Grow images in the generated trees

`Image` is the only widget in the repository whose size hint is a length in
pixels -- everything else hints a share, or nothing -- so it is the only one
that exercises a rule beside a hint, a box a widget knows before it is drawn,
and the answer the commit before this one changed. The generated trees had
none, which is why nothing there could reach that case.

`Kind::Image` is a fifth leaf, drawn one time in five, and it steps to a plain
rect when the shrinker reduces it: a picture measures nothing either, but its
length is its own, so the leaf that takes whatever it is given is the simpler
one. The picture is a 64x64 checkerboard of purple and black in 8 px cells,
committed at `src/assets/checkerboard.png` beside the generator that draws it
-- the way `examples/tabs` keeps its own -- and included rather than opened, so
that growing a tree does not depend on a working directory and one seed is one
tree whatever anything else does.

One upload per tree, however many images it grows: a `TextureHandle` is a
counted reference, so the first image in a tree uploads the checkerboard and
every one after it clones the handle. Measured: seed 1 at depth 4 grows 13
images and holds 1 texture, seed 6 grows none and holds none, and
`a_tree_of_images_uploads_one_texture` asserts it. `Image::new` is what a
caller holding a handle needs, since `image` uploads what it is given.

A seed names a tree only while the generator draws the same things in the same
order, so every seed now grows a different tree. The seed list in
`generated.rs` says so: 20 and 86 no longer grow the trees whose defects they
once caught, and both of those live on as shrunk fixtures in `unsettled.rs`,
which are trees rather than numbers. The seeds those fixtures name are
similarly historical, and their file says that too.

Format, clippy with and without layout-diagnostics, and the suite (135 + 19 +
13 + 4) are clean. The cold dump is a new baseline of 34,571 boxes over the 400
depth-5 trees, since the trees themselves changed; all three seed scans pass
over the new ones -- 400 at depth 5 in 62.79s, 1,000 at depth 6 in 160.20s,
2,000 at depth 4 in 299.58s -- which is what actually checks that images lay
out warm the way they do cold.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/src/ui/painter.rs

@@ -187,10 +187,20 @@ impl<'a> Painter<'a> {
         id: &'s StrongWidget<W>,
         place: impl Into<PlaceDesc>,
     ) -> DrawResult<'s, 'a, W> {
-        let place = self.resolve_rel_base(place.into());
+        let mut place = self.resolve_rel_base(place.into());
         let region_node = self.rsc.widgets().is_region_node(id.id());
-        let declared = self.declared_lens(id);
         let align = self.rsc.widgets().alignment(id.id());
+        // A share fills what the pixels and fraction beside it leave of the
+        // box and overflows where they are longer, which is the rule a span
+        // follows with one child. Only the overflow is a box of the child's
+        // own: a share that fits is the box it was given, which is what this
+        // place already says.
+        for axis in Axis::BOTH {
+            if let Some(len) = self.share_past_the_offer(id.id(), place, align, axis) {
+                place[axis] = len.as_desc().fills();
+            }
+        }
+        let declared = self.declared_lens(id);
         let (rel_base, region) =
             place.rel_base_and_region(self.region, self.rel_base, declared, align);
         #[cfg(feature = "layout-diagnostics")]
@@ -299,6 +309,45 @@ impl<'a> Painter<'a> {
         self.rsc.widgets().declared_lens(id.id())
     }
 
+    /// The box a child's own share asks for where that is longer than the box
+    /// `place` gives it, and nothing where the share fits.
+    ///
+    /// A share is a length only to whoever divides one, and nothing divides a
+    /// box handed to one child: what is left of it after the pixels and the
+    /// fraction beside the share is what the share takes, so the length comes
+    /// to the whole box until those are longer than it and to them once they
+    /// are. Only that second case is a box this widget did not give, and the
+    /// crossing between them is a question in pixels, so this widget's drawing
+    /// holds for the windows on one side of it. Narrowed rather than stated,
+    /// because this widget may have read its own box as well, and a range it
+    /// pinned for that still holds.
+    fn share_past_the_offer(
+        &mut self,
+        id: WidgetId,
+        place: PlaceDesc,
+        align: RegionAlign,
+        axis: Axis,
+    ) -> Option<Len> {
+        // A place that is the child's placement outright is a box its parent
+        // decided, and a parent that divides one has already given the share
+        // whatever it was owed. Only an offer -- a box with the answer still
+        // to be placed inside it -- is a box a share reads.
+        if place[axis].fills {
+            return None;
+        }
+        // A share with nothing beside it is the box whatever the box is, so
+        // there is no comparison to make and no range to keep for one.
+        let stated = self.rsc.widgets().exact_len(id, axis)?;
+        if stated.leftover == Weight::ZERO || stated.is_only_leftover() {
+            return None;
+        }
+        let fixed = stated
+            .without_leftover()
+            .within_len(place.base(axis, self.rel_base));
+        let offer = place.of(self.region, align)[axis].len();
+        self.longer_than(fixed, offer, axis).then_some(fixed)
+    }
+
     /// What a child says its length is without being drawn, if it can say,
     /// as the length its draw would report: a fraction in it is resolved
     /// against this widget's rel base, which is the rel base a child asked with
@@ -475,6 +524,40 @@ impl<'a> Painter<'a> {
         len.to_px(window)
     }
 
