Re-land: cc: Fix anti-aliasing of axis-aligned quads.

Axis-aligned quads with edges not aligned to pixel boundaries
are rendered incorrectly. These quads need anti-aliasing but
current code that determines if anti-aliasing is needed thinks
that no axis-aligned quads need it.

This fixes the problem by adding alignment to pixel boundaries
as an additional requirement to avoid anti-aliasing.

BUG=169374
TEST=GLRendererPixelTest.AxisAligned,GLRendererShaderTest.DrawSolidColorShader

Review URL: https://chromiumcodereview.appspot.com/12538005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@196534 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 106 insertions, 12 deletions

diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index cf7b64b..19b215b 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -81,6 +81,10 @@ bool NeedsIOSurfaceReadbackWorkaround() {
 #endif
 }
 
+// Smallest unit that impact anti-aliasing output. We use this to
+// determine when anti-aliasing is unnecessary.
+const float kAntiAliasingEpsilon = 1.0f / 1024.0f;
+
 }  // anonymous namespace
 
 scoped_ptr<GLRenderer> GLRenderer::Create(RendererClient* client,
@@ -715,7 +719,8 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
 
   // Use anti-aliasing programs only when necessary.
   bool use_aa = (!device_quad.IsRectilinear() ||
-                 !device_quad.BoundingBox().IsExpressibleAsRect());
+                 !gfx::IsNearestRectWithinDistance(device_quad.BoundingBox(),
+                                                   kAntiAliasingEpsilon));
   if (use_aa) {
     device_layer_bounds.InflateAntiAliasingDistance();
     device_layer_edges.InflateAntiAliasingDistance();
@@ -1011,11 +1016,11 @@ bool GLRenderer::SetupQuadForAntialiasing(
       device_transform, gfx::QuadF(quad->visibleContentRect()), &clipped);
   DCHECK(!clipped);
 
-  // TODO(reveman): Axis-aligned is not enough to avoid anti-aliasing.
-  // Bounding rectangle for quad also needs to be expressible as an integer
-  // rectangle. crbug.com/169374
   bool is_axis_aligned_in_target = device_layer_quad.IsRectilinear();
-  bool use_aa = !clipped && !is_axis_aligned_in_target && quad->IsEdge();
+  bool is_nearest_rect_within_epsilon = is_axis_aligned_in_target &&
+      gfx::IsNearestRectWithinDistance(device_layer_quad.BoundingBox(),
+                                       kAntiAliasingEpsilon);
+  bool use_aa = !clipped && !is_nearest_rect_within_epsilon && quad->IsEdge();
 
   if (!use_aa)
     return false;
@@ -1200,13 +1205,16 @@ void GLRenderer::DrawContentQuad(const DrawingFrame* frame,
   // is mapped to the unit square by the vertex shader and mapped
   // back to normalized texture coordinates by the fragment shader
   // after being clamped to 0-1 range.
-  const float epsilon = 1.0f / 1024.0f;
-  float tex_clamp_x = std::min(0.5f, 0.5f * clamp_tex_rect.width() - epsilon);
-  float tex_clamp_y = std::min(0.5f, 0.5f * clamp_tex_rect.height() - epsilon);
-  float geom_clamp_x = std::min(tex_clamp_x * tex_to_geom_scale_x,
-                                0.5f * clamp_geom_rect.width() - epsilon);
-  float geom_clamp_y = std::min(tex_clamp_y * tex_to_geom_scale_y,
-                                0.5f * clamp_geom_rect.height() - epsilon);
+  float tex_clamp_x = std::min(
+      0.5f, 0.5f * clamp_tex_rect.width() - kAntiAliasingEpsilon);
+  float tex_clamp_y = std::min(
+      0.5f, 0.5f * clamp_tex_rect.height() - kAntiAliasingEpsilon);
+  float geom_clamp_x = std::min(
+      tex_clamp_x * tex_to_geom_scale_x,
+      0.5f * clamp_geom_rect.width() - kAntiAliasingEpsilon);
+  float geom_clamp_y = std::min(
+      tex_clamp_y * tex_to_geom_scale_y,
+      0.5f * clamp_geom_rect.height() - kAntiAliasingEpsilon);
   clamp_geom_rect.Inset(geom_clamp_x, geom_clamp_y, geom_clamp_x, geom_clamp_y);
   clamp_tex_rect.Inset(tex_clamp_x, tex_clamp_y, tex_clamp_x, tex_clamp_y);
 
