SingleChildScrollView does not clip semantics child (flutter#114194)

Author: chunhtai

packages/flutter/lib/src/widgets/single_child_scroll_view.dart

@@ -326,16 +326,13 @@ class _RenderSingleChildViewport extends RenderBox with RenderObjectWithChildMix
   _RenderSingleChildViewport({
     AxisDirection axisDirection = AxisDirection.down,
     required ViewportOffset offset,
-    double cacheExtent = RenderAbstractViewport.defaultCacheExtent,
     RenderBox? child,
     required Clip clipBehavior,
   }) : assert(axisDirection != null),
        assert(offset != null),
-       assert(cacheExtent != null),
        assert(clipBehavior != null),
        _axisDirection = axisDirection,
        _offset = offset,
-       _cacheExtent = cacheExtent,
        _clipBehavior = clipBehavior {
     this.child = child;
   }
@@ -370,18 +367,6 @@ class _RenderSingleChildViewport extends RenderBox with RenderObjectWithChildMix
     markNeedsLayout();
   }
 
-  /// {@macro flutter.rendering.RenderViewportBase.cacheExtent}
-  double get cacheExtent => _cacheExtent;
-  double _cacheExtent;
-  set cacheExtent(double value) {
-    assert(value != null);
-    if (value == _cacheExtent) {
-      return;
-    }
-    _cacheExtent = value;
-    markNeedsLayout();
-  }
-
   /// {@macro flutter.material.Material.clipBehavior}
   ///
   /// Defaults to [Clip.none], and must not be null.
@@ -700,19 +685,34 @@ class _RenderSingleChildViewport extends RenderBox with RenderObjectWithChildMix
   @override
   Rect describeSemanticsClip(RenderObject child) {
     assert(axis != null);
-    switch (axis) {
-      case Axis.vertical:
+    final double remainingOffset = _maxScrollExtent - offset.pixels;
+    switch (axisDirection) {
+      case AxisDirection.up:
         return Rect.fromLTRB(
           semanticBounds.left,
-          semanticBounds.top - cacheExtent,
+          semanticBounds.top - remainingOffset,
           semanticBounds.right,
-          semanticBounds.bottom + cacheExtent,
+          semanticBounds.bottom + offset.pixels,
         );
-      case Axis.horizontal:
+      case AxisDirection.right:
+        return Rect.fromLTRB(
+          semanticBounds.left - offset.pixels,
+          semanticBounds.top,
+          semanticBounds.right + remainingOffset,
+          semanticBounds.bottom,
+        );
+      case AxisDirection.down:
+        return Rect.fromLTRB(
+          semanticBounds.left,
+          semanticBounds.top - offset.pixels,
+          semanticBounds.right,
+          semanticBounds.bottom + remainingOffset,
+        );
+      case AxisDirection.left:
         return Rect.fromLTRB(
-          semanticBounds.left - cacheExtent,
+          semanticBounds.left - remainingOffset,
           semanticBounds.top,
-          semanticBounds.right + cacheExtent,
+          semanticBounds.right + offset.pixels,
           semanticBounds.bottom,
         );
     }

packages/flutter/test/material/tabs_test.dart

@@ -2995,14 +2995,15 @@ void main() {
     const String tab0title = 'This is a very wide tab #0\nTab 1 of 20';
     const String tab10title = 'This is a very wide tab #10\nTab 11 of 20';
 
+    const List<SemanticsFlag> hiddenFlags = <SemanticsFlag>[SemanticsFlag.isHidden, SemanticsFlag.isFocusable];
     expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollLeft]));
     expect(semantics, includesNodeWith(label: tab0title));
-    expect(semantics, isNot(includesNodeWith(label: tab10title)));
+    expect(semantics, includesNodeWith(label: tab10title, flags: hiddenFlags));
 
     controller.index = 10;
     await tester.pumpAndSettle();
 
-    expect(semantics, isNot(includesNodeWith(label: tab0title)));
+    expect(semantics, includesNodeWith(label: tab0title, flags: hiddenFlags));
     expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollLeft, SemanticsAction.scrollRight]));
     expect(semantics, includesNodeWith(label: tab10title));
 
@@ -3016,7 +3017,7 @@ void main() {
 
     expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollLeft]));
     expect(semantics, includesNodeWith(label: tab0title));
-    expect(semantics, isNot(includesNodeWith(label: tab10title)));
+    expect(semantics, includesNodeWith(label: tab10title, flags: hiddenFlags));
 
     semantics.dispose();
   });

packages/flutter/test/widgets/scrollable_semantics_traversal_order_test.dart

@@ -624,6 +624,25 @@ void main() {
       ),
     );
 
+    final List<TestSemantics> children = <TestSemantics>[];
+    for (int index = 0; index < 30; index += 1) {
+      final bool isHidden = index < 15 ||  index > 17;
+      children.add(
+        TestSemantics(
+          flags: isHidden ? <SemanticsFlag>[SemanticsFlag.isHidden] : 0,
+          label: 'Item ${index}a',
+          textDirection: TextDirection.ltr,
+        ),
+      );
+      children.add(
+        TestSemantics(
+          flags: isHidden ? <SemanticsFlag>[SemanticsFlag.isHidden] : 0,
+          label: 'item ${index}b',
+          textDirection: TextDirection.ltr,
+        ),
+      );
+    }
+
     expect(semantics, hasSemantics(
       TestSemantics.root(
         children: <TestSemantics>[
@@ -638,72 +657,7 @@ void main() {
                   SemanticsAction.scrollUp,
                   SemanticsAction.scrollDown,
                 ],
-                children: <TestSemantics>[
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'Item 13a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'item 13b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'Item 14a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'item 14b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    label: 'Item 15a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    label: 'item 15b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    label: 'Item 16a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    label: 'item 16b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    label: 'Item 17a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    label: 'item 17b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'Item 18a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'item 18b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'Item 19a',
-                    textDirection: TextDirection.ltr,
-                  ),
-                  TestSemantics(
-                    flags: <SemanticsFlag>[SemanticsFlag.isHidden],
-                    label: 'item 19b',
-                    textDirection: TextDirection.ltr,
-                  ),
-                ],
+                children: children,
               ),
             ],
           ),