cc: Don't add low res tilings for small layers

R=danakj@chromium.org
BUG=247465

Review URL: https://chromiumcodereview.appspot.com/16671003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@205657 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 62 insertions, 10 deletions

diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index f2eb6da..9488b4e 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -477,7 +477,7 @@ const PictureLayerTiling* PictureLayerImpl::GetTwinTiling(
 }
 
 gfx::Size PictureLayerImpl::CalculateTileSize(
-    gfx::Size content_bounds) {
+    gfx::Size content_bounds) const {
   if (is_mask_) {
     int max_size = layer_tree_impl()->MaxTextureSize();
     return gfx::Size(
@@ -880,6 +880,16 @@ void PictureLayerImpl::CalculateRasterContentsScale(
         *raster_contents_scale, 1.f * ideal_page_scale_ * ideal_device_scale_);
   }
 
+  // If this layer would only create one tile at this content scale,
+  // don't create a low res tiling.
+  gfx::Size content_bounds =
+      gfx::ToCeiledSize(gfx::ScaleSize(bounds(), *raster_contents_scale));
+  gfx::Size tile_size = CalculateTileSize(content_bounds);
+  if (tile_size == content_bounds) {
+    *low_res_raster_contents_scale = *raster_contents_scale;
+    return;
+  }
+
   float low_res_factor =
       layer_tree_impl()->settings().low_res_contents_scale_factor;
   *low_res_raster_contents_scale = std::max(
diff --git a/cc/layers/picture_layer_impl.h b/cc/layers/picture_layer_impl.h
index b9697a7..ad96c6f 100644
--- a/cc/layers/picture_layer_impl.h
+++ b/cc/layers/picture_layer_impl.h
@@ -57,7 +57,7 @@ class CC_EXPORT PictureLayerImpl
                                          gfx::Rect content_rect) OVERRIDE;
   virtual void UpdatePile(Tile* tile) OVERRIDE;
   virtual gfx::Size CalculateTileSize(
-      gfx::Size content_bounds) OVERRIDE;
+      gfx::Size content_bounds) const OVERRIDE;
   virtual const Region* GetInvalidation() OVERRIDE;
   virtual const PictureLayerTiling* GetTwinTiling(
       const PictureLayerTiling* tiling) OVERRIDE;
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index 30bccaf..855fa56 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -48,9 +48,8 @@ class PictureLayerImplTest : public testing::Test {
   virtual ~PictureLayerImplTest() {
   }
 
-  void SetupDefaultTrees() {
+  void SetupDefaultTrees(gfx::Size layer_bounds) {
     gfx::Size tile_size(100, 100);
-    gfx::Size layer_bounds(100, 100);
 
     scoped_refptr<FakePicturePileImpl> pending_pile =
         FakePicturePileImpl::CreateFilledPile(tile_size, layer_bounds);
@@ -137,6 +136,11 @@ class PictureLayerImplTest : public testing::Test {
         &result_bounds);
   }
 
+  void ResetTilingsAndRasterScales() {
+    pending_layer_->DidLoseOutputSurface();
+    active_layer_->DidLoseOutputSurface();
+  }
+
  protected:
   void TestTileGridAlignmentCommon() {
     // Layer to span 4 raster tiles in x and in y
@@ -645,7 +649,7 @@ TEST_F(PictureLayerImplTest, CleanUpTilings) {
   } while (false)
 
 TEST_F(PictureLayerImplTest, DontAddLowResDuringAnimation) {
-  SetupDefaultTrees();
+  SetupDefaultTrees(gfx::Size(300, 100));
 
   float low_res_factor = host_impl_.settings().low_res_contents_scale_factor;
   float contents_scale = 1.f;
@@ -686,6 +690,43 @@ TEST_F(PictureLayerImplTest, DontAddLowResDuringAnimation) {
   EXPECT_BOTH_EQ(num_tilings(), 4u);
 }
 