+    /// Whether `len` is longer than `than`, kept as the windows that comparison
+    /// comes out the same way on: a drawing that took one of two lengths holds
+    /// where the same one is the longer, and nowhere else.
+    ///
+    /// Which is longer is a question in pixels -- `rel(0.5)` is longer than 300
+    /// px at a box of 600 and shorter at 400 -- and it is asked of the
+    /// difference and answered back through that same difference, so the
+    /// boundary is the drawing's own rather than a second way of finding it.
+    /// Narrowed rather than stated, because whatever else this widget read
+    /// about the window is a reason its drawing holds where it does too.
+    ///
+    /// This is the one operation a length that is the longer of two needs: the
+    /// room a container has left for the shares it divides, and a share that
+    /// overflows the box it was given because the pixels beside it are longer
+    /// than the box.
+    pub fn longer_than(&mut self, len: Len, than: Len, axis: Axis) -> bool {
+        let over = len - than;
+        let window = self.window[axis];
+        let longer = over.to_px(window) > Px::ZERO;
+        let side = match longer {
+            true => Px::STEP..=Px::MAX,
+            false => Px::MIN..=Px::ZERO,
+        };
+        let holds = Holds::from(side).through(over);
+        debug_assert!(
+            holds.contains(window),
+            "'{}' ({:?}) compared two lengths and kept a range without this window",
+            self.label(),
+            self.id
+        );
+        self.own[axis].window = self.own[axis].window.and(holds);
+        longer
+    }
+
     /// The windows this drawing holds for, stated rather than taken: a
     /// container that branched on a length in pixels says which side of the
     /// boundary it was on, which is wider than the one window reading that
@@ -725,10 +808,7 @@ impl PlaceDesc {
         let mut rel_base = parent_rel_base;
         let mut region = given;
         for axis in Axis::BOTH {
-            let base = match self[axis].rel_base {
-                RelBase::Len(len) => len,
-                RelBase::Inherit | RelBase::WithRegion => parent_rel_base[axis],
-            };
+            let base = self.base(axis, parent_rel_base);
             let len = declared[axis]
                 .map(|len| len.within_len(base))
                 .unwrap_or(base);

core/src/ui/place.rs

@@ -1,5 +1,5 @@
 use crate::util::impl_axis_index;
-use crate::{Axis, AxisAlign, Len, PrimitiveHandle, RegionAlign, UiRegion, UiSpan};
+use crate::{Axis, AxisAlign, Len, PrimitiveHandle, RegionAlign, UiRegion, UiSpan, UiVec2};
 
 /// How a child's region along one axis comes from the region of the widget
 /// asking, and what its fractions are of.
@@ -123,6 +123,16 @@ impl PlaceDesc {
         self
     }
 
+    /// What a child's fractions on one axis are of, as a length of the
+    /// window: a length this place names, or the rel base of the widget
+    /// giving it, which is `parent_rel_base`.
+    pub(super) fn base(&self, axis: Axis, parent_rel_base: UiVec2) -> Len {
+        match self[axis].rel_base {
+            RelBase::Len(len) => len,
+            RelBase::Inherit | RelBase::WithRegion => parent_rel_base[axis],
+        }
+    }
+
     /// The box each axis names, in the coordinates `own` is in.
     pub fn of(self, own: UiRegion, align: RegionAlign) -> UiRegion {
         UiRegion::new(self.x.of(own.x, align.x), self.y.of(own.y, align.y))