diff --git a/cc/output/gl_renderer_pixeltest.cc b/cc/output/gl_renderer_pixeltest.cc
index 064b78b..8da1b24 100644
--- a/cc/output/gl_renderer_pixeltest.cc
+++ b/cc/output/gl_renderer_pixeltest.cc
@@ -524,6 +524,58 @@ TEST_F(GLRendererPixelTest, AntiAliasing) {
       base::FilePath(FILE_PATH_LITERAL("anti_aliasing.png")),
       ExactPixelComparator(true)));
 }
+
+TEST_F(GLRendererPixelTest, AxisAligned) {
+  gfx::Rect rect(0, 0, 200, 200);
+
+  RenderPass::Id id(1, 1);
+  gfx::Transform transform_to_root;
+  scoped_ptr<RenderPass> pass =
+      CreateTestRenderPass(id, rect, transform_to_root);
+
+  gfx::Transform red_content_to_target_transform;
+  red_content_to_target_transform.Translate(50, 50);
+  red_content_to_target_transform.Scale(
+      0.5f + 1.0f / (rect.width() * 2.0f),
+      0.5f + 1.0f / (rect.height() * 2.0f));
+  scoped_ptr<SharedQuadState> red_shared_state =
+      CreateTestSharedQuadState(red_content_to_target_transform, rect);
+
+  scoped_ptr<SolidColorDrawQuad> red = SolidColorDrawQuad::Create();
+  red->SetNew(red_shared_state.get(), rect, SK_ColorRED);
+
+  pass->quad_list.push_back(red.PassAs<DrawQuad>());
+
+  gfx::Transform yellow_content_to_target_transform;
+  yellow_content_to_target_transform.Translate(25.5f, 25.5f);
+  yellow_content_to_target_transform.Scale(0.5f, 0.5f);
+  scoped_ptr<SharedQuadState> yellow_shared_state =
+      CreateTestSharedQuadState(yellow_content_to_target_transform, rect);
+
+  scoped_ptr<SolidColorDrawQuad> yellow = SolidColorDrawQuad::Create();
+  yellow->SetNew(yellow_shared_state.get(), rect, SK_ColorYELLOW);
+
+  pass->quad_list.push_back(yellow.PassAs<DrawQuad>());
+
+  gfx::Transform blue_content_to_target_transform;
+  scoped_ptr<SharedQuadState> blue_shared_state =
+      CreateTestSharedQuadState(blue_content_to_target_transform, rect);
+
+  scoped_ptr<SolidColorDrawQuad> blue = SolidColorDrawQuad::Create();
+  blue->SetNew(blue_shared_state.get(), rect, SK_ColorBLUE);
+
+  pass->quad_list.push_back(blue.PassAs<DrawQuad>());
+
+  RenderPassList pass_list;
+  pass_list.push_back(pass.Pass());
+
+  renderer_->DrawFrame(&pass_list);
+
+  EXPECT_TRUE(PixelsMatchReference(
+      base::FilePath(FILE_PATH_LITERAL("axis_aligned.png")),
+      ExactPixelComparator(true)));
+}
+
 #endif
 
 }  // namespace
diff --git a/cc/output/gl_renderer_unittest.cc b/cc/output/gl_renderer_unittest.cc
index ef56cc2..bbd261a 100644
--- a/cc/output/gl_renderer_unittest.cc
+++ b/cc/output/gl_renderer_unittest.cc
@@ -325,6 +325,12 @@ class GLRendererShaderTest : public testing::Test {
         renderer_->render_pass_color_matrix_program_aa_->program());
   }
 
+  void TestSolidColorProgramAA() {
+    EXPECT_PROGRAM_VALID(renderer_->solid_color_program_aa_);
+    EXPECT_TRUE(renderer_->program_shadow_ ==
+        renderer_->solid_color_program_aa_->program());
+  }
+
   scoped_ptr<OutputSurface> output_surface_;
   FakeRendererClient mock_client_;
   scoped_ptr<ResourceProvider> resource_provider_;
@@ -1271,6 +1277,34 @@ TEST_F(GLRendererShaderTest, DrawRenderPassQuadShaderPermutations) {
   TestRenderPassMaskColorMatrixProgramAA();
 }
 
+TEST_F(GLRendererShaderTest, DrawSolidColorShader) {
+  gfx::Rect viewport_rect(mock_client_.DeviceViewportSize());
+  ScopedPtrVector<RenderPass>* render_passes =
+      mock_client_.render_passes_in_draw_order();
+
+  RenderPass::Id root_pass_id(1, 0);
+  TestRenderPass* root_pass;
+
+  gfx::Transform pixel_aligned_transform_causing_aa;
+  pixel_aligned_transform_causing_aa.Translate(25.5f, 25.5f);
+  pixel_aligned_transform_causing_aa.Scale(0.5f, 0.5f);
+
+  render_passes->clear();
+
+  root_pass = AddRenderPass(
+      render_passes, root_pass_id, viewport_rect, gfx::Transform());
+  AddTransformedQuad(root_pass,
+                     viewport_rect,
+                     SK_ColorYELLOW,
+                     pixel_aligned_transform_causing_aa);
+
+  renderer_->DecideRenderPassAllocationsForFrame(
+      *mock_client_.render_passes_in_draw_order());
+  renderer_->DrawFrame(mock_client_.render_passes_in_draw_order());
+
+  TestSolidColorProgramAA();
+}
+
 class OutputSurfaceMockContext : public TestWebGraphicsContext3D {
  public:
   // Specifically override methods even if they are unused (used in conjunction