Revert "Reland composite physical layers on all platforms (#29532)" (#29623)

This reverts commit 803b15e0.

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

@@ -1580,8 +1580,12 @@ abstract class _RenderPhysicalModelBase<T> extends _RenderCustomClip<T> {
     markNeedsPaint();
   }
 
+  static final Paint _transparentPaint = Paint()..color = const Color(0x00000000);
+
+  // On Fuchsia, the system compositor is responsible for drawing shadows
+  // for physical model layers with non-zero elevation.
   @override
-  bool get alwaysNeedsCompositing => _elevation != 0.0;
+  bool get alwaysNeedsCompositing => _elevation != 0.0 && defaultTargetPlatform == TargetPlatform.fuchsia;
 
   @override
   void describeSemanticsConfiguration(SemanticsConfiguration config) {
@@ -1711,6 +1715,7 @@ class RenderPhysicalModel extends _RenderPhysicalModelBase<RRect> {
         }
         return true;
       }());
+      if (needsCompositing) {
         final PhysicalModelLayer physicalModel = PhysicalModelLayer(
           clipPath: offsetRRectAsPath,
           clipBehavior: clipBehavior,
@@ -1719,6 +1724,28 @@ class RenderPhysicalModel extends _RenderPhysicalModelBase<RRect> {
           shadowColor: shadowColor,
         );
         context.pushLayer(physicalModel, super.paint, offset, childPaintBounds: offsetBounds);
+      } else {
+        final Canvas canvas = context.canvas;
+        if (elevation != 0.0 && paintShadows) {
+          // The drawShadow call doesn't add the region of the shadow to the
+          // picture's bounds, so we draw a hardcoded amount of extra space to
+          // account for the maximum potential area of the shadow.
+          // TODO(jsimmons): remove this when Skia does it for us.
+          canvas.drawRect(
+            offsetBounds.inflate(20.0),
+            _RenderPhysicalModelBase._transparentPaint,
+          );
+          canvas.drawShadow(
+            offsetRRectAsPath,
+            shadowColor,
+            elevation,
+            color.alpha != 0xFF,
+          );
+        }
+        canvas.drawRRect(offsetRRect, Paint()..color = color);
+        context.clipRRectAndPaint(offsetRRect, clipBehavior, offsetBounds, () => super.paint(context, offset));
+        assert(context.canvas == canvas, 'canvas changed even though needsCompositing was false');
+      }
     }
   }
 
@@ -1801,6 +1828,7 @@ class RenderPhysicalShape extends _RenderPhysicalModelBase<Path> {
         }
         return true;
       }());
+      if (needsCompositing) {
         final PhysicalModelLayer physicalModel = PhysicalModelLayer(
           clipPath: offsetPath,
           clipBehavior: clipBehavior,
@@ -1809,6 +1837,28 @@ class RenderPhysicalShape extends _RenderPhysicalModelBase<Path> {
           shadowColor: shadowColor,
         );
         context.pushLayer(physicalModel, super.paint, offset, childPaintBounds: offsetBounds);
+      } else {
+        final Canvas canvas = context.canvas;
+        if (elevation != 0.0 && paintShadows) {
+          // The drawShadow call doesn't add the region of the shadow to the
+          // picture's bounds, so we draw a hardcoded amount of extra space to
+          // account for the maximum potential area of the shadow.
+          // TODO(jsimmons): remove this when Skia does it for us.
+          canvas.drawRect(
+            offsetBounds.inflate(20.0),
+            _RenderPhysicalModelBase._transparentPaint,
+          );
+          canvas.drawShadow(
+            offsetPath,
+            shadowColor,
+            elevation,
+            color.alpha != 0xFF,
+          );
+        }
+        canvas.drawPath(offsetPath, Paint()..color = color..style = PaintingStyle.fill);
+        context.clipPathAndPaint(offsetPath, clipBehavior, offsetBounds, () => super.paint(context, offset));
+        assert(context.canvas == canvas, 'canvas changed even though needsCompositing was false');
+      }
     }
   }
 

packages/flutter/test/material/bottom_app_bar_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:io';
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
@@ -81,7 +79,7 @@ void main() {
       find.byKey(key),
       matchesGoldenFile('bottom_app_bar.custom_shape.2.png'),
     );
-  }, skip: !Platform.isLinux);
+  });
 
   testWidgets('color defaults to Theme.bottomAppBarColor', (WidgetTester tester) async {
     await tester.pumpWidget(

packages/flutter/test/material/outline_button_test.dart

@@ -10,27 +10,6 @@ import '../rendering/mock_canvas.dart';
 import '../widgets/semantics_tester.dart';
 
