craft-ui: combo footer remeasures reset once the footer is stable (#394)

* craft-ui: combo footer remeasures reset once the footer is stable

* craft-ui: test combo footer recovery after the remeasure cap

crates/ui/src/combo.rs

@@ -527,7 +527,8 @@ impl<'a> Menu<'a> {
         let remeasure_id = id.with("craft-remeasure");
         let remeasure = ctx.data_mut(|d| d.remove_temp::<bool>(remeasure_id)).unwrap_or(false);
         let (align, settled) = side(&popup, remeasure);
-        // At most two remeasures per open, so a footer that changes height on every pass settles.
+        // At most two remeasures in a row, so a footer that changes height on every pass settles.
+        // A pass where the footer keeps its height clears the count.
         let count_id = id.with("craft-remeasures");
         if ctx.read_response(id).is_none() {
             ctx.data_mut(|d| d.remove::<u8>(count_id));
@@ -571,12 +572,19 @@ impl<'a> Menu<'a> {
                     let top = ui.cursor().top();
                     let f = footer(ui);
                     let height = ui.min_rect().bottom() - top;
-                    if footer_height.is_none_or(|h| (h - height).abs() > 0.5) && remeasures < 2 {
+                    let changed = footer_height.is_none_or(|h| (h - height).abs() > 0.5);
+                    if !changed && remeasures > 0 {
+                        ui.data_mut(|d| d.remove::<u8>(count_id));
+                    }
+                    if changed {
+                        // Recorded even past the cap, so "unchanged" means unchanged since the last pass.
+                        ui.data_mut(|d| d.insert_temp(footer_id, height));
+                    }
+                    if changed && remeasures < 2 {
                         // The list took the wrong room: lay the menu out again next pass. Not a
                         // discarded pass: the header's side effects (focusing a search field on
                         // open) would run twice.
                         ui.data_mut(|d| {
-                            d.insert_temp(footer_id, height);
                             d.insert_temp(remeasure_id, true);
                             d.insert_temp(count_id, remeasures + 1);
                         });

crates/ui/src/combo/tests.rs

@@ -524,3 +524,77 @@ fn a_footer_that_changes_height_every_pass_settles() {
     h.run();
     assert!(*h.state() - before <= 4, "the menu keeps remeasuring: {} passes in two frames", *h.state() - before);
 }
+
+#[test]
+fn a_footer_that_changes_height_after_settling_still_lands() {
+    // (footer height, bottom of the footer)
+    let mut h = Harness::builder().with_size(egui::vec2(400.0, 600.0)).build_ui_state(
+        |ui, s: &mut (f32, f32)| {
+            let field = ui.button("Send");
+            let _ = super::Menu::new(ui, &field).height(300.0).show_ui_with_header_footer(
+                |ui| ui.label("Title"),
+                |ui, _| {
+                    for n in 0..50 {
+                        let _ = ui.label(format!("Row {n}"));
+                    }
+                },
+                |ui| {
+                    ui.add_space(s.0);
+                    s.1 = ui.min_rect().bottom();
+                },
+            );
+        },
+        (20.0, 0.0),
+    );
+    h.run();
+    h.get_by_label("Send").click();
+    h.run();
+    let bottom = h.state().1;
+    // The list fills the menu's height, so the footer's bottom stays put when the footer's height
+    // changes and the list gives or takes the room. Changes are spaced over several passes: the
+    // remeasure budget resets while the footer is stable.
+    for (n, height) in [60.0, 20.0, 80.0, 30.0].into_iter().enumerate() {
+        h.state_mut().0 = height;
+        h.run();
+        let now = h.state().1;
+        assert!((now - bottom).abs() < 1.0, "change {n} to {height}: the footer ends at {now}, was {bottom}");
+        h.run();
+        h.run();
+    }
+}
+
+#[test]
+fn a_footer_that_hits_the_remeasure_cap_recovers_once_it_holds_still() {
+    // (held footer height, footer passes so far, bottom of the footer)
+    let mut h = Harness::builder().with_size(egui::vec2(400.0, 600.0)).build_ui_state(
+        |ui, s: &mut (f32, u32, f32)| {
+            let field = ui.button("Send");
+            let _ = super::Menu::new(ui, &field).height(300.0).show_ui_with_header_footer(
+                |ui| ui.label("Title"),
+                |ui, _| {
+                    for n in 0..50 {
+                        let _ = ui.label(format!("Row {n}"));
+                    }
+                },
+                |ui| {
+                    s.1 += 1;
+                    // Grows on each of the first passes, past the cap of two remeasures.
+                    ui.add_space(if s.1 <= 5 { 20.0 + 15.0 * s.1 as f32 } else { s.0 });
+                    s.2 = ui.min_rect().bottom();
+                },
+            );
+        },
+        (40.0, 0, 0.0),
+    );
+    h.run();
+    h.get_by_label("Send").click();
+    // Passes with a stable footer follow the growth: each one resets the remeasure budget.
+    for _ in 0..3 {
+        h.step();
+    }
+    let bottom = h.state().2;
+    h.state_mut().0 = 90.0;
+    h.run();
+    let now = h.state().2;
+    assert!((now - bottom).abs() < 1.0, "the footer ends at {now}, was {bottom}");
+}