Revert "Dispose render objects when owning element is unmounted. (#82883)" (#83790)

This reverts commit c75edc26.

examples/layers/rendering/src/sector_layout.dart

@@ -455,6 +455,7 @@ class RenderSectorSlice extends RenderSectorWithChildren {
 }
 
 class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChildMixin<RenderSector> {
+
   RenderBoxToRenderSectorAdapter({ double innerRadius = 0.0, RenderSector? child })
     : _innerRadius = innerRadius {
     this.child = child;
@@ -566,6 +567,7 @@ class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChil
     result.add(BoxHitTestEntry(this, position));
     return true;
   }
+
 }
 
 class RenderSolidColor extends RenderDecoratedSector {

examples/layers/widgets/sectors.dart

@@ -90,13 +90,6 @@ class SectorAppState extends State<SectorApp> {
     });
   }
 
-  void recursivelyDisposeChildren(RenderObject parent) {
-    parent.visitChildren((RenderObject child) {
-      recursivelyDisposeChildren(child);
-      child.dispose();
-    });
-  }
-
   Widget buildBody() {
     return Column(
       mainAxisAlignment: MainAxisAlignment.spaceBetween,
@@ -114,12 +107,7 @@ class SectorAppState extends State<SectorApp> {
                       Container(
                         padding: const EdgeInsets.all(4.0),
                         margin: const EdgeInsets.only(right: 10.0),
-                        child: WidgetToRenderBoxAdapter(
-                          renderBox: sectorAddIcon,
-                          onUnmount: () {
-                            recursivelyDisposeChildren(sectorAddIcon);
-                          },
-                        ),
+                        child: WidgetToRenderBoxAdapter(renderBox: sectorAddIcon),
                       ),
                       const Text('ADD SECTOR'),
                     ],
@@ -134,12 +122,7 @@ class SectorAppState extends State<SectorApp> {
                       Container(
                         padding: const EdgeInsets.all(4.0),
                         margin: const EdgeInsets.only(right: 10.0),
-                        child: WidgetToRenderBoxAdapter(
-                          renderBox: sectorRemoveIcon,
-                          onUnmount: () {
-                            recursivelyDisposeChildren(sectorRemoveIcon);
-                          },
-                        ),
+                        child: WidgetToRenderBoxAdapter(renderBox: sectorRemoveIcon),
                       ),
                       const Text('REMOVE SECTOR'),
                     ],
@@ -159,9 +142,6 @@ class SectorAppState extends State<SectorApp> {
             child: WidgetToRenderBoxAdapter(
               renderBox: sectors,
               onBuild: doUpdates,
-              onUnmount: () {
-                recursivelyDisposeChildren(sectors);
-              },
             ),
           ),
         ),

packages/flutter/lib/src/rendering/editable.dart

@@ -283,15 +283,6 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   _RenderEditableCustomPaint? _foregroundRenderObject;
   _RenderEditableCustomPaint? _backgroundRenderObject;
 
-  @override
-  void dispose() {
-    _foregroundRenderObject?.dispose();
-    _foregroundRenderObject = null;
-    _backgroundRenderObject?.dispose();
-    _backgroundRenderObject = null;
-    super.dispose();
-  }
-
   void _updateForegroundPainter(RenderEditablePainter? newPainter) {
     final _CompositeRenderEditablePainter effectivePainter = newPainter == null
       ? _builtInForegroundPainters

packages/flutter/lib/src/rendering/image.dart

@@ -438,13 +438,6 @@ class RenderImage extends RenderBox {
     );
   }
 
-  @override
-  void dispose() {
-    _image?.dispose();
-    _image = null;
-    super.dispose();
-  }
-
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);

packages/flutter/lib/src/rendering/object.dart

@@ -1111,19 +1111,6 @@ class PipelineOwner {
 /// The [RenderBox] subclass introduces the opinion that the layout
 /// system uses Cartesian coordinates.
 ///
-/// ## Lifecycle
-///
-/// A [RenderObject] must [dispose] when it is no longer needed. The creator
-/// of the object is responsible for disposing of it. Typically, the creator is
-/// a [RenderObjectElement], and that element will dispose the object it creates
-/// when it is unmounted.
-///
-/// [RenderObject]s are responsible for cleaning up any expensive resources
-/// they hold when [dispose] is called, such as [Picture] or [Image] objects.
-/// This includes any [Layer]s that the render object has directly created. The
-/// base implementation of dispose will nullify the [layer] property. Subclasses
-/// must also nullify any other layer(s) it directly creates.
-///
 /// ## Writing a RenderObject subclass
 ///
 /// In most cases, subclassing [RenderObject] itself is overkill, and
@@ -1243,50 +1230,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     });
   }
 
