TransformPaintPropertyNode::MatrixWithOriginApplied()

It returns the matrix with transform origin applied. Useful where we
want to get whole matrix that this transform node will apply.

Also fix a bug in CullRect::ApplyTransforms() where we missed the
origin.

Change-Id: If671470a5c9ea0e8a46e128692862bb0779d005f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1757081Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688609}

third_party/blink/renderer/platform/graphics/paint/cull_rect.cc

@@ -58,7 +58,7 @@ static void MapRect(const TransformPaintPropertyNode& transform,
     float_rect.Move(-transform.Translation2D());
     rect = EnclosingIntRect(float_rect);
   } else {
-    rect = transform.Matrix().Inverse().MapRect(rect);
+    rect = transform.MatrixWithOriginApplied().Inverse().MapRect(rect);
   }
 }
 

third_party/blink/renderer/platform/graphics/paint/cull_rect_test.cc

@@ -289,6 +289,16 @@ TEST_F(CullRectTest, ApplyTransformsSingleScrollWholeScrollingContents) {
   EXPECT_EQ(IntRect(-3970, -3975, 8040, 8050), cull_rect3.Rect());
 }
 
+TEST_F(CullRectTest, ApplyTransformsWithOrigin) {
+  ScopedCompositeAfterPaintForTest cap(true);
+  auto t1 = CreateTransform(t0(), TransformationMatrix().Translate(1, 2));
+  auto t2 = CreateTransform(*t1, TransformationMatrix().Scale(0.5),
+                            FloatPoint3D(50, 100, 0));
+  CullRect cull_rect1(IntRect(0, 0, 50, 200));
+  cull_rect1.ApplyTransforms(*t1, *t2, base::nullopt);
+  EXPECT_EQ(IntRect(-50, -100, 100, 400), cull_rect1.Rect());
+}
+
 TEST_F(CullRectTest, ApplyTransformsSingleScrollPartialScrollingContents) {
   ScopedCompositeAfterPaintForTest cap(true);
   auto t1 = CreateTransform(t0(), TransformationMatrix().Translate(1, 2));

third_party/blink/renderer/platform/graphics/paint/geometry_mapper_transform_cache.cc

@@ -70,9 +70,7 @@ void GeometryMapperTransformCache::Update(
   root_of_2d_translation_ = &node;
   to_2d_translation_root_ = FloatSize();
 
-  TransformationMatrix local = node.Matrix();
-  local.ApplyTransformOrigin(node.Origin());
-
+  TransformationMatrix local = node.MatrixWithOriginApplied();
   bool is_plane_root = !local.IsFlat() || !local.IsInvertible();
   if (is_plane_root && root_of_2d_translation_ == &node) {
     // We don't need plane root transform because the plane root is the same
@@ -123,9 +121,7 @@ void GeometryMapperTransformCache::UpdateScreenTransform(
     screen_transform_->to_screen.Translate(translation.Width(),
                                            translation.Height());
   } else {
-    TransformationMatrix local = node.Matrix();
-    local.ApplyTransformOrigin(node.Origin());
-    screen_transform_->to_screen.Multiply(local);
+    screen_transform_->to_screen.Multiply(node.MatrixWithOriginApplied());
   }
 
   auto to_screen_flattened = screen_transform_->to_screen;

third_party/blink/renderer/platform/graphics/paint/transform_paint_property_node.h

@@ -263,6 +263,9 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
   const TransformationMatrix& Matrix() const {
     return state_.transform_and_origin.Matrix();
   }
+  TransformationMatrix MatrixWithOriginApplied() const {
+    return TransformationMatrix(Matrix()).ApplyTransformOrigin(Origin());
+  }
   // The slow version always return meaningful TransformationMatrix regardless
   // of IsIdentityOr2DTranslation(). Should be used only in contexts that are
   // not performance sensitive.