src/random.rs

@@ -190,6 +190,9 @@ pub enum Kind {
         color: usize,
         alpha: u8,
     },
+    /// The one leaf whose own length is a number of pixels it knows before it
+    /// is drawn, which is the hint a rule beside it has to win over.
+    Image,
     /// Scrolling reads the pixel length of its box, which nothing else here
     /// does, and gives its child a box longer than its own.
     Scroll {
@@ -443,9 +446,11 @@ impl Kind {
         }
         match self {
             // The one leaf that reads the width it is given, then the one
-            // that does not, then the one that measures nothing at all.
+            // that does not, then the one that measures nothing at all. A
+            // picture measures nothing either, but its length is its own, so
+            // it steps to the leaf that takes whatever it is given.
             Kind::Wrapped => out.push(Kind::OneLine),
-            Kind::OneLine => out.push(Kind::Rect {
+            Kind::OneLine | Kind::Image => out.push(Kind::Rect {
                 color: 0,
                 alpha: 255,
             }),
@@ -627,9 +632,10 @@ struct Sow<'a> {
 
 impl Sow<'_> {
     fn leaf(&mut self) -> Plan {
-        Plan::bare(match self.rng.below(4) {
+        Plan::bare(match self.rng.below(5) {
             0 => Kind::Wrapped,
             1 => Kind::OneLine,
+            2 => Kind::Image,
             _ => {
                 let color = self.rng.below(COLORS.len());
                 let alpha = (self.rng.below(5) * 63) as u8;
@@ -793,6 +799,7 @@ pub fn build<Rsc: UiRsc + 'static>(rsc: &mut Rsc, plan: &Plan) -> (StrongWidget,
     let mut build = Build {
         rsc,
         tree: Tree::default(),
+        checkerboard: None,
     };
     let root = build.node(plan);
     (root, build.tree)
@@ -801,6 +808,10 @@ pub fn build<Rsc: UiRsc + 'static>(rsc: &mut Rsc, plan: &Plan) -> (StrongWidget,
 struct Build<'a, Rsc> {
     rsc: &'a mut Rsc,
     tree: Tree,
+    /// The checkerboard, uploaded when the first image in this tree is built.
+    /// A handle is a reference to the texture, so every image after that one
+    /// clones this rather than uploading the same picture again.
+    checkerboard: Option<TextureHandle>,
 }
 
 impl<Rsc: UiRsc + 'static> Build<'_, Rsc> {
@@ -826,6 +837,20 @@ impl<Rsc: UiRsc + 'static> Build<'_, Rsc> {
         built
     }
 
+    /// The one picture the generated trees draw: a 64x64 checkerboard of purple
+    /// and black in 8 px cells. Committed rather than drawn here, so that one
+    /// seed is one tree whatever anything else does, and included rather than
+    /// opened, so that growing a tree does not depend on a working directory.
+    fn checkerboard(&mut self) -> TextureHandle {
+        if self.checkerboard.is_none() {
+            let image = include_bytes!("assets/checkerboard.png")
+                .get_image()
+                .expect("the checkerboard is committed beside this file");
+            self.checkerboard = Some(self.rsc.ui_mut().textures.add(image));
+        }
+        self.checkerboard.clone().unwrap()
+    }
+
     fn kind(&mut self, kind: &Kind) -> StrongWidget {
         let id: StrongWidget = match kind {
             Kind::Wrapped => wtext(WORDS).size(16).wrap(true).add_strong(self.rsc),
@@ -834,6 +859,7 @@ impl<Rsc: UiRsc + 'static> Build<'_, Rsc> {
                 .wrap(false)
                 .add_strong(self.rsc),
             Kind::Rect { color, alpha } => rect(COLORS[*color].alpha(*alpha)).add_strong(self.rsc),
+            Kind::Image => Image::new(self.checkerboard()).add_strong(self.rsc),
             Kind::Scroll { axis, inner } => {
                 let inner = self.node(inner);
                 let id = Scroll::new(inner, *axis).add(self.rsc);

src/widget/image.rs

@@ -16,6 +16,15 @@ impl Widget for Image {
     }
 }
 
+impl Image {
+    /// One texture already uploaded, for a caller holding its handle: [`image`]
+    /// uploads what it is given, and several widgets showing one picture want
+    /// one upload and one slot between them.
+    pub fn new(handle: TextureHandle) -> Self {
+        Self { handle }
+    }
+}
+
 pub fn image<State: UiRsc>(image: impl LoadableImage) -> impl WidgetFn<State, Image> {
     let image = image.get_image().expect("Failed to load image");
     move |state| Image {