-  /// Whether this has been disposed.
-  ///
-  /// If asserts are disabled, this property is always null.
-  bool? get debugDisposed {
-    bool? disposed;
-    assert(() {
-      disposed = _debugDisposed;
-      return true;
-    }());
-    return disposed;
-  }
-
-  bool _debugDisposed = false;
-
-  /// Release any resources held by this render object.
-  ///
-  /// The object that creates a RenderObject is in charge of disposing it.
-  /// If this render object has created any children directly, it must dispose
-  /// of those children in this method as well. It must not dispose of any
-  /// children that were created by some other object, such as
-  /// a [RenderObjectElement]. Those children will be disposed when that
-  /// element unmounts, which may be delayed if the element is moved to another
-  /// part of the tree.
-  ///
-  /// Implementations of this method must end with a call to the inherited
-  /// method, as in `super.dispose()`.
-  ///
-  /// The object is no longer usable after calling dispose.
-  @mustCallSuper
-  void dispose() {
-    assert(!_debugDisposed);
-    _layer = null;
-    assert(() {
-      visitChildren((RenderObject child) {
-        assert(
-          child.debugDisposed!,
-          '${child.runtimeType} (child of $runtimeType) must be disposed before calling super.dispose().',
-        );
-      });
-      _debugDisposed = true;
-      return true;
-    }());
-  }
-
   // LAYOUT
 
   /// Data for use by the parent render object.
@@ -1424,10 +1367,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   bool get _debugCanPerformMutations {
     late bool result;
     assert(() {
-      if (_debugDisposed) {
-        result = false;
-        return true;
-      }
       if (owner != null && !owner!.debugDoingLayout) {
         result = true;
         return true;
@@ -1462,7 +1401,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
 
   @override
   void attach(PipelineOwner owner) {
-    assert(!_debugDisposed);
     super.attach(owner);
     // If the node was dirtied in some way while unattached, make sure to add
     // it to the appropriate dirty list now that an owner is available
@@ -1674,7 +1612,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   ///
   /// See [RenderView] for an example of how this function is used.
   void scheduleInitialLayout() {
-    assert(!_debugDisposed);
     assert(attached);
     assert(parent is! RenderObject);
     assert(!owner!._debugDoingLayout);
@@ -1744,7 +1681,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   /// work to update its layout information.
   @pragma('vm:notify-debugger-on-exception')
   void layout(Constraints constraints, { bool parentUsesSize = false }) {
-    assert(!_debugDisposed);
     if (!kReleaseMode && debugProfileLayoutsEnabled)
       Timeline.startSync('$runtimeType',  arguments: timelineArgumentsIndicatingLandmarkEvent);
 
@@ -2104,7 +2040,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   /// it cannot be the case that _only_ the compositing bits changed,
   /// something else will have scheduled a frame for us.
   void markNeedsCompositingBitsUpdate() {
-    assert(!_debugDisposed);
     if (_needsCompositingBitsUpdate)
       return;
     _needsCompositingBitsUpdate = true;
@@ -2203,7 +2138,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   ///    layer, thus limiting the number of nodes that [markNeedsPaint] must mark
   ///    dirty.
   void markNeedsPaint() {
-    assert(!_debugDisposed);
     assert(owner == null || !owner!.debugDoingPaint);
     if (_needsPaint)
       return;
@@ -2288,7 +2222,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   ///
   /// This might be called if, e.g., the device pixel ratio changed.
   void replaceRootLayer(OffsetLayer rootLayer) {
-    assert(!_debugDisposed);
     assert(rootLayer.attached);
     assert(attached);
     assert(parent is! RenderObject);
@@ -2301,7 +2234,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   }
 
