2 {
-    Vec2::new(x.to_f32(), y.to_f32())
-}
-
 impl Vec2 {
     pub const ZERO: Self = Self::new(0.0, 0.0);
     pub const ONE: Self = Self::new(1.0, 1.0);
@@ -68,30 +65,12 @@ impl Vec2 {
     }
 }
 
-impl<T: const UiNum + Copy> const From<T> for Vec2 {
-    fn from(v: T) -> Self {
-        Self {
-            x: v.to_f32(),
-            y: v.to_f32(),
-        }
-    }
-}
-
 // this version looks kinda cool... is it more readable? more annoying to copy and change though
 impl_op!(impl Add for Vec2: add x y);
 impl_op!(Vec2 Sub sub; x y);
 impl_op!(Vec2 Mul mul; x y);
 impl_op!(Vec2 Div div; x y);
 
-impl const DivOr for Vec2 {
-    fn div_or(self, rhs: Self, other: Self) -> Self {
-        Self {
-            x: self.x.div_or(rhs.x, other.x),
-            y: self.y.div_or(rhs.y, other.y),
-        }
-    }
-}
-
 impl Neg for Vec2 {
     type Output = Self;
 
@@ -102,18 +81,6 @@ impl Neg for Vec2 {
     }
 }
 
-impl<T: const UiNum, U: const UiNum> const From<(T, U)> for Vec2
-where
-    (T, U): const Destruct,
-{
-    fn from((x, y): (T, U)) -> Self {
-        Self {
-            x: x.to_f32(),
-            y: y.to_f32(),
-        }
-    }
-}
-
 impl std::fmt::Debug for Vec2 {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(f, "({}, {})", self.x, self.y)

core/src/widget/data.rs

@@ -0,0 +1,22 @@
+use crate::Widget;
+
+pub struct WidgetData {
+    pub widget: Box<dyn Widget>,
+    pub label: String,
+    /// dynamic borrow checking
+    pub borrowed: bool,
+}
+
+impl WidgetData {
+    pub fn new<W: Widget>(widget: W) -> Self {
+        let mut label = std::any::type_name::<W>().to_string();
+        if let (Some(first), Some(last)) = (label.find(":"), label.rfind(":")) {
+            label = label.split_at(first).0.to_string() + "::" + label.split_at(last + 1).1;
+        }
+        Self {
+            widget: Box::new(widget),
+            label,
+            borrowed: false,
+        }
+    }
+}

core/src/widget/handle.rs

@@ -0,0 +1,164 @@
+use std::{marker::Unsize, ops::CoerceUnsized, sync::mpsc::Sender};
+
+use crate::{
+    UiRsc, Widget,
+    util::{RefCounter, SlotId},
+};
+
+pub type WidgetId = SlotId;
+
+/// An identifier for a widget that can index a UI or event ctx to get it.
+/// This is a strong handle that does not impl Clone, and when it is dropped,
+/// a signal is sent to the owning UI to clean up the resources.
+///
+/// TODO: ergonomic clones when they get put in rust-analyzer & don't cause ICEs?
+pub struct StrongWidget<W: ?Sized = dyn Widget> {
+    pub(super) id: WidgetId,
+    counter: RefCounter,
+    send: Sender<WidgetId>,
+    ty: *const W,
+}
+
+/// A weak handle to a widget.
+/// Will not keep it alive, but can still be used for indexing like WidgetHandle.
+pub struct WeakWidget<W: ?Sized = dyn Widget> {
+    pub(super) id: WidgetId,
+    #[allow(unused)]
+    ty: *const W,
+}
+
+impl<W: Widget + ?Sized + Unsize<dyn Widget>> StrongWidget<W> {
+    pub fn any(self) -> StrongWidget<dyn Widget> {
+        self
+    }
+}
+
+impl<W: ?Sized> StrongWidget<W> {
+    pub(crate) fn new(id: WidgetId, send: Sender<WidgetId>) -> Self {
+        Self {
+            id,
+            counter: RefCounter::new(),
+            send,
+            ty: null_ptr(),
+        }
+    }
+
+    pub fn id(&self) -> WidgetId {
+        self.id
+    }
+
+    pub fn refs(&self) -> u32 {
+        self.counter.refs()
+    }
+
+    pub fn weak(&self) -> WeakWidget<W> {
+        let Self { ty, id, .. } = *self;
+        WeakWidget { ty, id }
+    }
+}
+
+impl<W: ?Sized> WeakWidget<W> {
+    pub(crate) fn new(id: WidgetId) -> Self {
+        Self { id, ty: null_ptr() }
+    }
+
+    pub fn id(&self) -> WidgetId {
+        self.id
+    }
+
+    #[track_caller]
+    pub fn upgrade(self, ui: &mut impl UiRsc) -> StrongWidget<W> {
+        ui.widgets_mut().upgrade(self)
+    }
+}
+
+impl<W: ?Sized> Drop for StrongWidget<W> {
+    fn drop(&mut self) {
+        if self.counter.drop() {
+            let _ = self.send.send(self.id);
+        }
+    }
+}
+
+pub trait WidgetIdFn<Rsc, W: ?Sized = dyn Widget>: FnOnce(&mut Rsc) -> WeakWidget<W> {}
+impl<Rsc, W: ?Sized, F: FnOnce(&mut Rsc) -> WeakWidget<W>> WidgetIdFn<Rsc, W> for F {}
+
+pub trait IdLike {
+    type Widget: ?Sized;
+    fn id(&self) -> WidgetId;
+}
+
+impl<W: ?Sized> IdLike for &StrongWidget<W> {
+    type Widget = W;
+    fn id(&self) -> WidgetId {
+        self.id
+    }
+}
+
+impl<W: ?Sized> IdLike for StrongWidget<W> {
+    type Widget = W;
+    fn id(&self) -> WidgetId {
+        self.id
+    }
+}
+
+impl<W: ?Sized> IdLike for WeakWidget<W> {
+    type Widget = W;
+    fn id(&self) -> WidgetId {
+        self.id
+    }
+}
+
+impl IdLike for WidgetId {
+    type Widget = dyn Widget;
+    fn id(&self) -> WidgetId {
+        *self
+    }
+}
+
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<StrongWidget<U>> for StrongWidget<T> {}
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<WeakWidget<U>> for WeakWidget<T> {}
+
+impl<W: ?Sized> Clone for WeakWidget<W> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+impl<W: ?Sized> Copy for WeakWidget<W> {}
+impl<W: ?Sized> PartialEq for WeakWidget<W> {
+    fn eq(&self, other: &Self) -> bool {
+        self.id == other.id
+    }
+}
+
+impl<W> PartialEq for StrongWidget<W> {
+    fn eq(&self, other: &Self) -> bool {
+        self.id == other.id
+    }
+}
+
+impl<W> std::fmt::Debug for StrongWidget<W> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.id.fmt(f)
+    }
+}
+
+impl<'a, W: Widget + 'a, State: UiRsc> FnOnce<(&'a mut State,)> for WeakWidget<W> {
+    type Output = &'a mut W;
+
+    extern "rust-call" fn call_once(self, args: (&'a mut State,)) -> Self::Output {
+        &mut args.0.widgets_mut()[self]
+    }
+}
+
+fn null_ptr<W: ?Sized>() -> *const W {
+    if size_of::<&W>() == size_of::<*const dyn Widget>() {
+        let w: *const dyn Widget = &();
+        unsafe { std::mem::transmute_copy(&w) }
+    } else {
+        unsafe { std::mem::transmute_copy(&[0usize; 1]) }
+    }
+}
+
+unsafe impl<W: ?Sized> Send for WeakWidget<W> {}
+unsafe impl<W: ?Sized> Sync for WeakWidget<W> {}

core/src/widget/like.rs

@@ -0,0 +1,75 @@
+use crate::UiRsc;
+
+use super::*;
+use std::marker::Unsize;
+
+pub trait WidgetLike<Rsc: UiRsc, Tag>: Sized {
+    type Widget: Widget + ?Sized + Unsize<dyn Widget>;
+
+    fn add(self, rsc: &mut Rsc) -> WeakWidget<Self::Widget>;
+
+    fn add_strong(self, rsc: &mut Rsc) -> StrongWidget<Self::Widget> {
+        self.add(rsc).upgrade(rsc)
+    }
+
+    fn with_id<W2>(
+        self,
+        f: impl FnOnce(&mut Rsc, WeakWidget<Self::Widget>) -> WeakWidget<W2>,
+    ) -> impl WidgetIdFn<Rsc, W2> {
+        move |state| {
+            let id = self.add(state);
+            f(state, id)
+        }
+    }
+
+    fn set_root(self, rsc: &mut Rsc, root: &mut impl HasRoot) {
+        let id = self.add_strong(rsc);
+        root.set_root(id);
+    }
+}
+
+pub trait HasRoot {
+    fn set_root(&mut self, root: StrongWidget);
+}
+
+pub trait WidgetArrLike<Rsc, const LEN: usize, Tag> {
+    #[track_caller]
+    fn add(self, state: &mut Rsc) -> WidgetArr<LEN>;
+}
+
+impl<Rsc, const LEN: usize> WidgetArrLike<Rsc, LEN, ArrTag> for WidgetArr<LEN> {
+    fn add(self, _: &mut Rsc) -> WidgetArr<LEN> {
+        self
+    }
+}
+
+// variadic generics please save us
+macro_rules! impl_widget_arr {
+    ($n:expr;$($W:ident)*) => {
+        impl_widget_arr!($n;$($W)*;$(${concat($W,Tag)})*);
+    };
+    ($n:expr;$($W:ident)*;$($Tag:ident)*) => {
+        impl<Rsc: UiRsc, $($W: WidgetLike<Rsc, $Tag>,$Tag,)*> WidgetArrLike<Rsc, $n, ($($Tag,)*)> for ($($W,)*) {
+            fn add(self, rsc: &mut Rsc) -> WidgetArr<$n> {
+                #[allow(non_snake_case)]
+                let ($($W,)*) = self;
+                WidgetArr::new(
+                    [$($W.add(rsc).upgrade(rsc),)*],
+                )
+            }
+        }
+    };
+}
+
+impl_widget_arr!(1;A);
+impl_widget_arr!(2;A B);
+impl_widget_arr!(3;A B C);
+impl_widget_arr!(4;A B C D);
+impl_widget_arr!(5;A B C D E);
+impl_widget_arr!(6;A B C D E F);
+impl_widget_arr!(7;A B C D E F G);
+impl_widget_arr!(8;A B C D E F G H);
+impl_widget_arr!(9;A B C D E F G H I);
+impl_widget_arr!(10;A B C D E F G H I J);
+impl_widget_arr!(11;A B C D E F G H I J K);
+impl_widget_arr!(12;A B C D E F G H I J K L);

core/src/widget/mod.rs

@@ -0,0 +1,100 @@
+use crate::{Axis, Len, Painter, Size};
+use std::any::Any;
+
+mod data;
+mod handle;
+mod like;
+mod tag;
+mod view;
+mod widgets;
+
+pub use data::*;
+pub use handle::*;
+pub use like::*;
+pub use tag::*;
+pub use view::*;
+pub use widgets::*;
+
+/// What may be done to a widget's drawing when the box it was given changes
+/// on this axis, instead of drawing it again. Asked per axis, because wrapped
+/// text reads the width it is offered and not the height.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum OnResize {
+    Scale,
+    Translate,
+    #[default]
+    Redraw,
+}
+
+pub trait Widget: Any {
+    /// Draws the widget, and returns what it used of the box it was given.
+    fn draw(&mut self, painter: &mut Painter) -> Size;
+
+    /// An exact length the widget can give without a painter or its children.
+    /// Optional, and saves a draw rather than changing one: a hint that
+    /// disagrees with the eventual draw fails a debug assertion.
+    fn size_hint(&self, _axis: Axis) -> Option<Len> {
+        None
+    }
+
+    fn on_resize(&self, _axis: Axis) -> OnResize {
+        OnResize::default()
+    }
+}
+
+impl Widget for () {
+    /// A gap: nothing drawn, at the default length, so a span gives it a share.
+    fn draw(&mut self, _: &mut Painter) -> Size {
+        Size::default()
+    }
+
+    fn size_hint(&self, _axis: Axis) -> Option<Len> {
+        Some(Len::default())
+    }
+
+    fn on_resize(&self, _axis: Axis) -> OnResize {
+        OnResize::Scale
+    }
+}
+
+impl dyn Widget {
+    pub fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    pub fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+}
+
+/// A function that returns a widget given a UI.
+/// Useful for defining trait functions on widgets that create a parent widget so that the children
+/// don't need to be IDs yet
+pub trait WidgetFn<State, W: Widget + ?Sized>: FnOnce(&mut State) -> W {}
+impl<State, W: Widget + ?Sized, F: FnOnce(&mut State) -> W> WidgetFn<State, W> for F {}
+
+pub struct WidgetArr<const LEN: usize> {
+    pub arr: [StrongWidget; LEN],
+}
+
+impl<const LEN: usize> WidgetArr<LEN> {
+    pub fn new(arr: [StrongWidget; LEN]) -> Self {
+        Self { arr }
+    }
+}
+
+pub trait WidgetOption<State> {
+    fn get(self, state: &mut State) -> Option<StrongWidget>;
+}
+
+impl<State> WidgetOption<State> for () {
+    fn get(self, _: &mut State) -> Option<StrongWidget> {
+        None
+    }
+}
+
+impl<State, F: FnOnce(&mut State) -> Option<StrongWidget>> WidgetOption<State> for F {
+    fn get(self, state: &mut State) -> Option<StrongWidget> {
+        self(state)
+    }
+}

core/src/widget/tag.rs

@@ -0,0 +1,64 @@
+use super::*;
+use crate::UiRsc;
+use std::marker::Unsize;
+
+pub struct WidgetTag;
+impl<Rsc: UiRsc, W: Widget> WidgetLike<Rsc, WidgetTag> for W {
+    type Widget = W;
+    fn add(self, rsc: &mut Rsc) -> WeakWidget<W> {
+        let w = rsc.ui_mut().widgets.add_weak(self);
+        rsc.on_add(w);
+        w
+    }
+}
+
+pub struct FnTag;
+impl<Rsc: UiRsc, W: Widget, F: FnOnce(&mut Rsc) -> W> WidgetLike<Rsc, FnTag> for F {
+    type Widget = W;
+    fn add(self, rsc: &mut Rsc) -> WeakWidget<W> {
+        self(rsc).add(rsc)
+    }
+}
+
+pub trait WidgetFnTrait<Rsc> {
+    type Widget: Widget;
+    fn run(self, rsc: &mut Rsc) -> Self::Widget;
+}
+pub struct FnTraitTag;
+impl<Rsc: UiRsc, T: WidgetFnTrait<Rsc>> WidgetLike<Rsc, FnTraitTag> for T {
+    type Widget = T::Widget;
+    #[track_caller]
+    fn add(self, rsc: &mut Rsc) -> WeakWidget<T::Widget> {
+        self.run(rsc).add(rsc)
+    }
+}
+
+pub struct RefTag;
+impl<Rsc: UiRsc, W: ?Sized + Widget + Unsize<dyn Widget>> WidgetLike<Rsc, RefTag>
+    for WeakWidget<W>
+{
+    type Widget = W;
+    fn add(self, _: &mut Rsc) -> WeakWidget<W> {
+        self
+    }
+}
+
+pub struct RefFnTag;
+impl<Rsc: UiRsc, W: ?Sized + Widget + Unsize<dyn Widget>, F: FnOnce(&mut Rsc) -> WeakWidget<W>>
+    WidgetLike<Rsc, RefFnTag> for F
+{
+    type Widget = W;
+    fn add(self, rsc: &mut Rsc) -> WeakWidget<W> {
+        self(rsc)
+    }
+}
+
+pub struct ViewTag;
+impl<Rsc: UiRsc, V: WidgetView> WidgetLike<Rsc, ViewTag> for V {
+    type Widget = V::Widget;
+    fn add(self, _: &mut Rsc) -> WeakWidget<Self::Widget> {
+        self.root()
+    }
+}
+
+pub struct ArrTag;

core/src/widget/view.rs

@@ -0,0 +1,24 @@
+use std::marker::Unsize;
+
+use crate::{IdLike, WeakWidget, Widget};
+
+pub trait WidgetView {
+    type Widget: Widget + ?Sized + Unsize<dyn Widget>;
+    fn root(&self) -> WeakWidget<Self::Widget>;
+}
+
+pub trait HasWidget {
+    type Widget: Widget + ?Sized + Unsize<dyn Widget>;
+}
+
+impl<W: Widget + Unsize<dyn Widget> + ?Sized> HasWidget for WeakWidget<W> {
+    type Widget = W;
+}
+
+impl<WV: WidgetView> IdLike for WV {
+    type Widget = WV::Widget;
+
+    fn id(&self) -> super::WidgetId {
+        self.root().id
+    }
+}

core/src/widget/widgets.rs

@@ -0,0 +1,145 @@
+use std::sync::mpsc::{Receiver, Sender, channel};
+
+use crate::{
+    IdLike, StrongWidget, WeakWidget, Widget, WidgetData, WidgetId,
+    util::{DynBorrower, HashSet, SlotVec, forget_mut, to_mut},
+};
+
+pub struct Widgets {
+    pub needs_redraw: HashSet<WidgetId>,
+    vec: SlotVec<WidgetData>,
+    send: Sender<WidgetId>,
+    recv: Receiver<WidgetId>,
+    pub(crate) waiting: HashSet<WidgetId>,
+}
+
+impl Widgets {
+    pub fn new() -> Self {
+        let (send, recv) = channel();
+        Self {
+            needs_redraw: Default::default(),
+            vec: Default::default(),
+            waiting: Default::default(),
+            send,
+            recv,
+        }
+    }
+
+    pub fn has_updates(&self) -> bool {
+        !self.needs_redraw.is_empty()
+    }
+
+    pub fn get_dyn(&self, id: WidgetId) -> Option<&dyn Widget> {
+        Some(self.vec.get(id)?.widget.as_ref())
+    }
+
+    pub fn get_dyn_mut(&mut self, id: WidgetId) -> Option<&mut dyn Widget> {
+        self.needs_redraw.insert(id);
+        Some(self.vec.get_mut(id)?.widget.as_mut())
+    }
+
+    /// get_dyn but dynamic borrow checking of widgets
+    /// lets you do recursive (tree) operations, like the painter does
+    pub(crate) fn get_dyn_dynamic<'a>(&self, id: WidgetId) -> WidgetWrapper<'a> {
+        // SAFETY: must guarantee no other mutable references to this widget exist
+        // done through the borrow variable
+        let data = unsafe { forget_mut(to_mut(self.vec.get(id).unwrap())) };
+        if data.borrowed {
+            panic!("tried to mutably borrow the same widget twice");
+        }
+        WidgetWrapper::new(data.widget.as_mut(), &mut data.borrowed)
+    }
+
+    pub fn get<I: IdLike>(&self, id: &I) -> Option<&I::Widget>
+    where
+        I::Widget: Sized + Widget,
+    {
+        self.get_dyn(id.id())?.as_any().downcast_ref()
+    }
+
+    pub fn get_mut<I: IdLike>(&mut self, id: &I) -> Option<&mut I::Widget>
+    where
+        I::Widget: Sized + Widget,
+    {
+        self.get_dyn_mut(id.id())?.as_any_mut().downcast_mut()
+    }
+
+    pub fn add_strong<W: Widget>(&mut self, widget: W) -> StrongWidget<W> {
+        let id = self.vec.add(WidgetData::new(widget));
+        StrongWidget::new(id, self.send.clone())
+    }
+
+    pub fn add_weak<W: Widget>(&mut self, widget: W) -> WeakWidget<W> {
+        let id = self.vec.add(WidgetData::new(widget));
+        self.waiting.insert(id);
+        WeakWidget::new(id)
+    }
+
+    #[track_caller]
+    pub fn upgrade<W: ?Sized>(&mut self, rf: WeakWidget<W>) -> StrongWidget<W> {
+        if !self.waiting.remove(&rf.id()) {
+            let label = self.label(rf);
+            let id = rf.id();
+            panic!(
+                "widget '{label}' ({id:?}) was already added\ncannot add a widget twice; consider creating two"
+            )
+        }
+        StrongWidget::new(rf.id(), self.send.clone())
+    }
+
+    pub fn data(&self, id: impl IdLike) -> Option<&WidgetData> {
+        self.vec.get(id.id())
+    }
+
+    pub fn label(&self, id: impl IdLike) -> &String {
+        &self.data(id.id()).unwrap().label
+    }
+
+    /// useful for debugging
+    pub fn set_label(&mut self, id: impl IdLike, label: String) {
+        self.data_mut(id.id()).unwrap().label = label;
+    }
+
+    pub fn data_mut(&mut self, id: impl IdLike) -> Option<&mut WidgetData> {
+        self.vec.get_mut(id.id())
+    }
+
+    pub fn free_next(&mut self) -> Option<WidgetId> {
+        let next = self.recv.try_recv().ok()?;
+        self.vec.free(next);
+        Some(next)
+    }
+
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        self.vec.len()
+    }
+}
+
+impl Default for Widgets {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+pub type WidgetWrapper<'a> = DynBorrower<'a, dyn Widget>;
+
+impl<I: IdLike> std::ops::Index<I> for Widgets
+where
+    I::Widget: Sized + Widget,
+{
+    type Output = I::Widget;
+
+    fn index(&self, id: I) -> &Self::Output {
+        self.get(&id).unwrap()
+    }
+}
+
+impl<I: IdLike> std::ops::IndexMut<I> for Widgets
+where
+    I::Widget: Sized + Widget,
+{
+    fn index_mut(&mut self, id: I) -> &mut Self::Output {
+        self.get_mut(&id).unwrap()
+    }
+}

examples/minimal.rs

@@ -1,14 +1,17 @@
-use iris::{prelude::*, winit::*};
+use iris::prelude::*;
 
 fn main() {
     DefaultApp::<State>::run();
 }
 
-struct State;
+#[derive(DefaultUiState)]
+struct State {
+    ui_state: DefaultUiState,
+}
 
 impl DefaultAppState for State {
-    fn new(ui: &mut Ui, _state: &UiState, _proxy: Proxy<Self::Event>) -> Self {
-        rect(Color::RED).set_root(ui);
-        Self
+    fn new(mut ui_state: DefaultUiState, rsc: &mut DefaultRsc<Self>, _: Proxy<Self>) -> Self {
+        rect(Color::RED).set_root(rsc, &mut ui_state);
+        Self { ui_state }
     }
 }

examples/tabs/main.rs

@@ -1,23 +1,21 @@
-use cosmic_text::Family;
-use iris::{
-    prelude::*,
-    winit::{attr::Selectable, event::Submit, *},
-};
-use len_fns::*;
+use std::{cell::RefCell, rc::Rc};
 use winit::event::WindowEvent;
 
+use iris::prelude::*;
+type ClientRsc = DefaultRsc<Client>;
+
 fn main() {
     DefaultApp::<Client>::run();
 }
 
+#[derive(DefaultUiState)]
 pub struct Client {
-    info: WidgetId<Text>,
+    ui_state: DefaultUiState,
+    info: WeakWidget<Text>,
 }
 