src/widget/position/span.rs

@@ -52,25 +52,15 @@ impl Widget for Span {
 
         // What is left for the shares to divide: the row less everything
         // fixed, as a length of the rel base rather than a number of pixels.
-        let room = row - total.without_leftover();
-        // Whether anything is left over is a question in pixels: `rel(0.5)`
-        // beside 300 px is full at 600 and overfull at 400. Asked of `room`
-        // itself, and answered back through the same expression, so the
-        // boundary is the drawing's own and not a second way of finding it:
-        // the three cases a rounded division needed -- the fixed parts
+        let all_fixed = total.without_leftover();
+        let room = row - all_fixed;
+        // The three cases a rounded division needed -- the fixed parts
         // growing slower than the box, faster, or exactly with it -- are the
-        // sign of `room.rel`, which `through` already reads. What the
-        // generated oracle checks is the consequence, since which children
-        // exist at all turns on this.
+        // sign of `room.rel`, which the range `longer_than` keeps already
+        // reads. What the generated oracle checks is the consequence, since
+        // which children exist at all turns on this.
         let any_leftover = total.leftover > Weight::ZERO;
-        let has_room = any_leftover && painter.to_px(room, axis) > Px::ZERO;
-        if any_leftover {
-            let holds = match has_room {
-                true => Holds::from(Px::STEP..=Px::MAX),
-                false => Holds::from(Px::MIN..=Px::ZERO),
-            };
-            painter.window_holds(axis, holds.through(room));
-        }
+        let has_room = any_leftover && painter.longer_than(row, all_fixed, axis);
 
         // Across itself a span is as long as its longest child -- unless a
         // rule beside it gives that length outright, and then reading them

tests/cases/layout.rs

@@ -260,6 +260,66 @@ fn a_share_rule_beats_the_widgets_own_pixel_size() {
     assert_eq!(asked.get(), 400.0, "the share is all of the box");
 }
 
+/// A share with pixels or a fraction beside it is the longer of the two: it
+/// fills what they leave of the box and overflows the box where they are
+/// longer than it. A parent that divides nothing gives the same length as a
+/// span with one child, because in both there is nobody else to divide with.
+#[test]
+fn a_share_is_a_minimum_wherever_nothing_divides_it() {
+    let asked = |rule: LayoutLen, in_a_span: bool| {
+        let mut h = Harness::new((400, 200));
+        let probe = rect(Color::RED).add(&mut h.rsc);
+        h.set_len(probe, Axis::X, rule);
+        match in_a_span {
+            true => h.set_root((probe,).span(Dir::RIGHT)),
+            false => h.set_root(probe.wrapper()),
+        }
+        h.region(&probe).unwrap().size().x
+    };
+    for (rule, want) in [
+        (LayoutLen::LEFTOVER, 400),
+        (LayoutLen::px(50) + LayoutLen::LEFTOVER, 400),
+        (LayoutLen::px(500) + LayoutLen::LEFTOVER, 500),
+        (LayoutLen::rel(0.5) + LayoutLen::LEFTOVER, 400),
+        (LayoutLen::px(500), 500),
+    ] {
+        let want = Px::from_int(want);
+        assert_eq!(asked(rule, false), want, "{rule:?} where nothing divides");
+        assert_eq!(asked(rule, true), want, "{rule:?} in a span");
+    }
+}
+
+/// Which of the two is longer is a question in pixels, so the box is decided
+/// again wherever the answer can change: a window that crosses the length the
+/// pixels ask for, and the rule itself crossing it while the window holds
+/// still. The first is a range the drawing holds for; the second cannot be
+/// seen in what the widget declares, since a share declares nothing either
+/// way, so it reaches the parent as a length only the parent can resolve.
+#[test]
+fn a_share_past_the_box_is_decided_again_on_either_side_of_the_crossing() {
+    let mut h = Harness::new((400, 200));
+    let probe = rect(Color::RED).add(&mut h.rsc);
+    h.set_len(probe, Axis::X, LayoutLen::px(500) + LayoutLen::LEFTOVER);
+    h.set_root(probe.wrapper());
+    assert_eq!(h.region(&probe).unwrap().size().x, Px::from_int(500));
+
+    h.resize((900, 200));
+    h.frame();
+    assert_eq!(h.region(&probe).unwrap().size().x, Px::from_int(900));
+
+    h.resize((400, 200));
+    h.frame();
+    assert_eq!(h.region(&probe).unwrap().size().x, Px::from_int(500));
+
+    h.set_len(probe, Axis::X, LayoutLen::px(50) + LayoutLen::LEFTOVER);
+    h.frame();
+    assert_eq!(h.region(&probe).unwrap().size().x, Px::from_int(400));
+
+    h.set_len(probe, Axis::X, LayoutLen::px(500) + LayoutLen::LEFTOVER);
+    h.frame();
+    assert_eq!(h.region(&probe).unwrap().size().x, Px::from_int(500));
+}
+
 #[test]
 fn a_child_drawn_twice_moves_once() {
     let mut h = Harness::new((400, 200));