   void _paintWithContext(PaintingContext context, Offset offset) {
-    assert(!_debugDisposed);
     assert(() {
       if (_debugDoingThisPaint) {
         throw FlutterError.fromParts(<DiagnosticsNode>[
@@ -2525,7 +2457,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   ///
   /// See [RendererBinding] for an example of how this function is used.
   void scheduleInitialSemantics() {
-    assert(!_debugDisposed);
     assert(attached);
     assert(parent is! RenderObject);
     assert(!owner!._debugDoingSemantics);
@@ -2648,7 +2579,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   /// [RenderObject] as annotated by [describeSemanticsConfiguration] changes in
   /// any way to update the semantics tree.
   void markNeedsSemanticsUpdate() {
-    assert(!_debugDisposed);
     assert(!attached || !owner!._debugDoingSemantics);
     if (!attached || owner!._semanticsOwner == null) {
       _cachedSemanticsConfiguration = null;
@@ -2894,10 +2824,6 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   @override
   String toStringShort() {
     String header = describeIdentity(this);
-    if (_debugDisposed) {
-      header += ' DISPOSED';
-      return header;
-    }
     if (_relayoutBoundary != null && _relayoutBoundary != this) {
       int count = 1;
       RenderObject? target = parent as RenderObject?;
@@ -3283,7 +3209,6 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
       }
     }
   }
-
   /// Insert child into this render object's child list after the given child.
   ///
   /// If `after` is null, then this inserts the child at the start of the list,

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -3152,6 +3152,7 @@ class RenderRepaintBoundary extends RenderProxyBox {
     return offsetLayer.toImage(Offset.zero & size, pixelRatio: pixelRatio);
   }
 
+
   /// The number of times that this render object repainted at the same time as
   /// its parent. Repaint boundaries are only useful when the parent and child
   /// paint at different times. When both paint at the same time, the repaint

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

@@ -6232,11 +6232,6 @@ class DefaultAssetBundle extends InheritedWidget {
 /// A given render object can be placed at most once in the widget tree. This
 /// widget enforces that restriction by keying itself using a [GlobalObjectKey]
 /// for the given render object.
-///
-/// This widget will call [RenderObject.dispose] on the [renderBox] when it is
-/// unmounted. After that point, the [renderBox] will be unusable. If any
-/// children have been added to the [renderBox], they must be disposed in the
-/// [onUnmount] callback.
 class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
   /// Creates an adapter for placing a specific [RenderBox] in the widget tree.
   ///
@@ -6244,7 +6239,6 @@ class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
   WidgetToRenderBoxAdapter({
     required this.renderBox,
     this.onBuild,
-    this.onUnmount,
   }) : assert(renderBox != null),
        // WidgetToRenderBoxAdapter objects are keyed to their render box. This
        // prevents the widget being used in the widget hierarchy in two different
@@ -6253,9 +6247,6 @@ class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
        super(key: GlobalObjectKey(renderBox));
 
   /// The render box to place in the widget tree.
-  ///
-  /// This widget takes ownership of the render object. When it is unmounted,
-  /// it also calls [RenderObject.dispose].
   final RenderBox renderBox;
 
   /// Called when it is safe to update the render box and its descendants. If
@@ -6264,25 +6255,6 @@ class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
   /// tree will be dirty.
   final VoidCallback? onBuild;
 
-  /// Called when it is safe to dispose of children that were manually added to
-  /// the [renderBox].
-  ///
-  /// Do not dispose the [renderBox] itself, as it will be disposed by the
-  /// framework automatically. However, during that process the framework will
-  /// check that all children of the [renderBox] have also been disposed.
-  /// Typically, child [RenderObject]s are disposed by corresponding [Element]s
-  /// when they are unmounted. However, child render objects that were manually
-  /// added do not have corresponding [Element]s to manage their lifecycle, and
-  /// need to be manually disposed here.
-  ///
-  /// See also:
-  ///
-  ///   * [RenderObjectElement.unmount], which invokes this callback before
-  ///     disposing of its render object.
-  ///   * [RenderObject.dispose], which instructs a render object to release
-  ///     any resources it may be holding.
-  final VoidCallback? onUnmount;
-
   @override
   RenderBox createRenderObject(BuildContext context) => renderBox;
 