-event_ctx!(Client);
-
 impl DefaultAppState for Client {
-    fn new(ui: &mut Ui, _state: &UiState, _proxy: Proxy<Self::Event>) -> Self {
+    fn new(mut ui_state: DefaultUiState, rsc: &mut DefaultRsc<Self>, _: Proxy<Self>) -> Self {
         let rrect = rect(Color::WHITE).radius(20);
         let pad_test = (
             rrect.color(Color::BLUE),
@@ -40,7 +38,7 @@ impl DefaultAppState for Client {
                 .width(rest(3)),
         )
             .span(Dir::RIGHT)
-            .add(ui);
+            .add(rsc);
 
         let span_test = (
             rrect.color(Color::GREEN).width(100),
@@ -51,33 +49,30 @@ impl DefaultAppState for Client {
             rrect.color(Color::RED).width(100),
         )
             .span(Dir::LEFT)
-            .add(ui);
+            .add(rsc);
 
-        let span_add = Span::empty(Dir::RIGHT).add(ui);
-        let span_add_ = span_add.clone();
+        let span_add = Span::empty(Dir::RIGHT).add(rsc);
 
         let add_button = rect(Color::LIME)
             .radius(30)
-            .on(CursorSense::click(), move |ctx| {
-                let child = ctx
-                    .ui
-                    .add(image(include_bytes!("assets/sungals.png")).center())
-                    .any();
-                ctx.ui[&span_add_].children.push(child);
+            .on(CursorSense::click(), move |_, rsc| {
+                let child = image(include_bytes!("assets/sungals.png"))
+                    .center()
+                    .add_strong(rsc);
+                span_add(rsc).push(child);
             })
             .sized((150, 150))
             .align(Align::BOT_RIGHT);
 
-        let span_add_ = span_add.clone();
         let del_button = rect(Color::RED)
             .radius(30)
-            .on(CursorSense::click(), move |ctx| {
-                ctx.ui[&span_add_].children.pop();
+            .on(CursorSense::click(), move |_, rsc| {
+                span_add(rsc).pop();
             })
             .sized((150, 150))
             .align(Align::BOT_LEFT);
 
-        let span_add_test = (span_add, add_button, del_button).stack().add(ui);
+        let span_add_test = (span_add, add_button, del_button).stack().add(rsc);
 
         let btext = |content| wtext(content).size(30);
 
@@ -100,36 +95,40 @@ impl DefaultAppState for Client {
             wtext("pretty cool right?").size(50),
         )
             .span(Dir::DOWN)
-            .add(ui);
+            .add(rsc);
 
-        let texts = Span::empty(Dir::DOWN).gap(10).add(ui);
-        let msg_area = texts.clone().scroll().masked().background(rect(Color::SKY));
+        let texts = Span::empty(Dir::DOWN).gap(10).add(rsc);
+        let msg_area = texts.scrollable().masked().background(rect(Color::SKY));
         let add_text = wtext("add")
-            .editable(false)
+            .editable(EditMode::MultiLine)
             .text_align(Align::LEFT)
             .size(30)
             .attr::<Selectable>(())
-            .on(Submit, move |ctx| {
-                let content = ctx.ui.text(ctx.id).take();
+            .on(Submit, move |ctx, rsc| {
+                let w = ctx.widget;
+                let content = w.edit(rsc).take();
                 let text = wtext(content)
-                    .editable(false)
+                    .editable(EditMode::MultiLine)
                     .size(30)
                     .text_align(Align::LEFT)
                     .wrap(true)
                     .attr::<Selectable>(());
-                let msg_box = text.background(rect(Color::WHITE.darker(0.5))).add(ctx.ui);
-                ctx.ui[&texts].children.push(msg_box.any());
+                let msg_box = text
+                    .background(rect(Color::WHITE.darker(0.5)))
+                    .add_strong(rsc);
+                texts(rsc).push(msg_box);
             })
-            .add(ui);
+            .add(rsc);
+
         let text_edit_scroll = (
             msg_area.height(rest(1)),
             (
                 Rect::new(Color::WHITE.darker(0.9)),
                 (
-                    add_text.clone().width(rest(1)),
+                    add_text.width(rest(1)),
                     Rect::new(Color::GREEN)
-                        .on(CursorSense::click(), move |ctx| {
-                            ctx.ui.run_event(ctx.state, &add_text, Submit, ());
+                        .on(CursorSense::click(), move |ctx, rsc: &mut ClientRsc| {
+                            rsc.run_event::<Submit>(add_text, (), ctx.state);
                         })
                         .sized((40, 40)),
                 )
@@ -142,64 +141,80 @@ impl DefaultAppState for Client {
                 .align(Align::BOT),
         )
             .span(Dir::DOWN)
-            .add(ui);
+            .add(rsc);
 
-        let main = pad_test.clone().pad(10).add(ui);
+        let main = WidgetPtr::new().add(rsc);
 
-        let switch_button = |color, to: WidgetId, label| {
-            let main_ = main.clone();
+        let vals = Rc::new(RefCell::new((0, Vec::new())));
+        let mut switch_button = |color, to: WeakWidget, label| {
+            let to = to.upgrade(rsc);
+            let vec = &mut vals.borrow_mut().1;
+            let i = vec.len();
+            if vec.is_empty() {
+                vec.push(None);
+                main(rsc).set(to);
+            } else {
+                vec.push(Some(to));
+            }
+            let vals = vals.clone();
             let rect = rect(color)
-                .on(CursorSense::click(), move |ctx| {
-                    ctx.ui[&main_.clone()].inner = to.clone();
-                    ctx.ui[ctx.id].color = color.darker(0.3);
+                .on(CursorSense::click(), move |ctx, rsc| {
+                    let (prev, vec) = &mut *vals.borrow_mut();
+                    if let Some(h) = vec[i].take() {
+                        vec[*prev] = main(rsc).replace(h);
+                        *prev = i;
+                    }
+                    ctx.widget(rsc).color = color.darker(0.3);
                 })
                 .on(
                     CursorSense::HoverStart | CursorSense::unclick(),
-                    move |ctx| {
-                        ctx.ui[ctx.id].color = color.brighter(0.2);
+                    move |ctx, rsc| {
+                        ctx.widget(rsc).color = color.brighter(0.2);
                     },
                 )
-                .on(CursorSense::HoverEnd, move |ctx| {
-                    ctx.ui[ctx.id].color = color;
+                .on(CursorSense::HoverEnd, move |ctx, rsc| {
+                    ctx.widget(rsc).color = color;
                 });
             (rect, wtext(label).size(30).text_align(Align::CENTER)).stack()
         };
 
         let tabs = (
-            switch_button(Color::RED, pad_test.any(), "pad"),
-            switch_button(Color::GREEN, span_test.any(), "span"),
-            switch_button(Color::BLUE, span_add_test.any(), "image span"),
-            switch_button(Color::MAGENTA, text_test.any(), "text layout"),
+            switch_button(Color::RED, pad_test, "pad"),
+            switch_button(Color::GREEN, span_test, "span"),
+            switch_button(Color::BLUE, span_add_test, "image span"),
+            switch_button(Color::MAGENTA, text_test, "text layout"),
             switch_button(
                 Color::YELLOW.mul_rgb(0.5),
-                text_edit_scroll.any(),
+                text_edit_scroll,
                 "text edit scroll",
             ),
         )
             .span(Dir::RIGHT);
 
-        let info = wtext("").add(ui);
-        let info_sect = info.clone().pad(10).align(Align::RIGHT);
+        let info = wtext("").add(rsc);
+        let info_sect = info.pad(10).align(Align::RIGHT);
 
-        ((tabs.height(40), main).span(Dir::DOWN), info_sect)
+        ((tabs.height(40), main.pad(10)).span(Dir::DOWN), info_sect)
             .stack()
-            .set_root(ui);
+            .set_root(rsc, &mut ui_state);
 
-        Self { info }
+        Self { ui_state, info }
     }
 
-    fn window_event(&mut self, _: WindowEvent, ui: &mut Ui, state: &UiState) {
+    fn window_event(
+        &mut self,
+        _: WindowEvent,
+        rsc: &mut DefaultRsc<Self>,
+        render: &mut UiRenderState,
+    ) {
         let new = format!(
-            "widgets: {}\nactive:{}\nviews: {}",
-            ui.num_widgets(),
-            ui.active_widgets(),
-            state.renderer.ui.view_count()
+            "widgets: {}\nactive: {}\ntextures: {}",
+            rsc.widgets().len(),
+            render.active_widgets(),
+            rsc.ui().textures.count(),
         );
-        if new != *ui[&self.info].content {
-            *ui[&self.info].content = new;
-        }
-        if ui.needs_redraw() {
-            state.window.request_redraw();
+        if new != *rsc.widgets()[self.info].content {
+            *rsc.widgets_mut()[self.info].content = new;
         }
     }
 }

examples/task.rs

@@ -0,0 +1,30 @@
+use iris::prelude::*;
+use std::time::Duration;
+
+fn main() {
+    DefaultApp::<State>::run();
+}
+
+#[derive(DefaultUiState)]
+struct State {
+    ui_state: DefaultUiState,
+}
+
+impl DefaultAppState for State {
+    fn new(mut ui_state: DefaultUiState, rsc: &mut DefaultRsc<Self>, _: Proxy<Self>) -> Self {
+        let rect = rect(Color::RED).add(rsc);
+        rect.task_on(CursorSense::click(), async move |mut ctx| {
+            tokio::time::sleep(Duration::from_secs(1)).await;
+            ctx.update(move |_, rsc| {
+                let rect = rect(rsc);
+                if rect.color == Color::RED {
+                    rect.color = Color::BLUE;
+                } else {
+                    rect.color = Color::RED;
+                }
+            });
+        })
+        .set_root(rsc, &mut ui_state);
+        Self { ui_state }
+    }
+}

examples/text.rs

@@ -0,0 +1,63 @@
+//! Text sizing: wrapped text reads the width it is offered, fixed text does
+//! not, and both report a height their container lays out around.
+
+use iris::prelude::*;
+
+fn main() {
+    DefaultApp::<State>::run();
+}
+
+#[derive(DefaultUiState)]
+struct State {
+    ui_state: DefaultUiState,
+}
+
+const SAMPLE: &str = "Wrapping shapes one source into as many lines as its container \
+    leaves room for, so the height of a paragraph is an answer rather than a setting, and \
+    the same words in a narrower box come back taller. Resize the window and watch the \
+    text below reflow into a different number of lines while nothing about it changes.";
+
+impl DefaultAppState for State {
+    fn new(mut ui_state: DefaultUiState, rsc: &mut DefaultRsc<Self>, _: Proxy<Self>) -> Self {
+        let panel = || rect(Color::WHITE.darker(0.85));
+
+        let wrapped = wtext(SAMPLE)
+            .size(28)
+            .wrap(true)
+            .text_align(Align::LEFT)
+            .pad(16)
+            .background(panel());
+
+        let aligned = (
+            wtext("left").size(24).text_align(Align::LEFT),
+            wtext("centred").size(24).text_align(Align::CENTER),
+            wtext("right").size(24).text_align(Align::RIGHT),
+        )
+            .span(Dir::DOWN)
+            .gap(8)
+            .pad(16)
+            .background(panel());
+
+        // The same words in half the width, which is a different number of
+        // lines and so a different height. A declared width only holds along
+        // a span's own axis, hence the row.
+        let narrow = (
+            wtext(SAMPLE)
+                .size(20)
+                .wrap(true)
+                .pad(16)
+                .background(panel())
+                .align(Align::TOP)
+                .width(rel(0.5)),
+            rect(Color::WHITE.darker(0.95)),
+        )
+            .span(Dir::RIGHT);
+
+        (wrapped, aligned, narrow)
+            .span(Dir::DOWN)
+            .gap(12)
+            .pad(12)
+            .set_root(rsc, &mut ui_state);
+        Self { ui_state }
+    }
+}

examples/view.rs

@@ -0,0 +1,49 @@
+use iris::prelude::*;
+
+fn main() {
+    DefaultApp::<State>::run();
+}
+
+#[derive(DefaultUiState)]
+struct State {
+    ui_state: DefaultUiState,
+}
+
+type Rsc = DefaultRsc<State>;
+
+#[derive(Clone, Copy, WidgetView)]
+struct Test {
+    #[root]
+    root: WeakWidget<Rect>,
+    cur: WeakState<bool>,
+}
+
+impl Test {
+    pub fn new(rsc: &mut Rsc) -> Self {
+        let root = rect(Color::RED).add(rsc);
+        let cur = rsc.create_state(root, false);
+        Self { root, cur }
+    }
+    pub fn toggle(&self, rsc: &mut Rsc) {
+        let cur = &mut rsc[self.cur];
+        *cur = !*cur;
+        if *cur {
+            rsc[self.root].color = Color::BLUE;
+        } else {
+            rsc[self.root].color = Color::RED;
+        }
+    }
+}
+
+impl DefaultAppState for State {
+    fn new(mut ui_state: DefaultUiState, rsc: &mut DefaultRsc<Self>, _: Proxy<Self>) -> Self {
+        let test = Test::new(rsc);
+
+        test.on(CursorSense::click(), move |_, rsc| {
+            test.toggle(rsc);
+        })
+        .set_root(rsc, &mut ui_state);
+
+        Self { ui_state }
+    }
+}

macro/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "iris-macro"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+proc-macro2 = "1.0.103"
+quote = "1.0.42"
+syn = { version = "2.0.111", features = ["full"] }
+
+[lib]
+proc-macro = true

macro/src/lib.rs

@@ -0,0 +1,196 @@
+extern crate proc_macro;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{
+    Attribute, Block, Error, GenericParam, Generics, Ident, ItemStruct, ItemTrait, Signature,
+    Token, Type, Visibility,
+    parse::{Parse, ParseStream, Result},
+    parse_macro_input, parse_quote,
+    spanned::Spanned,
+};
+
+struct Input {
+    attrs: Vec<Attribute>,
+    vis: Visibility,
+    name: Ident,
+    generics: Generics,
+    fns: Vec<InputFn>,
+}
+
+struct InputFn {
+    sig: Signature,
+    body: Block,
+}
+
+impl Parse for Input {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        let vis = input.parse()?;
+        input.parse::<Token![trait]>()?;
+        let name = input.parse()?;
+        let generics = input.parse::<Generics>()?;
+        input.parse::<Token![;]>()?;
+        let mut fns = Vec::new();
+        while !input.is_empty() {
+            let sig = input.parse()?;
+            let body = input.parse()?;
+            fns.push(InputFn { sig, body })
+        }
+        if !input.is_empty() {
+            input.error("function expected");
+        }
+        Ok(Input {
+            attrs,
+            vis,
+            name,
+            generics,
+            fns,
+        })
+    }
+}
+
+#[proc_macro]
+pub fn widget_trait(input: TokenStream) -> TokenStream {
+    let Input {
+        attrs,
+        vis,
+        name,
+        mut generics,
+        fns,
+    } = parse_macro_input!(input as Input);
+
+    let sigs: Vec<_> = fns.iter().map(|f| f.sig.clone()).collect();
+    let impls: Vec<_> = fns
+        .iter()
+        .map(|InputFn { sig, body }| quote! { #sig #body })
+        .collect();
+
+    let Some(GenericParam::Type(state)) = generics.params.first() else {
+        return Error::new(name.span(), "expected state generic parameter")
+            .into_compile_error()
+            .into();
+    };
+
+    let state = &state.ident;
+
+    generics
+        .params
+        .push(parse_quote!(WL: WidgetLike<#state, Tag>));
+    generics.params.push(parse_quote!(Tag));
+
+    let mut trai: ItemTrait = parse_quote!(
+        #vis trait #name #generics {
+            #(#sigs;)*
+        }
+    );
+
+    trai.attrs = attrs;
+
+    quote! {
+        #trai
+
+        impl #generics #name<Rsc, WL, Tag> for WL {
+            #(#impls)*
+        }
+    }
+    .into()
+}
+
+#[proc_macro_derive(DefaultUiState, attributes(default_ui_state))]
+pub fn derive_default_ui_state(input: TokenStream) -> TokenStream {
+    let mut output = proc_macro2::TokenStream::new();
+
+    let state: ItemStruct = parse_macro_input!(input);
+
+    let mut found_attr = false;
+    let mut state_field = None;
+    for field in &state.fields {
+        if !found_attr
+            && let Type::Path(path) = &field.ty
+            && path.path.is_ident("DefaultUiState")
+        {
+            state_field = Some(field);
+        }
+        let Some(attr) = field
+            .attrs
+            .iter()
+            .find(|a| a.path().is_ident("default_ui_state"))
+        else {
+            continue;
+        };
+        if found_attr {
+            output.extend(
+                Error::new(
+                    attr.span(),
+                    "cannot have more than one default_ui_state attribute",
+                )
+                .into_compile_error(),
+            );
+            continue;
+        }
+        found_attr = true;
+        state_field = Some(field);
+    }
+    let Some(field) = state_field else {
+        output.extend(
+            Error::new(state.ident.span(), "no DefaultUiState field found").into_compile_error(),
+        );
+        return output.into();
+    };
+    let sname = &state.ident;
+    let fname = field.ident.as_ref().unwrap();
+    output.extend(quote! {
+        impl iris::default::HasDefaultUiState for #sname {
+            fn default_state(&self) -> &iris::default::DefaultUiState {
+                &self.#fname
+            }
+            fn default_state_mut(&mut self) -> &mut iris::default::DefaultUiState {
+                &mut self.#fname
+            }
+        }
+    });
+    output.into()
+}
+
+#[proc_macro_derive(WidgetView, attributes(root))]
+pub fn derive_widget_view(input: TokenStream) -> TokenStream {
+    let mut output = proc_macro2::TokenStream::new();
+
+    let state: ItemStruct = parse_macro_input!(input);
+
+    let mut found_attr = false;
+    let mut state_field = None;
+    for field in &state.fields {
+        let Some(attr) = field.attrs.iter().find(|a| a.path().is_ident("root")) else {
+            continue;
+        };
+        if found_attr {
+            output.extend(
+                Error::new(attr.span(), "cannot have more than one root widget")
+                    .into_compile_error(),
+            );
+            continue;
+        }
+        found_attr = true;
+        state_field = Some(field);
+    }
+    let Some(field) = state_field else {
+        output.extend(
+            Error::new(state.ident.span(), "no root widget field found (#[root])")
+                .into_compile_error(),
+        );
+        return output.into();
+    };
+    let sname = &state.ident;
+    let fname = field.ident.as_ref().unwrap();
+    let fty = &field.ty;
+    output.extend(quote! {
+        impl iris::core::WidgetView for #sname {
+            type Widget = <#fty as iris::core::HasWidget>::Widget;
+            fn root(&self) -> #fty {
+                self.#fname
+            }
+        }
+    });
+    output.into()
+}

readme.md

@@ -1,22 +1,25 @@
 # iris
 
-my take on a rust ui library (also my first ui library)
+My experimental attempt at a rust ui library (also my first ui library).
 
-it's called iris because it's the structure around what you actually want to display and colorful
+It's currently designed around using retained data structures (widgets), rather than diffing generated trees from data like xilem or iced. This is an experiment and I'm not sure if it's a good idea or not.
 
-there's a `main.rs` that runs a testing window, so can just `cargo run` to see it working
+Examples are in `examples`, eg. `cargo run --example tabs`.
 
-goals, in general order:
+Goals, in general order:
 1. does what I want it to (text, images, video, animations)
 2. very easy to use ignoring ergonomic ref counting
-3. reasonably fast / efficient (a lot faster than electron, save battery life)
+3. reasonably fast / efficient (a lot faster than electron, save battery life, try to beat iced and xilem)
 
-not targeting web rn cause wanna use actual nice gpu features & entire point of this is to make desktop apps
+## dev details
+
+not targeting web rn cause wanna use actual nice gpu features & entire point of this is to make desktop apps / not need a web browser
 
 general ideas trynna use rn / experiment with:
 - retained mode
-- specifically designed around wgpu
+- specifically designed around wgpu so there's no translation
 - postfix functions for most things to prevent unreadable indentation (going very well)
+- events can be done directly where you draw the widgets
 - almost no macros in user code & actual LSP typechecking (variadic generics if you can hear me please save us)
 - relative anchor + absolute offset coord system (+ "rest" / leftover during widget layout)
 - single threaded ui & pass context around to make non async usage straightforward (pretty unsure about this)
@@ -24,3 +27,5 @@ general ideas trynna use rn / experiment with:
 
 under heavy initial development so not gonna try to explain status, maybe check TODO for that;
 sizable chance it gets a rewrite once I know everything I need and what seems to work best
+
+it's called iris because it's the structure around what you actually want to display and colorful

rig-input/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "rig-input"
+version.workspace = true
+edition.workspace = true
+
+# Replays `.touch` recordings through Wayland's virtual-pointer protocol;
+# headless sway has no input devices for coordinate-driving tools to move.
+[[bin]]
+name = "replay-touch"
+path = "src/main.rs"
+
+[dependencies]
+# Share the harness parser so both ways of replaying read a file the same.
+iris = { path = ".." }
+wayland-client = { workspace = true }
+wayland-protocols-wlr = { workspace = true }

