Adding support for per vertex opacity on textured layer

cc/texture_draw_quad.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/texture_draw_quad.h"
 
 #include "base/logging.h"
 
 namespace cc {
 
 TextureDrawQuad::TextureDrawQuad()
     : resource_id(0),
       premultiplied_alpha(false),
       flipped(false) {
 }
 
 scoped_ptr<TextureDrawQuad> TextureDrawQuad::Create() {
   return make_scoped_ptr(new TextureDrawQuad);
 }
 
 void TextureDrawQuad::SetNew(const SharedQuadState* shared_quad_state,
-                             gfx::Rect rect,
-                             gfx::Rect opaque_rect,
-                             unsigned resource_id,
-                             bool premultiplied_alpha,
+                             gfx::Rect rect, gfx::Rect opaque_rect,
+                             unsigned resource_id, bool premultiplied_alpha,
                              const gfx::RectF& uv_rect,
-                             bool flipped) {
+                             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
+      || 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;
 }
 
 void TextureDrawQuad::SetAll(const SharedQuadState* shared_quad_state,
-                             gfx::Rect rect,
-                             gfx::Rect opaque_rect,
-                             gfx::Rect visible_rect,
-                             bool needs_blending,
-                             unsigned resource_id,
-                             bool premultiplied_alpha,
+                             gfx::Rect rect, gfx::Rect opaque_rect,
+                             gfx::Rect visible_rect, bool needs_blending,
+                             unsigned resource_id, bool premultiplied_alpha,
                              const gfx::RectF& uv_rect,
-                             bool flipped) {
+                             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;
 }
 
-const TextureDrawQuad* TextureDrawQuad::MaterialCast(
-    const DrawQuad* quad) {
+const TextureDrawQuad* TextureDrawQuad::MaterialCast(const DrawQuad* quad) {
   DCHECK(quad->material == DrawQuad::TEXTURE_CONTENT);
   return static_cast<const TextureDrawQuad*>(quad);
 }
 
 bool TextureDrawQuad::PerformClipping() {
   // This only occurs if the rect is only scaled and translated (and thus still
   // axis aligned).
   if (!quadTransform().IsScaleOrTranslation())
     return false;
 
   // Grab our scale and make sure it's positive.
-  float x_scale = quadTransform().matrix().getDouble(0,0);
-  float y_scale = quadTransform().matrix().getDouble(1,1);
+  float x_scale = quadTransform().matrix().getDouble(0, 0);
+  float y_scale = quadTransform().matrix().getDouble(1, 1);
   if (x_scale <= 0.0f || y_scale <= 0.0f)
     return false;
 
   // Grab our offset.
-  gfx::Vector2dF offset(
-      quadTransform().matrix().getDouble(0,3),
-      quadTransform().matrix().getDouble(1,3));
+  gfx::Vector2dF offset(quadTransform().matrix().getDouble(0, 3),
+                        quadTransform().matrix().getDouble(1, 3));
 
   // Transform the rect by the scale and offset.
   gfx::RectF rectF = rect;
   rectF.Scale(x_scale, y_scale);
   rectF += offset;
 
   // Perform clipping and check to see if the result is empty.
   gfx::RectF clippedRect = IntersectRects(rectF, clipRect());
   if (clippedRect.IsEmpty()) {
     rect = gfx::Rect();
     uv_rect = gfx::RectF();
     return true;
   }
 
   // Create a new uv-rect by clipping the old one to the new bounds.
   uv_rect = gfx::RectF(
-      uv_rect.x()+uv_rect.width ()/rectF.width ()*(clippedRect.x()-rectF.x()),
-      uv_rect.y()+uv_rect.height()/rectF.height()*(clippedRect.y()-rectF.y()),
-      uv_rect.width () / rectF.width () * clippedRect.width (),
+      uv_rect.x()
+          + uv_rect.width() / rectF.width() * (clippedRect.x() - rectF.x()),
+      uv_rect.y()
+          + uv_rect.height() / rectF.height() * (clippedRect.y() - rectF.y()),
+      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]
+      || 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);
-  rect = gfx::Rect(
-      static_cast<int>(clippedRect.x() + 0.5f),
-      static_cast<int>(clippedRect.y() + 0.5f),
-      static_cast<int>(clippedRect.width() + 0.5f),
-      static_cast<int>(clippedRect.height() + 0.5f));
+  rect = gfx::Rect(static_cast<int>(clippedRect.x() + 0.5f),
+                   static_cast<int>(clippedRect.y() + 0.5f),
+                   static_cast<int>(clippedRect.width() + 0.5f),
+                   static_cast<int>(clippedRect.height() + 0.5f));
   return true;
 }
 
 }  // namespace cc