Revert "Make sure Opacity widgets/layers do not drop the offset (#89264)" (#89999)

This reverts commit 0d0f7a4f.

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

@@ -1741,7 +1741,7 @@ class TransformLayer extends OffsetLayer {
 ///
 /// Try to avoid an [OpacityLayer] with no children. Remove that layer if
 /// possible to save some tree walks.
-class OpacityLayer extends OffsetLayer {
+class OpacityLayer extends ContainerLayer {
   /// Creates an opacity layer.
   ///
   /// The [alpha] property must be non-null before the compositing phase of
@@ -1750,7 +1750,7 @@ class OpacityLayer extends OffsetLayer {
     int? alpha,
     Offset offset = Offset.zero,
   }) : _alpha = alpha,
-       super(offset: offset);
+       _offset = offset;
 
   /// The amount to multiply into the alpha channel.
   ///
@@ -1764,14 +1764,28 @@ class OpacityLayer extends OffsetLayer {
   set alpha(int? value) {
     assert(value != null);
     if (value != _alpha) {
-      if (value == 255 || _alpha == 255) {
-        engineLayer = null;
-      }
       _alpha = value;
       markNeedsAddToScene();
     }
   }
 
+  /// Offset from parent in the parent's coordinate system.
+  Offset? get offset => _offset;
+  Offset? _offset;
+  set offset(Offset? value) {
+    if (value != _offset) {
+      _offset = value;
+      markNeedsAddToScene();
+    }
+  }
+
+  @override
+  void applyTransform(Layer? child, Matrix4 transform) {
+    assert(child != null);
+    assert(transform != null);
+    transform.translate(offset!.dx, offset!.dy);
+  }
+
   @override
   void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) {
     assert(alpha != null);
@@ -1781,32 +1795,24 @@ class OpacityLayer extends OffsetLayer {
       return true;
     }());
 
-    final int realizedAlpha = alpha!;
-    // The type assertions work because the [alpha] setter nulls out the
-    // engineLayer if it would have changed type (i.e. changed to or from 255).
-    if (enabled && realizedAlpha < 255) {
-      assert(_engineLayer is ui.OpacityEngineLayer?);
+    if (enabled)
       engineLayer = builder.pushOpacity(
-        realizedAlpha,
-        offset: offset + layerOffset,
+        alpha!,
+        offset: offset! + layerOffset,
         oldLayer: _engineLayer as ui.OpacityEngineLayer?,
       );
-    } else {
-      assert(_engineLayer is ui.OffsetEngineLayer?);
-      engineLayer = builder.pushOffset(
-        layerOffset.dx + offset.dx,
-        layerOffset.dy + offset.dy,
-        oldLayer: _engineLayer as ui.OffsetEngineLayer?,
-      );
-    }
+    else
+      engineLayer = null;
     addChildrenToScene(builder);
-    builder.pop();
+    if (enabled)
+      builder.pop();
   }
 
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(IntProperty('alpha', alpha));
+    properties.add(DiagnosticsProperty<Offset>('offset', offset));
   }
 }
 

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

@@ -843,7 +843,7 @@ class RenderOpacity extends RenderProxyBox {
        super(child);
 
   @override
-  bool get alwaysNeedsCompositing => child != null && (_alpha > 0);
+  bool get alwaysNeedsCompositing => child != null && (_alpha != 0 && _alpha != 255);
 
   int _alpha;
 
@@ -897,6 +897,12 @@ class RenderOpacity extends RenderProxyBox {
         layer = null;
         return;
       }
+      if (_alpha == 255) {
+        // No need to keep the layer. We'll create a new one if necessary.
+        layer = null;
+        context.paintChild(child!, offset);
+        return;
+      }
       assert(needsCompositing);
       layer = context.pushOpacity(offset, _alpha, super.paint, oldLayer: layer as OpacityLayer?);
     }
@@ -987,7 +993,7 @@ mixin RenderAnimatedOpacityMixin<T extends RenderObject> on RenderObjectWithChil
     _alpha = ui.Color.getAlphaFromOpacity(opacity.value);
     if (oldAlpha != _alpha) {
       final bool? didNeedCompositing = _currentlyNeedsCompositing;
-      _currentlyNeedsCompositing = _alpha! > 0;
+      _currentlyNeedsCompositing = _alpha! > 0 && _alpha! < 255;
       if (child != null && didNeedCompositing != _currentlyNeedsCompositing)
         markNeedsCompositingBitsUpdate();
       markNeedsPaint();
@@ -1004,6 +1010,12 @@ mixin RenderAnimatedOpacityMixin<T extends RenderObject> on RenderObjectWithChil
         layer = null;
         return;
       }
+      if (_alpha == 255) {
+        // No need to keep the layer. We'll create a new one if necessary.
+        layer = null;
+        context.paintChild(child!, offset);
+        return;
+      }
       assert(needsCompositing);
       layer = context.pushOpacity(offset, _alpha!, super.paint, oldLayer: layer as OpacityLayer?);
     }

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

@@ -112,7 +112,7 @@ class RenderSliverOpacity extends RenderProxySliver {
   }
 
   @override
-  bool get alwaysNeedsCompositing => child != null && (_alpha > 0);
+  bool get alwaysNeedsCompositing => child != null && (_alpha != 0 && _alpha != 255);
 
   int _alpha;
 