rig-input/src/main.rs

@@ -0,0 +1,141 @@
+use iris::harness::{TouchAction, TouchScript};
+use std::time::Duration;
+use wayland_client::protocol::wl_pointer::ButtonState;
+use wayland_client::protocol::{wl_registry, wl_seat};
+use wayland_client::{Connection, Dispatch, QueueHandle, delegate_noop};
+use wayland_protocols_wlr::virtual_pointer::v1::client::{
+    zwlr_virtual_pointer_manager_v1::ZwlrVirtualPointerManagerV1,
+    zwlr_virtual_pointer_v1::ZwlrVirtualPointerV1,
+};
+
+const BTN_LEFT: u32 = 0x110;
+
+const SETTLE: Duration = Duration::from_millis(200);
+
+#[derive(Default)]
+struct Globals {
+    seat: Option<wl_seat::WlSeat>,
+    manager: Option<ZwlrVirtualPointerManagerV1>,
+}
+
+impl Dispatch<wl_registry::WlRegistry, ()> for Globals {
+    fn event(
+        state: &mut Self,
+        registry: &wl_registry::WlRegistry,
+        event: wl_registry::Event,
+        _: &(),
+        _: &Connection,
+        qh: &QueueHandle<Self>,
+    ) {
+        let wl_registry::Event::Global {
+            name,
+            interface,
+            version,
+        } = event
+        else {
+            return;
+        };
+        match interface.as_str() {
+            "wl_seat" => {
+                state.seat = Some(registry.bind(name, version.min(7), qh, ()));
+            }
+            "zwlr_virtual_pointer_manager_v1" => {
+                state.manager = Some(registry.bind(name, version.min(2), qh, ()));
+            }
+            _ => {}
+        }
+    }
+}
+
+delegate_noop!(Globals: ignore wl_seat::WlSeat);
+delegate_noop!(Globals: ZwlrVirtualPointerManagerV1);
+delegate_noop!(Globals: ZwlrVirtualPointerV1);
+
+fn main() {
+    let args: Vec<String> = std::env::args().skip(1).collect();
+    let [width, height, path] = args.as_slice() else {
+        eprintln!("usage: replay-touch WIDTH HEIGHT FILE");
+        std::process::exit(2);
+    };
+    let (width, height) = (parse(width, "WIDTH"), parse(height, "HEIGHT"));
+    let text = std::fs::read_to_string(path)
+        .unwrap_or_else(|e| fail(&format!("could not read {path}: {e}")));
+    let script = TouchScript::parse(&text).unwrap_or_else(|e| fail(&e));
+
+    let conn = Connection::connect_to_env().unwrap_or_else(|e| {
+        fail(&format!(
+            "no wayland display ({e}); is WAYLAND_DISPLAY set?"
+        ))
+    });
+    let mut queue = conn.new_event_queue();
+    let qh = queue.handle();
+    let display = conn.display();
+    display.get_registry(&qh, ());
+    let mut globals = Globals::default();
+    queue
+        .roundtrip(&mut globals)
+        .unwrap_or_else(|e| fail(&format!("wayland roundtrip failed: {e}")));
+
+    let manager = globals.manager.as_ref().unwrap_or_else(|| {
+        fail(
+            "this compositor does not offer zwlr_virtual_pointer_manager_v1, so a pointer cannot \
+             be synthesised; sway and every wlroots compositor do",
+        )
+    });
+    let pointer = manager.create_virtual_pointer(globals.seat.as_ref(), &qh, ());
+
+    // Put the pointer where the gesture starts and let the compositor
+    // settle before anything is pressed. Without this the press is
+    // dropped: sway has just learned about this pointer, and a button
+    // sent in the same breath as the motion that first puts it over a
+    // window arrives before there is a focused surface to send it to --
+    // winit sees `CursorEntered`, the moves and the *release*, never the
+    // press, so the gesture reads as a hover and nothing scrolls. Found
+    // by printing winit's own events; the settle is what fixed it.
+    if let Some(first) = script.samples.first() {
+        pointer.motion_absolute(0, first.pos.x as u32, first.pos.y as u32, width, height);
+        pointer.frame();
+        conn.flush()
+            .unwrap_or_else(|e| fail(&format!("flush: {e}")));
+        std::thread::sleep(SETTLE);
+    }
+
+    let mut previous = 0;
+    for sample in &script.samples {
+        std::thread::sleep(Duration::from_millis(sample.t_ms - previous));
+        previous = sample.t_ms;
+        let t = sample.t_ms as u32;
+        pointer.motion_absolute(t, sample.pos.x as u32, sample.pos.y as u32, width, height);
+        pointer.frame();
+        // The button goes in a frame of its own, *after* the motion has
+        // been committed. Sent in the same frame as the motion that
+        // first puts the pointer over the window, sway drops it: the
+        // client sees `CursorEntered` and the moves but never a
+        // `MouseInput { state: Pressed }`, so the whole gesture reads as
+        // a hover and nothing scrolls. Found exactly that way, by
+        // printing winit's events.
+        let state = match sample.action {
+            TouchAction::Down => Some(ButtonState::Pressed),
+            TouchAction::Up => Some(ButtonState::Released),
+            TouchAction::Move => None,
+        };
+        if let Some(state) = state {
+            pointer.button(t, BTN_LEFT, state);
+            pointer.frame();
+        }
+        conn.flush()
+            .unwrap_or_else(|e| fail(&format!("flush: {e}")));
+    }
+    pointer.destroy();
+    conn.flush().ok();
+}
+
+fn parse(text: &str, what: &str) -> u32 {
+    text.parse()
+        .unwrap_or_else(|_| fail(&format!("{what} is not a whole number: {text:?}")))
+}
+
+fn fail(message: &str) -> ! {
+    eprintln!("replay-touch: {message}");
+    std::process::exit(1);
+}

rust-toolchain.toml

@@ -0,0 +1,3 @@
+[toolchain]
+channel = "nightly"
+components = ["clippy", "rustfmt"]

scripts/headless.conf

@@ -0,0 +1,14 @@
+# The compositor `scripts/run-headless.sh` starts, so that an example has a
+# surface where there is no display. Nothing here is meant to be looked at
+# directly; `grim` is.
+#
+# No Xwayland: winit talks Wayland natively, so an X server is a second thing
+# to go wrong for no gain.
+xwayland disable
+
+# The default output, overridden per run by `--mode`. Larger than the window
+# an example opens, so nothing is scaled or clipped.
+output HEADLESS-1 mode 1920x1200@60Hz
+
+default_border none
+focus_follows_mouse no

scripts/run-headless.sh

@@ -0,0 +1,170 @@
+#!/bin/sh
+# Run an iris example on a machine with no display.
+#
+#   ./scripts/run-headless.sh tabs
+#   ./scripts/run-headless.sh tabs --shot /tmp/tabs.png --seconds 4
+#   ./scripts/run-headless.sh tabs --replay taps.touch --shot /tmp/tabs.png
+#   ./scripts/run-headless.sh app --dir ../elsewhere --mode 1080x2424@120Hz
+#
+# `--dir DIR` names the workspace to build in, defaulting to this one, so a
+# project that depends on iris can be run through the same rig. `--bin` runs a
+# crate binary rather than an example, and takes its own argv from
+# `$RUN_HEADLESS_ARGS`, word-split on purpose.
+#
+# `--mode` sets the output, for running something at a size other than a
+# desktop's -- a phone's, say. Set every run rather than only when it changes:
+# the compositor is reused between runs, so a default-shaped run after a
+# custom one would otherwise inherit the other's output and quietly screenshot
+# the wrong size.
+#
+# `--replay FILE` drives a `.touch` recording into the window through
+# `replay-touch`, which reads it with the same parser `iris::harness` uses. A
+# recording is `<ms> down|move|up <x> <y>` in the output's own pixels. With
+# `--shot` it also writes `<shot>-before.png` from just before the gesture,
+# since "it moved" is a claim about two pictures.
+#
+# What it supplies is a compositor for winit to open a surface on: a headless
+# sway, and `grim` to screenshot it. Sway gets its own socket and runtime
+# directory rather than joining whatever else is running, because it tiles --
+# adding a window to someone else's compositor resizes theirs.
+set -eu
+
+need() {
+    command -v "$1" >/dev/null 2>&1 || {
+        echo "run-headless: $1 is not installed ($2)" >&2
+        exit 127
+    }
+}
+need sway "the compositor an example opens its window on"
+need swaymsg "sway's control socket"
+
+scripts=$(cd "$(dirname "$0")" && pwd)
+root=$(cd "$scripts/.." && pwd)
+workdir="$root"
+cd "$root"
+run="${XDG_RUNTIME_DIR:-/tmp}/iris-headless"
+seconds=3
+shot=""
+replay=""
+example=""
+kind=example
+mode=1920x1200@60Hz
+
+
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --shot) shot=$2; shift 2 ;;
+        --seconds) seconds=$2; shift 2 ;;
+        --bin) kind=bin; shift ;;
+        --mode) mode=$2; shift 2 ;;
+        --replay) replay=$2; shift 2 ;;
+        --dir) workdir=$(cd "$2" && pwd); shift 2 ;;
+        --) shift; break ;;
+        *) example=$1; shift ;;
+    esac
+done
+[ -n "$example" ] || { echo "usage: $0 NAME [--bin] [--dir DIR] [--mode WxH@Hz] [--replay TOUCH] [--shot PNG] [--seconds N] [-- cargo args]" >&2; exit 2; }
+[ -z "$replay" ] || [ -f "$replay" ] || { echo "run-headless: no touch script at $replay" >&2; exit 2; }
+[ -z "$shot" ] || need grim "the screenshot --shot writes"
+
+mkdir -p "$run"
+export SWAYSOCK="$run/sway.sock"
+
+# Named rather than left to sway's pid-based default, so a second run reuses
+# this compositor instead of starting another beside it.
+if ! swaymsg -t get_version >/dev/null 2>&1; then
+    rm -f "$SWAYSOCK"
+    WLR_BACKENDS=headless WLR_LIBINPUT_NO_DEVICES=1 LIBSEAT_BACKEND=noop \
+        setsid sway -c "$scripts/headless.conf" >"$run/sway.log" 2>&1 &
+    i=0
+    while [ $i -lt 20 ]; do
+        swaymsg -t get_version >/dev/null 2>&1 && break
+        i=$((i + 1)); sleep 0.5
+    done
+    swaymsg -t get_version >/dev/null 2>&1 || {
+        echo "run-headless: compositor did not start; see $run/sway.log" >&2
+        exit 1
+    }
+fi
+
+rm -f "$run/display"
+swaymsg exec -- "sh -c 'printf %s \"\$WAYLAND_DISPLAY\" > $run/display'" >/dev/null
+i=0
+while [ $i -lt 20 ]; do
+    [ -s "$run/display" ] && break
+    i=$((i + 1)); sleep 0.5
+done
+[ -s "$run/display" ] || { echo "run-headless: could not read WAYLAND_DISPLAY" >&2; exit 1; }
+WAYLAND_DISPLAY=$(cat "$run/display")
+export WAYLAND_DISPLAY
+
+echo "run-headless: $WAYLAND_DISPLAY (sway $(swaymsg -t get_version --raw | sed -n 's/.*"human_readable":"\([^"]*\)".*/\1/p'))" >&2
+
+swaymsg output HEADLESS-1 mode "$mode" >/dev/null
+# The extent `replay-touch` positions against, so a script's coordinates
+# are the output's own pixels.
+out_w=${mode%x*}
+out_h=${mode#*x}; out_h=${out_h%@*}
+
+# Built before the app starts, so a compile error is not reported as a
+# window that failed to move.
+[ -z "$replay" ] || (cd "$root" && cargo build --bin replay-touch -p rig-input) >&2
+
+cd "$workdir"
+if [ "$kind" = bin ]; then
+    cargo build --bin "$example" "$@" >&2
+    bin="$workdir/target/debug/$example"
+else
+    cargo build --example "$example" "$@" >&2
+    bin="$workdir/target/debug/examples/$example"
+fi
+
+# Deliberately word-split: this is the binary's own argv, not a single path.
+# shellcheck disable=SC2086
+"$bin" ${RUN_HEADLESS_ARGS:-} >"$run/$example.log" 2>&1 &
+pid=$!
+trap 'kill "$pid" 2>/dev/null || true' EXIT INT TERM
+
+# Wait for the window to be mapped rather than for a number of seconds. A
+# fixed sleep took an all-black screenshot the first time this ran, when sway
+# had started in the same invocation and had not composited its output yet --
+# which is indistinguishable from an app that draws nothing.
+i=0
+while [ $i -lt 40 ]; do
+    kill -0 "$pid" 2>/dev/null || break
+    swaymsg -t get_tree --raw 2>/dev/null | grep -q "\"pid\":$pid," && break
+    i=$((i + 1)); sleep 0.25
+done
+
+i=0
+while [ $i -lt "$((seconds * 2))" ]; do
+    kill -0 "$pid" 2>/dev/null || break
+    i=$((i + 1)); sleep 0.5
+done
+
+if [ -n "$replay" ] && kill -0 "$pid" 2>/dev/null; then
+    if [ -n "$shot" ]; then
+        grim "${shot%.png}-before.png"
+        echo "run-headless: wrote ${shot%.png}-before.png (before the gesture)" >&2
+    fi
+    "$root/target/debug/replay-touch" "$out_w" "$out_h" "$replay"
+    # A fling outlives the finger: the gesture's own last sample is not
+    # when the list stops. Long enough for Android's spline to settle
+    # (`FlingCalculator::duration` tops out around a second and a half).
+    sleep 2
+fi
+
+if kill -0 "$pid" 2>/dev/null; then
+    [ -n "$shot" ] && grim "$shot" && echo "run-headless: wrote $shot" >&2
+    kill "$pid" 2>/dev/null || true
+    wait "$pid" 2>/dev/null || true
+    status=0
+else
+    wait "$pid" 2>/dev/null || status=$?
+    echo "run-headless: $example exited early (status ${status:-0})" >&2
+    status=${status:-1}
+fi
+
+echo "--- $example output ---" >&2
+cat "$run/$example.log" >&2
+exit "$status"

src/core/mask.rs

@@ -1,20 +0,0 @@
-use crate::prelude::*;
-
-pub struct Masked {
-    pub inner: WidgetId,
-}
-
-impl Widget for Masked {
-    fn draw(&mut self, painter: &mut Painter) {
-        painter.set_mask(painter.region());
-        painter.widget(&self.inner);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.width(&self.inner)
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.height(&self.inner)
-    }
-}

src/core/position/align.rs

@@ -1,35 +0,0 @@
-use crate::prelude::*;
-
-pub struct Aligned {
-    pub inner: WidgetId,
-    pub align: Align,
-}
-
-impl Widget for Aligned {
-    fn draw(&mut self, painter: &mut Painter) {
-        let region = match self.align.tuple() {
-            (Some(x), Some(y)) => painter
-                .size(&self.inner)
-                .to_uivec2()
-                .align(RegionAlign { x, y }),
-            (Some(x), None) => {
-                let x = painter.size_ctx().width(&self.inner).apply_rest().align(x);
-                UiRegion::new(x, UiSpan::FULL)
-            }
-            (None, Some(y)) => {
-                let y = painter.size_ctx().height(&self.inner).apply_rest().align(y);
-                UiRegion::new(UiSpan::FULL, y)
-            }
-            (None, None) => UiRegion::FULL,
-        };
-        painter.widget_within(&self.inner, region);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.width(&self.inner)
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.height(&self.inner)
-    }
-}

src/core/position/layer.rs

@@ -1,23 +0,0 @@
-use crate::prelude::*;
-
-pub struct LayerOffset {
-    pub inner: WidgetId,
-    pub offset: usize,
-}
-
-impl Widget for LayerOffset {
-    fn draw(&mut self, painter: &mut Painter) {
-        for _ in 0..self.offset {
-            painter.next_layer();
-        }
-        painter.widget(&self.inner);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.width(&self.inner)
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.height(&self.inner)
-    }
-}

src/core/position/max_size.rs

@@ -1,48 +0,0 @@
-use crate::prelude::*;
-
-pub struct MaxSize {
-    pub inner: WidgetId,
-    pub x: Option<Len>,
-    pub y: Option<Len>,
-}
-
-impl MaxSize {
-    fn apply_to_outer(&self, ctx: &mut SizeCtx) {
-        if let Some(x) = self.x {
-            ctx.outer.x.select_len(x.apply_rest());
-        }
-        if let Some(y) = self.y {
-            ctx.outer.y.select_len(y.apply_rest());
-        }
-    }
-}
-
-impl Widget for MaxSize {
-    fn draw(&mut self, painter: &mut Painter) {
-        painter.widget(&self.inner);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.apply_to_outer(ctx);
-        let width = ctx.width(&self.inner);
-        if let Some(x) = self.x {
-            let width_px = width.apply_rest().to_abs(ctx.output_size().x);
-            let x_px = x.apply_rest().to_abs(ctx.output_size().x);
-            if width_px > x_px { x } else { width }
-        } else {
-            width
-        }
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.apply_to_outer(ctx);
-        let height = ctx.height(&self.inner);
-        if let Some(y) = self.y {
-            let height_px = height.apply_rest().to_abs(ctx.output_size().y);
-            let y_px = y.apply_rest().to_abs(ctx.output_size().y);
-            if height_px > y_px { y } else { height }
-        } else {
-            height
-        }
-    }
-}

src/core/position/offset.rs

@@ -1,21 +0,0 @@
-use crate::prelude::*;
-
-pub struct Offset {
-    pub inner: WidgetId,
-    pub amt: UiVec2,
-}
-
-impl Widget for Offset {
-    fn draw(&mut self, painter: &mut Painter) {
-        let region = UiRegion::FULL.offset(self.amt);
-        painter.widget_within(&self.inner, region);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.width(&self.inner)
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        ctx.height(&self.inner)
-    }
-}

src/core/position/sized.rs

@@ -1,34 +0,0 @@
-use crate::prelude::*;
-
-pub struct Sized {
-    pub inner: WidgetId,
-    pub x: Option<Len>,
-    pub y: Option<Len>,
-}
-
-impl Sized {
-    fn apply_to_outer(&self, ctx: &mut SizeCtx) {
-        if let Some(x) = self.x {
-            ctx.outer.x.select_len(x.apply_rest());
-        }
-        if let Some(y) = self.y {
-            ctx.outer.y.select_len(y.apply_rest());
-        }
-    }
-}
-
-impl Widget for Sized {
-    fn draw(&mut self, painter: &mut Painter) {
-        painter.widget(&self.inner);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.apply_to_outer(ctx);
-        self.x.unwrap_or_else(|| ctx.width(&self.inner))
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.apply_to_outer(ctx);
-        self.y.unwrap_or_else(|| ctx.height(&self.inner))
-    }
-}

src/core/position/span.rs

@@ -1,196 +0,0 @@
-use crate::prelude::*;
-use std::marker::PhantomData;
-
-pub struct Span {
-    pub children: Vec<WidgetId>,
-    pub dir: Dir,
-    pub gap: f32,
-}
-
-impl Widget for Span {
-    fn draw(&mut self, painter: &mut Painter) {
-        let total = self.len_sum(&mut painter.size_ctx());
-        let mut start = UiScalar::rel_min();
-        for child in &self.children {
-            let mut span = UiSpan::FULL;
-            span.start = start;
-            let len = painter.len_axis(child, self.dir.axis);
-            if len.rest > 0.0 {
-                let offset = UiScalar::new(total.rel, total.abs);
-                let rel_end = UiScalar::rel(len.rest / total.rest);
-                let end = (UiScalar::rel_max() + start) - offset;
-                start = rel_end.within(&start.to(end));
-            }
-            start.abs += len.abs;
-            start.rel += len.rel;
-            span.end = start;
-            let mut child_region = UiRegion::from_axis(self.dir.axis, span, UiSpan::FULL);
-            if self.dir.sign == Sign::Neg {
-                child_region.flip(self.dir.axis);
-            }
-            painter.widget_within(child, child_region);
-            start.abs += self.gap;
-        }
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        match self.dir.axis {
-            Axis::X => self.desired_len(ctx),
-            Axis::Y => self.desired_ortho(ctx),
-        }
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        match self.dir.axis {
-            Axis::X => self.desired_ortho(ctx),
-            Axis::Y => self.desired_len(ctx),
-        }
-    }
-}
-
-impl Span {
-    pub fn empty(dir: Dir) -> Self {
-        Self {
-            children: Vec::new(),
-            dir,
-            gap: 0.0,
-        }
-    }
-
-    pub fn gap(mut self, gap: impl UiNum) -> Self {
-        self.gap = gap.to_f32();
-        self
-    }
-
-    fn len_sum(&mut self, ctx: &mut SizeCtx) -> Len {
-        let gap = self.gap * self.children.len().saturating_sub(1) as f32;
-        self.children.iter().fold(Len::abs(gap), |mut s, id| {
-            // it's tempting to subtract the abs & rel from the ctx outer,
-            // but that would create inconsistent sizing if you put
-            // a rest first vs last & only speed up in one direction.
-            // I think this is only solvable by restricting how you can
-            // compute size, bc currently you need child to define parent's
-            // sectioning and you need parent's sectioning to define child.
-            // Fortunately, that doesn't matter in most cases
-            let len = ctx.len_axis(id, self.dir.axis);
-            s += len;
-            s
-        })
-    }
-
-    fn desired_len(&mut self, ctx: &mut SizeCtx) -> Len {
-        let len = self.len_sum(ctx);
-        if len.rest == 0.0 && len.rel == 0.0 {
-            len
-        } else {
-            Len::default()
-        }
-    }
-
-    fn desired_ortho(&mut self, ctx: &mut SizeCtx) -> Len {
-        // this is a weird hack to get text wrapping to work properly when in a downward span
-        // the correct solution here is to add a function to widget that lets them
-        // request that ctx.outer has an axis "resolved" before checking the other,
-        // and panicking or warning if two request opposite axis (unsolvable in that case)
-        let outer = ctx.outer.axis(self.dir.axis);
-        if self.dir.axis == Axis::X {
-            // so....... this literally copies draw so that the lengths are correctly set in the
-            // context, which makes this slow and not cool
-            let total = self.len_sum(ctx);
-            let mut start = UiScalar::rel_min();
-            let mut ortho_len = Len::ZERO;
-            for child in &self.children {
-                let mut span = UiSpan::FULL;
-                span.start = start;
-                let len = ctx.len_axis(child, self.dir.axis);
-                if len.rest > 0.0 {
-                    let offset = UiScalar::new(total.rel, total.abs);
-                    let rel_end = UiScalar::rel(len.rest / total.rest);
-                    let end = (UiScalar::rel_max() + start) - offset;
-                    start = rel_end.within(&start.to(end));
-                }
-                start.abs += len.abs;
-                start.rel += len.rel;
-                span.end = start;
-
-                let scalar = span.len();
-                *ctx.outer.axis_mut(self.dir.axis) = outer.select_len(scalar);
-                let ortho = ctx.len_axis(child, !self.dir.axis);
-                // TODO: rel shouldn't do this, but no easy way before actually calculating pixels
-                if ortho.rel > 0.0 || ortho.rest > 0.0 {
-                    ortho_len.rest = 1.0;
-                    ortho_len.abs = 0.0;
-                    break;
-                }
-                ortho_len.abs = ortho_len.abs.max(ortho.abs);
-                start.abs += self.gap;
-            }
-            ortho_len
-        } else {
-            let mut ortho_len = Len::ZERO;
-            let ortho = !self.dir.axis;
-            for child in &self.children {
-                let len = ctx.len_axis(child, ortho);
-                // TODO: rel shouldn't do this, but no easy way before actually calculating pixels
-                if len.rel > 0.0 || len.rest > 0.0 {
-                    ortho_len.rest = 1.0;
-                    ortho_len.abs = 0.0;
-                    break;
-                }
-                ortho_len.abs = ortho_len.abs.max(len.abs);
-            }
-            ortho_len
-        }
-    }
-}
-
-pub struct SpanBuilder<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> {
-    pub children: Wa,
-    pub dir: Dir,
-    pub gap: f32,
-    _pd: PhantomData<Tag>,
-}
-
-impl<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> FnOnce<(&mut Ui,)>
-    for SpanBuilder<LEN, Wa, Tag>
-{
-    type Output = Span;
-
-    extern "rust-call" fn call_once(self, args: (&mut Ui,)) -> Self::Output {
-        Span {
-            children: self.children.ui(args.0).arr.to_vec(),
-            dir: self.dir,
-            gap: self.gap,
-        }
-    }
-}
-
-impl<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> SpanBuilder<LEN, Wa, Tag> {
-    pub fn new(children: Wa, dir: Dir) -> Self {
-        Self {
-            children,
-            dir,
-            gap: 0.0,
-            _pd: PhantomData,
-        }
-    }
-
-    pub fn gap(mut self, gap: impl UiNum) -> Self {
-        self.gap = gap.to_f32();
-        self
-    }
-}
-
-impl std::ops::Deref for Span {
-    type Target = Vec<WidgetId>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.children
-    }
-}
-
-impl std::ops::DerefMut for Span {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.children
-    }
-}