@@ -6290,12 +6262,6 @@ class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
   void updateRenderObject(BuildContext context, RenderBox renderObject) {
     onBuild?.call();
   }
-
-  @override
-  void didUnmountRenderObject(RenderObject renderObject) {
-    assert(renderObject == renderBox);
-    onUnmount?.call();
-  }
 }
 
 

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

@@ -3199,13 +3199,10 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
     RenderObject? result;
     void visit(Element element) {
       assert(result == null); // this verifies that there's only one child
-      if (element._lifecycleState == _ElementLifecycle.defunct) {
-        return;
-      } else if (element is RenderObjectElement) {
+      if (element is RenderObjectElement)
         result = element.renderObject;
-      } else {
+      else
         element.visitChildren(visit);
-      }
     }
     visit(this);
     return result;
@@ -3844,10 +3841,6 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
   /// After this function is called, the element will not be incorporated into
   /// the tree again.
   ///
-  /// Any resources this element holds should be released at this point. For
-  /// example, [RenderObjectElement.unmount] calls [RenderObject.dispose] and
-  /// nulls out its reference to the render object.
-  ///
   /// See the lifecycle documentation for [Element] for additional information.
   ///
   /// Implementations of this method should end with a call to the inherited
@@ -5429,13 +5422,8 @@ abstract class RenderObjectElement extends Element {
   RenderObjectWidget get widget => super.widget as RenderObjectWidget;
 
   /// The underlying [RenderObject] for this element.
-  ///
-  /// If this element has been [unmount]ed, this getter will throw.
   @override
-  RenderObject get renderObject {
-    assert(_renderObject != null, '$runtimeType unmounted');
-    return _renderObject!;
-  }
+  RenderObject get renderObject => _renderObject!;
   RenderObject? _renderObject;
 
   bool _debugDoingBuild = false;
@@ -5503,7 +5491,6 @@ abstract class RenderObjectElement extends Element {
       return true;
     }());
     _renderObject = widget.createRenderObject(this);
-    assert(!_renderObject!.debugDisposed!);
     assert(() {
       _debugDoingBuild = false;
       return true;
@@ -5781,11 +5768,6 @@ abstract class RenderObjectElement extends Element {
 
   @override
   void unmount() {
-    assert(
-      !renderObject.debugDisposed!,
-      'A RenderObject was disposed prior to its owning element being unmounted: '
-      '$renderObject',
-    );
     final RenderObjectWidget oldWidget = widget;
     super.unmount();
     assert(
@@ -5794,8 +5776,6 @@ abstract class RenderObjectElement extends Element {
       'RenderObjectElement: $renderObject',
     );
     oldWidget.didUnmountRenderObject(renderObject);
-    _renderObject!.dispose();
-    _renderObject = null;
   }
 
   void _updateParentData(ParentDataWidget<ParentData> parentDataWidget) {

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

@@ -268,8 +268,8 @@ class _SliverPersistentHeaderElement extends RenderObjectElement {
 
   @override
   void unmount() {
-    renderObject._element = null;
     super.unmount();
+    renderObject._element = null;
   }
 
   @override

packages/flutter/test/rendering/image_test.dart

@@ -175,7 +175,7 @@ Future<void> main() async {
     expect(image.colorBlendMode, BlendMode.color);
   });
 
-  test('RenderImage disposes its image', () async {
+  test('Render image disposes its image', () async {
     final ui.Image image = await createTestImage(width: 10, height: 10, cache: false);
     expect(image.debugGetOpenHandleStackTraces()!.length, 1);
 
@@ -192,7 +192,7 @@ Future<void> main() async {
     expect(image.debugGetOpenHandleStackTraces()!.length, 0);
   }, skip: kIsWeb); // Web doesn't track open image handles.
 