 void main() {
-    PhysicalModelLayer findPhysicalLayer(Element element) {
-      expect(element, isNotNull);
-      RenderObject object = element.renderObject;
-      while (object != null && object is! RenderRepaintBoundary && object is! RenderView) {
-        object = object.parent;
-      }
-      expect(object.debugLayer, isNotNull);
-      expect(object.debugLayer.firstChild, isInstanceOf<PhysicalModelLayer>());
-      final PhysicalModelLayer layer = object.debugLayer.firstChild;
-      return layer.firstChild is PhysicalModelLayer ? layer.firstChild : layer;
-    }
-
-    void checkPhysicalLayer(Element element, Color expectedColor, {Path clipPath, Rect clipRect}) {
-      final PhysicalModelLayer expectedLayer = findPhysicalLayer(element);
-      expect(expectedLayer.elevation, 0.0);
-      expect(expectedLayer.color, expectedColor);
-      if (clipPath != null) {
-        expect(clipRect, isNotNull);
-        expect(expectedLayer.clipPath, coversSameAreaAs(clipPath, areaToCompare: clipRect.inflate(10.0)));
-      }
-    }
   testWidgets('Outline button responds to tap when enabled', (WidgetTester tester) async {
     int pressedCount = 0;
 
@@ -135,13 +114,8 @@ void main() {
     expect(
       outlineButton,
       paints
+        ..clipPath(pathMatcher: coversSameAreaAs(clipPath, areaToCompare: clipRect.inflate(10.0)))
         ..path(color: disabledBorderColor, strokeWidth: borderWidth));
-    checkPhysicalLayer(
-      tester.element(outlineButton),
-      const Color(0),
-      clipPath: clipPath,
-      clipRect: clipRect,
-    );
 
     // Pump a new button with a no-op onPressed callback to make it enabled.
     await tester.pumpWidget(
@@ -156,14 +130,10 @@ void main() {
     expect(
       outlineButton,
       paints
+        // initially the interior of the button is transparent
+        ..path(color: fillColor.withAlpha(0x00))
+        ..clipPath(pathMatcher: coversSameAreaAs(clipPath, areaToCompare: clipRect.inflate(10.0)))
         ..path(color: borderColor, strokeWidth: borderWidth));
-    // initially, the interior of the button is transparent
-    checkPhysicalLayer(
-      tester.element(outlineButton),
-      fillColor.withAlpha(0x00),
-      clipPath: clipPath,
-      clipRect: clipRect,
-    );
 
     final Offset center = tester.getCenter(outlineButton);
     final TestGesture gesture = await tester.startGesture(center);
@@ -174,13 +144,9 @@ void main() {
     expect(
       outlineButton,
       paints
+        ..path(color: fillColor.withAlpha(0xFF))
+        ..clipPath(pathMatcher: coversSameAreaAs(clipPath, areaToCompare: clipRect.inflate(10.0)))
         ..path(color: highlightedBorderColor, strokeWidth: borderWidth));
-    checkPhysicalLayer(
-      tester.element(outlineButton),
-      fillColor.withAlpha(0xFF),
-      clipPath: clipPath,
-      clipRect: clipRect,
-    );
 
     // Tap gesture completes, button returns to its initial configuration.
     await gesture.up();
@@ -188,13 +154,9 @@ void main() {
     expect(
       outlineButton,
       paints
+        ..path(color: fillColor.withAlpha(0x00))
+        ..clipPath(pathMatcher: coversSameAreaAs(clipPath, areaToCompare: clipRect.inflate(10.0)))
         ..path(color: borderColor, strokeWidth: borderWidth));
-    checkPhysicalLayer(
-      tester.element(outlineButton),
-      fillColor.withAlpha(0x00),
-      clipPath: clipPath,
-      clipRect: clipRect,
-    );
   });
 
   testWidgets('OutlineButton has no clip by default', (WidgetTester tester) async {
@@ -260,6 +222,7 @@ void main() {
     semantics.dispose();
   });
 
+
   testWidgets('OutlineButton scales textScaleFactor', (WidgetTester tester) async {
     await tester.pumpWidget(
       Directionality(
@@ -377,7 +340,6 @@ void main() {
 
     await tester.pumpWidget(buildFrame(ThemeData.dark()));
     final Finder button = find.byType(OutlineButton);
-    final Element buttonElement = tester.element(button);
     final Offset center = tester.getCenter(button);
 
     // Default value for dark Theme.of(context).canvasColor as well as
@@ -385,18 +347,18 @@ void main() {
     Color fillColor = Colors.grey[850];
 
     // Initially the interior of the button is transparent.
-    checkPhysicalLayer(buttonElement, fillColor.withAlpha(0x00));
+    expect(button, paints..path(color: fillColor.withAlpha(0x00)));
 
