exo: Improve damage tracking.

This sends the exact damage region reported by clients to the
compositor instead of a bounding box for the damage.

BUG=549781
TEST=exo_unittests --gtest_filter=Surface.Damage

Review URL: https://codereview.chromium.org/1688273002

Cr-Commit-Position: refs/heads/master@{#374996}

3 files changed, 15 insertions, 9 deletions

diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index fc09e13..5639d18 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -138,7 +138,7 @@ void Surface::Attach(Buffer* buffer) {
 void Surface::Damage(const gfx::Rect& damage) {
   TRACE_EVENT1("exo", "Surface::Damage", "damage", damage.ToString());
 
-  pending_damage_.Union(damage);
+  pending_damage_.op(gfx::RectToSkIRect(damage), SkRegion::kUnion_Op);
 }
 
 void Surface::RequestFrameCallback(const FrameCallback& callback) {
@@ -296,8 +296,11 @@ void Surface::CommitSurfaceHierarchy() {
     }
 
     // Schedule redraw of the damage region.
-    layer()->SchedulePaint(pending_damage_);
-    pending_damage_ = gfx::Rect();
+    for (SkRegion::Iterator it(pending_damage_); !it.done(); it.next())
+      layer()->SchedulePaint(gfx::SkIRectToRect(it.rect()));
+
+    // Reset damage.
+    pending_damage_.setEmpty();
   }
 
   ui::Compositor* compositor = layer()->GetCompositor();
diff --git a/components/exo/surface.h b/components/exo/surface.h
index 93396d0..d5377d3 100644
--- a/components/exo/surface.h
+++ b/components/exo/surface.h
@@ -101,7 +101,9 @@ class Surface : public aura::Window, public ui::CompositorObserver {
   // Returns a trace value representing the state of the surface.
   scoped_refptr<base::trace_event::TracedValue> AsTracedValue() const;
 
-  bool HasPendingDamageForTesting() const { return !pending_damage_.IsEmpty(); }
+  bool HasPendingDamageForTesting(const gfx::Rect& damage) const {
+    return pending_damage_.contains(gfx::RectToSkIRect(damage));
+  }
 
   // Overridden from ui::CompositorObserver:
   void OnCompositingDidCommit(ui::Compositor* compositor) override;
@@ -128,9 +130,7 @@ class Surface : public aura::Window, public ui::CompositorObserver {
   base::WeakPtr<Buffer> pending_buffer_;
 
   // The damage region to schedule paint for when Commit() is called.
-  // TODO(reveman): Use SkRegion here after adding a version of
-  // ui::Layer::SchedulePaint that takes a SkRegion.
-  gfx::Rect pending_damage_;
+  SkRegion pending_damage_;
 
   // These lists contains the callbacks to notify the client when it is a good
   // time to start producing a new frame. These callbacks move to
diff --git a/components/exo/surface_unittest.cc b/components/exo/surface_unittest.cc
index b1351a4..d8aba4a 100644
--- a/components/exo/surface_unittest.cc
+++ b/components/exo/surface_unittest.cc
@@ -56,10 +56,13 @@ TEST_F(SurfaceTest, Damage) {
   // the surface to the buffer size.
   surface->Attach(buffer.get());
 
-  // Mark area inside the bounds of the surface as damaged. This should result
+  // Mark areas inside the bounds of the surface as damaged. This should result
   // in pending damage.
   surface->Damage(gfx::Rect(0, 0, 10, 10));
-  EXPECT_TRUE(surface->HasPendingDamageForTesting());
+  surface->Damage(gfx::Rect(10, 10, 10, 10));
+  EXPECT_TRUE(surface->HasPendingDamageForTesting(gfx::Rect(0, 0, 10, 10)));
+  EXPECT_TRUE(surface->HasPendingDamageForTesting(gfx::Rect(10, 10, 10, 10)));
+  EXPECT_FALSE(surface->HasPendingDamageForTesting(gfx::Rect(5, 5, 10, 10)));
 }
 
 void SetFrameTime(base::TimeTicks* result, base::TimeTicks frame_time) {