Adding support for per vertex opacity on textured layer

cc/texture_draw_quad.cc

Index: cc/texture_draw_quad.cc
diff --git a/cc/texture_draw_quad.cc b/cc/texture_draw_quad.cc
index 5ad73b69dc28731925dcf31518cd61148feedc72..11d17d8183a3d0955f184e3be07effab9577dc81 100644
--- a/cc/texture_draw_quad.cc
+++ b/cc/texture_draw_quad.cc
@@ -24,14 +24,22 @@ void TextureDrawQuad::SetNew(const SharedQuadState* shared_quad_state,
                              unsigned resource_id,
                              bool premultiplied_alpha,
                              const gfx::RectF& uv_rect,
+                             const float vertex_opacity[4],
                              bool flipped) {
   gfx::Rect visible_rect = rect;
-  bool needs_blending = false;
+  bool needs_blending = vertex_opacity[0] != 1.0f
+      || vertex_opacity[1] != 1.0f

[jamesr, 2012/12/14 21:18:20]

chromium style is to have the operator on the previous line and line up the !=s

[Jerome, 2012/12/14 21:48:47]

Done.

+      || vertex_opacity[2] != 1.0f
+      || vertex_opacity[3] != 1.0f;
   DrawQuad::SetAll(shared_quad_state, DrawQuad::TEXTURE_CONTENT, rect,
                    opaque_rect, visible_rect, needs_blending);
   this->resource_id = resource_id;
   this->premultiplied_alpha = premultiplied_alpha;
   this->uv_rect = uv_rect;
+  this->vertex_opacity[0] = vertex_opacity[0];
+  this->vertex_opacity[1] = vertex_opacity[1];
+  this->vertex_opacity[2] = vertex_opacity[2];
+  this->vertex_opacity[3] = vertex_opacity[3];
   this->flipped = flipped;
 }
 
@@ -43,12 +51,17 @@ void TextureDrawQuad::SetAll(const SharedQuadState* shared_quad_state,
                              unsigned resource_id,
                              bool premultiplied_alpha,
                              const gfx::RectF& uv_rect,
+                             const float vertex_opacity[4],
                              bool flipped) {
   DrawQuad::SetAll(shared_quad_state, DrawQuad::TEXTURE_CONTENT, rect,
                    opaque_rect, visible_rect, needs_blending);
   this->resource_id = resource_id;
   this->premultiplied_alpha = premultiplied_alpha;
   this->uv_rect = uv_rect;
+  this->vertex_opacity[0] = vertex_opacity[0];
+  this->vertex_opacity[1] = vertex_opacity[1];
+  this->vertex_opacity[2] = vertex_opacity[2];
+  this->vertex_opacity[3] = vertex_opacity[3];
   this->flipped = flipped;
 }
 
@@ -95,6 +108,27 @@ bool TextureDrawQuad::PerformClipping() {
       uv_rect.width () / rectF.width () * clippedRect.width (),
       uv_rect.height() / rectF.height() * clippedRect.height());
 
+  // Indexing according to the quad vertex generation:
+  // 1--2
+  // |  |
+  // 0--3
+  if (vertex_opacity[0] != vertex_opacity[1]
+      || vertex_opacity[0] != vertex_opacity[2]

[jamesr, 2012/12/14 21:18:20]

||s on previous line

[Jerome, 2012/12/14 21:48:47]

Done.

+      || vertex_opacity[0] != vertex_opacity[3]) {
+    const float x1 = (clippedRect.x() - rectF.x()) / rectF.width();
+    const float y1 = (clippedRect.y() - rectF.y()) / rectF.height();
+    const float x3 = (clippedRect.right() - rectF.x()) / rectF.width();
+    const float y3 = (clippedRect.bottom() - rectF.y()) / rectF.height();
+    const float x1y1 = x1 * vertex_opacity[2] + (1.0f - x1) * vertex_opacity[1];
+    const float x1y3 = x1 * vertex_opacity[3] + (1.0f - x1) * vertex_opacity[0];
+    const float x3y1 = x3 * vertex_opacity[2] + (1.0f - x3) * vertex_opacity[1];
+    const float x3y3 = x3 * vertex_opacity[3] + (1.0f - x3) * vertex_opacity[0];
+    vertex_opacity[0] = y3 * x1y3 + (1.0f - y3) * x1y1;
+    vertex_opacity[1] = y1 * x1y3 + (1.0f - y1) * x1y1;
+    vertex_opacity[2] = y1 * x3y3 + (1.0f - y1) * x3y1;
+    vertex_opacity[3] = y3 * x3y3 + (1.0f - y3) * x3y1;
+  }
+
   // Move the clipped rectangle back into its space.
   clippedRect -= offset;
   clippedRect.Scale(1.0f / x_scale, 1.0f / y_scale);