+TEST_F(PictureLayerImplTest, DontAddLowResForSmallLayers) {
+  gfx::Size tile_size(host_impl_.settings().default_tile_size);
+  SetupDefaultTrees(tile_size);
+
+  float low_res_factor = host_impl_.settings().low_res_contents_scale_factor;
+  float contents_scale = 1.f;
+  float device_scale = 1.f;
+  float page_scale = 1.f;
+  bool animating_transform = false;
+  SetContentsScaleOnBothLayers(
+      contents_scale, device_scale, page_scale, animating_transform);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), contents_scale);
+  EXPECT_BOTH_EQ(num_tilings(), 1u);
+
+  ResetTilingsAndRasterScales();
+
+  // Any content bounds that would create more than one tile will
+  // generate a low res tiling.
+  contents_scale = 1.2f;
+  SetContentsScaleOnBothLayers(
+      contents_scale, device_scale, page_scale, animating_transform);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), contents_scale);
+  EXPECT_BOTH_EQ(LowResTiling()->contents_scale(),
+                 contents_scale * low_res_factor);
+  EXPECT_BOTH_EQ(num_tilings(), 2u);
+
+  ResetTilingsAndRasterScales();
+
+  // Mask layers dont create low res since they always fit on one tile.
+  pending_layer_->SetIsMask(true);
+  active_layer_->SetIsMask(true);
+  SetContentsScaleOnBothLayers(
+      contents_scale, device_scale, page_scale, animating_transform);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), contents_scale);
+  EXPECT_BOTH_EQ(num_tilings(), 1u);
+}
+
 TEST_F(PictureLayerImplTest, DidLoseOutputSurface) {
   gfx::Size tile_size(400, 400);
   gfx::Size layer_bounds(1300, 1900);
diff --git a/cc/resources/picture_layer_tiling.h b/cc/resources/picture_layer_tiling.h
index 3f4a5daa..390b849 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -32,7 +32,7 @@ class CC_EXPORT PictureLayerTilingClient {
     gfx::Rect content_rect) = 0;
   virtual void UpdatePile(Tile* tile) = 0;
   virtual gfx::Size CalculateTileSize(
-    gfx::Size content_bounds) = 0;
+    gfx::Size content_bounds) const = 0;
   virtual const Region* GetInvalidation() = 0;
   virtual const PictureLayerTiling* GetTwinTiling(
       const PictureLayerTiling* tiling) = 0;
diff --git a/cc/test/fake_picture_layer_impl.cc b/cc/test/fake_picture_layer_impl.cc
index 0bd16c6..d55d680 100644
--- a/cc/test/fake_picture_layer_impl.cc
+++ b/cc/test/fake_picture_layer_impl.cc
@@ -32,7 +32,8 @@ void FakePictureLayerImpl::AppendQuads(QuadSink* quad_sink,
   ++append_quads_count_;
 }
 
-gfx::Size FakePictureLayerImpl::CalculateTileSize(gfx::Size content_bounds) {
+gfx::Size FakePictureLayerImpl::CalculateTileSize(
+    gfx::Size content_bounds) const {
   if (fixed_tile_size_.IsEmpty()) {
     return PictureLayerImpl::CalculateTileSize(content_bounds);
   }
diff --git a/cc/test/fake_picture_layer_impl.h b/cc/test/fake_picture_layer_impl.h
index 6ac1126..a0c7829 100644
--- a/cc/test/fake_picture_layer_impl.h
+++ b/cc/test/fake_picture_layer_impl.h
@@ -26,7 +26,7 @@ class FakePictureLayerImpl : public PictureLayerImpl {
       OVERRIDE;
   virtual void AppendQuads(QuadSink* quad_sink,
                            AppendQuadsData* append_quads_data) OVERRIDE;
-  virtual gfx::Size CalculateTileSize(gfx::Size content_bounds) OVERRIDE;
+  virtual gfx::Size CalculateTileSize(gfx::Size content_bounds) const OVERRIDE;
 
   using PictureLayerImpl::AddTiling;
   using PictureLayerImpl::CleanUpTilingsOnActiveLayer;
diff --git a/cc/test/fake_picture_layer_tiling_client.cc b/cc/test/fake_picture_layer_tiling_client.cc
index ebd530a7..39f1190 100644
--- a/cc/test/fake_picture_layer_tiling_client.cc
+++ b/cc/test/fake_picture_layer_tiling_client.cc
@@ -56,7 +56,7 @@ void FakePictureLayerTilingClient::SetTileSize(gfx::Size tile_size) {
 }
 
 gfx::Size FakePictureLayerTilingClient::CalculateTileSize(
-    gfx::Size /* content_bounds */) {
+    gfx::Size /* content_bounds */) const {
   return tile_size_;
 }
 
diff --git a/cc/test/fake_picture_layer_tiling_client.h b/cc/test/fake_picture_layer_tiling_client.h
index 1050705..9b2aa52 100644
--- a/cc/test/fake_picture_layer_tiling_client.h
+++ b/cc/test/fake_picture_layer_tiling_client.h
@@ -25,7 +25,7 @@ class FakePictureLayerTilingClient : public PictureLayerTilingClient {
       PictureLayerTiling* tiling, gfx::Rect rect) OVERRIDE;
   virtual void UpdatePile(Tile* tile) OVERRIDE {}
   virtual gfx::Size CalculateTileSize(
-      gfx::Size content_bounds) OVERRIDE;
+      gfx::Size content_bounds) const OVERRIDE;
 
   void SetTileSize(gfx::Size tile_size);
   gfx::Size TileSize() const { return tile_size_; }