tests/cases/plan.rs

@@ -5,7 +5,9 @@
 //! and the oracle another. And reducing a plan has to end, or a shrinker
 //! searching for the smallest counterexample never returns.
 
-use iris::random::{Edits, Kind, Plan, Rng, SpanEdit, plan};
+use iris::harness::Harness;
+use iris::prelude::*;
+use iris::random::{Edits, Kind, Plan, Rng, SpanEdit, grow, plan};
 use std::collections::HashMap;
 
 fn some_edits(seed: u64, of: &Plan) -> Edits {
@@ -67,8 +69,6 @@ fn some_edits(seed: u64, of: &Plan) -> Edits {
     }
 }
 
-use iris::prelude::*;
-
 /// The two routes to an edited tree are one tree. `plan` resolves edits out
 /// of the random stream as it draws; `edited` puts them on a tree that
 /// already exists, which is the only route a shrunk plan has, since no seed
@@ -137,3 +137,20 @@ fn reducing_a_plan_all_the_way_ends() {
         );
     }
 }
+
+/// Every image in a tree is the same picture, and a handle is a reference to
+/// the texture rather than a copy of it, so one upload and one slot serve all
+/// of them however many a tree grows -- and the trees are grown in hundreds.
+#[test]
+fn a_tree_of_images_uploads_one_texture() {
+    let mut images = 0;
+    let mut tree = plan(1, 4, &Edits::default());
+    tree.walk_mut(&mut |p| images += (p.kind == Kind::Image) as usize);
+    assert!(images > 1, "a tree of {images} images tests nothing");
+
+    let mut h = Harness::new((900, 1200));
+    let (root, _) = grow(&mut h.rsc, 1, 4, &Edits::default());
+    h.state.root = Some(root);
+    h.frame();
+    assert_eq!(h.rsc.ui().textures.count(), 1);
+}

tests/cases/unsettled.rs

@@ -9,6 +9,12 @@
 //! reached through a region node's own entry rather than through the offer
 //! that node was given. The last is a wrapping text handed back the width
 //! it measured, rounded to a step below the line it measured there.
+//!
+//! Each says which seed it was shrunk from, of the generator as it stood when
+//! it was found. Those numbers no longer grow those trees -- a seed names one
+//! only while the generator draws the same things in the same order, and the
+//! leaves have grown an image since -- so what is written out below is the
+//! record of the case, and the seed is where it came from.
 
 use std::collections::HashSet;
 

tests/generated.rs

@@ -25,10 +25,14 @@ fn depth() -> usize {
     env("IRIS_GENERATED_DEPTH", 4)
 }
 
-/// The seeds the ordinary tests take. Eight that have never failed; 86,
-/// which a `Scroll` fixed point once settled differently on; and 20, which
-/// caught a locally redrawn widget being placed twice in the box its parent
-/// had already placed it in.
+/// The seeds the ordinary tests take: a corpus rather than a set of
+/// regression cases, since a seed names a tree only for as long as the
+/// generator draws the same things in the same order. Adding images to the
+/// leaves moved every one of them, so 20 and 86 -- which once caught a widget
+/// placed twice in a box its parent had already placed it in, and a `Scroll`
+/// fixed point settling differently -- no longer grow those trees. Both
+/// defects are pinned by the shrunk fixtures in `cases/unsettled.rs`, which
+/// are trees rather than numbers.
 const SEEDS: [u64; 10] = [1, 2, 3, 5, 8, 10, 13, 20, 86, 98];
 
 fn check(seed: u64, depth: usize, case: Case) {