From 8ccf169df62b7dd070aa06a70644848399b013dc Mon Sep 17 00:00:00 2001
From: Jason Simmons <jsimmons@google.com>
Date: Thu, 29 Jun 2023 23:34:13 +0000
Subject: [PATCH] Apply the transform of an image filter layer to paint bounds
 in the CanvasKit backend

Fixes https://github.com/flutter/flutter/issues/128788
---
 .../src/engine/canvaskit/color_filter.dart    |  4 +++
 .../src/engine/canvaskit/image_filter.dart    | 10 +++++++
 .../lib/src/engine/canvaskit/layer.dart       | 12 +++++++++
 lib/web_ui/test/canvaskit/layer_test.dart     | 26 +++++++++++++++++++
 4 files changed, 52 insertions(+)

diff --git a/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart b/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart
index bb40093ae73b6..8114aa3cedc01 100644
--- a/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart
+++ b/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart
@@ -4,6 +4,7 @@
 
 import 'dart:typed_data';
 
+import 'package:ui/src/engine/vector_math.dart';
 import 'package:ui/ui.dart' as ui;
 
 import '../color_filter.dart';
@@ -79,6 +80,9 @@ abstract class CkColorFilter implements CkManagedSkImageFilterConvertible {
     borrow(skImageFilter);
     skImageFilter.delete();
   }
+
+  @override
+  Matrix4 get transform => Matrix4.identity();
 }
 
 /// A reusable identity transform matrix.
diff --git a/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart b/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart
index 46eda4f2ce4be..2032ccdd88670 100644
--- a/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart
+++ b/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart
@@ -23,6 +23,8 @@ typedef SkImageFilterBorrow = void Function(SkImageFilter);
 /// Currently implemented by [CkImageFilter] and [CkColorFilter].
 abstract class CkManagedSkImageFilterConvertible implements ui.ImageFilter {
   void imageFilter(SkImageFilterBorrow borrow);
+
+  Matrix4 get transform;
 }
 
 /// The CanvasKit implementation of [ui.ImageFilter].
@@ -40,6 +42,9 @@ abstract class CkImageFilter implements CkManagedSkImageFilterConvertible {
       required ui.FilterQuality filterQuality}) = _CkMatrixImageFilter;
 
   CkImageFilter._();
+
+  @override
+  Matrix4 get transform => Matrix4.identity();
 }
 
 class CkColorFilterImageFilter extends CkImageFilter {
@@ -149,6 +154,7 @@ class _CkMatrixImageFilter extends CkImageFilter {
   _CkMatrixImageFilter(
       {required Float64List matrix, required this.filterQuality})
       : matrix = Float64List.fromList(matrix),
+        _transform = Matrix4.fromFloat32List(toMatrix32(matrix)),
         super._() {
     final SkImageFilter skImageFilter = canvasKit.ImageFilter.MakeMatrixTransform(
       toSkMatrixFromFloat64(matrix),
@@ -160,6 +166,7 @@ class _CkMatrixImageFilter extends CkImageFilter {
 
   final Float64List matrix;
   final ui.FilterQuality filterQuality;
+  final Matrix4 _transform;
 
   late final UniqueRef<SkImageFilter> _ref;
 
@@ -183,4 +190,7 @@ class _CkMatrixImageFilter extends CkImageFilter {
 
   @override
   String toString() => 'ImageFilter.matrix($matrix, $filterQuality)';
+
+  @override
+  Matrix4 get transform => _transform;
 }
diff --git a/lib/web_ui/lib/src/engine/canvaskit/layer.dart b/lib/web_ui/lib/src/engine/canvaskit/layer.dart
index b357465e7668c..314aa4870b43b 100644
--- a/lib/web_ui/lib/src/engine/canvaskit/layer.dart
+++ b/lib/web_ui/lib/src/engine/canvaskit/layer.dart
@@ -7,6 +7,7 @@ import 'package:ui/ui.dart' as ui;
 import '../vector_math.dart';
 import 'canvas.dart';
 import 'embedded_views.dart';
+import 'image_filter.dart';
 import 'n_way_canvas.dart';
 import 'painting.dart';
 import 'path.dart';
@@ -396,6 +397,17 @@ class ImageFilterEngineLayer extends ContainerLayer
   final ui.Offset _offset;
   final ui.ImageFilter _filter;
 
+  @override
+  void preroll(PrerollContext prerollContext, Matrix4 matrix) {
+    final Matrix4 transform = (_filter as CkManagedSkImageFilterConvertible).transform;
+    final Matrix4 childMatrix = matrix.multiplied(transform);
+    prerollContext.mutatorsStack.pushTransform(transform);
+    final ui.Rect childPaintBounds =
+        prerollChildren(prerollContext, childMatrix);
+    paintBounds = transform.transformRect(childPaintBounds);
+    prerollContext.mutatorsStack.pop();
+  }
+
   @override
   void paint(PaintContext paintContext) {
     assert(needsPainting);
diff --git a/lib/web_ui/test/canvaskit/layer_test.dart b/lib/web_ui/test/canvaskit/layer_test.dart
index 4dae7c63addb9..7ed4051b7c930 100644
--- a/lib/web_ui/test/canvaskit/layer_test.dart
+++ b/lib/web_ui/test/canvaskit/layer_test.dart
@@ -72,5 +72,31 @@ void testMain() {
         region: kDefaultRegion,
       );
     });
+
+    test('ImageFilter layer applies matrix in preroll', () async {
+      final CkPicture picture =
+          paintPicture(const ui.Rect.fromLTRB(0, 0, 100, 100), (CkCanvas canvas) {
+        canvas.drawRect(const ui.Rect.fromLTRB(0, 0, 100, 100),
+            CkPaint()..style = ui.PaintingStyle.fill);
+      });
+
+      final LayerSceneBuilder sb = LayerSceneBuilder();
+      sb.pushImageFilter(
+        ui.ImageFilter.matrix(
+          (
+            Matrix4.identity()
+              ..scale(0.5, 0.5)
+              ..translate(20)
+          ).toFloat64(),
+        ),
+      );
+      sb.addPicture(ui.Offset.zero, picture);
+
+      final LayerTree layerTree = sb.build().layerTree;
+      CanvasKitRenderer.instance.rasterizer.draw(layerTree);
+
+      final ImageFilterEngineLayer imageFilterLayer = layerTree.rootLayer.debugLayers.single as ImageFilterEngineLayer;
+      expect(imageFilterLayer.paintBounds, const ui.Rect.fromLTRB(10, 0, 60, 50));
+    });
   });
 }