     // Tap-press gesture on the button triggers the fill animation.
     TestGesture gesture = await tester.startGesture(center);
     await tester.pump(); // Start the button fill animation.
     await tester.pump(const Duration(milliseconds: 200)); // Animation is complete.
-    checkPhysicalLayer(buttonElement, fillColor.withAlpha(0xFF));
+    expect(button, paints..path(color: fillColor.withAlpha(0xFF)));
 
     // Tap gesture completes, button returns to its initial configuration.
     await gesture.up();
     await tester.pumpAndSettle();
-    checkPhysicalLayer(buttonElement, fillColor.withAlpha(0x00));
+    expect(button,  paints..path(color: fillColor.withAlpha(0x00)));
 
     await tester.pumpWidget(buildFrame(ThemeData.light()));
     await tester.pumpAndSettle(); // Finish the theme change animation.
@@ -406,17 +368,17 @@ void main() {
     fillColor = Colors.grey[50];
 
     // Initially the interior of the button is transparent.
-    // expect(button, paints..path(color: fillColor.withAlpha(0x00)));
+    expect(button, paints..path(color: fillColor.withAlpha(0x00)));
 
     // Tap-press gesture on the button triggers the fill animation.
     gesture = await tester.startGesture(center);
     await tester.pump(); // Start the button fill animation.
     await tester.pump(const Duration(milliseconds: 200)); // Animation is complete.
-    checkPhysicalLayer(buttonElement, fillColor.withAlpha(0xFF));
+    expect(button, paints..path(color: fillColor.withAlpha(0xFF)));
 
     // Tap gesture completes, button returns to its initial configuration.
     await gesture.up();
     await tester.pumpAndSettle();
-    checkPhysicalLayer(buttonElement, fillColor.withAlpha(0x00));
+    expect(button,  paints..path(color: fillColor.withAlpha(0x00)));
   });
 }

packages/flutter/test/rendering/proxy_box_test.dart

@@ -64,10 +64,10 @@ void main() {
     layout(root, phase: EnginePhase.composite);
     expect(root.needsCompositing, isFalse);
 
-    // Flutter now composites physical shapes on all platforms.
+    // On non-Fuchsia platforms, Flutter draws its own shadows.
     root.elevation = 1.0;
     pumpFrame(phase: EnginePhase.composite);
-    expect(root.needsCompositing, isTrue);
+    expect(root.needsCompositing, isFalse);
 
     root.elevation = 0.0;
     pumpFrame(phase: EnginePhase.composite);
@@ -127,10 +127,10 @@ void main() {
       layout(root, phase: EnginePhase.composite);
       expect(root.needsCompositing, isFalse);
 
-      // On non-Fuchsia platforms, we composite physical shape layers
+      // On non-Fuchsia platforms, Flutter draws its own shadows.
       root.elevation = 1.0;
       pumpFrame(phase: EnginePhase.composite);
-      expect(root.needsCompositing, isTrue);
+      expect(root.needsCompositing, isFalse);
 
       root.elevation = 0.0;
       pumpFrame(phase: EnginePhase.composite);

packages/flutter/test/widgets/nested_scroll_view_test.dart

@@ -6,7 +6,8 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;
-import 'package:flutter/rendering.dart';
+
+import '../rendering/mock_canvas.dart';
 
