cc: Support anti-aliasing for solid color layers.

cc/gl_renderer.cc

Index: cc/gl_renderer.cc
diff --git a/cc/gl_renderer.cc b/cc/gl_renderer.cc
index e9f8254a16b5629a6033aeb278a040d58821218d..424a571ed3dee354603f001320271586c0a30687 100644
--- a/cc/gl_renderer.cc
+++ b/cc/gl_renderer.cc
@@ -685,18 +685,131 @@ void GLRenderer::drawRenderPassQuad(DrawingFrame& frame, const RenderPassDrawQua
         m_context->flush();
 }
 
+struct SolidColorProgramUniforms {
+    unsigned program;
+    unsigned matrixLocation;
+    unsigned colorLocation;
+    unsigned pointLocation;
+    unsigned texScaleLocation;
+    unsigned edgeLocation;
+};
+
+template<class T>
+static void solidColorUniformLocation(T program, SolidColorProgramUniforms& uniforms)
+{
+    uniforms.program = program->program();
+    uniforms.matrixLocation = program->vertexShader().matrixLocation();
+    uniforms.colorLocation = program->fragmentShader().colorLocation();
+    uniforms.pointLocation = program->vertexShader().pointLocation();
+    uniforms.texScaleLocation = program->vertexShader().texScaleLocation();
+    uniforms.edgeLocation = program->fragmentShader().edgeLocation();
+}
+
 void GLRenderer::drawSolidColorQuad(const DrawingFrame& frame, const SolidColorDrawQuad* quad)
 {
-    const SolidColorProgram* program = solidColorProgram();
-    setUseProgram(program->program());
+    gfx::Rect tileRect = quad->visible_rect;
+
+    gfx::QuadF localQuad;
+    gfx::Transform deviceTransform = MathUtil::to2dTransform(frame.windowMatrix * frame.projectionMatrix * quad->quadTransform());
+    if (!deviceTransform.IsInvertible())
+        return;
+
+    bool clipped = false;
+    gfx::QuadF deviceLayerQuad = MathUtil::mapQuad(deviceTransform, gfx::QuadF(quad->visibleContentRect()), clipped);
+    DCHECK(!clipped);
+
+    SolidColorProgramUniforms uniforms;
+    // For now, we simply skip anti-aliasing with the quad is clipped. This only happens
+    // on perspective transformed layers that go partially behind the camera.
+    if (quad->IsAntialiased() && !clipped)
+      solidColorUniformLocation(solidColorProgramAA(), uniforms);
+    else
+      solidColorUniformLocation(solidColorProgram(), uniforms);
+
+    setUseProgram(uniforms.program);
 
     SkColor color = quad->color;
     float opacity = quad->opacity();
     float alpha = (SkColorGetA(color) / 255.0) * opacity;
 
-    GLC(context(), context()->uniform4f(program->fragmentShader().colorLocation(), (SkColorGetR(color) / 255.0) * alpha, (SkColorGetG(color) / 255.0) * alpha, (SkColorGetB(color) / 255.0) * alpha, alpha));
+    GLC(context(), context()->uniform4f(uniforms.colorLocation, (SkColorGetR(color) / 255.0) * alpha, (SkColorGetG(color) / 255.0) * alpha, (SkColorGetB(color) / 255.0) * alpha, alpha));
 