src/core/position/stack.rs

@@ -1,77 +0,0 @@
-use std::marker::PhantomData;
-
-use crate::prelude::*;
-
-pub struct Stack {
-    pub children: Vec<WidgetId>,
-    pub size: StackSize,
-}
-
-impl Widget for Stack {
-    fn draw(&mut self, painter: &mut Painter) {
-        let mut iter = self.children.iter();
-        if let Some(child) = iter.next() {
-            painter.child_layer();
-            painter.widget(child);
-        }
-        for child in iter {
-            painter.next_layer();
-            painter.widget(child);
-        }
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        match self.size {
-            StackSize::Default => Len::default(),
-            StackSize::Child(i) => ctx.width(&self.children[i]),
-        }
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        match self.size {
-            StackSize::Default => Len::default(),
-            StackSize::Child(i) => ctx.height(&self.children[i]),
-        }
-    }
-}
-
-#[derive(Default, Debug)]
-pub enum StackSize {
-    #[default]
-    Default,
-    Child(usize),
-}
-
-pub struct StackBuilder<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> {
-    pub children: Wa,
-    pub size: StackSize,
-    _pd: PhantomData<Tag>,
-}
-
-impl<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> FnOnce<(&mut Ui,)>
-    for StackBuilder<LEN, Wa, Tag>
-{
-    type Output = Stack;
-
-    extern "rust-call" fn call_once(self, args: (&mut Ui,)) -> Self::Output {
-        Stack {
-            children: self.children.ui(args.0).arr.to_vec(),
-            size: self.size,
-        }
-    }
-}
-
-impl<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> StackBuilder<LEN, Wa, Tag> {
-    pub fn new(children: Wa) -> Self {
-        Self {
-            children,
-            size: StackSize::default(),
-            _pd: PhantomData,
-        }
-    }
-
-    pub fn size(mut self, size: StackSize) -> Self {
-        self.size = size;
-        self
-    }
-}

src/core/ptr.rs

@@ -1,30 +0,0 @@
-use crate::prelude::*;
-
-#[derive(Default)]
-pub struct WidgetPtr {
-    pub inner: Option<WidgetId>,
-}
-
-impl Widget for WidgetPtr {
-    fn draw(&mut self, painter: &mut Painter) {
-        if let Some(id) = &self.inner {
-            painter.widget(id);
-        }
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        if let Some(id) = &self.inner {
-            ctx.width(id)
-        } else {
-            Len::ZERO
-        }
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        if let Some(id) = &self.inner {
-            ctx.height(id)
-        } else {
-            Len::ZERO
-        }
-    }
-}

src/core/sense.rs

@@ -1,395 +0,0 @@
-use crate::prelude::*;
-
-use std::{
-    ops::{BitOr, Deref, DerefMut},
-    rc::Rc,
-};
-
-use crate::{
-    layout::{UiModule, UiRegion, Vec2},
-    util::{HashMap, Id},
-};
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum Button {
-    Left,
-    Right,
-    Middle,
-}
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum CursorSense {
-    PressStart(Button),
-    Pressing(Button),
-    PressEnd(Button),
-    HoverStart,
-    Hovering,
-    HoverEnd,
-    Scroll,
-}
-
-pub struct CursorSenses(Vec<CursorSense>);
-
-impl CursorSense {
-    pub fn click() -> Self {
-        Self::PressStart(Button::Left)
-    }
-    pub fn click_or_drag() -> CursorSenses {
-        Self::click() | Self::Pressing(Button::Left)
-    }
-    pub fn unclick() -> Self {
-        Self::PressEnd(Button::Left)
-    }
-    pub fn is_dragging(&self) -> bool {
-        matches!(self, CursorSense::Pressing(Button::Left))
-    }
-}
-
-#[derive(Default, Clone)]
-pub struct CursorState {
-    pub pos: Vec2,
-    pub exists: bool,
-    pub buttons: CursorButtons,
-    pub scroll_delta: Vec2,
-}
-
-#[derive(Default, Clone)]
-pub struct CursorButtons {
-    pub left: ActivationState,
-    pub middle: ActivationState,
-    pub right: ActivationState,
-}
-
-impl CursorButtons {
-    pub fn select(&self, button: &Button) -> &ActivationState {
-        match button {
-            Button::Left => &self.left,
-            Button::Right => &self.right,
-            Button::Middle => &self.middle,
-        }
-    }
-
-    pub fn end_frame(&mut self) {
-        self.left.end_frame();
-        self.middle.end_frame();
-        self.right.end_frame();
-    }
-}
-
-impl CursorState {
-    pub fn end_frame(&mut self) {
-        self.buttons.end_frame();
-        self.scroll_delta = Vec2::ZERO;
-    }
-}
-
-#[derive(Debug, Clone, Copy, Default, PartialEq)]
-pub enum ActivationState {
-    Start,
-    On,
-    End,
-    #[default]
-    Off,
-}
-
-/// this and other similar stuff has a generic
-/// because I kind of want to make CursorModule generic
-/// or basically have some way to have custom senses
-/// that depend on active widget positions
-/// but I'm not sure how or if worth it
-pub struct Sensor<Ctx, Data> {
-    pub senses: CursorSenses,
-    pub f: Rc<dyn EventFn<Ctx, Data>>,
-}
-
-pub type SensorMap<Ctx, Data> = HashMap<Id, SensorGroup<Ctx, Data>>;
-pub type SenseShape = UiRegion;
-pub struct SensorGroup<Ctx, Data> {
-    pub hover: ActivationState,
-    pub sensors: Vec<Sensor<Ctx, Data>>,
-}
-
-#[derive(Clone)]
-pub struct CursorData {
-    pub cursor: Vec2,
-    pub size: Vec2,
-    pub scroll_delta: Vec2,
-    /// the (first) sense that triggered this event
-    /// the senses are checked in order
-    pub sense: CursorSense,
-}
-
-pub struct CursorModule<Ctx> {
-    map: SensorMap<Ctx, CursorData>,
-    active: HashMap<usize, HashMap<Id, SenseShape>>,
-}
-
-impl<Ctx: 'static> UiModule for CursorModule<Ctx> {
-    fn on_draw(&mut self, inst: &WidgetInstance) {
-        if self.map.contains_key(&inst.id) {
-            self.active
-                .entry(inst.layer)
-                .or_default()
-                .insert(inst.id, inst.region);
-        }
-    }
-
-    fn on_undraw(&mut self, inst: &WidgetInstance) {
-        if let Some(layer) = self.active.get_mut(&inst.layer) {
-            layer.remove(&inst.id);
-        }
-    }
-
-    fn on_remove(&mut self, id: &Id) {
-        self.map.remove(id);
-        for layer in self.active.values_mut() {
-            layer.remove(id);
-        }
-    }
-
-    fn on_move(&mut self, inst: &WidgetInstance) {
-        if let Some(map) = self.active.get_mut(&inst.layer)
-            && let Some(region) = map.get_mut(&inst.id)
-        {
-            *region = inst.region;
-        }
-    }
-}
-
-impl<Ctx> CursorModule<Ctx> {
-    pub fn merge(&mut self, other: Self) {
-        for (id, group) in other.map {
-            for sensor in group.sensors {
-                self.map.entry(id).or_default().sensors.push(sensor);
-            }
-        }
-    }
-}
-
-impl Ui {
-    pub fn run_sensors<Ctx: 'static>(
-        &mut self,
-        ctx: &mut Ctx,
-        cursor: &CursorState,
-        window_size: Vec2,
-    ) {
-        CursorModule::<Ctx>::run(self, ctx, cursor, window_size);
-    }
-}
-
-impl<Ctx: 'static> CursorModule<Ctx> {
-    pub fn run(ui: &mut Ui, ctx: &mut Ctx, cursor: &CursorState, window_size: Vec2) {
-        let layers = std::mem::take(&mut ui.data.layers);
-        let mut module = std::mem::take(ui.data.modules.get_mut::<Self>());
-
-        for i in layers.indices().rev() {
-            let Some(list) = module.active.get_mut(&i) else {
-                continue;
-            };
-            let mut sensed = false;
-            for (id, shape) in list.iter() {
-                let group = module.map.get_mut(id).unwrap();
-                let region = shape.to_px(window_size);
-                let in_shape = cursor.exists && region.contains(cursor.pos);
-                group.hover.update(in_shape);
-                if group.hover == ActivationState::Off {
-                    continue;
-                }
-                sensed = true;
-
-                for sensor in &mut group.sensors {
-                    if let Some(sense) = should_run(&sensor.senses, cursor, group.hover) {
-                        let data = CursorData {
-                            cursor: cursor.pos - region.top_left,
-                            size: region.bot_right - region.top_left,
-                            scroll_delta: cursor.scroll_delta,
-                            sense,
-                        };
-                        (sensor.f)(EventCtx { ui, state: ctx, data });
-                    }
-                }
-            }
-            if sensed {
-                break;
-            }
-        }
-
-        let ui_mod = ui.data.modules.get_mut::<Self>();
-        std::mem::swap(ui_mod, &mut module);
-        ui_mod.merge(module);
-        ui.data.layers = layers;
-    }
-}
-
-pub fn should_run(
-    senses: &CursorSenses,
-    cursor: &CursorState,
-    hover: ActivationState,
-) -> Option<CursorSense> {
-    for sense in senses.iter() {
-        if match sense {
-            CursorSense::PressStart(button) => cursor.buttons.select(button).is_start(),
-            CursorSense::Pressing(button) => cursor.buttons.select(button).is_on(),
-            CursorSense::PressEnd(button) => cursor.buttons.select(button).is_end(),
-            CursorSense::HoverStart => hover.is_start(),
-            CursorSense::Hovering => hover.is_on(),
-            CursorSense::HoverEnd => hover.is_end(),
-            CursorSense::Scroll => cursor.scroll_delta != Vec2::ZERO,
-        } {
-            return Some(*sense);
-        }
-    }
-    None
-}
-
-impl ActivationState {
-    pub fn is_start(&self) -> bool {
-        *self == Self::Start
-    }
-    pub fn is_on(&self) -> bool {
-        *self == Self::Start || *self == Self::On
-    }
-    pub fn is_end(&self) -> bool {
-        *self == Self::End
-    }
-    pub fn is_off(&self) -> bool {
-        *self == Self::End || *self == Self::Off
-    }
-    pub fn update(&mut self, on: bool) {
-        *self = match *self {
-            Self::Start => match on {
-                true => Self::On,
-                false => Self::End,
-            },
-            Self::On => match on {
-                true => Self::On,
-                false => Self::End,
-            },
-            Self::End => match on {
-                true => Self::Start,
-                false => Self::Off,
-            },
-            Self::Off => match on {
-                true => Self::Start,
-                false => Self::Off,
-            },
-        }
-    }
-
-    pub fn end_frame(&mut self) {
-        match self {
-            Self::Start => *self = Self::On,
-            Self::End => *self = Self::Off,
-            _ => (),
-        }
-    }
-}
-
-impl Event for CursorSenses {
-    type Module<Ctx: 'static> = CursorModule<Ctx>;
-    type Data = CursorData;
-}
-
-impl Event for CursorSense {
-    type Module<Ctx: 'static> = CursorModule<Ctx>;
-    type Data = CursorData;
-}
-
-impl<E: Event<Data = <CursorSenses as Event>::Data> + Into<CursorSenses>, Ctx: 'static>
-    EventModule<E, Ctx> for CursorModule<Ctx>
-{
-    fn register(&mut self, id: Id, senses: E, f: impl EventFn<Ctx, <E as Event>::Data>) {
-        // TODO: does not add to active if currently active
-        self.map.entry(id).or_default().sensors.push(Sensor {
-            senses: senses.into(),
-            f: Rc::new(f),
-        });
-    }
-
-    fn run<'a>(
-        &self,
-        id: &Id,
-        event: E,
-    ) -> Option<impl Fn(EventCtx<Ctx, <E as Event>::Data>) + use<'a, E, Ctx>> {
-        let senses = event.into();
-        if let Some(group) = self.map.get(id) {
-            let fs: Vec<_> = group
-                .sensors
-                .iter()
-                .filter_map(|sensor| {
-                    if sensor.senses.iter().any(|s| senses.contains(s)) {
-                        Some(sensor.f.clone())
-                    } else {
-                        None
-                    }
-                })
-                .collect();
-            Some(move |ctx: EventCtx<Ctx, CursorData>| {
-                for f in &fs {
-                    f(EventCtx {
-                        state: ctx.state,
-                        ui: ctx.ui,
-                        data: ctx.data.clone(),
-                    });
-                }
-            })
-        } else {
-            None
-        }
-    }
-}
-
-impl<Ctx, Data> Default for SensorGroup<Ctx, Data> {
-    fn default() -> Self {
-        Self {
-            hover: Default::default(),
-            sensors: Default::default(),
-        }
-    }
-}
-
-impl Deref for CursorSenses {
-    type Target = Vec<CursorSense>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl DerefMut for CursorSenses {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
-    }
-}
-
-impl From<CursorSense> for CursorSenses {
-    fn from(val: CursorSense) -> Self {
-        CursorSenses(vec![val])
-    }
-}
-
-impl BitOr for CursorSense {
-    type Output = CursorSenses;
-
-    fn bitor(self, rhs: Self) -> Self::Output {
-        CursorSenses(vec![self, rhs])
-    }
-}
-
-impl BitOr<CursorSense> for CursorSenses {
-    type Output = Self;
-
-    fn bitor(mut self, rhs: CursorSense) -> Self::Output {
-        self.0.push(rhs);
-        self
-    }
-}
-
-impl<Ctx> Default for CursorModule<Ctx> {
-    fn default() -> Self {
-        Self {
-            map: Default::default(),
-            active: Default::default(),
-        }
-    }
-}

src/core/text/build.rs

@@ -1,128 +0,0 @@
-use crate::prelude::*;
-use cosmic_text::{Attrs, Family, Metrics};
-use std::marker::Sized;
-
-pub struct TextBuilder<O = TextOutput, H: WidgetOption = ()> {
-    pub content: String,
-    pub attrs: TextAttrs,
-    pub hint: H,
-    pub output: O,
-}
-
-impl<O, H: WidgetOption> TextBuilder<O, H> {
-    pub fn size(mut self, size: impl UiNum) -> Self {
-        self.attrs.font_size = size.to_f32();
-        self.attrs.line_height = self.attrs.font_size * LINE_HEIGHT_MULT;
-        self
-    }
-    pub fn color(mut self, color: UiColor) -> Self {
-        self.attrs.color = color;
-        self
-    }
-    pub fn family(mut self, family: Family<'static>) -> Self {
-        self.attrs.family = family;
-        self
-    }
-    pub fn line_height(mut self, height: f32) -> Self {
-        self.attrs.line_height = height;
-        self
-    }
-    pub fn text_align(mut self, align: impl Into<RegionAlign>) -> Self {
-        self.attrs.align = align.into();
-        self
-    }
-    pub fn center_text(mut self) -> Self {
-        self.attrs.align = Align::CENTER;
-        self
-    }
-    pub fn wrap(mut self, wrap: bool) -> Self {
-        self.attrs.wrap = wrap;
-        self
-    }
-    pub fn editable(self, single_line: bool) -> TextBuilder<TextEditOutput, H> {
-        TextBuilder {
-            content: self.content,
-            attrs: self.attrs,
-            hint: self.hint,
-            output: TextEditOutput { single_line },
-        }
-    }
-}
-
-impl<O> TextBuilder<O> {
-    pub fn hint<W: WidgetLike<Tag>, Tag>(self, hint: W) -> TextBuilder<O, impl WidgetOption> {
-        TextBuilder {
-            content: self.content,
-            attrs: self.attrs,
-            hint: move |ui: &mut Ui| Some(hint.add(ui).any()),
-            output: self.output,
-        }
-    }
-}
-
-pub trait TextBuilderOutput: Sized {
-    type Output;
-    fn run<H: WidgetOption>(ui: &mut Ui, builder: TextBuilder<Self, H>) -> Self::Output;
-}
-
-pub struct TextOutput;
-impl TextBuilderOutput for TextOutput {
-    type Output = Text;
-
-    fn run<H: WidgetOption>(ui: &mut Ui, builder: TextBuilder<Self, H>) -> Self::Output {
-        let mut buf = TextBuffer::new_empty(Metrics::new(
-            builder.attrs.font_size,
-            builder.attrs.line_height,
-        ));
-        let hint = builder.hint.get(ui);
-        let font_system = &mut ui.data.text.font_system;
-        buf.set_text(font_system, &builder.content, &Attrs::new(), SHAPING, None);
-        let mut text = Text {
-            content: builder.content.into(),
-            view: TextView::new(buf, builder.attrs, hint),
-        };
-        text.content.changed = false;
-        builder.attrs.apply(font_system, &mut text.view.buf, None);
-        text
-    }
-}
-
-pub struct TextEditOutput {
-    single_line: bool,
-}
-impl TextBuilderOutput for TextEditOutput {
-    type Output = TextEdit;
-
-    fn run<H: WidgetOption>(ui: &mut Ui, builder: TextBuilder<Self, H>) -> Self::Output {
-        let buf = TextBuffer::new_empty(Metrics::new(
-            builder.attrs.font_size,
-            builder.attrs.line_height,
-        ));
-        let mut text = TextEdit::new(
-            TextView::new(buf, builder.attrs, builder.hint.get(ui)),
-            builder.output.single_line,
-        );
-        let font_system = &mut ui.data.text.font_system;
-        text.buf
-            .set_text(font_system, &builder.content, &Attrs::new(), SHAPING, None);
-        builder.attrs.apply(font_system, &mut text.buf, None);
-        text
-    }
-}
-
-impl<O: TextBuilderOutput, H: WidgetOption> FnOnce<(&mut Ui,)> for TextBuilder<O, H> {
-    type Output = O::Output;
-
-    extern "rust-call" fn call_once(self, args: (&mut Ui,)) -> Self::Output {
-        O::run(args.0, self)
-    }
-}
-
-pub fn wtext(content: impl Into<String>) -> TextBuilder {
-    TextBuilder {
-        content: content.into(),
-        attrs: TextAttrs::default(),
-        hint: (),
-        output: TextOutput,
-    }
-}