 class _CustomPhysics extends ClampingScrollPhysics {
   const _CustomPhysics({ ScrollPhysics parent }) : super(parent: parent);
@@ -468,38 +469,12 @@ void main() {
         // END
       )),
     );
-
-    PhysicalModelLayer _dfsFindPhysicalLayer(ContainerLayer layer) {
-      expect(layer, isNotNull);
-      Layer child = layer.firstChild;
-      while (child != null) {
-        if (child is PhysicalModelLayer) {
-          return child;
-        }
-        if (child is ContainerLayer) {
-          final PhysicalModelLayer candidate = _dfsFindPhysicalLayer(child);
-          if (candidate != null) {
-            return candidate;
-          }
-        }
-        child = child.nextSibling;
-      }
-      return null;
-    }
-
-    final ContainerLayer nestedScrollViewLayer = find.byType(NestedScrollView).evaluate().first.renderObject.debugLayer;
-    void _checkPhysicalLayer({@required double elevation}) {
-      final PhysicalModelLayer layer = _dfsFindPhysicalLayer(nestedScrollViewLayer);
-      expect(layer, isNotNull);
-      expect(layer.elevation, equals(elevation));
-    }
-
     int expectedBuildCount = 0;
     expectedBuildCount += 1;
     expect(buildCount, expectedBuildCount);
     expect(find.text('Item 2'), findsOneWidget);
     expect(find.text('Item 18'), findsNothing);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     // scroll down
     final TestGesture gesture0 = await tester.startGesture(tester.getCenter(find.text('Item 2')));
     await gesture0.moveBy(const Offset(0.0, -120.0)); // tiny bit more than the pinned app bar height (56px * 2)
@@ -513,22 +488,22 @@ void main() {
     expect(buildCount, expectedBuildCount);
     await tester.pump(const Duration(milliseconds: 1)); // during shadow animation
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 0.00018262863159179688);
+    expect(find.byType(NestedScrollView), paints..shadow());
     await tester.pump(const Duration(seconds: 1)); // end shadow animation
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 4);
+    expect(find.byType(NestedScrollView), paints..shadow());
     // scroll down
     final TestGesture gesture1 = await tester.startGesture(tester.getCenter(find.text('Item 2')));
     await gesture1.moveBy(const Offset(0.0, -800.0));
     await tester.pump();
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 4);
+    expect(find.byType(NestedScrollView), paints..shadow());
     expect(find.text('Item 2'), findsNothing);
     expect(find.text('Item 18'), findsOneWidget);
     await gesture1.up();
     await tester.pump(const Duration(seconds: 1));
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 4);
+    expect(find.byType(NestedScrollView), paints..shadow());
     // swipe left to bring in tap on the right
     final TestGesture gesture2 = await tester.startGesture(tester.getCenter(find.byType(NestedScrollView)));
     await gesture2.moveBy(const Offset(-400.0, 0.0));
@@ -539,7 +514,7 @@ void main() {
     expect(find.text('Item 0'), findsOneWidget);
     expect(tester.getTopLeft(find.ancestor(of: find.text('Item 0'), matching: find.byType(ListTile))).dy,
            tester.getBottomLeft(find.byType(AppBar)).dy + 8.0);
-    _checkPhysicalLayer(elevation: 4);
+    expect(find.byType(NestedScrollView), paints..shadow());
     await gesture2.up();
     await tester.pump(); // start sideways scroll
     await tester.pump(const Duration(seconds: 1)); // end sideways scroll, triggers shadow going away
@@ -551,7 +526,7 @@ void main() {
     expect(buildCount, expectedBuildCount);
     expect(find.text('Item 18'), findsNothing);
     expect(find.text('Item 2'), findsOneWidget);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     await tester.pump(const Duration(seconds: 1)); // just checking we don't rebuild...
     expect(buildCount, expectedBuildCount);
     // peek left to see it's still in the right place
@@ -564,10 +539,10 @@ void main() {
     expect(buildCount, expectedBuildCount);
     expect(find.text('Item 18'), findsOneWidget);
     expect(find.text('Item 2'), findsOneWidget);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     await tester.pump(const Duration(seconds: 1)); // shadow finishes coming back
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 4);
+    expect(find.byType(NestedScrollView), paints..shadow());
     await gesture3.moveBy(const Offset(-400.0, 0.0));
     await gesture3.up();
     await tester.pump(); // left tab view goes away
@@ -575,10 +550,10 @@ void main() {
     await tester.pump(); // shadow goes away starting here
     expectedBuildCount += 1;
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 4);
+    expect(find.byType(NestedScrollView), paints..shadow());
     await tester.pump(const Duration(seconds: 1)); // shadow finishes going away
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     // scroll back up
     final TestGesture gesture4 = await tester.startGesture(tester.getCenter(find.byType(NestedScrollView)));
     await gesture4.moveBy(const Offset(0.0, 200.0)); // expands the appbar again
@@ -586,11 +561,11 @@ void main() {
     expect(buildCount, expectedBuildCount);
     expect(find.text('Item 2'), findsOneWidget);
     expect(find.text('Item 18'), findsNothing);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     await gesture4.up();
     await tester.pump(const Duration(seconds: 1));
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     // peek left to see it's now back at zero
     final TestGesture gesture5 = await tester.startGesture(tester.getCenter(find.byType(NestedScrollView)));
     await gesture5.moveBy(const Offset(400.0, 0.0));
@@ -599,14 +574,14 @@ void main() {
     expect(buildCount, expectedBuildCount);
     expect(find.text('Item 18'), findsNothing);
     expect(find.text('Item 2'), findsNWidgets(2));
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     await tester.pump(const Duration(seconds: 1)); // shadow would be finished coming back
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     await gesture5.up();
     await tester.pump(); // right tab view goes away
     await tester.pumpAndSettle();
     expect(buildCount, expectedBuildCount);
-    _checkPhysicalLayer(elevation: 0);
+    expect(find.byType(NestedScrollView), isNot(paints..shadow()));
     debugDisableShadows = true;
   });