From cb9ce54b77bf1e9f25427e651487b377e3bbb2b2 Mon Sep 17 00:00:00 2001
From: Yegor <yjbanov@google.com>
Date: Mon, 13 Sep 2021 13:07:01 -0700
Subject: [PATCH] [web] fix the last matrix element in CkPath.shift
 (flutter/engine#28589)

---
 .../web_ui/lib/src/engine/canvaskit/path.dart    | 16 ++++++++++------
 .../lib/web_ui/test/canvaskit/path_test.dart     | 15 +++++++++++++++
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/path.dart b/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/path.dart
index a9ed3864198..c11233ad639 100644
--- a/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/path.dart
+++ b/engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/path.dart
@@ -257,12 +257,16 @@ class CkPath extends ManagedSkiaObject<SkPath> implements ui.Path {
   }
 
   @override
-  ui.Path shift(ui.Offset offset) {
-    // Since CanvasKit does not expose `SkPath.offset`, create a copy of this
-    // path and call `transform` on it.
-    final SkPath newPath = skiaObject.copy();
-    newPath.transform(1.0, 0.0, offset.dx, 0.0, 1.0, offset.dy, 0.0, 0.0, 0.0);
-    return CkPath.fromSkPath(newPath, _fillType);
+  CkPath shift(ui.Offset offset) {
+    // `SkPath.transform` mutates the existing path, so create a copy and call
+    // `transform` on the copy.
+    final SkPath shiftedPath = skiaObject.copy();
+    shiftedPath.transform(
+      1.0, 0.0, offset.dx,
+      0.0, 1.0, offset.dy,
+      0.0, 0.0, 1.0,
+    );
+    return CkPath.fromSkPath(shiftedPath, _fillType);
   }
 
   static CkPath combine(
diff --git a/engine/src/flutter/lib/web_ui/test/canvaskit/path_test.dart b/engine/src/flutter/lib/web_ui/test/canvaskit/path_test.dart
index 40f93595678..5ef031f9aa9 100644
--- a/engine/src/flutter/lib/web_ui/test/canvaskit/path_test.dart
+++ b/engine/src/flutter/lib/web_ui/test/canvaskit/path_test.dart
@@ -85,6 +85,21 @@ void testMain() {
       expect(path.contains(const ui.Offset(5, 5)), isFalse);
     });
 
+    test('CkPath.shift creates a shifted copy of the path', () {
+      const ui.Rect testRect = ui.Rect.fromLTRB(0, 0, 10, 10);
+      final CkPath path = CkPath();
+      path.addRect(testRect);
+      expect(path.getBounds(), testRect);
+
+      expect(
+        path.shift(const ui.Offset(20, 20)).getBounds(),
+        testRect.shift(const ui.Offset(20, 20)),
+      );
+
+      // Make sure the original path wasn't mutated.
+      expect(path.getBounds(), testRect);
+    });
+
     test('CkPath resurrection', () {
       const ui.Rect rect = ui.Rect.fromLTRB(0, 0, 10, 10);
       final CkPath path = CkPath();