From 7bb35d8a86037577ac435a11b2ce4c817738e479 Mon Sep 17 00:00:00 2001
From: Harry Terkelsen <1961493+harryterkelsen@users.noreply.github.com>
Date: Thu, 5 Sep 2024 15:23:37 -0700
Subject: [PATCH] [canvaskit] Fix incorrect calculation of ImageFilter paint
 bounds (flutter/engine#54980)

Fixes calculation of `ImageFilter` bounds by taking into account the
offset.

Fixes https://github.com/flutter/flutter/issues/154303

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- [x] I added new tests to check the change I am making or feature I am
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- [x] All existing and new tests are passing.

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---
 .../lib/src/engine/canvaskit/layer.dart       | 30 ++++++++++---------
 .../web_ui/test/ui/scene_builder_test.dart    | 25 ++++++++++++++++
 2 files changed, 41 insertions(+), 14 deletions(-)

diff --git a/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/layer.dart b/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/layer.dart
index b4d419a9265..010fc012786 100644
--- a/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/layer.dart
+++ b/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/layer.dart
@@ -415,32 +415,34 @@ class ImageFilterEngineLayer extends ContainerLayer
     } else {
       convertible = _filter as CkManagedSkImageFilterConvertible;
     }
-    final ui.Rect childPaintBounds =
+    ui.Rect childPaintBounds =
         prerollChildren(prerollContext, childMatrix);
-      if (_filter is ui.ColorFilter) {
-        // If the filter is a ColorFilter, the extended paint bounds will be the
-        // entire screen, which is not what we want.
-        paintBounds = childPaintBounds;
-      } else {
-        convertible.withSkImageFilter((skFilter) {
-          paintBounds = rectFromSkIRect(
-            skFilter.getOutputBounds(toSkRect(childPaintBounds)),
-          );
-        });
-      }
+    childPaintBounds = childPaintBounds.translate(_offset.dx, _offset.dy);
+    if (_filter is ui.ColorFilter) {
+      // If the filter is a ColorFilter, the extended paint bounds will be the
+      // entire screen, which is not what we want.
+      paintBounds = childPaintBounds;
+    } else {
+      convertible.withSkImageFilter((skFilter) {
+        paintBounds = rectFromSkIRect(
+          skFilter.getOutputBounds(toSkRect(childPaintBounds)),
+        );
+      });
+    }
     prerollContext.mutatorsStack.pop();
   }
 
   @override
   void paint(PaintContext paintContext) {
     assert(needsPainting);
+    final ui.Rect offsetPaintBounds = paintBounds.shift(-_offset);
     paintContext.internalNodesCanvas.save();
     paintContext.internalNodesCanvas.translate(_offset.dx, _offset.dy);
     paintContext.internalNodesCanvas
-        .clipRect(paintBounds, ui.ClipOp.intersect, false);
+        .clipRect(offsetPaintBounds, ui.ClipOp.intersect, false);
     final CkPaint paint = CkPaint();
     paint.imageFilter = _filter;
-    paintContext.internalNodesCanvas.saveLayer(paintBounds, paint);
+    paintContext.internalNodesCanvas.saveLayer(offsetPaintBounds, paint);
     paintChildren(paintContext);
     paintContext.internalNodesCanvas.restore();
     paintContext.internalNodesCanvas.restore();
diff --git a/engine/src/flutter/lib/web_ui/test/ui/scene_builder_test.dart b/engine/src/flutter/lib/web_ui/test/ui/scene_builder_test.dart
index fc77fd98c2d..aeaef07ad0c 100644
--- a/engine/src/flutter/lib/web_ui/test/ui/scene_builder_test.dart
+++ b/engine/src/flutter/lib/web_ui/test/ui/scene_builder_test.dart
@@ -262,6 +262,31 @@ Future<void> testMain() async {
       await matchGoldenFile('scene_builder_image_filter.png', region: region);
     });
 
+    // Regression test for https://github.com/flutter/flutter/issues/154303
+    test('image filter layer with offset', () async {
+      final ui.SceneBuilder sceneBuilder = ui.SceneBuilder();
+
+      sceneBuilder.pushClipRect(const ui.Rect.fromLTWH(100, 100, 100, 100));
+      sceneBuilder.pushImageFilter(
+        ui.ImageFilter.blur(
+          sigmaX: 5.0,
+          sigmaY: 5.0,
+        ),
+        offset: const ui.Offset(100, 100),
+      );
+
+      sceneBuilder.addPicture(ui.Offset.zero, drawPicture((ui.Canvas canvas) {
+        canvas.drawCircle(const ui.Offset(50, 50), 25,
+            ui.Paint()..color = const ui.Color(0xFF00FF00));
+      }));
+
+      await renderScene(sceneBuilder.build());
+      await matchGoldenFile(
+        'scene_builder_image_filter_with_offset.png',
+        region: region,
+      );
+    });
+
     test('color filter layer', () async {
       final ui.SceneBuilder sceneBuilder = ui.SceneBuilder();
       const ui.ColorFilter sepia = ui.ColorFilter.matrix(<double>[