Enable MapRectReverse() for a blur filter to map backward

Current implementation of FilterOperation::MapRectReverse() for a blur
filter actually does a forward (outset) map of the rect. This patch
fixes the erroneous behavior by supporting MapRectReverse() to map
backward for a blur filter.

Bug: 916583
Change-Id: I43bf4498b89e18ba9c2d1eb341e977944e2226c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1986646Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Md. Hasanur Rashid <hasanur.r@samsung.com>
Cr-Commit-Position: refs/heads/master@{#732570}

cc/layers/render_surface_impl.cc

@@ -211,7 +211,7 @@ gfx::Rect RenderSurfaceImpl::CalculateExpandedClipForFilters(
   gfx::Rect clip_in_surface_space =
       MathUtil::ProjectEnclosingClippedRect(target_to_surface, clip_rect());
   gfx::Rect expanded_clip_in_surface_space =
-      Filters().MapRectReverse(clip_in_surface_space, SurfaceScale().matrix());
+      Filters().MapRect(clip_in_surface_space, SurfaceScale().matrix());
   gfx::Rect expanded_clip_in_target_space = MathUtil::MapEnclosingClippedRect(
       draw_transform(), expanded_clip_in_surface_space);
   return expanded_clip_in_target_space;

cc/paint/filter_operation.cc

@@ -353,10 +353,8 @@ gfx::Rect MapRectInternal(const FilterOperation& op,
       // Mapping a blur forward requires an outset (negative inset) because a
       // smaller source rectangle gets blurred to a larger destination
       // rectangle.
-      // TODO(916583): Fix this function for reverse mapping:
-      // float sign = (direction == SkImageFilter::kForward_MapDirection) ? -1.0
-      // : 1.0;
-      float sign = -1.0;
+      float sign =
+          (direction == SkImageFilter::kForward_MapDirection) ? -1.0 : 1.0;
       float spread_x = std::abs(spread.x()) * sign;
       float spread_y = std::abs(spread.y()) * sign;
       gfx::RectF result(rect);

cc/paint/filter_operations_unittest.cc

@@ -39,13 +39,13 @@ TEST(FilterOperationsTest, MapRectBlurOverflow) {
 TEST(FilterOperationsTest, MapRectReverseBlur) {
   FilterOperations ops;
   ops.Append(FilterOperation::CreateBlurFilter(20));
-  EXPECT_EQ(gfx::Rect(-60, -60, 130, 130),
-            ops.MapRectReverse(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
+  EXPECT_EQ(gfx::Rect(60, 60, 30, 30),
+            ops.MapRectReverse(gfx::Rect(0, 0, 150, 150), SkMatrix::I()));
   EXPECT_EQ(
-      gfx::Rect(-120, -120, 260, 260),
-      ops.MapRectReverse(gfx::Rect(0, 0, 20, 20), SkMatrix::MakeScale(2, 2)));
-  EXPECT_EQ(gfx::Rect(-60, -70, 130, 130),
-            ops.MapRectReverse(gfx::Rect(0, -10, 10, 10),
+      gfx::Rect(120, 120, 60, 60),
+      ops.MapRectReverse(gfx::Rect(0, 0, 300, 300), SkMatrix::MakeScale(2, 2)));
+  EXPECT_EQ(gfx::Rect(60, 50, 30, 30),
+            ops.MapRectReverse(gfx::Rect(0, -10, 150, 150),
                                SkMatrix::MakeScale(1, -1)));
 }
 

cc/trees/draw_property_utils.cc

@@ -191,7 +191,7 @@ bool ApplyClipNodeToAccumulatedClip(const PropertyTrees* property_trees,
 
       // Do the expansion.
       gfx::RectF expanded_clip_in_expanding_space =
-          gfx::RectF(clip_node->clip_expander->MapRectReverse(
+          gfx::RectF(clip_node->clip_expander->MapRect(
               ToEnclosingClipRect(accumulated_clip_rect_in_expanding_space),
               property_trees));
 

cc/trees/occlusion_tracker.cc

@@ -20,8 +20,7 @@
 namespace cc {
 
 OcclusionTracker::OcclusionTracker(const gfx::Rect& screen_space_clip_rect)
-    : screen_space_clip_rect_(screen_space_clip_rect) {
-}
+    : screen_space_clip_rect_(screen_space_clip_rect) {}
 
 OcclusionTracker::~OcclusionTracker() = default;
 
@@ -29,8 +28,7 @@ Occlusion OcclusionTracker::GetCurrentOcclusionForLayer(
     const gfx::Transform& draw_transform) const {
   DCHECK(!stack_.empty());
   const StackObject& back = stack_.back();
-  return Occlusion(draw_transform,
-                   back.occlusion_from_outside_target,
+  return Occlusion(draw_transform, back.occlusion_from_outside_target,
                    back.occlusion_from_inside_target);
 }
 
@@ -160,10 +158,8 @@ void OcclusionTracker::EnterRenderTarget(
       new_target_surface->render_target() == new_target_surface;
 
   bool copy_outside_occlusion_forward =
-      stack_.size() > 1 &&
-      !entering_unoccluded_subtree &&
-      have_transform_from_screen_to_new_target &&
-      !entering_root_target;
+      stack_.size() > 1 && !entering_unoccluded_subtree &&
+      have_transform_from_screen_to_new_target && !entering_root_target;
   if (!copy_outside_occlusion_forward) {
     stack_.back().ignores_parent_occlusion = true;
     return;
@@ -227,8 +223,12 @@ static void ReduceOcclusionBelowSurface(
     return;
 
   gfx::Rect affected_area_in_target =
-      contributing_surface->BackdropFilters().MapRectReverse(target_rect,
-                                                             SkMatrix::I());
+      contributing_surface->BackdropFilters().HasFilterOfType(
+          FilterOperation::FilterType::BLUR)
+          ? contributing_surface->BackdropFilters().MapRect(target_rect,
+                                                            SkMatrix::I())
+          : contributing_surface->BackdropFilters().MapRectReverse(
+                target_rect, SkMatrix::I());
   // Unite target_rect because we only care about positive outsets.
   affected_area_in_target.Union(target_rect);
 

cc/trees/property_tree_builder_unittest.cc

@@ -362,9 +362,9 @@ TEST_F(PropertyTreeBuilderTest, VisibleRectWithClippingAndFilters) {
 
   CommitAndActivate();
 
-  EXPECT_EQ(gfx::Rect(49, 39, 12, 21),
+  EXPECT_EQ(gfx::Rect(50, 40, 10, 20),
             ImplOf(filter_child)->visible_layer_rect());
-  EXPECT_EQ(gfx::Rect(-1, -11, 12, 21),
+  EXPECT_EQ(gfx::Rect(0, -10, 10, 20),
             GetRenderSurfaceImpl(filter)->content_rect());
 }
 
@@ -422,9 +422,9 @@ TEST_F(PropertyTreeBuilderTest, VisibleRectWithScalingClippingAndFilters) {
 
   CommitAndActivate();
 
-  EXPECT_EQ(gfx::Rect(49, 39, 12, 21),
+  EXPECT_EQ(gfx::Rect(50, 40, 10, 20),
             ImplOf(filter_child)->visible_layer_rect());
-  EXPECT_EQ(gfx::Rect(-1, -31, 32, 61),
+  EXPECT_EQ(gfx::Rect(0, -30, 30, 60),
             GetRenderSurfaceImpl(filter)->content_rect());
 }