From b3d79da158df6cc783b632d73e8610fa14e04430 Mon Sep 17 00:00:00 2001
From: Jim Graham <flar@google.com>
Date: Fri, 14 Nov 2025 12:58:05 -0800
Subject: [PATCH] Fix crash when doing a SaveLayer under a non-invertible
 transform (#178507)

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Fixes a bug where executing a SaveLayer when the matrix is singular
(non-invertible) will currently crash.

Fixes: https://github.com/flutter/flutter/issues/177603

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- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
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Fixes] where supported.
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---
 .../display_list/display_list_unittests.cc    | 61 +++++++++++++++++++
 engine/src/flutter/display_list/dl_builder.cc |  6 +-
 2 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/engine/src/flutter/display_list/display_list_unittests.cc b/engine/src/flutter/display_list/display_list_unittests.cc
index b234b049f53..98f97b51c9c 100644
--- a/engine/src/flutter/display_list/display_list_unittests.cc
+++ b/engine/src/flutter/display_list/display_list_unittests.cc
@@ -5939,5 +5939,66 @@ TEST_F(DisplayListTest, DisplayListDetectsRuntimeEffect) {
   }
 }
 
+namespace {
+typedef void BuilderTransformer(DisplayListBuilder& builder);
+
+sk_sp<DisplayList> TestSaveLayerWithMatrix(BuilderTransformer transform) {
+  const DlScalar xoffset = 50;
+  const DlScalar yoffset = 50;
+  const DlScalar sigma = 10.0;
+
+  DisplayListBuilder builder;
+
+  const auto blur_filter =
+      DlImageFilter::MakeBlur(sigma, sigma, DlTileMode::kClamp);
+
+  builder.Translate(xoffset, yoffset);
+  transform(builder);
+
+  const DlPaint paint;
+  builder.DrawImage(kTestImage1, DlPoint(100.0, 100.0),
+                    DlImageSampling::kNearestNeighbor, &paint);
+
+  DlPaint save_paint;
+  save_paint.setBlendMode(DlBlendMode::kSrc);
+  builder.SaveLayer(std::nullopt, &save_paint, blur_filter.get());
+  builder.Restore();
+
+  return builder.Build();
+}
+}  // namespace
+
+TEST_F(DisplayListTest, SaveLayerWithValidScaleDoesNotCrash) {
+  EXPECT_NE(TestSaveLayerWithMatrix([](DisplayListBuilder& builder) {
+              builder.Scale(0.7, 0.7);
+              EXPECT_TRUE(builder.GetMatrix().IsInvertible());
+            }),
+            nullptr);
+}
+
+TEST_F(DisplayListTest, SaveLayerWithZeroXScaleDoesNotCrash) {
+  EXPECT_NE(TestSaveLayerWithMatrix([](DisplayListBuilder& builder) {
+              builder.Scale(0.0, 0.7);
+              EXPECT_FALSE(builder.GetMatrix().IsInvertible());
+            }),
+            nullptr);
+}
+
+TEST_F(DisplayListTest, SaveLayerWithZeroYScaleDoesNotCrash) {
+  EXPECT_NE(TestSaveLayerWithMatrix([](DisplayListBuilder& builder) {
+              builder.Scale(0.7, 0.0);
+              EXPECT_FALSE(builder.GetMatrix().IsInvertible());
+            }),
+            nullptr);
+}
+
+TEST_F(DisplayListTest, SaveLayerWithLinearSkewDoesNotCrash) {
+  EXPECT_NE(TestSaveLayerWithMatrix([](DisplayListBuilder& builder) {
+              builder.Skew(1.0f, 1.0f);
+              EXPECT_FALSE(builder.GetMatrix().IsInvertible());
+            }),
+            nullptr);
+}
+
 }  // namespace testing
 }  // namespace flutter
diff --git a/engine/src/flutter/display_list/dl_builder.cc b/engine/src/flutter/display_list/dl_builder.cc
index a5a70aea621..0ac5796dd5f 100644
--- a/engine/src/flutter/display_list/dl_builder.cc
+++ b/engine/src/flutter/display_list/dl_builder.cc
@@ -461,11 +461,7 @@ void DisplayListBuilder::saveLayer(const DlRect& bounds,
   // with its full bounds and the right op_index so that it doesn't
   // get culled during rendering.
   if (will_be_unbounded) {
-    // Accumulate should always return true here because if the
-    // clip was empty then that would have been caught up above
-    // when we tested the PaintResult.
-    [[maybe_unused]] bool unclipped = AccumulateUnbounded();
-    FML_DCHECK(unclipped);
+    AccumulateUnbounded();
   }
 
   // Accumulate information for the SaveInfo we are about to push onto the