@@ -166,6 +166,12 @@ class RenderSliverOpacity extends RenderProxySliver {
         layer = null;
         return;
       }
+      if (_alpha == 255) {
+        // No need to keep the layer. We'll create a new one if necessary.
+        layer = null;
+        context.paintChild(child!, offset);
+        return;
+      }
       assert(needsCompositing);
       layer = context.pushOpacity(
         offset,

packages/flutter/test/rendering/debug_test.dart

@@ -208,30 +208,4 @@ void main() {
     expect(error, isNull);
     debugPaintSizeEnabled = false;
   });
-
-  test('debugDisableOpacity keeps things in the right spot', () {
-    debugDisableOpacityLayers = true;
-
-    final RenderDecoratedBox blackBox = RenderDecoratedBox(
-      decoration: const BoxDecoration(color: Color(0xff000000)),
-      child: RenderConstrainedBox(
-        additionalConstraints: BoxConstraints.tight(const Size.square(20.0)),
-      ),
-    );
-    final RenderOpacity root = RenderOpacity(
-      opacity: .5,
-      child: blackBox,
-    );
-    layout(root, phase: EnginePhase.compositingBits);
-
-    final OffsetLayer rootLayer = OffsetLayer(offset: Offset.zero);
-    final PaintingContext context = PaintingContext(
-      rootLayer,
-      const Rect.fromLTWH(0, 0, 500, 500),
-    );
-    root.paint(context, const Offset(40, 40));
-    final OpacityLayer opacityLayer = rootLayer.firstChild! as OpacityLayer;
-    expect(opacityLayer.offset, const Offset(40, 40));
-    debugDisableOpacityLayers = false;
-  });
 }

packages/flutter/test/rendering/proxy_box_test.dart

@@ -274,14 +274,14 @@ void main() {
     expect(renderOpacity.needsCompositing, false);
   });
 
-  test('RenderOpacity does composite if it is opaque', () {
+  test('RenderOpacity does not composite if it is opaque', () {
     final RenderOpacity renderOpacity = RenderOpacity(
       opacity: 1.0,
       child: RenderSizedBox(const Size(1.0, 1.0)), // size doesn't matter
     );
 
     layout(renderOpacity, phase: EnginePhase.composite);
-    expect(renderOpacity.needsCompositing, true);
+    expect(renderOpacity.needsCompositing, false);
   });
 
   test('RenderOpacity reuses its layer', () {
@@ -306,7 +306,7 @@ void main() {
     expect(renderAnimatedOpacity.needsCompositing, false);
   });
 
-  test('RenderAnimatedOpacity does composite if it is opaque', () {
+  test('RenderAnimatedOpacity does not composite if it is opaque', () {
     final Animation<double> opacityAnimation = AnimationController(
       vsync: FakeTickerProvider(),
     )..value = 1.0;
@@ -318,7 +318,7 @@ void main() {
     );
 
     layout(renderAnimatedOpacity, phase: EnginePhase.composite);
-    expect(renderAnimatedOpacity.needsCompositing, true);
+    expect(renderAnimatedOpacity.needsCompositing, false);
   });
 
   test('RenderAnimatedOpacity reuses its layer', () {

packages/flutter/test/rendering/proxy_sliver_test.dart

@@ -29,7 +29,7 @@ void main() {
     expect(renderSliverOpacity.needsCompositing, false);
   });
 
-  test('RenderSliverOpacity does composite if it is opaque', () {
+  test('RenderSliverOpacity does not composite if it is opaque', () {
     final RenderSliverOpacity renderSliverOpacity = RenderSliverOpacity(
       opacity: 1.0,
       sliver: RenderSliverToBoxAdapter(
@@ -46,7 +46,7 @@ void main() {
     );
 
     layout(root, phase: EnginePhase.composite);
-    expect(renderSliverOpacity.needsCompositing, true);
+    expect(renderSliverOpacity.needsCompositing, false);
   });
   test('RenderSliverOpacity reuses its layer', () {
     final RenderSliverOpacity renderSliverOpacity = RenderSliverOpacity(
@@ -102,7 +102,7 @@ void main() {
     expect(renderSliverAnimatedOpacity.needsCompositing, false);
   });
 
-  test('RenderSliverAnimatedOpacity does composite if it is opaque', () {
+  test('RenderSliverAnimatedOpacity does not composite if it is opaque', () {
     final Animation<double> opacityAnimation = AnimationController(
       vsync: FakeTickerProvider(),
     )..value = 1.0;
@@ -124,7 +124,7 @@ void main() {
     );
 
     layout(root, phase: EnginePhase.composite);
-    expect(renderSliverAnimatedOpacity.needsCompositing, true);
+    expect(renderSliverAnimatedOpacity.needsCompositing, false);
   });
 
   test('RenderSliverAnimatedOpacity reuses its layer', () {

packages/flutter/test/widgets/opacity_test.dart

@@ -195,35 +195,4 @@ void main() {
     final OffsetLayer offsetLayer = element.renderObject!.debugLayer! as OffsetLayer;
     await offsetLayer.toImage(const Rect.fromLTRB(0.0, 0.0, 1.0, 1.0));
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/49857
-
-  testWidgets('Child shows up in the right spot when opacity is disabled', (WidgetTester tester) async {
-    debugDisableOpacityLayers = true;
-    final GlobalKey key = GlobalKey();
-    await tester.pumpWidget(
-      RepaintBoundary(
-        key: key,
-        child: Directionality(
-          textDirection: TextDirection.ltr,
-          child: Stack(
-            children: <Widget>[
-              Positioned(
-                top: 40,
-                left: 140,
-                child: Opacity(
-                  opacity: .5,
-                  child: Container(height: 100, width: 100, color: Colors.red),
-                ),
-              ),
-            ],
-          ),
-        ),
-      ),
-    );
-
-    await expectLater(
-      find.byKey(key),
-      matchesGoldenFile('opacity_disabled_with_child.png'),
-    );
-    debugDisableOpacityLayers = false;
-  });
 }