src/core/text/edit.rs

@@ -1,612 +0,0 @@
-use std::ops::{Deref, DerefMut};
-
-use crate::prelude::*;
-use cosmic_text::{Affinity, Attrs, Cursor, FontSystem, LayoutRun, Motion};
-use unicode_segmentation::UnicodeSegmentation;
-use winit::{
-    event::KeyEvent,
-    keyboard::{Key, NamedKey},
-};
-
-pub struct TextEdit {
-    view: TextView,
-    selection: TextSelection,
-    history: Vec<(String, TextSelection)>,
-    double_hit: Option<Cursor>,
-    pub single_line: bool,
-}
-
-impl TextEdit {
-    pub fn new(view: TextView, single_line: bool) -> Self {
-        Self {
-            view,
-            selection: Default::default(),
-            history: Default::default(),
-            double_hit: None,
-            single_line,
-        }
-    }
-    pub fn select_content(&self, start: Cursor, end: Cursor) -> String {
-        let (start, end) = sort_cursors(start, end);
-        let mut iter = self.buf.lines.iter().skip(start.line);
-        let first = iter.next().unwrap();
-        if start.line == end.line {
-            first.text()[start.index..end.index].to_string()
-        } else {
-            let mut str = first.text()[start.index..].to_string();
-            for _ in (start.line + 1)..end.line {
-                str = str + "\n" + iter.next().unwrap().text();
-            }
-            let last = iter.next().unwrap();
-            str = str + "\n" + &last.text()[..end.index];
-            str
-        }
-    }
-}
-
-impl Widget for TextEdit {
-    fn draw(&mut self, painter: &mut Painter) {
-        let base = painter.layer;
-        painter.child_layer();
-        self.view.draw(painter);
-        painter.layer = base;
-        let region = self.region();
-
-        let size = vec2(1, self.attrs.line_height);
-        match self.selection {
-            TextSelection::None => (),
-            TextSelection::Pos(cursor) => {
-                if let Some(offset) = cursor_pos(cursor, &self.buf) {
-                    painter.primitive_within(
-                        RectPrimitive::color(Color::WHITE),
-                        size.align(Align::TOP_LEFT).offset(offset).within(&region),
-                    );
-                }
-            }
-            TextSelection::Span { start, end } => {
-                let (start, end) = sort_cursors(start, end);
-                for (l, x, width) in iter_layout_lines(start, end, &self.buf) {
-                    let top_left = vec2(x, self.attrs.line_height * l as f32);
-                    painter.primitive_within(
-                        RectPrimitive::color(Color::SKY),
-                        size.with_x(width)
-                            .align(Align::TOP_LEFT)
-                            .offset(top_left)
-                            .within(&region),
-                    );
-                }
-                if let Some(end_offset) = cursor_pos(end, &self.buf) {
-                    painter.primitive_within(
-                        RectPrimitive::color(Color::WHITE),
-                        size.align(Align::TOP_LEFT)
-                            .offset(end_offset)
-                            .within(&region),
-                    );
-                }
-            }
-        }
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.view.desired_width(ctx)
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.view.desired_height(ctx)
-    }
-}
-
-/// provides top left + width
-fn iter_layout_lines(
-    start: Cursor,
-    end: Cursor,
-    buf: &TextBuffer,
-) -> impl Iterator<Item = (usize, f32, f32)> {
-    gen move {
-        let mut iter = buf.layout_runs().enumerate();
-        for (i, line) in iter.by_ref() {
-            if line.line_i == start.line
-                && let Some(start_x) = index_x(&line, start.index)
-            {
-                if start.line == end.line
-                    && let Some(end_x) = index_x(&line, end.index)
-                {
-                    yield (i, start_x, end_x - start_x);
-                    return;
-                }
-                yield (i, start_x, line.line_w - start_x);
-                break;
-            }
-        }
-        for (i, line) in iter {
-            if line.line_i > end.line {
-                return;
-            }
-            if line.line_i == end.line
-                && let Some(end_x) = index_x(&line, end.index)
-            {
-                yield (i, 0.0, end_x);
-                return;
-            }
-            yield (i, 0.0, line.line_w);
-        }
-    }
-}
-
-/// copied & modified from fn found in Editor in cosmic_text
-/// returns x pos of a (non layout) index within an layout run
-fn index_x(run: &LayoutRun, index: usize) -> Option<f32> {
-    for glyph in run.glyphs.iter() {
-        if index == glyph.start {
-            return Some(glyph.x);
-        } else if index > glyph.start && index < glyph.end {
-            // Guess x offset based on characters
-            let mut before = 0;
-            let mut total = 0;
-
-            let cluster = &run.text[glyph.start..glyph.end];
-            for (i, _) in cluster.grapheme_indices(true) {
-                if glyph.start + i < index {
-                    before += 1;
-                }
-                total += 1;
-            }
-
-            let offset = glyph.w * (before as f32) / (total as f32);
-            return Some(glyph.x + offset);
-        }
-    }
-    None
-}
-
-/// returns top of line segment where cursor should visually select
-fn cursor_pos(cursor: Cursor, buf: &TextBuffer) -> Option<Vec2> {
-    let mut prev = None;
-    for run in buf
-        .layout_runs()
-        .skip_while(|r| r.line_i < cursor.line)
-        .take_while(|r| r.line_i == cursor.line)
-    {
-        prev = Some(vec2(run.line_w, run.line_top));
-        if let Some(pos) = index_x(&run, cursor.index) {
-            return Some(vec2(pos, run.line_top));
-        }
-    }
-    prev
-}
-
-pub struct TextEditCtx<'a> {
-    pub text: &'a mut TextEdit,
-    pub font_system: &'a mut FontSystem,
-}
-
-impl<'a> TextEditCtx<'a> {
-    pub fn take(&mut self) -> String {
-        let text = self
-            .text
-            .buf
-            .lines
-            .drain(..)
-            .map(|l| l.into_text())
-            .collect::<Vec<_>>()
-            .join("\n");
-        self.text
-            .buf
-            .set_text(self.font_system, "", &Attrs::new(), SHAPING, None);
-        self.text.selection.clear();
-        text
-    }
-
-    pub fn set(&mut self, text: &str) {
-        let text = self.string(text);
-        self.text
-            .buf
-            .set_text(self.font_system, &text, &Attrs::new(), SHAPING, None);
-        self.text.selection.clear();
-    }
-
-    pub fn motion(&mut self, motion: Motion, select: bool) {
-        if let TextSelection::Pos(cursor) = self.text.selection
-            && let Some(new) = self.buf_motion(cursor, motion)
-        {
-            if select {
-                self.text.selection = TextSelection::Span {
-                    start: cursor,
-                    end: new,
-                };
-            } else {
-                self.text.selection = TextSelection::Pos(new);
-            }
-        } else if let TextSelection::Span { start, end } = self.text.selection {
-            if select {
-                if let Some(cursor) = self.buf_motion(end, motion) {
-                    self.text.selection = TextSelection::Span { start, end: cursor };
-                }
-            } else {
-                let (start, end) = sort_cursors(start, end);
-                let sel = &mut self.text.selection;
-                match motion {
-                    Motion::Left | Motion::LeftWord => *sel = TextSelection::Pos(start),
-                    Motion::Right | Motion::RightWord => *sel = TextSelection::Pos(end),
-                    _ => {
-                        if let Some(cursor) = self.buf_motion(end, motion) {
-                            self.text.selection = TextSelection::Pos(cursor);
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    pub fn replace(&mut self, len: usize, text: &str) {
-        let text = self.string(text);
-        for _ in 0..len {
-            self.delete(false);
-        }
-        self.insert_inner(&text, false);
-    }
-
-    fn string(&self, text: &str) -> String {
-        if self.text.single_line {
-            text.replace('\n', "")
-        } else {
-            text.to_string()
-        }
-    }
-
-    pub fn insert(&mut self, text: &str) {
-        let text = self.string(text);
-        let mut lines = text.split('\n');
-        let Some(first) = lines.next() else {
-            return;
-        };
-        self.insert_inner(first, true);
-        for line in lines {
-            self.newline();
-            self.insert_inner(line, true);
-        }
-    }
-
-    pub fn clear_span(&mut self) -> bool {
-        if let TextSelection::Span { start, end } = self.text.selection {
-            self.delete_between(start, end);
-            let (start, _) = sort_cursors(start, end);
-            self.text.selection = TextSelection::Pos(start);
-            true
-        } else {
-            false
-        }
-    }
-
-    pub fn delete_between(&mut self, start: Cursor, end: Cursor) {
-        let lines = &mut self.text.view.buf.lines;
-        let (start, end) = sort_cursors(start, end);
-        if start.line == end.line {
-            let line = &mut lines[start.line];
-            let text = line.text();
-            let text = text[..start.index].to_string() + &text[end.index..];
-            edit_line(line, text);
-        } else {
-            // start
-            let start_text = lines[start.line].text()[..start.index].to_string();
-            let end_text = &lines[end.line].text()[end.index..];
-            let text = start_text + end_text;
-            edit_line(&mut lines[start.line], text);
-        }
-        // between
-        let range = (start.line + 1)..=end.line;
-        if !range.is_empty() {
-            lines.splice(range, None);
-        }
-    }
-
-    fn insert_inner(&mut self, text: &str, mov: bool) {
-        self.clear_span();
-        if let TextSelection::Pos(cursor) = &mut self.text.selection {
-            let line = &mut self.text.view.buf.lines[cursor.line];
-            let mut line_text = line.text().to_string();
-            line_text.insert_str(cursor.index, text);
-            edit_line(line, line_text);
-            if mov {
-                for _ in 0..text.chars().count() {
-                    self.motion(Motion::Right, false);
-                }
-            }
-        }
-    }
-
-    pub fn newline(&mut self) {
-        if self.text.single_line {
-            return;
-        }
-        self.clear_span();
-        if let TextSelection::Pos(cursor) = &mut self.text.selection {
-            let lines = &mut self.text.view.buf.lines;
-            let line = &mut lines[cursor.line];
-            let new = line.split_off(cursor.index);
-            cursor.line += 1;
-            lines.insert(cursor.line, new);
-            cursor.index = 0;
-        }
-    }
-
-    pub fn backspace(&mut self, word: bool) {
-        if !self.clear_span()
-            && let TextSelection::Pos(cursor) = &mut self.text.selection
-            && (cursor.index != 0 || cursor.line != 0)
-        {
-            self.motion(if word { Motion::LeftWord } else { Motion::Left }, false);
-            self.delete(word);
-        }
-    }
-
-    pub fn delete(&mut self, word: bool) {
-        if !self.clear_span()
-            && let TextSelection::Pos(cursor) = &mut self.text.selection
-        {
-            if word {
-                let start = *cursor;
-                if let Some(end) = self.buf_motion(start, Motion::RightWord) {
-                    self.delete_between(start, end);
-                }
-            } else {
-                let lines = &mut self.text.view.buf.lines;
-                let line = &mut lines[cursor.line];
-                if cursor.index == line.text().len() {
-                    if cursor.line == lines.len() - 1 {
-                        return;
-                    }
-                    let add = lines.remove(cursor.line + 1).into_text();
-                    let line = &mut lines[cursor.line];
-                    let mut cur = line.text().to_string();
-                    cur.push_str(&add);
-                    edit_line(line, cur);
-                } else {
-                    let mut text = line.text().to_string();
-                    text.remove(cursor.index);
-                    edit_line(line, text);
-                }
-            }
-        }
-    }
-
-    fn buf_motion(&mut self, cursor: Cursor, motion: Motion) -> Option<Cursor> {
-        self.text
-            .buf
-            .cursor_motion(self.font_system, cursor, None, motion)
-            .map(|r| r.0)
-    }
-
-    pub fn select_word_at(&mut self, cursor: Cursor) {
-        if let (Some(start), Some(end)) = (
-            self.buf_motion(cursor, Motion::LeftWord),
-            self.buf_motion(cursor, Motion::RightWord),
-        ) {
-            self.text.selection = TextSelection::Span { start, end };
-        }
-    }
-
-    pub fn select_line_at(&mut self, cursor: Cursor) {
-        let end = self.text.buf.lines[cursor.line].text().len();
-        self.text.selection = TextSelection::Span {
-            start: Cursor::new(cursor.line, 0),
-            end: Cursor::new(cursor.line, end),
-        }
-    }
-
-    pub fn select(&mut self, pos: Vec2, size: Vec2, drag: bool, recent: bool) {
-        let pos = pos - self.text.region().top_left().to_abs(size);
-        let hit = self.text.buf.hit(pos.x, pos.y);
-        let sel = &mut self.text.selection;
-        match sel {
-            TextSelection::None => {
-                if !drag && let Some(hit) = hit {
-                    *sel = TextSelection::Pos(hit)
-                }
-            }
-            TextSelection::Pos(pos) => match (hit, drag) {
-                (None, false) => *sel = TextSelection::None,
-                (None, true) => (),
-                (Some(hit), false) => {
-                    if recent && hit == *pos {
-                        self.text.double_hit = Some(hit);
-                        return self.select_word_at(hit);
-                    } else {
-                        *pos = hit
-                    }
-                }
-                (Some(end), true) => *sel = TextSelection::Span { start: *pos, end },
-            },
-            TextSelection::Span { start, end } => match (hit, drag) {
-                (None, false) => *sel = TextSelection::None,
-                (None, true) => *sel = TextSelection::Pos(*start),
-                (Some(hit), false) => {
-                    if recent
-                        && let Some(double) = self.text.double_hit
-                        && double == hit
-                    {
-                        return self.select_line_at(hit);
-                    } else {
-                        *sel = TextSelection::Pos(hit)
-                    }
-                }
-                (Some(hit), true) => *end = hit,
-            },
-        }
-        if let TextSelection::Span { start, end } = sel
-            && start == end
-        {
-            *sel = TextSelection::Pos(*start);
-        }
-    }
-
-    pub fn deselect(&mut self) {
-        self.text.selection = TextSelection::None;
-    }
-
-    pub fn apply_event(&mut self, event: &KeyEvent, modifiers: &Modifiers) -> TextInputResult {
-        let old = (self.text.content(), self.text.selection);
-        let mut undo = false;
-        let res = self.apply_event_inner(event, modifiers, &mut undo);
-        if undo && let Some((old, selection)) = self.text.history.pop() {
-            self.set(&old);
-            self.text.selection = selection;
-        } else if self.text.content() != old.0 {
-            self.text.history.push(old);
-        }
-        res
-    }
-
-    fn apply_event_inner(
-        &mut self,
-        event: &KeyEvent,
-        modifiers: &Modifiers,
-        undo: &mut bool,
-    ) -> TextInputResult {
-        match &event.logical_key {
-            Key::Named(named) => match named {
-                NamedKey::Backspace => self.backspace(modifiers.control),
-                NamedKey::Delete => self.delete(modifiers.control),
-                NamedKey::Space => self.insert(" "),
-                NamedKey::Enter => {
-                    if modifiers.shift {
-                        self.newline();
-                    } else {
-                        return TextInputResult::Submit;
-                    }
-                }
-                NamedKey::ArrowRight => {
-                    if modifiers.control {
-                        self.motion(Motion::RightWord, modifiers.shift)
-                    } else {
-                        self.motion(Motion::Right, modifiers.shift)
-                    }
-                }
-                NamedKey::ArrowLeft => {
-                    if modifiers.control {
-                        self.motion(Motion::LeftWord, modifiers.shift)
-                    } else {
-                        self.motion(Motion::Left, modifiers.shift)
-                    }
-                }
-                NamedKey::ArrowUp => self.motion(Motion::Up, modifiers.shift),
-                NamedKey::ArrowDown => self.motion(Motion::Down, modifiers.shift),
-                NamedKey::Escape => {
-                    self.deselect();
-                    return TextInputResult::Unfocus;
-                }
-                _ => return TextInputResult::Unused,
-            },
-            Key::Character(text) => {
-                if modifiers.control {
-                    match text.as_str() {
-                        "v" => return TextInputResult::Paste,
-                        "c" => {
-                            if let TextSelection::Span { start, end } = self.text.selection {
-                                let content = self.text.select_content(start, end);
-                                return TextInputResult::Copy(content);
-                            }
-                        }
-                        "x" => {
-                            if let TextSelection::Span { start, end } = self.text.selection {
-                                let content = self.text.select_content(start, end);
-                                self.clear_span();
-                                return TextInputResult::Copy(content);
-                            }
-                        }
-                        "a" => {
-                            if !self.text.buf.lines[0].text().is_empty()
-                                || self.text.buf.lines.len() > 1
-                            {
-                                let lines = &self.text.buf.lines;
-                                let last_line = lines.len() - 1;
-                                let last_idx = lines[last_line].text().len();
-                                self.text.selection = TextSelection::Span {
-                                    start: Cursor::new(0, 0),
-                                    end: Cursor::new(last_line, last_idx),
-                                };
-                            }
-                        }
-                        "z" => {
-                            *undo = true;
-                        }
-                        _ => self.insert(text),
-                    }
-                } else {
-                    self.insert(text);
-                }
-            }
-            _ => return TextInputResult::Unused,
-        }
-        TextInputResult::Used
-    }
-}
-
-#[derive(Default)]
-pub struct Modifiers {
-    pub shift: bool,
-    pub control: bool,
-}
-
-impl Modifiers {
-    pub fn clear(&mut self) {
-        self.shift = false;
-        self.control = false;
-    }
-}
-
-pub enum TextInputResult {
-    Used,
-    Unused,
-    Unfocus,
-    Submit,
-    Copy(String),
-    Paste,
-}
-
-#[derive(Debug, Default, Clone, Copy)]
-pub enum TextSelection {
-    #[default]
-    None,
-    Pos(Cursor),
-    Span {
-        start: Cursor,
-        end: Cursor,
-    },
-}
-
-impl TextSelection {
-    pub fn clear(&mut self) {
-        match self {
-            TextSelection::None => (),
-            TextSelection::Pos(cursor) => {
-                cursor.line = 0;
-                cursor.index = 0;
-                cursor.affinity = Affinity::default();
-            }
-            TextSelection::Span { start: _, end: _ } => {
-                *self = TextSelection::None;
-            }
-        }
-    }
-}
-
-impl TextInputResult {
-    pub fn unfocus(&self) -> bool {
-        matches!(self, TextInputResult::Unfocus)
-    }
-}
-
-impl Deref for TextEdit {
-    type Target = TextView;
-
-    fn deref(&self) -> &Self::Target {
-        &self.view
-    }
-}
-
-impl DerefMut for TextEdit {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.view
-    }
-}

src/core/text/mod.rs

@@ -1,202 +0,0 @@
-mod build;
-mod edit;
-
-pub use build::*;
-pub use edit::*;
-
-use crate::{prelude::*, util::MutDetect};
-use cosmic_text::{Attrs, BufferLine, Cursor, Metrics, Shaping};
-use std::ops::{Deref, DerefMut};
-
-pub const SHAPING: Shaping = Shaping::Advanced;
-
-pub struct Text {
-    pub content: MutDetect<String>,
-    view: TextView,
-}
-
-pub struct TextView {
-    pub attrs: MutDetect<TextAttrs>,
-    pub buf: MutDetect<TextBuffer>,
-    // cache
-    tex: Option<RenderedText>,
-    width: Option<f32>,
-    pub hint: Option<WidgetId>,
-}
-
-impl TextView {
-    pub fn new(buf: TextBuffer, attrs: TextAttrs, hint: Option<WidgetId>) -> Self {
-        Self {
-            attrs: attrs.into(),
-            buf: buf.into(),
-            tex: None,
-            width: None,
-            hint,
-        }
-    }
-
-    /// region where the text should be draw
-    /// does not include extra height or width from weird unicode
-    pub fn region(&self) -> UiRegion {
-        self.tex()
-            .map(|t| t.size)
-            .unwrap_or(Vec2::ZERO)
-            .align(self.align)
-    }
-
-    fn tex_region(&self, tex: &RenderedText) -> UiRegion {
-        let region = tex.size.align(self.align);
-        let dims = tex.handle.size();
-        let mut region = region.offset(tex.top_left_offset);
-        region.x.end = region.x.start + UiScalar::abs(dims.x);
-        region.y.end = region.y.start + UiScalar::abs(dims.y);
-        region
-    }
-
-    fn render(&mut self, ctx: &mut SizeCtx) -> RenderedText {
-        let width = if self.attrs.wrap {
-            Some(ctx.px_size().x)
-        } else {
-            None
-        };
-        if width == self.width
-            && let Some(tex) = &self.tex
-            && !self.attrs.changed
-            && !self.buf.changed
-        {
-            return tex.clone();
-        }
-        self.width = width;
-        let font_system = &mut ctx.text.font_system;
-        self.attrs.apply(font_system, &mut self.buf, width);
-        self.buf.shape_until_scroll(font_system, false);
-        let tex = ctx.draw_text(&mut self.buf, &self.attrs);
-        self.tex = Some(tex.clone());
-        self.attrs.changed = false;
-        self.buf.changed = false;
-        tex
-    }
-    pub fn tex(&self) -> Option<&RenderedText> {
-        self.tex.as_ref()
-    }
-    pub fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        if let Some(hint) = &self.hint
-            && let [line] = &self.buf.lines[..]
-            && line.text().is_empty()
-        {
-            ctx.width(hint)
-        } else {
-            Len::abs(self.render(ctx).size.x)
-        }
-    }
-    pub fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        if let Some(hint) = &self.hint
-            && let [line] = &self.buf.lines[..]
-            && line.text().is_empty()
-        {
-            ctx.height(hint)
-        } else {
-            Len::abs(self.render(ctx).size.y)
-        }
-    }
-    pub fn draw(&mut self, painter: &mut Painter) -> UiRegion {
-        let tex = self.render(&mut painter.size_ctx());
-        let region = self.tex_region(&tex);
-        if let Some(hint) = &self.hint
-            && let [line] = &self.buf.lines[..]
-            && line.text().is_empty()
-        {
-            painter.widget(hint);
-        } else {
-            painter.texture_within(&tex.handle, region);
-        }
-        region
-    }
-
-    pub fn content(&self) -> String {
-        self.buf
-            .lines
-            .iter()
-            .map(|l| l.text())
-            .collect::<Vec<_>>()
-            .join("\n")
-    }
-}
-
-impl Text {
-    pub fn new(content: impl Into<String>) -> Self {
-        let attrs = TextAttrs::default();
-        let buf = TextBuffer::new_empty(Metrics::new(attrs.font_size, attrs.line_height));
-        Self {
-            content: content.into().into(),
-            view: TextView::new(buf, attrs, None),
-        }
-    }
-    fn update_buf(&mut self, ctx: &mut SizeCtx) {
-        if self.content.changed {
-            self.content.changed = false;
-            self.view.buf.set_text(
-                &mut ctx.text.font_system,
-                &self.content,
-                &Attrs::new().family(self.view.attrs.family),
-                SHAPING,
-                None,
-            );
-        }
-    }
-}
-
-impl Widget for Text {
-    fn draw(&mut self, painter: &mut Painter) {
-        self.update_buf(&mut painter.size_ctx());
-        self.view.draw(painter);
-    }
-
-    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.update_buf(ctx);
-        self.view.desired_width(ctx)
-    }
-
-    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
-        self.update_buf(ctx);
-        self.view.desired_height(ctx)
-    }
-}
-
-pub fn sort_cursors(a: Cursor, b: Cursor) -> (Cursor, Cursor) {
-    let start = a.min(b);
-    let end = a.max(b);
-    (start, end)
-}
-
-pub fn edit_line(line: &mut BufferLine, text: String) {
-    line.set_text(text, line.ending(), line.attrs_list().clone());
-}
-
-impl Deref for Text {
-    type Target = TextAttrs;
-
-    fn deref(&self) -> &Self::Target {
-        &self.view
-    }
-}
-
-impl DerefMut for Text {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.view
-    }
-}
-
-impl Deref for TextView {
-    type Target = TextAttrs;
-
-    fn deref(&self) -> &Self::Target {
-        &self.attrs
-    }
-}
-
-impl DerefMut for TextView {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.attrs
-    }
-}

src/core/trait_fns.rs

@@ -1,160 +0,0 @@
-use super::*;
-use crate::prelude::*;
-
-// these methods should "not require any context" (require unit) because they're in core
-event_ctx!(());
-
-pub trait CoreWidget<W, Tag> {
-    fn pad(self, padding: impl Into<Padding>) -> impl WidgetFn<Pad>;
-    fn align(self, align: impl Into<Align>) -> impl WidgetFn<Aligned>;
-    fn center(self) -> impl WidgetFn<Aligned>;
-    fn label(self, label: impl Into<String>) -> impl WidgetIdFn<W>;
-    fn sized(self, size: impl Into<Size>) -> impl WidgetFn<Sized>;
-    fn width(self, len: impl Into<Len>) -> impl WidgetFn<Sized>;
-    fn height(self, len: impl Into<Len>) -> impl WidgetFn<Sized>;
-    fn max_width(self, width: impl Into<Len>) -> impl WidgetFn<MaxSize>;
-    fn max_height(self, height: impl Into<Len>) -> impl WidgetFn<MaxSize>;
-    fn offset(self, amt: impl Into<UiVec2>) -> impl WidgetFn<Offset>;
-    fn scroll(self) -> impl WidgetIdFn<Scroll>;
-    fn masked(self) -> impl WidgetFn<Masked>;
-    fn background<T>(self, w: impl WidgetLike<T>) -> impl WidgetFn<Stack>;
-    fn foreground<T>(self, w: impl WidgetLike<T>) -> impl WidgetFn<Stack>;
-    fn layer_offset(self, offset: usize) -> impl WidgetFn<LayerOffset>;
-    fn to_any(self) -> impl WidgetRet;
-}
-
-impl<W: WidgetLike<Tag>, Tag> CoreWidget<W::Widget, Tag> for W {
-    fn pad(self, padding: impl Into<Padding>) -> impl WidgetFn<Pad> {
-        |ui| Pad {
-            padding: padding.into(),
-            inner: self.add(ui).any(),
-        }
-    }
-
-    fn align(self, align: impl Into<Align>) -> impl WidgetFn<Aligned> {
-        move |ui| Aligned {
-            inner: self.add(ui).any(),
-            align: align.into(),
-        }
-    }
-
-    fn center(self) -> impl WidgetFn<Aligned> {
-        self.align(Align::CENTER)
-    }
-
-    fn label(self, label: impl Into<String>) -> impl WidgetIdFn<W::Widget> {
-        |ui| {
-            let id = self.add(ui);
-            ui.set_label(&id, label.into());
-            id
-        }
-    }
-
-    fn sized(self, size: impl Into<Size>) -> impl WidgetFn<Sized> {
-        let size = size.into();
-        move |ui| Sized {
-            inner: self.add(ui).any(),
-            x: Some(size.x),
-            y: Some(size.y),
-        }
-    }
-
-    fn max_width(self, len: impl Into<Len>) -> impl WidgetFn<MaxSize> {
-        let len = len.into();
-        move |ui| MaxSize {
-            inner: self.add(ui).any(),
-            x: Some(len),
-            y: None,
-        }
-    }
-
-    fn max_height(self, len: impl Into<Len>) -> impl WidgetFn<MaxSize> {
-        let len = len.into();
-        move |ui| MaxSize {
-            inner: self.add(ui).any(),
-            x: None,
-            y: Some(len),
-        }
-    }
-
-    fn width(self, len: impl Into<Len>) -> impl WidgetFn<Sized> {
-        let len = len.into();
-        move |ui| Sized {
-            inner: self.add(ui).any(),
-            x: Some(len),
-            y: None,
-        }
-    }
-
-    fn height(self, len: impl Into<Len>) -> impl WidgetFn<Sized> {
-        let len = len.into();
-        move |ui| Sized {
-            inner: self.add(ui).any(),
-            x: None,
-            y: Some(len),
-        }
-    }
-
-    fn offset(self, amt: impl Into<UiVec2>) -> impl WidgetFn<Offset> {
-        move |ui| Offset {
-            inner: self.add(ui).any(),
-            amt: amt.into(),
-        }
-    }
-
-    fn scroll(self) -> impl WidgetIdFn<Scroll> {
-        move |ui| {
-            Scroll::new(self.add(ui).any(), Axis::Y)
-                .on(CursorSense::Scroll, |ctx| {
-                    let s = &mut ctx.ui[ctx.id];
-                    s.scroll(ctx.data.scroll_delta.y * 50.0);
-                })
-                .add(ui)
-        }
-    }
-
-    fn masked(self) -> impl WidgetFn<Masked> {
-        move |ui| Masked {
-            inner: self.add(ui).any(),
-        }
-    }
-
-    fn background<T>(self, w: impl WidgetLike<T>) -> impl WidgetFn<Stack> {
-        move |ui| Stack {
-            children: vec![w.add(ui).any(), self.add(ui).any()],
-            size: StackSize::Child(1),
-        }
-    }
-
-    fn foreground<T>(self, w: impl WidgetLike<T>) -> impl WidgetFn<Stack> {
-        move |ui| Stack {
-            children: vec![self.add(ui).any(), w.add(ui).any()],
-            size: StackSize::Child(0),
-        }
-    }
-
-    fn layer_offset(self, offset: usize) -> impl WidgetFn<LayerOffset> {
-        move |ui| LayerOffset {
-            inner: self.add(ui).any(),
-            offset,
-        }
-    }
-
-    fn to_any(self) -> impl WidgetRet {
-        |ui| self.add(ui).any()
-    }
-}
-
-pub trait CoreWidgetArr<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> {
-    fn span(self, dir: Dir) -> SpanBuilder<LEN, Wa, Tag>;
-    fn stack(self) -> StackBuilder<LEN, Wa, Tag>;
-}
-
-impl<const LEN: usize, Wa: WidgetArrLike<LEN, Tag>, Tag> CoreWidgetArr<LEN, Wa, Tag> for Wa {
-    fn span(self, dir: Dir) -> SpanBuilder<LEN, Wa, Tag> {
-        SpanBuilder::new(self, dir)
-    }
-    fn stack(self) -> StackBuilder<LEN, Wa, Tag> {
-        StackBuilder::new(self)
-    }
-}

