Retain request dependencies only when discovery supplies the answer

tests/layout_diagnostics.rs

@@ -13,11 +13,12 @@
 //!
 //! `IRIS_PHASE` is `cold`, `repaint`, `many`, `size`, `scroll`, `resize`, or
 //! `all`. `IRIS_SEED`, `IRIS_DEPTH`, and `IRIS_FRAMES` select the load, and
-//! `IRIS_DIRTY` how many widgets `many` marks at once.
+//! `IRIS_DIRTY` how many widgets `many` marks at once. `IRIS_UNBOUNDED=1`
+//! removes intrinsic bounds while preserving the rest of the generated tree.
 
 use iris::harness::Harness;
 use iris::prelude::*;
-use iris::random::{Edits, Tree, grow};
+use iris::random::{Edits, Tree, build, plan};
 use std::time::Instant;
 
 const OUTPUT: (f32, f32) = (1920.0, 1200.0);
@@ -125,9 +126,25 @@ fn rig_edits() -> Edits {
     }
 }
 
+fn fixture(harness: &mut Harness, seed: u64, depth: usize) -> (StrongWidget, Tree) {
+    let mut plan = plan(seed, depth, &rig_edits());
+    if env("IRIS_UNBOUNDED", 0_u8) != 0 {
+        plan.walk_mut(&mut |node| {
+            if let Some(rules) = &mut node.size {
+                for axis in Axis::BOTH {
+                    if rules[axis].bound() != Bound::ANY {
+                        rules[axis] = SizeRule::Free;
+                    }
+                }
+            }
+        });
+    }
+    build(&mut harness.rsc, &plan)
+}
+
 fn warm(seed: u64, depth: usize) -> (Harness, Tree) {
     let mut harness = Harness::new(OUTPUT);
-    let (root, tree) = grow(&mut harness.rsc, seed, depth, &rig_edits());
+    let (root, tree) = fixture(&mut harness, seed, depth);
     harness.state.root = Some(root);
     harness.frame();
     println!(
@@ -209,7 +226,7 @@ fn layout_cost() {
 
     if selected("cold") {
         let mut harness = Harness::new(OUTPUT);
-        let (root, tree) = grow(&mut harness.rsc, seed, depth, &rig_edits());
+        let (root, tree) = fixture(&mut harness, seed, depth);
         harness.state.root = Some(root);
         println!(
             "fixture: seed {seed}, depth {depth}, {} widgets",
@@ -276,3 +293,19 @@ fn layout_cost() {
         });
     }
 }
+
+#[cfg(feature = "layout-diagnostics")]
+#[test]
+fn repainting_measured_text_does_not_invalidate_its_span() {
+    use iris::core::layout_diagnostics as diag;
+
+    let mut h = Harness::new((400, 200));
+    let text = wtext("a paragraph that fits").wrap(true).add(&mut h.rsc);
+    h.set_root((text, wtext("another paragraph")).span(Dir::DOWN));
+    let _ = diag::take();
+    h.rsc.widgets_mut().mark_for_redraw(text);
+    h.frame();
+    let report = diag::take();
+    assert_eq!(report.distinct_widgets(), 1);
+    assert_eq!(report.hot_widgets()[0].id, text.id());
+}