Does not replace the root layer unnecessarily (#101748)

peggyart · May 6, 2022 · b20e27e · b20e27e
1 parent 82afe3e
commit b20e27e
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Showing 3 changed files with 20 additions and 2 deletions.
diff --git a/packages/flutter/lib/src/rendering/view.dart b/packages/flutter/lib/src/rendering/view.dart
@@ -82,6 +82,7 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
   /// The constraints used for the root layout.
   ViewConfiguration get configuration => _configuration;
   ViewConfiguration _configuration;
+
   /// The configuration is initially set by the `configuration` argument
   /// passed to the constructor.
   ///
@@ -90,8 +91,11 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
     assert(value != null);
     if (configuration == value)
       return;
+    final ViewConfiguration oldConfiguration = _configuration;
     _configuration = value;
-    replaceRootLayer(_updateMatricesAndCreateNewRootLayer());
+    if (oldConfiguration.toMatrix() != _configuration.toMatrix()) {
+      replaceRootLayer(_updateMatricesAndCreateNewRootLayer());
+    }
     assert(_rootTransform != null);
     markNeedsLayout();
   }

diff --git a/packages/flutter/test/rendering/view_test.dart b/packages/flutter/test/rendering/view_test.dart
@@ -47,6 +47,20 @@ void main() {
       view.configuration = createViewConfiguration(devicePixelRatio: 5.0);
       expect(identical(view.debugLayer, firstLayer), false);
     });
+
+    test('does not replace the root layer unnecessarily when window resize', () {
+      final ui.FlutterView window = TestWindow(window: RendererBinding.instance.window);
+      final RenderView view = RenderView(
+        configuration: createViewConfiguration(size: const Size(100.0, 100.0)),
+        window: window,
+      );
+      final PipelineOwner owner = PipelineOwner();
+      view.attach(owner);
+      view.prepareInitialFrame();
+      final ContainerLayer firstLayer = view.debugLayer!;
+      view.configuration = createViewConfiguration(size: const Size(100.0, 1117.0));
+      expect(identical(view.debugLayer, firstLayer), true);
+    });
   });
 
   test('ViewConfiguration == and hashCode', () {

diff --git a/packages/flutter_test/lib/src/binding.dart b/packages/flutter_test/lib/src/binding.dart
@@ -1779,7 +1779,7 @@ class TestViewConfiguration extends ViewConfiguration {
   TestViewConfiguration._(Size size, ui.FlutterView window)
     : _paintMatrix = _getMatrix(size, window.devicePixelRatio, window),
       _hitTestMatrix = _getMatrix(size, 1.0, window),
-      super(size: size);
+      super(size: size, devicePixelRatio: window.devicePixelRatio);
 
   static Matrix4 _getMatrix(Size size, double devicePixelRatio, ui.FlutterView window) {
     final double inverseRatio = devicePixelRatio / window.devicePixelRatio;