src/default/app.rs

@@ -11,6 +11,13 @@ pub trait AppState {
     fn window_event(&mut self, event: WindowEvent, event_loop: &ActiveEventLoop);
     fn event(&mut self, event: Self::Event, event_loop: &ActiveEventLoop);
     fn exit(&mut self);
+
+    fn run()
+    where
+        Self: Sized,
+    {
+        App::<Self>::run();
+    }
 }
 
 pub struct App<State: AppState> {

src/default/attr.rs

@@ -0,0 +1,78 @@
+use crate::prelude::*;
+use std::time::{Duration, Instant};
+use winit::dpi::{LogicalPosition, LogicalSize};
+
+pub struct Selector;
+
+impl<Rsc: HasEvents, W: Widget + 'static> WidgetAttr<Rsc, W> for Selector
+where
+    Rsc::State: HasDefaultUiState,
+{
+    type Input = WeakWidget<TextEdit>;
+
+    fn run(rsc: &mut Rsc, container: WeakWidget<W>, id: Self::Input) {
+        rsc.register_event(container, CursorSense::click_or_drag(), move |ctx, rsc| {
+            let region = ctx.data.render.window_region(&id).unwrap();
+            let id_pos = region.top_left;
+            let container_pos = ctx.data.render.window_region(&container).unwrap().top_left;
+            let pos = ctx.data.pos + container_pos - id_pos;
+            let size = region.size();
+            select(
+                rsc,
+                ctx.data.render,
+                ctx.state,
+                id,
+                pos,
+                size,
+                ctx.data.sense.is_dragging(),
+            );
+        });
+    }
+}
+
+pub struct Selectable;
+
+impl<Rsc: HasEvents> WidgetAttr<Rsc, TextEdit> for Selectable
+where
+    Rsc::State: HasDefaultUiState,
+{
+    type Input = ();
+
+    fn run(rsc: &mut Rsc, id: WeakWidget<TextEdit>, _: Self::Input) {
+        rsc.register_event(id, CursorSense::click_or_drag(), move |ctx, rsc| {
+            select(
+                rsc,
+                ctx.data.render,
+                ctx.state,
+                id,
+                ctx.data.pos,
+                ctx.data.size,
+                ctx.data.sense.is_dragging(),
+            );
+        });
+    }
+}
+
+fn select(
+    rsc: &mut impl UiRsc,
+    render: &UiRenderState,
+    state: &mut impl HasDefaultUiState,
+    id: WeakWidget<TextEdit>,
+    pos: Vec2,
+    size: Vec2,
+    dragging: bool,
+) {
+    let state = state.default_state_mut();
+    let now = Instant::now();
+    let recent = (now - state.last_click) < Duration::from_millis(300);
+    state.last_click = now;
+    id.edit(rsc).select(pos, size, dragging, recent);
+    if let Some(region) = render.window_region(&id) {
+        state.window.set_ime_allowed(true);
+        state.window.set_ime_cursor_area(
+            LogicalPosition::<f32>::from(region.top_left.tuple()),
+            LogicalSize::<f32>::from(region.size().tuple()),
+        );
+    }
+    state.focus = Some(id);
+}

src/default/event.rs

@@ -0,0 +1,9 @@
+use iris_core::Event;
+
+#[derive(Eq, PartialEq, Hash, Clone)]
+pub struct Submit;
+impl Event for Submit {}
+
+#[derive(Eq, PartialEq, Hash, Clone)]
+pub struct Edited;
+impl Event for Edited {}

src/default/input.rs

@@ -1,8 +1,4 @@
-use crate::{
-    core::{CursorState, Modifiers},
-    layout::Vec2,
-    winit::UiState,
-};
+use crate::prelude::*;
 use winit::{
     event::{MouseButton, MouseScrollDelta, WindowEvent},
     keyboard::{Key, NamedKey},
@@ -70,7 +66,7 @@ impl Input {
     }
 }
 
-impl UiState {
+impl DefaultUiState {
     pub fn window_size(&self) -> Vec2 {
         let size = self.renderer.window().inner_size();
         (size.width, size.height).into()

src/default/mod.rs

@@ -0,0 +1,367 @@
+use crate::prelude::*;
+use arboard::Clipboard;
+use std::{marker::PhantomData, sync::Arc, time::Instant};
+use winit::{
+    event::{Ime, WindowEvent},
+    event_loop::{ActiveEventLoop, EventLoopProxy},
+    window::{Window, WindowAttributes},
+};
+
+mod app;
+mod attr;
+mod event;
+mod input;
+mod render;
+mod sense;
+mod state;
+mod task;
+
+pub use app::*;
+pub use attr::*;
+pub use event::*;
+pub use input::*;
+pub use render::*;
+pub use sense::*;
+pub use state::*;
+pub use task::*;
+
+/// Sends an application's own events to its event loop. It wraps the proxy
+/// rather than being one because task updates travel the same way: what an
+/// application sends is its `Event`, not the loop's whole message type.
+pub struct Proxy<State: DefaultAppState>(EventLoopProxy<DefaultEvent<State>>);
+
+impl<State: DefaultAppState> Clone for Proxy<State> {
+    fn clone(&self) -> Self {
+        Self(self.0.clone())
+    }
+}
+
+impl<State: DefaultAppState> Proxy<State> {
+    pub fn send_event(&self, event: State::Event) {
+        let _ = self.0.send_event(DefaultEvent::User(event));
+    }
+}
+
+/// What the event loop carries: the application's own events, and the
+/// updates tasks send back to the ui thread.
+pub enum DefaultEvent<State: DefaultAppState> {
+    User(State::Event),
+    Update(Box<dyn TaskUpdate<DefaultRsc<State>>>),
+}
+
+impl<State: DefaultAppState> TaskQueue<DefaultRsc<State>> for Proxy<State> {
+    fn send(&self, update: Box<dyn TaskUpdate<DefaultRsc<State>>>) {
+        let _ = self.0.send_event(DefaultEvent::Update(update));
+    }
+}
+
+pub struct DefaultUiState {
+    pub root: Option<StrongWidget>,
+    pub renderer: UiRenderer,
+    pub input: Input,
+    pub focus: Option<WeakWidget<TextEdit>>,
+    pub clipboard: Clipboard,
+    pub window: Arc<Window>,
+    pub ime: usize,
+    pub last_click: Instant,
+}
+
+impl HasRoot for DefaultUiState {
+    fn set_root(&mut self, root: StrongWidget) {
+        self.root = Some(root);
+    }
+}
+
+impl DefaultUiState {
+    pub fn new(window: impl Into<Arc<Window>>) -> Self {
+        let window = window.into();
+        Self {
+            root: None,
+            renderer: UiRenderer::new(window.clone()),
+            window,
+            input: Input::default(),
+            clipboard: Clipboard::new().unwrap(),
+            ime: 0,
+            last_click: Instant::now(),
+            focus: None,
+        }
+    }
+}
+
+pub trait HasDefaultUiState: Sized + 'static {
+    fn default_state(&self) -> &DefaultUiState;
+    fn default_state_mut(&mut self) -> &mut DefaultUiState;
+}
+
+pub trait DefaultAppState: HasDefaultUiState {
+    type Event: Send = ();
+    fn new(ui_state: DefaultUiState, rsc: &mut DefaultRsc<Self>, proxy: Proxy<Self>) -> Self;
+    #[allow(unused_variables)]
+    fn event(
+        &mut self,
+        event: Self::Event,
+        rsc: &mut DefaultRsc<Self>,
+        render: &mut UiRenderState,
+    ) {
+    }
+    #[allow(unused_variables)]
+    fn exit(&mut self, rsc: &mut DefaultRsc<Self>, render: &mut UiRenderState) {}
+    #[allow(unused_variables)]
+    fn window_event(
+        &mut self,
+        event: WindowEvent,
+        rsc: &mut DefaultRsc<Self>,
+        render: &mut UiRenderState,
+    ) {
+    }
+    fn window_attributes() -> WindowAttributes {
+        Default::default()
+    }
+}
+
+pub struct DefaultRsc<State: 'static> {
+    pub ui: UiData,
+    pub events: EventManager<Self>,
+    pub tasks: Tasks<Self>,
+    pub state: WidgetState,
+    _state: PhantomData<State>,
+}
+
+impl<State> DefaultRsc<State> {
+    pub fn init(queue: Arc<dyn TaskQueue<Self>>) -> Self {
+        Self {
+            ui: Default::default(),
+            events: Default::default(),
+            tasks: Tasks::init(queue),
+            state: Default::default(),
+            _state: Default::default(),
+        }
+    }
+
+    pub fn create_state<T: 'static>(&mut self, id: impl IdLike, data: T) -> WeakState<T> {
+        self.state.add(id.id(), data)
+    }
+}
+
+impl<State> UiRsc for DefaultRsc<State> {
+    fn ui(&self) -> &UiData {
+        &self.ui
+    }
+
+    fn ui_mut(&mut self) -> &mut UiData {
+        &mut self.ui
+    }
+
+    fn on_draw(&mut self, active: &ActiveData) {
+        self.events.draw(active);
+    }
+
+    fn on_undraw(&mut self, active: &ActiveData) {
+        self.events.undraw(active);
+    }
+
+    fn on_remove(&mut self, id: WidgetId) {
+        self.events.remove(id);
+        self.state.remove(id);
+    }
+}
+
+impl<State: 'static> HasState for DefaultRsc<State> {
+    type State = State;
+}
+
+impl<State: 'static> HasEvents for DefaultRsc<State> {
+    fn events(&self) -> &EventManager<Self> {
+        &self.events
+    }
+
+    fn events_mut(&mut self) -> &mut EventManager<Self> {
+        &mut self.events
+    }
+}
+
+impl<State: 'static> HasTasks for DefaultRsc<State> {
+    fn tasks_mut(&mut self) -> &mut Tasks<Self> {
+        &mut self.tasks
+    }
+}
+
+impl<State: 'static> HasWidgetState for DefaultRsc<State> {
+    fn widget_state(&self) -> &WidgetState {
+        &self.state
+    }
+
+    fn widget_state_mut(&mut self) -> &mut WidgetState {
+        &mut self.state
+    }
+}
+
+pub struct DefaultApp<State: DefaultAppState> {
+    rsc: DefaultRsc<State>,
+    render: UiRenderState,
+    state: State,
+}
+
+impl<State: DefaultAppState> AppState for DefaultApp<State> {
+    type Event = DefaultEvent<State>;
+
+    fn new(event_loop: &ActiveEventLoop, proxy: EventLoopProxy<Self::Event>) -> Self {
+        let window = event_loop
+            .create_window(State::window_attributes())
+            .unwrap();
+        let default_state = DefaultUiState::new(window);
+        let mut rsc = DefaultRsc::init(Arc::new(Proxy(proxy.clone())));
+        let state = State::new(default_state, &mut rsc, Proxy(proxy));
+        let render = UiRenderState::new();
+        Self { rsc, state, render }
+    }
+
+    fn event(&mut self, event: Self::Event, _: &ActiveEventLoop) {
+        match event {
+            DefaultEvent::User(event) => self.state.event(event, &mut self.rsc, &mut self.render),
+            DefaultEvent::Update(update) => update(&mut self.state, &mut self.rsc),
+        }
+        self.request_redraw_if_needed();
+    }
+
+    fn window_event(&mut self, event: WindowEvent, event_loop: &ActiveEventLoop) {
+        let Self { rsc, render, state } = self;
+
+        let ui_state = state.default_state_mut();
+        let input_changed = ui_state.input.event(&event);
+        let cursor_state = ui_state.cursor_state().clone();
+        let old = ui_state.focus;
+        if cursor_state.buttons.left.is_start() {
+            ui_state.focus = None;
+        }
+        if input_changed {
+            render.run_sensors(rsc, state, cursor_state);
+        }
+        let ui_state = state.default_state_mut();
+        if old != ui_state.focus
+            && let Some(old) = old
+        {
+            old.edit(rsc).deselect();
+        }
+        match &event {
+            WindowEvent::CloseRequested => event_loop.exit(),
+            WindowEvent::RedrawRequested => {
+                render.update(&ui_state.root, rsc);
+                ui_state.renderer.update(&mut rsc.ui, render);
+                ui_state.renderer.draw();
+            }
+            WindowEvent::Resized(size) => {
+                render.resize((size.width, size.height));
+                ui_state.renderer.resize(size)
+            }
+            WindowEvent::KeyboardInput { event, .. } => {
+                if let Some(sel) = ui_state.focus
+                    && event.state.is_pressed()
+                {
+                    let mut text = sel.edit(rsc);
+                    match text.apply_event(event, &ui_state.input.modifiers) {
+                        TextInputResult::Unfocus => {
+                            ui_state.focus = None;
+                            ui_state.window.set_ime_allowed(false);
+                        }
+                        TextInputResult::Submit => {
+                            rsc.run_event::<Submit>(sel, (), state);
+                        }
+                        TextInputResult::Paste => {
+                            if let Ok(t) = ui_state.clipboard.get_text() {
+                                text.insert(&t);
+                            }
+                            rsc.run_event::<Edited>(sel, (), state);
+                        }
+                        TextInputResult::Copy(text) => {
+                            if let Err(err) = ui_state.clipboard.set_text(text) {
+                                eprintln!("failed to copy text to clipboard: {err}")
+                            }
+                        }
+                        TextInputResult::Used => {
+                            rsc.run_event::<Edited>(sel, (), state);
+                        }
+                        TextInputResult::Unused => {}
+                    }
+                }
+            }
+            WindowEvent::Ime(ime) => {
+                if let Some(sel) = ui_state.focus {
+                    let mut text = sel.edit(rsc);
+                    match ime {
+                        Ime::Enabled | Ime::Disabled => (),
+                        Ime::Preedit(content, _pos) => {
+                            // TODO: highlight once that's real
+                            text.replace(ui_state.ime, content);
+                            ui_state.ime = content.chars().count();
+                        }
+                        Ime::Commit(content) => {
+                            text.insert(content);
+                        }
+                    }
+                }
+            }
+            _ => (),
+        }
+        state.window_event(event, rsc, render);
+        self.request_redraw_if_needed();
+        self.state.default_state_mut().input.end_frame();
+    }
+
+    fn exit(&mut self) {
+        self.state.exit(&mut self.rsc, &mut self.render);
+    }
+}
+
+impl<State: DefaultAppState> DefaultApp<State> {
+    fn request_redraw_if_needed(&mut self) {
+        let ui_state = self.state.default_state_mut();
+        if self.render.needs_redraw(&ui_state.root, self.rsc.widgets()) {
+            ui_state.renderer.window().request_redraw();
+        }
+    }
+}
+
+pub trait RscIdx<Rsc> {
+    type Output;
+    fn get(self, rsc: &Rsc) -> &Self::Output;
+    fn get_mut(self, rsc: &mut Rsc) -> &mut Self::Output;
+}
+
+impl<State: 'static, I: RscIdx<DefaultRsc<State>>> std::ops::Index<I> for DefaultRsc<State> {
+    type Output = I::Output;
+
+    fn index(&self, index: I) -> &Self::Output {
+        index.get(self)
+    }
+}
+
+impl<State: 'static, I: RscIdx<DefaultRsc<State>>> std::ops::IndexMut<I> for DefaultRsc<State> {
+    fn index_mut(&mut self, index: I) -> &mut Self::Output {
+        index.get_mut(self)
+    }
+}
+
+impl<W: Widget, Rsc: UiRsc> RscIdx<Rsc> for WeakWidget<W> {
+    type Output = W;
+
+    fn get(self, rsc: &Rsc) -> &Self::Output {
+        &rsc.ui().widgets[self]
+    }
+
+    fn get_mut(self, rsc: &mut Rsc) -> &mut Self::Output {
+        &mut rsc.ui_mut().widgets[self]
+    }
+}
+
+impl<T: 'static, Rsc: HasWidgetState> RscIdx<Rsc> for WeakState<T> {
+    type Output = T;
+
+    fn get(self, rsc: &Rsc) -> &Self::Output {
+        rsc.widget_state().get(self)
+    }
+
+    fn get_mut(self, rsc: &mut Rsc) -> &mut Self::Output {
+        rsc.widget_state_mut().get_mut(self)
+    }
+}

src/default/render.rs

@@ -1,10 +1,7 @@
-use crate::{
-    layout::Ui,
-    render::{UiLimits, UiRenderNode},
-};
+use iris_core::{UiData, UiRenderNode, UiRenderState};
 use pollster::FutureExt;
 use std::sync::Arc;
-use wgpu::{util::StagingBelt, *};
+use wgpu::*;
 use winit::{dpi::PhysicalSize, window::Window};
 
 pub const CLEAR_COLOR: Color = Color::BLACK;
@@ -16,17 +13,29 @@ pub struct UiRenderer {
     queue: Queue,
     config: SurfaceConfiguration,
     encoder: CommandEncoder,
-    staging_belt: StagingBelt,
     pub ui: UiRenderNode,
 }
 
 impl UiRenderer {
-    pub fn update(&mut self, updates: &mut Ui) {
-        self.ui.update(&self.device, &self.queue, updates);
+    pub fn update(&mut self, ui: &mut UiData, render: &mut UiRenderState) {
+        self.ui.update(&self.device, &self.queue, ui, render);
     }
 
     pub fn draw(&mut self) {
-        let output = self.surface.get_current_texture().unwrap();
+        let output = match self.surface.get_current_texture() {
+            CurrentSurfaceTexture::Success(texture) => texture,
+            CurrentSurfaceTexture::Suboptimal(texture) => {
+                self.surface.configure(&self.device, &self.config);
+                texture
+            }
+            CurrentSurfaceTexture::Outdated | CurrentSurfaceTexture::Lost => {
+                self.surface.configure(&self.device, &self.config);
+                return;
+            }
+            CurrentSurfaceTexture::Timeout
+            | CurrentSurfaceTexture::Occluded
+            | CurrentSurfaceTexture::Validation => return,
+        };
         let view = output
             .texture
             .create_view(&TextureViewDescriptor::default());
@@ -49,16 +58,15 @@ impl UiRenderer {
         }
 
         self.queue.submit(std::iter::once(encoder.finish()));
-        self.staging_belt.finish();
-        output.present();
-        self.staging_belt.recall();
+        self.window.pre_present_notify();
+        self.queue.present(output);
     }
 
     pub fn resize(&mut self, size: &PhysicalSize<u32>) {
         self.config.width = size.width;
         self.config.height = size.height;
         self.surface.configure(&self.device, &self.config);
-        self.ui.resize(size, &self.queue);
+        self.ui.resize((size.width, size.height), &self.queue);
     }
 
     fn create_encoder(device: &Device) -> CommandEncoder {
@@ -70,10 +78,10 @@ impl UiRenderer {
     pub fn new(window: Arc<Window>) -> Self {
         let size = window.inner_size();
 
-        let instance = Instance::new(&InstanceDescriptor {
+        let instance = Instance::new(InstanceDescriptor {
             backends: Backends::PRIMARY,
-            flags: InstanceFlags::empty(),
-            ..Default::default()
+            display: Some(Box::new(window.clone())),
+            ..InstanceDescriptor::new_without_display_handle()
         });
 
         let surface = instance
@@ -85,22 +93,14 @@ impl UiRenderer {
                 power_preference: PowerPreference::default(),
                 compatible_surface: Some(&surface),
                 force_fallback_adapter: false,
+                apply_limit_buckets: false,
             })
             .block_on()
             .expect("Could not get adapter!");
 
-        let ui_limits = UiLimits::default();
-
         let (device, queue) = adapter
             .request_device(&DeviceDescriptor {
-                required_features: Features::TEXTURE_BINDING_ARRAY
-                    | Features::PARTIALLY_BOUND_BINDING_ARRAY
-                    | Features::SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING,
                 required_limits: Limits {
-                    max_binding_array_elements_per_shader_stage: ui_limits
-                        .max_binding_array_elements_per_shader_stage(),
-                    max_binding_array_sampler_elements_per_shader_stage: ui_limits
-                        .max_binding_array_sampler_elements_per_shader_stage(),
                     max_buffer_size: 1 << 30,
                     ..Default::default()
                 },
@@ -120,6 +120,7 @@ impl UiRenderer {
         let config = SurfaceConfiguration {
             usage: TextureUsages::RENDER_ATTACHMENT,
             format: surface_format,
+            color_space: SurfaceColorSpace::Auto,
             width: size.width,
             height: size.height,
             present_mode: PresentMode::AutoVsync,
@@ -130,10 +131,9 @@ impl UiRenderer {
 
         surface.configure(&device, &config);
 
-        let staging_belt = StagingBelt::new(4096 * 4);
         let encoder = Self::create_encoder(&device);
 
-        let shape_pipeline = UiRenderNode::new(&device, &queue, &config, ui_limits);
+        let ui = UiRenderNode::new(&device, &config);
 
