Ensure that scroll offset is in bounds after layout

src/widget/scroll_view.rs

@@ -116,11 +116,24 @@ impl Widget for ScrollView {
                 height: f64::INFINITY,
             },
         );
-        let size = self.child.layout(cx, &cbc);
-        Size {
-            width: size.width.min(bc.max().width),
-            height: size.height.min(bc.max().height),
+        let child_size = self.child.layout(cx, &cbc);
+        let size = Size {
+            width: child_size.width.min(bc.max().width),
+            height: child_size.height.min(bc.max().height),
+        };
+
+        // Ensure that scroll offset is within bounds
+        let max_offset = (child_size.height - size.height).max(0.0);
+        if max_offset < self.offset {
+            self.offset = max_offset;
+            let new_origin = Point {
+                x: 0.0,
+                y: -self.offset,
+            };
+            self.child.set_origin(cx.widget_state, new_origin);
         }
+
+        size
     }
 
     fn paint(&mut self, cx: &mut PaintCx, builder: &mut SceneBuilder) {