-  test('RenderImage does not dispose its image if setting the same image twice', () async {
+  test('Render image does not dispose its image if setting the same image twice', () async {
     final ui.Image image = await createTestImage(width: 10, height: 10, cache: false);
     expect(image.debugGetOpenHandleStackTraces()!.length, 1);
 
@@ -208,19 +208,4 @@ Future<void> main() async {
     image.dispose();
     expect(image.debugGetOpenHandleStackTraces()!.length, 0);
   }, skip: kIsWeb); // Web doesn't track open image handles.
-
-  test('Render image disposes its image when it is disposed', () async {
-    final ui.Image image = await createTestImage(width: 10, height: 10, cache: false);
-    expect(image.debugGetOpenHandleStackTraces()!.length, 1);
-
-    final RenderImage renderImage = RenderImage(image: image.clone());
-    expect(image.debugGetOpenHandleStackTraces()!.length, 2);
-
-    renderImage.dispose();
-    expect(image.debugGetOpenHandleStackTraces()!.length, 1);
-    expect(renderImage.image, null);
-
-    image.dispose();
-    expect(image.debugGetOpenHandleStackTraces()!.length, 0);
-  }, skip: kIsWeb); // Web doesn't track open image handles.
 }

packages/flutter/test/rendering/object_test.dart

@@ -144,38 +144,6 @@ void main() {
       return context.pushOpacity(offset, 100, painter, oldLayer: oldLayer as OpacityLayer?);
     });
   });
-
-  test('RenderObject.dispose sets debugDisposed to true', () {
-    final TestRenderObject renderObject = TestRenderObject();
-    expect(renderObject.debugDisposed, false);
-    renderObject.dispose();
-    expect(renderObject.debugDisposed, true);
-    expect(renderObject.toStringShort(), contains('DISPOSED'));
-  });
-
-  test('RenderObject.dispose null the layer on repaint boundaries', () {
-    final TestRenderObject renderObject = TestRenderObject(allowPaintBounds: true);
-    // Force a layer to get set.
-    renderObject.isRepaintBoundary = true;
-    PaintingContext.repaintCompositedChild(renderObject, debugAlsoPaintedParent: true);
-    expect(renderObject.debugLayer, isA<OffsetLayer>());
-
-    // Dispose with repaint boundary still being true.
-    renderObject.dispose();
-    expect(renderObject.debugLayer, null);
-  });
-
-  test('RenderObject.dispose nulls the layer on non-repaint boundaries', () {
-    final TestRenderObject renderObject = TestRenderObject(allowPaintBounds: true);
-    // Force a layer to get set.
-    renderObject.isRepaintBoundary = true;
-    PaintingContext.repaintCompositedChild(renderObject, debugAlsoPaintedParent: true);
-
-    // Dispose with repaint boundary being false.
-    renderObject.isRepaintBoundary = false;
-    renderObject.dispose();
-    expect(renderObject.debugLayer, null);
-  });
 }
 
 // Tests the create-update cycle by pumping two frames. The first frame has no
@@ -220,19 +188,12 @@ class _TestCustomLayerBox extends RenderBox {
 class TestParentData extends ParentData with ContainerParentDataMixin<RenderBox> { }
 
 class TestRenderObject extends RenderObject {
-  TestRenderObject({this.allowPaintBounds = false});
-
-  final bool allowPaintBounds;
-
-  @override
-  bool isRepaintBoundary = false;
-
   @override
   void debugAssertDoesMeetConstraints() { }
 
   @override
   Rect get paintBounds {
-    assert(allowPaintBounds); // For some tests, this should not get called.
+    assert(false); // The test shouldn't call this.
     return Rect.zero;
   }
 

packages/flutter/test/widgets/framework_test.dart

@@ -1619,18 +1619,6 @@ void main() {
     await pumpWidget(Container());
     expect(states, <String>['deactivate', 'dispose']);
   });
-
-  testWidgets('RenderObjectElement.unmount dispsoes of its renderObject', (WidgetTester tester) async {
-    await tester.pumpWidget(const Placeholder());
-    final RenderObjectElement element = tester.allElements.whereType<RenderObjectElement>().first;
-    final RenderObject renderObject = element.renderObject;
-    expect(renderObject.debugDisposed, false);
-
-    await tester.pumpWidget(Container());
-
-    expect(() => element.renderObject, throwsAssertionError);
-    expect(renderObject.debugDisposed, true);
-  });
 }
 
 class _WidgetWithNoVisitChildren extends StatelessWidget {