Stack with premeasured content now work

This makes nested scroll areas work correctly.

examples/nested-scroll.rs

@@ -0,0 +1,18 @@
+use gooey::widget::MakeWidget;
+use gooey::Run;
+use kludgine::figures::units::Lp;
+
+fn main() -> gooey::Result {
+    include_str!("./nested-scroll.rs")
+        .vertical_scroll()
+        .height(Lp::inches(3))
+        .and(
+            include_str!("./canvas.rs")
+                .vertical_scroll()
+                .height(Lp::inches(3)),
+        )
+        .into_rows()
+        .vertical_scroll()
+        .expand()
+        .run()
+}

src/widgets/stack.rs

@@ -296,7 +296,8 @@ struct Layout {
     total_weights: u32,
     allocated_space: (UPx, Lp),
     fractional: Vec<(LotId, u8)>,
-    measured: Vec<LotId>,
+    fit_to_content: Vec<LotId>,
+    premeasured: Vec<LotId>,
     pub orientation: StackDirection,
 }
 
@@ -316,7 +317,8 @@ impl Layout {
             total_weights: 0,
             allocated_space: (UPx(0), Lp(0)),
             fractional: Vec::new(),
-            measured: Vec::new(),
+            fit_to_content: Vec::new(),
+            premeasured: Vec::new(),
         }
     }
 
@@ -331,20 +333,23 @@ impl Layout {
 
         match dimension {
             StackDimension::FitContent => {
-                self.measured.retain(|&measured| measured != id);
+                self.fit_to_content.retain(|&measured| measured != id);
             }
             StackDimension::Fractional { weight } => {
                 self.fractional.retain(|(measured, _)| *measured != id);
                 self.total_weights -= u32::from(weight);
             }
-            StackDimension::Measured { min, .. } => match min {
-                Dimension::Px(pixels) => {
-                    self.allocated_space.0 -= pixels.into_unsigned();
+            StackDimension::Measured { min, .. } => {
+                self.premeasured.retain(|&measured| measured != id);
+                match min {
+                    Dimension::Px(pixels) => {
+                        self.allocated_space.0 -= pixels.into_unsigned();
+                    }
+                    Dimension::Lp(lp) => {
+                        self.allocated_space.1 -= lp;
+                    }
                 }
-                Dimension::Lp(lp) => {
-                    self.allocated_space.1 -= lp;
-                }
-            },
+            }
         }
 
         dimension
@@ -364,7 +369,7 @@ impl Layout {
         let id = self.children.insert(index, child);
         let layout = match child {
             StackDimension::FitContent => {
-                self.measured.push(id);
+                self.fit_to_content.push(id);
                 UPx(0)
             }
             StackDimension::Fractional { weight } => {
@@ -373,6 +378,7 @@ impl Layout {
                 UPx(0)
             }
             StackDimension::Measured { min, .. } => {
+                self.premeasured.push(id);
                 match min {
                     Dimension::Px(size) => self.allocated_space.0 += size.into_unsigned(),
                     Dimension::Lp(size) => self.allocated_space.1 += size,
@@ -407,7 +413,7 @@ impl Layout {
 
         // Measure the children that fit their content
         self.other = UPx(0);
-        for &id in &self.measured {
+        for &id in &self.fit_to_content {
             let index = self.children.index_of_id(id).expect("child not found");
             let (measured, other) = self.orientation.split_size(measure(
                 index,
@@ -420,6 +426,20 @@ impl Layout {
             remaining = remaining.saturating_sub(measured);
         }
 
+        // Measure measure the "other" dimension for children that we know their size already.
+        for &id in &self.premeasured {
+            let index = self.children.index_of_id(id).expect("child not found");
+            let (_, other) = self.orientation.split_size(measure(
+                index,
+                self.orientation.make_size(
+                    ConstraintLimit::Known(self.layouts[index].size),
+                    other_constraint,
+                ),
+                !needs_final_layout,
+            ));
+            self.other = self.other.max(other);
+        }
+
         // Measure the weighted children within the remaining space
         if self.total_weights > 0 {
             let space_per_weight = remaining / self.total_weights;

src/window.rs

@@ -868,7 +868,9 @@ where
                     ),
                     kludgine,
                 );
-                let last_rendered_at = context.last_layout().expect("passed hit test");
+                let Some(last_rendered_at) = context.last_layout() else {
+                    continue;
+                };
                 context.mouse_drag(location - last_rendered_at.origin, device_id, *button);
             }
         } else {
@@ -886,11 +888,10 @@ where
             self.mouse_state.widget = None;
             for widget in self.root.tree.widgets_at_point(location) {
                 let mut widget_context = context.for_other(&widget);
-                let relative = location
-                    - widget_context
-                        .last_layout()
-                        .expect("passed hit test")
-                        .origin;
+                let Some(widget_layout) = widget_context.last_layout() else {
+                    continue;
+                };
+                let relative = location - widget_layout.origin;
 
                 if widget_context.hit_test(relative) {
                     widget_context.hover(relative);
@@ -970,8 +971,10 @@ where
                             kludgine,
                         ),
                         |context| {
-                            let relative =
-                                *location - context.last_layout().expect("passed hit test").origin;
+                            let Some(layout) = context.last_layout() else {
+                                return IGNORED;
+                            };
+                            let relative = *location - layout.origin;
                             context.mouse_down(relative, device_id, button)
                         },
                     ) {