-    drawQuadGeometry(frame, quad->quadTransform(), quad->rect, program->vertexShader().matrixLocation());
+    GLC(context(), context()->uniform2f(uniforms.texScaleLocation, 1.0f, 1.0f));
+
+    bool useAA = !clipped && quad->IsAntialiased();
+    if (useAA) {
+        LayerQuad deviceLayerBounds = LayerQuad(gfx::QuadF(deviceLayerQuad.BoundingBox()));
+        deviceLayerBounds.inflateAntiAliasingDistance();
+
+        LayerQuad deviceLayerEdges = LayerQuad(deviceLayerQuad);
+        deviceLayerEdges.inflateAntiAliasingDistance();
+
+        float edge[24];
+        deviceLayerEdges.toFloatArray(edge);
+        deviceLayerBounds.toFloatArray(&edge[12]);
+        GLC(context(), context()->uniform3fv(uniforms.edgeLocation, 8, edge));
+
+        gfx::PointF bottomRight = tileRect.bottom_right();
+        gfx::PointF bottomLeft = tileRect.bottom_left();
+        gfx::PointF topLeft = tileRect.origin();
+        gfx::PointF topRight = tileRect.top_right();
+
+        // Map points to device space.
+        bottomRight = MathUtil::mapPoint(deviceTransform, bottomRight, clipped);
+        DCHECK(!clipped);
+        bottomLeft = MathUtil::mapPoint(deviceTransform, bottomLeft, clipped);
+        DCHECK(!clipped);
+        topLeft = MathUtil::mapPoint(deviceTransform, topLeft, clipped);
+        DCHECK(!clipped);
+        topRight = MathUtil::mapPoint(deviceTransform, topRight, clipped);
+        DCHECK(!clipped);
+
+        LayerQuad::Edge bottomEdge(bottomRight, bottomLeft);
+        LayerQuad::Edge leftEdge(bottomLeft, topLeft);
+        LayerQuad::Edge topEdge(topLeft, topRight);
+        LayerQuad::Edge rightEdge(topRight, bottomRight);
+
+        // Only apply anti-aliasing to edges not clipped by culling or scissoring.
+        if (quad->top_edge_aa && tileRect.y() == quad->rect.y())
+            topEdge = deviceLayerEdges.top();
+        if (quad->left_edge_aa && tileRect.x() == quad->rect.x())
+            leftEdge = deviceLayerEdges.left();
+        if (quad->right_edge_aa && tileRect.right() == quad->rect.right())
+            rightEdge = deviceLayerEdges.right();
+        if (quad->bottom_edge_aa && tileRect.bottom() == quad->rect.bottom())
+            bottomEdge = deviceLayerEdges.bottom();
+
+        float sign = gfx::QuadF(tileRect).IsCounterClockwise() ? -1 : 1;
+        bottomEdge.scale(sign);
+        leftEdge.scale(sign);
+        topEdge.scale(sign);
+        rightEdge.scale(sign);
+
+        // Create device space quad.
+        LayerQuad deviceQuad(leftEdge, topEdge, rightEdge, bottomEdge);
+
+        // Map device space quad to local space. deviceTransform has no 3d component since it was generated with to2dTransform() so we don't need to project.
+        gfx::Transform deviceTransformInverse = MathUtil::inverse(deviceTransform);
+        localQuad = MathUtil::mapQuad(deviceTransformInverse, deviceQuad.ToQuadF(), clipped);
+
+        // We should not DCHECK(!clipped) here, because anti-aliasing inflation may cause deviceQuad to become
+        // clipped. To our knowledge this scenario does not need to be handled differently than the unclipped case.
+    } else {
+        localQuad = gfx::RectF(tileRect);
+    }
+
+    // Normalize to tileRect.
+    localQuad.Scale(1.0f / tileRect.width(), 1.0f / tileRect.height());
+
+    setShaderQuadF(localQuad, uniforms.pointLocation);
+
+    // The tile quad shader behaves differently compared to all other shaders.
+    // The transform and vertex data are used to figure out the extents that the
+    // un-antialiased quad should have and which vertex this is and the float
+    // quad passed in via uniform is the actual geometry that gets used to draw
+    // it. This is why this centered rect is used and not the original quadRect.
+    gfx::RectF centeredRect(gfx::PointF(-0.5 * tileRect.width(), -0.5 * tileRect.height()), tileRect.size());
+    drawQuadGeometry(frame, quad->quadTransform(), centeredRect, uniforms.matrixLocation);
 }
 
 struct TileProgramUniforms {
@@ -1585,6 +1698,17 @@ const GLRenderer::SolidColorProgram* GLRenderer::solidColorProgram()
     return m_solidColorProgram.get();
 }
 
+const GLRenderer::SolidColorProgramAA* GLRenderer::solidColorProgramAA()
+{
+    if (!m_solidColorProgramAA)
+        m_solidColorProgramAA = make_scoped_ptr(new SolidColorProgramAA(m_context));
+    if (!m_solidColorProgramAA->initialized()) {
+        TRACE_EVENT0("cc", "GLRenderer::solidColorProgramAA::initialize");
+        m_solidColorProgramAA->initialize(m_context, m_isUsingBindUniform);
+    }
+    return m_solidColorProgramAA.get();
+}
+
 const GLRenderer::RenderPassProgram* GLRenderer::renderPassProgram()
 {
     DCHECK(m_renderPassProgram);
@@ -1791,6 +1915,8 @@ void GLRenderer::cleanupSharedObjects()
 
     if (m_solidColorProgram)
         m_solidColorProgram->cleanup(m_context);
+    if (m_solidColorProgramAA)
+        m_solidColorProgramAA->cleanup(m_context);
 
     if (m_offscreenFramebufferId)
         GLC(m_context, m_context->deleteFramebuffer(m_offscreenFramebufferId));