         Self {
             surface,
@@ -141,8 +141,7 @@ impl UiRenderer {
             queue,
             config,
             encoder,
-            staging_belt,
-            ui: shape_pipeline,
+            ui,
             window,
         }
     }

src/default/sense.rs

@@ -0,0 +1,376 @@
+use crate::prelude::*;
+use std::{
+    ops::{BitOr, Deref, DerefMut},
+    rc::Rc,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum CursorButton {
+    Left,
+    Right,
+    Middle,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum CursorSense {
+    PressStart(CursorButton),
+    Pressing(CursorButton),
+    PressEnd(CursorButton),
+    HoverStart,
+    Hovering,
+    HoverEnd,
+    Scroll,
+}
+
+#[derive(Clone)]
+pub struct CursorSenses(Vec<CursorSense>);
+
+impl Event for CursorSenses {
+    type Data<'a> = CursorData<'a>;
+    type Global = Hovered;
+    fn should_run<'a>(&self, data: &Self::Data<'a>) -> Option<Self::Data<'a>> {
+        if let Some(sense) = should_run(self, &data.cursor, data.hover) {
+            let mut data = data.clone();
+            data.sense = sense;
+            Some(data)
+        } else {
+            None
+        }
+    }
+
+    /// A press or a scroll is used up by whatever answered it, so it stops
+    /// there. Hovering is not: a cursor resting somewhere goes on resting.
+    fn consumes(&self, data: &Self::Data<'_>) -> bool {
+        !data.sense.position_only()
+    }
+}
+
+/// Who the cursor was inside, before and after an input. The difference is
+/// whose hover has ended -- including a widget a higher layer has covered,
+/// which the walk stops before reaching.
+///
+/// Two buffers that swap rather than one rebuilt, so an input allocates
+/// nothing once they have grown.
+#[derive(Default)]
+pub struct Hovered {
+    was: Vec<WidgetId>,
+    now: Vec<WidgetId>,
+}
+
+impl CursorSense {
+    pub fn click() -> Self {
+        Self::PressStart(CursorButton::Left)
+    }
+    pub fn click_or_drag() -> CursorSenses {
+        Self::click() | Self::Pressing(CursorButton::Left)
+    }
+    pub fn unclick() -> Self {
+        Self::PressEnd(CursorButton::Left)
+    }
+    pub fn is_dragging(&self) -> bool {
+        matches!(self, CursorSense::Pressing(CursorButton::Left))
+    }
+
+    /// False if the sense is a button or a scroll, true if it is only about
+    /// where the cursor is.
+    fn position_only(&self) -> bool {
+        matches!(self, Self::HoverStart | Self::Hovering | Self::HoverEnd)
+    }
+}
+
+#[derive(Default, Clone)]
+pub struct CursorState {
+    pub pos: Vec2,
+    pub exists: bool,
+    pub buttons: CursorButtons,
+    pub scroll_delta: Vec2,
+}
+
+#[derive(Default, Clone)]
+pub struct CursorButtons {
+    pub left: ActivationState,
+    pub middle: ActivationState,
+    pub right: ActivationState,
+}
+
+impl CursorButtons {
+    pub fn select(&self, button: &CursorButton) -> &ActivationState {
+        match button {
+            CursorButton::Left => &self.left,
+            CursorButton::Right => &self.right,
+            CursorButton::Middle => &self.middle,
+        }
+    }
+
+    pub fn end_frame(&mut self) {
+        self.left.end_frame();
+        self.middle.end_frame();
+        self.right.end_frame();
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (CursorButton, &ActivationState)> {
+        [
+            CursorButton::Left,
+            CursorButton::Middle,
+            CursorButton::Right,
+        ]
+        .into_iter()
+        .map(|b| (b, self.select(&b)))
+    }
+}
+
+impl CursorState {
+    /// True if the cursor is only reporting where it is: no button and no
+    /// scroll this frame.
+    pub fn position_only(&self) -> bool {
+        self.scroll_delta == Vec2::ZERO && self.buttons.iter().all(|(_, state)| state.is_off())
+    }
+
+    pub fn end_frame(&mut self) {
+        self.buttons.end_frame();
+        self.scroll_delta = Vec2::ZERO;
+    }
+}
+
+#[derive(Debug, Clone, Copy, Default, PartialEq)]
+pub enum ActivationState {
+    Start,
+    On,
+    End,
+    #[default]
+    Off,
+}
+
+/// this and other similar stuff has a generic
+/// because I kind of want to make CursorModule generic
+/// or basically have some way to have custom senses
+/// that depend on active widget positions
+/// but I'm not sure how or if worth it
+pub struct Sensor<Ctx: HasEvents, Data> {
+    pub senses: CursorSenses,
+    pub f: Rc<dyn EventFn<Ctx, Data>>,
+}
+
+pub type SenseShape = UiRegion;
+
+#[derive(Clone)]
+pub struct CursorData<'a> {
+    /// where this widget was hit
+    pub pos: Vec2,
+    pub size: Vec2,
+    pub scroll_delta: Vec2,
+    pub hover: ActivationState,
+    pub cursor: CursorState,
+    /// the first sense that triggered this
+    pub sense: CursorSense,
+    pub render: &'a UiRenderState,
+}
+
+pub trait SensorUi {
+    fn run_sensors<Rsc: HasEvents>(
+        &self,
+        rsc: &mut Rsc,
+        state: &mut Rsc::State,
+        cursor: CursorState,
+    );
+}
+
+impl SensorUi for UiRenderState {
+    fn run_sensors<Rsc: HasEvents>(
+        &self,
+        rsc: &mut Rsc,
+        state: &mut Rsc::State,
+        cursor: CursorState,
+    ) {
+        // in order to remove this take, need to store active list in UiRenderState somehow
+        // this would probably be done through a generic parameter that adds yet another rsc /
+        // state like thing, but local to render state, and is passed to UiRsc events so you can
+        // update it there?
+        let active = std::mem::take(&mut rsc.events_mut().get_type::<CursorSense>().active);
+        let mut hovered = std::mem::take(&mut rsc.events_mut().get_type::<CursorSense>().global);
+        hovered.now.clear();
+        let position_only = cursor.position_only();
+        let region_of = |id| self.window_region(&id);
+
+        for layer in self.layers.indices().rev() {
+            let mut consumed = false;
+            for id in active.get(&layer).into_flat_iter().map(|(id, _)| *id) {
+                let Some(region) = region_of(id) else {
+                    continue;
+                };
+                if !cursor.exists || !region.contains(cursor.pos) {
+                    continue;
+                }
+                hovered.now.push(id);
+                let hover = match hovered.was.contains(&id) {
+                    true => ActivationState::On,
+                    false => ActivationState::Start,
+                };
+                // A press or a scroll stops where something answered it, so a
+                // button over a list does not swallow the list's scrolling.
+                consumed |= deliver(self, rsc, state, id, hover, &cursor, region);
+                // A cursor doing neither stops at whatever it is over, so
+                // hovering does not reach through.
+                consumed |= position_only;
+            }
+            // Applied after the layer, never during it: senses on one layer do
+            // not block each other.
+            if consumed {
+                break;
+            }
+        }
+
+        // Whatever the cursor was inside and is not now, whether it left or a
+        // layer above took the input before the walk reached it. A widget that
+        // stopped being drawn has no region to report and is simply dropped.
+        for &id in &hovered.was {
+            if !hovered.now.contains(&id)
+                && let Some(region) = region_of(id)
+            {
+                deliver(self, rsc, state, id, ActivationState::End, &cursor, region);
+            }
+        }
+        std::mem::swap(&mut hovered.was, &mut hovered.now);
+
+        let senses = rsc.events_mut().get_type::<CursorSense>();
+        senses.active = active;
+        senses.global = hovered;
+    }
+}
+
+/// Runs one widget's cursor senses, and says whether they used up the input.
+fn deliver<Rsc: HasEvents>(
+    render: &UiRenderState,
+    rsc: &mut Rsc,
+    state: &mut Rsc::State,
+    id: WidgetId,
+    hover: ActivationState,
+    cursor: &CursorState,
+    region: PixelRegion,
+) -> bool {
+    let data = CursorData {
+        pos: cursor.pos - region.top_left,
+        size: region.bot_right - region.top_left,
+        scroll_delta: cursor.scroll_delta,
+        hover,
+        cursor: cursor.clone(),
+        // this does not have any meaning;
+        // might wanna set up Event to have a prepare stage
+        sense: CursorSense::Hovering,
+        render,
+    };
+    rsc.run_event::<CursorSense>(id, data, state)
+}
+
+pub fn should_run(
+    senses: &CursorSenses,
+    cursor: &CursorState,
+    hover: ActivationState,
+) -> Option<CursorSense> {
+    for sense in senses.iter() {
+        // A widget the cursor is no longer inside senses only its position:
+        // the press that ended its hover landed on something else.
+        if !hover.is_on() && !sense.position_only() {
+            continue;
+        }
+        if match sense {
+            CursorSense::PressStart(button) => cursor.buttons.select(button).is_start(),
+            CursorSense::Pressing(button) => cursor.buttons.select(button).is_on(),
+            CursorSense::PressEnd(button) => cursor.buttons.select(button).is_end(),
+            CursorSense::HoverStart => hover.is_start(),
+            CursorSense::Hovering => hover.is_on(),
+            CursorSense::HoverEnd => hover.is_end(),
+            CursorSense::Scroll => cursor.scroll_delta != Vec2::ZERO,
+        } {
+            return Some(*sense);
+        }
+    }
+    None
+}
+
+impl ActivationState {
+    pub fn is_start(&self) -> bool {
+        *self == Self::Start
+    }
+    pub fn is_on(&self) -> bool {
+        *self == Self::Start || *self == Self::On
+    }
+    pub fn is_end(&self) -> bool {
+        *self == Self::End
+    }
+    pub fn is_off(&self) -> bool {
+        *self == Self::End || *self == Self::Off
+    }
+    pub fn update(&mut self, on: bool) {
+        *self = match *self {
+            Self::Start => match on {
+                true => Self::On,
+                false => Self::End,
+            },
+            Self::On => match on {
+                true => Self::On,
+                false => Self::End,
+            },
+            Self::End => match on {
+                true => Self::Start,
+                false => Self::Off,
+            },
+            Self::Off => match on {
+                true => Self::Start,
+                false => Self::Off,
+            },
+        }
+    }
+
+    pub fn end_frame(&mut self) {
+        match self {
+            Self::Start => *self = Self::On,
+            Self::End => *self = Self::Off,
+            _ => (),
+        }
+    }
+}
+
+impl EventLike for CursorSense {
+    type Event = CursorSenses;
+    fn into_event(self) -> Self::Event {
+        self.into()
+    }
+}
+
+impl Deref for CursorSenses {
+    type Target = Vec<CursorSense>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for CursorSenses {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl From<CursorSense> for CursorSenses {
+    fn from(val: CursorSense) -> Self {
+        CursorSenses(vec![val])
+    }
+}
+
+impl BitOr for CursorSense {
+    type Output = CursorSenses;
+
+    fn bitor(self, rhs: Self) -> Self::Output {
+        CursorSenses(vec![self, rhs])
+    }
+}
+
+impl BitOr<CursorSense> for CursorSenses {
+    type Output = Self;
+
+    fn bitor(mut self, rhs: CursorSense) -> Self::Output {
+        self.0.push(rhs);
+        self
+    }
+}

src/default/state.rs

@@ -0,0 +1,75 @@
+use iris_core::{
+    WidgetId,
+    util::{HashMap, HashSet},
+};
+use std::{
+    any::{Any, TypeId},
+    marker::PhantomData,
+};
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+struct Key {
+    id: WidgetId,
+    ty: TypeId,
+    i: usize,
+}
+
+#[derive(Default)]
+pub struct WidgetState {
+    widgets: HashMap<WidgetId, HashSet<(TypeId, usize)>>,
+    counts: HashMap<(WidgetId, TypeId), usize>,
+    map: HashMap<Key, Box<dyn Any>>,
+}
+
+impl WidgetState {
+    pub fn new() -> Self {
+        Self::default()
+    }
+    pub fn add<T: 'static>(&mut self, id: WidgetId, data: T) -> WeakState<T> {
+        let ty = TypeId::of::<T>();
+        let count = self.counts.entry((id, ty)).or_default();
+        let i = *count;
+        let key = Key { ty, i, id };
+        self.map.insert(key, Box::new(data));
+        self.widgets.entry(id).or_default().insert((ty, i));
+        *count += 1;
+        WeakState {
+            key,
+            _pd: PhantomData,
+        }
+    }
+    pub fn remove(&mut self, id: WidgetId) {
+        for &(ty, i) in self.widgets.get(&id).into_iter().flatten() {
+            self.map.remove(&Key { id, ty, i });
+        }
+    }
+    pub fn get<T: 'static>(&self, state: WeakState<T>) -> &T {
+        self.map.get(&state.key).unwrap().downcast_ref().unwrap()
+    }
+    pub fn get_mut<T: 'static>(&mut self, state: WeakState<T>) -> &mut T {
+        self.map
+            .get_mut(&state.key)
+            .unwrap()
+            .downcast_mut()
+            .unwrap()
+    }
+}
+
+#[derive(Clone, Copy)]
+pub struct WeakState<T> {
+    key: Key,
+    _pd: PhantomData<T>,
+}
+
+pub trait HasWidgetState {
+    fn widget_state(&self) -> &WidgetState;
+    fn widget_state_mut(&mut self) -> &mut WidgetState;
+}
+
+impl<'a, T: 'static> FnOnce<(&'a mut WidgetState,)> for WeakState<T> {
+    type Output = &'a mut T;
+
+    extern "rust-call" fn call_once(self, (state,): (&'a mut WidgetState,)) -> Self::Output {
+        state.get_mut(self)
+    }
+}

src/default/task.rs

@@ -0,0 +1,64 @@
+use iris_core::HasState;
+use std::{pin::Pin, sync::Arc};
+use tokio::{
+    runtime::Runtime,
+    sync::mpsc::{
+        UnboundedReceiver as AsyncReceiver, UnboundedSender as AsyncSender,
+        unbounded_channel as async_channel,
+    },
+};
+
+pub trait TaskUpdate<Rsc: HasState>: FnOnce(&mut Rsc::State, &mut Rsc) + Send {}
+impl<F: FnOnce(&mut Rsc::State, &mut Rsc) + Send, Rsc: HasState> TaskUpdate<Rsc> for F {}
+
+/// Hands an update from a task to the thread that owns the ui. Delivery and
+/// waking are one act: a host posts the update as a message its loop already
+/// carries, so nothing has to wake the loop separately, or claim a redraw to
+/// be looked at.
+pub trait TaskQueue<Rsc: HasState>: Send + Sync + 'static {
+    fn send(&self, update: Box<dyn TaskUpdate<Rsc>>);
+}
+
+pub struct Tasks<Rsc: HasState> {
+    start: AsyncSender<BoxTask>,
+    queue: Arc<dyn TaskQueue<Rsc>>,
+}
+
+pub struct TaskCtx<Rsc: HasState> {
+    queue: Arc<dyn TaskQueue<Rsc>>,
+}
+
+impl<Rsc: HasState> TaskCtx<Rsc> {
+    pub fn update(&mut self, f: impl TaskUpdate<Rsc> + 'static) {
+        self.queue.send(Box::new(f));
+    }
+}
+
+type BoxTask = Pin<Box<dyn Future<Output = ()> + Send>>;
+
+impl<Rsc: HasState> Tasks<Rsc> {
+    pub fn init(queue: Arc<dyn TaskQueue<Rsc>>) -> Self {
+        let (start, start_recv) = async_channel();
+        std::thread::spawn(|| {
+            let rt = Runtime::new().unwrap();
+            rt.block_on(listen(start_recv))
+        });
+        Self { start, queue }
+    }
+
+    pub fn spawn<F: AsyncFnOnce(TaskCtx<Rsc>) + 'static + std::marker::Send>(&mut self, task: F)
+    where
+        F::CallOnceFuture: Send,
+    {
+        let queue = self.queue.clone();
+        let _ = self.start.send(Box::pin(async move {
+            task(TaskCtx { queue }).await;
+        }));
+    }
+}
+
+async fn listen(mut recv: AsyncReceiver<BoxTask>) {
+    while let Some(task) = recv.recv().await {
+        tokio::spawn(task);
+    }
+}

src/event.rs

@@ -0,0 +1,87 @@
+use iris_core::*;
+use iris_macro::*;
+use std::sync::Arc;
+
+use crate::default::{TaskCtx, TaskUpdate, Tasks};
+
+pub trait Eventable<Rsc: HasEvents, Tag>: WidgetLike<Rsc, Tag> {
+    fn on<E: EventLike>(
+        self,
+        event: E,
+        f: impl for<'a> WidgetEventFn<Rsc, <E::Event as Event>::Data<'a>, Self::Widget>,
+    ) -> impl WidgetIdFn<Rsc, Self::Widget> {
+        move |rsc| {
+            let id = self.add(rsc);
+            rsc.register_event(id, event.into_event(), move |ctx, rsc| {
+                f(
+                    EventIdCtx {
+                        widget: id,
+                        state: ctx.state,
+                        data: ctx.data,
+                    },
+                    rsc,
+                );
+            });
+            id
+        }
+    }
+}
+impl<WL: WidgetLike<Rsc, Tag>, Rsc: HasEvents, Tag> Eventable<Rsc, Tag> for WL {}
+
+widget_trait! {
+    pub trait TaskEventable<Rsc: HasEvents + HasTasks>;
+    fn task_on<'a, E: EventLike, F: AsyncWidgetEventFn<Rsc, WL::Widget>>(
+        self,
+        event: E,
+        f: F,
+    ) -> impl WidgetIdFn<Rsc, WL::Widget>
+        where <E::Event as Event>::Data<'a>: Send,
+        for<'b> F::CallRefFuture<'b>: Send,
+    {
+        let f = Arc::new(f);
+        move |rsc| {
+            let id = self.add(rsc);
+            rsc.register_event(id, event.into_event(), move |_, rsc| {
+                let f = f.clone();
+                rsc.tasks_mut().spawn(async move |task| {
+                    f(AsyncEventIdCtx {
+                        widget: id,
+                        task,
+                    }).await;
+                });
+            });
+            id
+        }
+    }
+}
+
+pub trait HasTasks: Sized + HasState + HasEvents {
+    fn tasks_mut(&mut self) -> &mut Tasks<Self>;
+
+    fn spawn_task<F: AsyncFnOnce(TaskCtx<Self>) + 'static + std::marker::Send>(&mut self, task: F)
+    where
+        F::CallOnceFuture: Send,
+    {
+        self.tasks_mut().spawn(task);
+    }
+}
+
+pub trait AsyncWidgetEventFn<Rsc: HasEvents, W: ?Sized>:
+    AsyncFn(AsyncEventIdCtx<Rsc, W>) + Send + Sync + 'static
+{
+}
+impl<Rsc: HasEvents, F: AsyncFn(AsyncEventIdCtx<Rsc, W>) + Send + Sync + 'static, W: ?Sized>
+    AsyncWidgetEventFn<Rsc, W> for F
+{
+}
+
+pub struct AsyncEventIdCtx<Rsc: HasEvents, W: ?Sized> {
+    pub widget: WeakWidget<W>,
+    task: TaskCtx<Rsc>,
+}
+
+impl<Rsc: HasEvents, W: ?Sized> AsyncEventIdCtx<Rsc, W> {
+    pub fn update(&mut self, f: impl TaskUpdate<Rsc> + 'static) {
+        self.task.update(f);
+    }
+}

