Files
iris/src/widget/position/stack.rs
T
iris-ai 4cb6f6882a Hold a bound's length where it is decided, and say each thing once
A quality sweep over the deferred request system, which no earlier round
has reviewed.

`Bound::outside` said which end a length fell outside and left the caller
to look that end up through `Bound::at`, which `expect`s an end the value
it is given does not promise: only the pairing of the two calls kept
`at(Shorter)` off a bound with no floor. It already had the length in
hand, so it returns that, and `Outside` and `at` go with the state that
could panic.

`measured_request` pinned the rel base for any bound at all, so a measured
share under a cap in pixels was invalidated by a change to a base its
answer cannot depend on. That question is `Bound::has_fraction` now, which
is also the one `Placing::ask` and `SizeRule::has_fraction` were each
writing out over a bare array.

The rest is one name where there were several spellings: `Span::gaps`,
`Padding::along`, `Plan::drop_bounds` behind one `IRIS_UNBOUNDED` in both
rigs that had grown their own, and `Stack::size_request` resolving its
sizing child the way its draw already does. `Span`'s placement loop asked
three times whether the row was allocated, twice to decide one child's
length; one match answers all three, so the allocated and plain rules are
read side by side.

The buffers `draw_at` now reuses for their capacity are empty only because
every path to it drains them in `remove`; a `debug_assert` says so, since
a drawing over primitives left in one would record them twice.

Comments: `with_requests` named discovery as the hazard where it is a
child drawn mid-row, `Painter::allocate` documented the window it holds
for rather than what it does, `minimum_request` had none, and the note
saying a span carries its children's weight whole -- which is still what
the unallocated path does, and still the surprising part -- had been
replaced by one about the other path.
2026-09-20 18:24:37 -04:00

117 lines
3.7 KiB
Rust

use std::marker::PhantomData;
use crate::prelude::*;
pub struct Stack {
pub children: Vec<StrongWidget>,
pub size: StackSize,
}
impl Widget for Stack {
fn size_request(&self, requests: &mut SizeRequests, axis: Axis) -> Option<RequestedLen> {
let sizing = match self.size {
StackSize::Default => None,
StackSize::Child(i) => self.children.get(i),
};
// With nothing sizing it a stack is a share of the box it is given,
// which is what its draw answers too.
match sizing {
Some(child) => requests.widget(child, axis),
None => Some(LayoutLen::LEFTOVER.into()),
}
}
fn draw(&mut self, painter: &mut Painter) -> Size {
let sizing = match self.size {
StackSize::Default => None,
StackSize::Child(i) => Some(i),
};
// Whichever child sizes the stack is given the stack's whole box --
// the stack is the length that child asked for, so placing that
// answer inside the box it decided would apply it twice.
let size = match sizing.and_then(|i| self.children.get(i).map(|c| (i, c))) {
// On the layer that child ends up on, so the ask below is a reuse
// rather than a second drawing of it somewhere else: a retained
// drawing belongs to the layer it was made on.
Some((i, child)) => {
painter.child_layer_at(i);
painter.widget_at(child, PlaceDesc::WHOLE.fills()).size()
}
None => Size::LEFTOVER,
};
// Every other child gets the box the sizing child decided: the
// stack is that length, so that is the box they are asked in, and a
// fraction under them is a fraction of it. A share leaves the axis
// to whoever gave the stack its box. Where a child sits in a box
// bigger than itself is its own business.
let place = PlaceDesc::from_axes(|axis| {
let len = size[axis];
match len.leftover == Weight::ZERO {
true => len.without_leftover().as_desc().fills(),
false => PlaceDescAxis::WHOLE,
}
});
for (i, child) in self.children.iter().enumerate() {
if sizing == Some(i) {
continue;
}
painter.child_layer_at(i);
painter.widget_at(child, place);
}
size
}
/// Without a sizing child a stack is whatever box it is given, which it
/// can say without drawing anything.
fn size_hint(&self, _: Axis) -> Option<LayoutLen> {
match self.size {
StackSize::Default => Some(LayoutLen::LEFTOVER),
StackSize::Child(_) => None,
}
}
}
#[derive(Default, Debug)]
pub enum StackSize {
#[default]
Default,
Child(usize),
}
pub struct StackBuilder<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag> {
pub children: Wa,
pub size: StackSize,
_pd: PhantomData<(State, Tag)>,
}
impl<Rsc, const LEN: usize, Wa: WidgetArrLike<Rsc, LEN, Tag>, Tag> WidgetFnTrait<Rsc>
for StackBuilder<Rsc, LEN, Wa, Tag>
{
type Widget = Stack;
#[track_caller]
fn run(self, rsc: &mut Rsc) -> Self::Widget {
Stack {
children: self.children.add(rsc).arr.into_iter().collect(),
size: self.size,
}
}
}
impl<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag>
StackBuilder<State, 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
}
}