src/harness.rs

@@ -0,0 +1,320 @@
+//! A ui with no window: build a tree, run frames, move a pointer, and read
+//! back where widgets landed.
+//!
+//! It does not draw. A claim about pixels still needs a real surface.
+
+use crate::prelude::*;
+use std::{
+    sync::{
+        Arc,
+        mpsc::{Receiver, SyncSender, sync_channel},
+    },
+    time::Duration,
+};
+
+/// There is no loop here to post to, so updates queue until the test asks
+/// for them.
+struct Queue(SyncSender<Box<dyn TaskUpdate<DefaultRsc<HarnessState>>>>);
+
+impl TaskQueue<DefaultRsc<HarnessState>> for Queue {
+    fn send(&self, update: Box<dyn TaskUpdate<DefaultRsc<HarnessState>>>) {
+        let _ = self.0.send(update);
+    }
+}
+
+/// `assert_eq!` for where a frame put a widget, written as its two corners.
+#[macro_export]
+macro_rules! assert_corners {
+    ($harness:expr, $id:expr, ($x0:expr, $y0:expr), ($x1:expr, $y1:expr)) => {
+        assert_eq!(
+            $harness.region(&$id).expect("widget drew nothing"),
+            $crate::core::PixelRegion {
+                top_left: $crate::core::util::Vec2::new($x0 as f32, $y0 as f32),
+                bot_right: $crate::core::util::Vec2::new($x1 as f32, $y1 as f32),
+            }
+        );
+    };
+}
+pub use crate::assert_corners;
+
+/// One replayed pointer sample, cut down to what a window delivers: where the
+/// pointer is, and whether the button changed.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum TouchAction {
+    Down,
+    Move,
+    Up,
+}
+
+impl TouchAction {
+    fn parse(word: &str) -> Option<Self> {
+        match word {
+            "down" => Some(Self::Down),
+            "move" => Some(Self::Move),
+            "up" => Some(Self::Up),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct TouchSample {
+    pub t_ms: u64,
+    pub action: TouchAction,
+    pub pos: Vec2,
+}
+
+/// A recorded gesture, in the output's own pixels: `<ms> down|move|up <x> <y>`
+/// a line, `#` to end of line ignored.
+///
+/// One parser for both ways of replaying a recording -- into a harness, and
+/// into a real window -- so the two cannot read the same file differently.
+pub struct TouchScript {
+    pub samples: Vec<TouchSample>,
+}
+
+impl TouchScript {
+    pub fn parse(text: &str) -> Result<Self, String> {
+        let mut samples: Vec<TouchSample> = Vec::new();
+        for (i, line) in text.lines().enumerate() {
+            let line = line.split('#').next().unwrap_or("").trim();
+            if line.is_empty() {
+                continue;
+            }
+            let at = |what: &str| format!("touch script line {}: {what}: {line:?}", i + 1);
+            let mut words = line.split_whitespace();
+            let (Some(t), Some(action), Some(x), Some(y), None) = (
+                words.next(),
+                words.next(),
+                words.next(),
+                words.next(),
+                words.next(),
+            ) else {
+                return Err(at("expected `t_ms action x y`"));
+            };
+            let t_ms: u64 = t.parse().map_err(|_| at("t_ms is not a whole number"))?;
+            let action =
+                TouchAction::parse(action).ok_or_else(|| at("action is not down/move/up"))?;
+            let x: f32 = x.parse().map_err(|_| at("x is not a number"))?;
+            let y: f32 = y.parse().map_err(|_| at("y is not a number"))?;
+            if let Some(last) = samples.last()
+                && t_ms < last.t_ms
+            {
+                return Err(at("samples must be in time order"));
+            }
+            samples.push(TouchSample {
+                t_ms,
+                action,
+                pos: Vec2::new(x, y),
+            });
+        }
+        Ok(Self { samples })
+    }
+}
+
+#[derive(Default)]
+pub struct HarnessState {
+    pub root: Option<StrongWidget>,
+}
+
+impl HasRoot for HarnessState {
+    fn set_root(&mut self, root: StrongWidget) {
+        self.root = Some(root);
+    }
+}
+
+pub struct Harness {
+    pub rsc: DefaultRsc<HarnessState>,
+    pub render: UiRenderState,
+    pub state: HarnessState,
+    updates: Receiver<Box<dyn TaskUpdate<DefaultRsc<HarnessState>>>>,
+    cursor: CursorState,
+}
+
+impl Harness {
+    /// `size` is the output in physical pixels.
+    pub fn new(size: impl Into<Vec2>) -> Self {
+        // A `TaskQueue` must be `Sync`, which `mpsc::Sender` is not; the
+        // bound that comes with `SyncSender` is far past anything a test
+        // leaves unread.
+        let (send, updates) = sync_channel(1024);
+        let rsc = DefaultRsc::init(Arc::new(Queue(send)));
+        let mut render = UiRenderState::new();
+        render.resize(size);
+        Self {
+            rsc,
+            render,
+            state: HarnessState::default(),
+            updates,
+            cursor: CursorState::default(),
+        }
+    }
+
+    pub fn size(&self) -> Vec2 {
+        self.render.output_size()
+    }
+
+    pub fn resize(&mut self, size: impl Into<Vec2>) {
+        self.render.resize(size);
+    }
+
+    /// Sets the root and lays it out, so a pointer event has something to hit.
+    pub fn set_root<T>(&mut self, widget: impl WidgetLike<DefaultRsc<HarnessState>, T>) {
+        widget.set_root(&mut self.rsc, &mut self.state);
+        self.frame();
+    }
+
+    pub fn needs_redraw(&self) -> bool {
+        self.render
+            .needs_redraw(&self.state.root, self.rsc.widgets())
+    }
+
+    pub fn apply_updates(&mut self) -> usize {
+        let mut applied = 0;
+        while let Ok(update) = self.updates.try_recv() {
+            update(&mut self.state, &mut self.rsc);
+            applied += 1;
+        }
+        applied
+    }
+
+    /// Waits for a task's first update, then applies everything waiting.
+    /// False if none arrived in time.
+    #[must_use]
+    pub fn await_update(&mut self, timeout: Duration) -> bool {
+        let Ok(update) = self.updates.recv_timeout(timeout) else {
+            return false;
+        };
+        update(&mut self.state, &mut self.rsc);
+        self.apply_updates();
+        true
+    }
+
+    /// Lays the tree out and builds its primitives.
+    pub fn frame(&mut self) {
+        self.apply_updates();
+        self.render.update(&self.state.root, &mut self.rsc);
+    }
+
+    /// Where the last frame put a widget, or `None` if it drew nothing.
+    pub fn region(&self, id: &impl IdLike) -> Option<PixelRegion> {
+        self.render.window_region(id)
+    }
+
+    pub fn move_to(&mut self, pos: impl Into<Vec2>) {
+        self.cursor.pos = pos.into();
+        self.cursor.exists = true;
+        self.sense();
+    }
+
+    pub fn leave(&mut self) {
+        self.cursor.exists = false;
+        self.sense();
+    }
+
+    pub fn press(&mut self, button: CursorButton) {
+        self.button(button).update(true);
+        self.sense();
+    }
+
+    pub fn release(&mut self, button: CursorButton) {
+        self.button(button).update(false);
+        self.sense();
+    }
+
+    /// A wheel carries no position, so this goes wherever the cursor was last
+    /// moved to -- nowhere, until it has been moved.
+    pub fn scroll(&mut self, delta: impl Into<Vec2>) {
+        self.cursor.scroll_delta = delta.into();
+        self.sense();
+    }
+
+    pub fn click(&mut self, pos: impl Into<Vec2>) {
+        self.move_to(pos);
+        self.press(CursorButton::Left);
+        self.release(CursorButton::Left);
+    }
+
+    /// Drives a recorded gesture through the harness.
+    pub fn replay(&mut self, script: &TouchScript) {
+        for sample in &script.samples {
+            match sample.action {
+                TouchAction::Down => {
+                    self.move_to(sample.pos);
+                    self.press(CursorButton::Left);
+                }
+                TouchAction::Move => self.move_to(sample.pos),
+                TouchAction::Up => {
+                    self.move_to(sample.pos);
+                    self.release(CursorButton::Left);
+                }
+            }
+        }
+    }
+
+    fn button(&mut self, button: CursorButton) -> &mut ActivationState {
+        let buttons = &mut self.cursor.buttons;
+        match button {
+            CursorButton::Left => &mut buttons.left,
+            CursorButton::Middle => &mut buttons.middle,
+            CursorButton::Right => &mut buttons.right,
+        }
+    }
+
+    /// Dispatches against the layout of the last frame, which is what a
+    /// window delivers input against too.
+    fn sense(&mut self) {
+        let cursor = self.cursor.clone();
+        self.render
+            .run_sensors(&mut self.rsc, &mut self.state, cursor);
+        self.cursor.end_frame();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn parse(text: &str) -> Result<Vec<(u64, TouchAction, f32, f32)>, String> {
+        Ok(TouchScript::parse(text)?
+            .samples
+            .iter()
+            .map(|s| (s.t_ms, s.action, s.pos.x, s.pos.y))
+            .collect())
+    }
+
+    #[test]
+    fn a_recording_is_time_action_and_a_point() {
+        assert_eq!(
+            parse("0 down 10 20\n16 move 10.5 24\n32 up 10.5 24").unwrap(),
+            [
+                (0, TouchAction::Down, 10.0, 20.0),
+                (16, TouchAction::Move, 10.5, 24.0),
+                (32, TouchAction::Up, 10.5, 24.0),
+            ]
+        );
+    }
+
+    #[test]
+    fn blank_lines_and_comments_are_not_samples() {
+        assert_eq!(
+            parse("# a flick\n\n 0 down 1 2   # the finger lands\n\n").unwrap(),
+            [(0, TouchAction::Down, 1.0, 2.0)]
+        );
+    }
+
+    #[test]
+    fn a_recording_that_goes_backwards_is_rejected() {
+        // Replay waits out the gap between samples, so time running backwards
+        // would silently become no wait at all.
+        let err = parse("16 down 1 2\n0 up 1 2").unwrap_err();
+        assert!(err.contains("time order"), "{err}");
+    }
+
+    #[test]
+    fn a_line_that_is_not_a_sample_says_which_line() {
+        let err = parse("0 down 1 2\n16 wiggle 1 2").unwrap_err();
+        assert!(err.contains("line 2"), "{err}");
+        assert!(err.contains("down/move/up"), "{err}");
+    }
+}

src/layout/attr.rs

@@ -1,20 +0,0 @@
-use crate::layout::{Ui, WidgetId, WidgetIdFn, WidgetLike};
-
-pub trait WidgetAttr<W> {
-    type Input;
-    fn run(ui: &mut Ui, id: &WidgetId<W>, input: Self::Input);
-}
-
-pub trait Attrable<W, Tag> {
-    fn attr<A: WidgetAttr<W>>(self, input: A::Input) -> impl WidgetIdFn<W>;
-}
-
-impl<WL: WidgetLike<Tag>, Tag> Attrable<WL::Widget, Tag> for WL {
-    fn attr<A: WidgetAttr<WL::Widget>>(self, input: A::Input) -> impl WidgetIdFn<WL::Widget> {
-        |ui| {
-            let id = self.add(ui);
-            A::run(ui, &id, input);
-            id
-        }
-    }
-}

src/layout/data.rs

@@ -1,27 +0,0 @@
-use std::any::{Any, TypeId};
-
-use crate::util::{HashMap, Id};
-
-#[derive(Default)]
-pub struct UiData {
-    map: HashMap<TypeId, Box<dyn Any>>,
-}
-
-impl UiData {
-    pub fn get<T: 'static>(&self) -> Option<&T> {
-        self.map
-            .get(&TypeId::of::<T>())
-            .map(|d| d.downcast_ref().unwrap())
-    }
-    pub fn get_mut<T: 'static>(&mut self) -> Option<&mut T> {
-        self.map
-            .get_mut(&TypeId::of::<T>())
-            .map(|d| d.downcast_mut().unwrap())
-    }
-
-    pub fn emit_remove(&mut self, id: &Id) {
-        for (tid, f) in &mut self.on_remove {
-            let data = self.map.get_mut(tid).unwrap().downcast_ref().unwrap();
-        }
-    }
-}

src/layout/event.rs

@@ -1,215 +0,0 @@
-use std::{hash::Hash, rc::Rc};
-
-use crate::{
-    layout::{IdFnTag, Ui, UiModule, WidgetId, WidgetIdFn, WidgetLike},
-    util::{HashMap, Id},
-};
-
-pub trait Event: Sized {
-    type Module<Ctx: 'static>: EventModule<Self, Ctx>;
-    type Data: Clone;
-}
-
-pub struct EventCtx<'a, Ctx, Data> {
-    pub ui: &'a mut Ui,
-    pub state: &'a mut Ctx,
-    pub data: Data,
-}
-
-pub type ECtx<'a, Ctx, Data, W> = EventIdCtx<'a, Ctx, Data, W>;
-pub struct EventIdCtx<'a, Ctx, Data, W> {
-    pub id: &'a WidgetId<W>,
-    pub ui: &'a mut Ui,
-    pub state: &'a mut Ctx,
-    pub data: Data,
-}
-
-pub trait EventFn<Ctx, Data>: Fn(EventCtx<Ctx, Data>) + 'static {}
-impl<F: Fn(EventCtx<Ctx, Data>) + 'static, Ctx, Data> EventFn<Ctx, Data> for F {}
-
-pub trait WidgetEventFn<Ctx, Data, W>: Fn(EventIdCtx<Ctx, Data, W>) + 'static {}
-impl<F: Fn(EventIdCtx<Ctx, Data, W>) + 'static, Ctx, Data, W> WidgetEventFn<Ctx, Data, W> for F {}
-
-// TODO: naming in here is a bit weird like eventable
-#[macro_export]
-macro_rules! event_ctx {
-    ($ty: ty) => {
-        mod local_event_trait {
-            use super::*;
-            #[allow(unused_imports)]
-            use $crate::prelude::*;
-
-            pub trait EventableCtx<W, Tag, Ctx: 'static> {
-                fn on<E: Event>(
-                    self,
-                    event: E,
-                    f: impl WidgetEventFn<Ctx, E::Data, W>,
-                ) -> impl WidgetIdFn<W> + EventableCtx<W, IdFnTag, Ctx>;
-            }
-
-            impl<WL: WidgetLike<Tag>, Tag> EventableCtx<WL::Widget, Tag, $ty> for WL {
-                fn on<E: Event>(
-                    self,
-                    event: E,
-                    f: impl WidgetEventFn<$ty, E::Data, WL::Widget>,
-                ) -> impl WidgetIdFn<WL::Widget> + EventableCtx<WL::Widget, IdFnTag, $ty> {
-                    eventable::Eventable::on(self, event, f)
-                }
-            }
-        }
-        use local_event_trait::*;
-    };
-}
-pub use event_ctx;
-
-pub mod eventable {
-    use super::*;
-
-    pub trait Eventable<W, Tag> {
-        fn on<E: Event, Ctx: 'static>(
-            self,
-            event: E,
-            f: impl WidgetEventFn<Ctx, E::Data, W>,
-        ) -> impl WidgetIdFn<W> + Eventable<W, IdFnTag>;
-    }
-
-    impl<WL: WidgetLike<Tag>, Tag> Eventable<WL::Widget, Tag> for WL {
-        fn on<E: Event, Ctx: 'static>(
-            self,
-            event: E,
-            f: impl WidgetEventFn<Ctx, E::Data, WL::Widget>,
-        ) -> impl WidgetIdFn<WL::Widget> {
-            move |ui| {
-                let id = self.add(ui);
-                let id_ = id.weak();
-                ui.register_event(&id, event, move |ctx| {
-                    f(EventIdCtx {
-                        id: &id_.strong(),
-                        state: ctx.state,
-                        data: ctx.data,
-                        ui: ctx.ui,
-                    });
-                });
-                id
-            }
-        }
-    }
-}
-
-pub trait DefaultEvent: Hash + Eq + 'static {
-    type Data: Clone;
-}
-
-impl<E: DefaultEvent> Event for E {
-    type Module<Ctx: 'static> = DefaultEventModule<E, Ctx>;
-    type Data = E::Data;
-}
-
-pub trait EventModule<E: Event, Ctx>: UiModule + Default {
-    fn register(&mut self, id: Id, event: E, f: impl EventFn<Ctx, E::Data>);
-    fn run<'a>(
-        &self,
-        id: &Id,
-        event: E,
-    ) -> Option<impl Fn(EventCtx<Ctx, E::Data>) + use<'a, Self, E, Ctx>>;
-}
-
-type EventFnMap<Ctx, Data> = HashMap<Id, Vec<Rc<dyn EventFn<Ctx, Data>>>>;
-pub struct DefaultEventModule<E: Event, Ctx> {
-    map: HashMap<E, EventFnMap<Ctx, <E as Event>::Data>>,
-}
-
-impl<E: Event + 'static, Ctx: 'static> UiModule for DefaultEventModule<E, Ctx> {
-    fn on_remove(&mut self, id: &Id) {
-        for map in self.map.values_mut() {
-            map.remove(id);
-        }
-    }
-}
-
-pub trait HashableEvent: Event + Hash + Eq + 'static {}
-impl<E: Event + Hash + Eq + 'static> HashableEvent for E {}
-
-impl<E: HashableEvent, Ctx: 'static> EventModule<E, Ctx> for DefaultEventModule<E, Ctx> {
-    fn register(&mut self, id: Id, event: E, f: impl EventFn<Ctx, <E as Event>::Data>) {
-        self.map
-            .entry(event)
-            .or_default()
-            .entry(id)
-            .or_default()
-            .push(Rc::new(f));
-    }
-
-    fn run<'a>(
-        &self,
-        id: &Id,
-        event: E,
-    ) -> Option<impl Fn(EventCtx<Ctx, E::Data>) + use<'a, E, Ctx>> {
-        if let Some(map) = self.map.get(&event)
-            && let Some(fs) = map.get(id)
-        {
-            let fs = fs.clone();
-            Some(move |ctx: EventCtx<Ctx, <E as Event>::Data>| {
-                for f in &fs {
-                    f(EventCtx {
-                        ui: ctx.ui,
-                        state: ctx.state,
-                        data: ctx.data.clone(),
-                    })
-                }
-            })
-        } else {
-            None
-        }
-    }
-}
-
-impl<E: HashableEvent, Ctx: 'static> DefaultEventModule<E, Ctx> {
-    pub fn run_all(&self, event: E, ctx: EventCtx<Ctx, E::Data>)
-    where
-        E::Data: Clone,
-    {
-        if let Some(map) = self.map.get(&event) {
-            for fs in map.values() {
-                for f in fs {
-                    f(EventCtx {
-                        ui: ctx.ui,
-                        state: ctx.state,
-                        data: ctx.data.clone(),
-                    })
-                }
-            }
-        }
-    }
-}
-
-impl<E: Event + 'static, Ctx: 'static> Default for DefaultEventModule<E, Ctx> {
-    fn default() -> Self {
-        Self {
-            map: Default::default(),
-        }
-    }
-}
-
-impl Ui {
-    pub fn run_event<E: Event, Ctx: 'static, W>(
-        &mut self,
-        ctx: &mut Ctx,
-        id: &WidgetId<W>,
-        event: E,
-        data: E::Data,
-    ) {
-        if let Some(f) = self
-            .data
-            .modules
-            .get_mut::<E::Module<Ctx>>()
-            .run(&id.id, event)
-        {
-            f(EventCtx {
-                ui: self,
-                state: ctx,
-                data,
-            });
-        }
-    }
-}

src/layout/id.rs

@@ -1,180 +0,0 @@
-use std::{any::TypeId, marker::PhantomData, sync::mpsc::Sender};
-
-use crate::{
-    layout::{Ui, WidgetLike},
-    util::{Id, RefCounter},
-};
-
-pub struct AnyWidget;
-
-/// An identifier for a widget that can index a UI to get the associated widget.
-/// It should always remain valid; it keeps a ref count and removes the widget from the UI if all
-/// references are dropped.
-///
-/// W does not need to implement widget so that AnyWidget is valid;
-/// Instead, add generic bounds on methods that take an ID if they need specific data.
-///
-/// TODO: ergonomic clones when they get put in rust-analyzer & don't cause ICEs?
-#[repr(C)]
-pub struct WidgetId<W = AnyWidget> {
-    pub(super) ty: TypeId,
-    pub(super) id: Id,
-    counter: RefCounter,
-    send: Sender<Id>,
-    _pd: PhantomData<W>,
-}
-
-#[repr(C)]
-pub struct WeakWidgetId<W = AnyWidget> {
-    pub(super) ty: TypeId,
-    pub(super) id: Id,
-    counter: RefCounter,
-    send: Sender<Id>,
-    _pd: PhantomData<W>,
-}
-
-impl<W> PartialEq for WidgetId<W> {
-    fn eq(&self, other: &Self) -> bool {
-        self.ty == other.ty && self.id == other.id
-    }
-}
-
-impl<W> std::fmt::Debug for WidgetId<W> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        self.id.fmt(f)
-    }
-}
-
-impl<W> Clone for WidgetId<W> {
-    fn clone(&self) -> Self {
-        Self {
-            id: self.id,
-            ty: self.ty,
-            counter: self.counter.clone(),
-            send: self.send.clone(),
-            _pd: PhantomData,
-        }
-    }
-}
-
-impl<W> WidgetId<W> {
-    pub(super) fn new(id: Id, ty: TypeId, send: Sender<Id>) -> Self {
-        Self {
-            ty,
-            id,
-            counter: RefCounter::new(),
-            send,
-            _pd: PhantomData,
-        }
-    }
-
-    pub fn any(self) -> WidgetId<AnyWidget> {
-        self.cast_type()
-    }
-
-    pub fn as_any(&self) -> &WidgetId<AnyWidget> {
-        // SAFETY: self is repr(C) and generic only used for phantom data
-        unsafe { std::mem::transmute(self) }
-    }
-
-    pub fn key(&self) -> Id {
-        self.id
-    }
-
-    pub(super) fn cast_type<W2>(self) -> WidgetId<W2> {
-        // SAFETY: self is repr(C) and generic only used for phantom data
-        unsafe { std::mem::transmute(self) }
-    }
-
-    pub fn refs(&self) -> u32 {
-        self.counter.refs()
-    }
-
-    pub fn weak(&self) -> WeakWidgetId<W> {
-        let Self {
-            ty,
-            id,
-            ref counter,
-            ref send,
-            _pd,
-        } = *self;
-        WeakWidgetId {
-            ty,
-            id,
-            counter: counter.quiet_clone(),
-            send: send.clone(),
-            _pd,
-        }
-    }
-}
-
-impl<W> WeakWidgetId<W> {
-    /// should guarantee that widget is still valid to prevent indexing failures
-    pub(crate) fn strong(&self) -> WidgetId<W> {
-        let Self {
-            ty,
-            id,
-            ref counter,
-            ref send,
-            _pd,
-        } = *self;
-        WidgetId {
-            ty,
-            id,
-            counter: counter.clone(),
-            send: send.clone(),
-            _pd,
-        }
-    }
-}
-
-impl<W> Drop for WidgetId<W> {
-    fn drop(&mut self) {
-        if self.counter.drop() {
-            let _ = self.send.send(self.id);
-        }
-    }
-}
-
-pub struct IdTag;
-pub struct IdFnTag;
-
-pub trait WidgetIdFn<W>: FnOnce(&mut Ui) -> WidgetId<W> {}
-impl<W, F: FnOnce(&mut Ui) -> WidgetId<W>> WidgetIdFn<W> for F {}
-
-pub trait WidgetRet: FnOnce(&mut Ui) -> WidgetId<AnyWidget> {}
-impl<F: FnOnce(&mut Ui) -> WidgetId<AnyWidget>> WidgetRet for F {}
-
-impl<W: 'static> WidgetLike<IdTag> for WidgetId<W> {
-    type Widget = W;
-    fn add(self, _: &mut Ui) -> WidgetId<W> {
-        self
-    }
-}
-
-impl<W: 'static, F: FnOnce(&mut Ui) -> WidgetId<W>> WidgetLike<IdFnTag> for F {
-    type Widget = W;
-    fn add(self, ui: &mut Ui) -> WidgetId<W> {
-        self(ui)
-    }
-}
-
-pub trait WidgetIdLike<W> {
-    fn id(self, send: &Sender<Id>) -> WidgetId<W>;
-}
-
-impl<W> WidgetIdLike<W> for &WidgetId<W> {
-    fn id(self, _: &Sender<Id>) -> WidgetId<W> {
-        self.clone()
-    }
-}
-
-pub trait IdLike<W> {
-    fn id(&self) -> Id;
-}
-
-impl<W> IdLike<W> for WidgetId<W> {
-    fn id(&self) -> Id {
-        self.id
-    }
-}

src/layout/mask.rs

@@ -1,46 +0,0 @@
-//! tree structure for masking
-
-use crate::layout::UiRegion;
-
-pub struct Masks {
-    data: Vec<MaskNode>,
-}
-
-#[repr(C)]
-#[derive(Clone, Copy)]
-pub struct MaskPtr(u32);
-
-#[repr(C)]
-pub struct MaskNode {
-    /// TODO: this is just a rect for now,
-    /// but would like to support arbitrary masks
-    /// at some point; custom shader
-    /// would probably handle that case
-    /// bc you'd need to render to a special target
-    /// anyways
-    region: UiRegion,
-    prev: MaskPtr,
-}
-
-impl MaskPtr {
-    const NONE: Self = Self(u32::MAX);
-}
-
-impl Masks {
-    pub fn push(&mut self, parent: MaskPtr, region: UiRegion) -> MaskPtr {
-        match parent.0 {
-            _ => {
-            }
-            u32::MAX => {
-                let i = self.data.len();
-                self.data.push(MaskNode {
-                    region,
-                    prev: parent,
-                });
-                MaskPtr(i as u32)
-            }
-        }
-    }
-
-    pub fn pop(&mut self, i: usize) {}
-}

src/layout/mod.rs

@@ -1,33 +0,0 @@
-mod color;
-mod event;
-mod id;
-mod layer;
-mod module;
-mod num;
-mod orientation;
-mod painter;
-mod text;
-mod texture;
-mod ui;
-mod attr;
-mod vec2;
-mod widget;
-mod widgets;
-
-pub use color::*;
-pub use event::*;
-pub use id::*;
-pub use layer::*;
-pub use module::*;
-pub use num::*;
-pub use orientation::*;
-pub use painter::*;
-pub use text::*;
-pub use texture::*;
-pub use ui::*;
-pub use attr::*;
-pub use vec2::*;
-pub use widget::*;
-pub use widgets::*;
-
-pub type UiColor = Color<u8>;

src/layout/module.rs

@@ -1,35 +0,0 @@
-use std::any::{Any, TypeId};
-
-use crate::{
-    layout::WidgetInstance,
-    util::{HashMap, Id},
-};
-
-#[allow(unused_variables)]
-pub trait UiModule: Any {
-    fn on_draw(&mut self, inst: &WidgetInstance) {}
-    fn on_undraw(&mut self, inst: &WidgetInstance) {}
-    fn on_remove(&mut self, id: &Id) {}
-    fn on_move(&mut self, inst: &WidgetInstance) {}
-}
-
-#[derive(Default)]
-pub struct Modules {
-    map: HashMap<TypeId, Box<dyn UiModule>>,
-}
-
-impl Modules {
-    pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut (dyn UiModule + 'static)> {
-        self.map.values_mut().map(|m| m.as_mut())
-    }
-
-    pub fn get_mut<M: UiModule + Default>(&mut self) -> &mut M {
-        let rf = self
-            .map
-            .entry(TypeId::of::<M>())
-            .or_insert_with(|| Box::new(M::default()))
-            .as_mut();
-        let any: &mut dyn Any = &mut *rf;
-        any.downcast_mut().unwrap()
-    }
-}