Adding support for per vertex opacity on textured layer

cc/geometry_binding.cc

 // Copyright 2011 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/geometry_binding.h"
 
 #include "cc/gl_renderer.h" // For the GLC() macro.
 #include "third_party/khronos/GLES2/gl2.h"
 #include "ui/gfx/rect_f.h"
 #include <public/WebGraphicsContext3D.h>
 
 namespace cc {
 
 GeometryBinding::GeometryBinding(WebKit::WebGraphicsContext3D* context, const gfx::RectF& quadVertexRect)
     : m_context(context)
     , m_quadVerticesVbo(0)
     , m_quadElementsVbo(0)
     , m_initialized(false)
 {
     float vertices[] = { quadVertexRect.x(), quadVertexRect.bottom(), 0.0f, 0.0f,  1.0f,
                          quadVertexRect.x(), quadVertexRect.y(), 0.0f, 0.0f,  0.0f,
                          quadVertexRect.right(), quadVertexRect.y(), 0.0f, 1.0f,  0.0f,
                          quadVertexRect.right(), quadVertexRect.bottom(), 0.0f, 1.0f,  1.0f };
 
     struct Vertex {
         float a_position[3];
         float a_texCoord[2];
-        float a_index; // index into the matrix array for this quad
+        float a_index; // index of the vertex, divide by 4 to have the matrix for this quad
     };
     struct Quad { Vertex v0, v1, v2, v3; };
     struct QuadIndex { uint16_t data[6]; };
 
     COMPILE_ASSERT(sizeof(Quad) == 24 * sizeof(float), struct_is_densely_packed);
     COMPILE_ASSERT(sizeof(QuadIndex) == 6 * sizeof(uint16_t), struct_is_densely_packed);
 
     Quad quad_list[8];
     QuadIndex quad_index_list[8];
     for (int i = 0; i < 8; i++) {

[whunt, 2012/12/15 00:55:00]

FYI: doing the math in integer land and using stati_cast<float>() would be more
efficient,  The change is unnecessary though because this is startup code and
the performance difference is small.

-        Vertex v0 = { quadVertexRect.x()    , quadVertexRect.bottom(), 0.0f,  0.0f, 1.0f, (float)i };
-        Vertex v1 = { quadVertexRect.x()    , quadVertexRect.y()     , 0.0f,  0.0f, 0.0f, (float)i };
-        Vertex v2 = { quadVertexRect.right(), quadVertexRect.y()     , 0.0f,  1.0f, 0.0f, (float)i };
-        Vertex v3 = { quadVertexRect.right(), quadVertexRect.bottom(), 0.0f,  1.0f, 1.0f, (float)i };
+        Vertex v0 = { quadVertexRect.x()    , quadVertexRect.bottom(), 0.0f,  0.0f, 1.0f, i * 4.0f + 0.0f };
+        Vertex v1 = { quadVertexRect.x()    , quadVertexRect.y()     , 0.0f,  0.0f, 0.0f, i * 4.0f + 1.0f };
+        Vertex v2 = { quadVertexRect.right(), quadVertexRect.y()     , 0.0f,  1.0f, 0.0f, i * 4.0f + 2.0f };
+        Vertex v3 = { quadVertexRect.right(), quadVertexRect.bottom(), 0.0f,  1.0f, 1.0f, i * 4.0f + 3.0f };
         Quad x = { v0, v1, v2, v3 };
         quad_list[i] = x;
         QuadIndex y = { 0 + 4 * i, 1 + 4 * i, 2 + 4 * i, 3 + 4 * i, 0 + 4 * i, 2 + 4 * i };
         quad_index_list[i] = y;
     }
 
     GLC(m_context, m_quadVerticesVbo = m_context->createBuffer());
     GLC(m_context, m_quadElementsVbo = m_context->createBuffer());
     GLC(m_context, m_quadListVerticesVbo = m_context->createBuffer());
     GLC(m_context, m_context->bindBuffer(GL_ARRAY_BUFFER, m_quadVerticesVbo));
@@ skipping 17 matching lines @@
     GLC(m_context, m_context->bindBuffer(GL_ARRAY_BUFFER, quadVerticesVbo()));
     GLC(m_context, m_context->vertexAttribPointer(positionAttribLocation(), 3, GL_FLOAT, false, 6 * sizeof(float), 0));
     GLC(m_context, m_context->vertexAttribPointer(texCoordAttribLocation(), 2, GL_FLOAT, false, 6 * sizeof(float), 3 * sizeof(float)));
     GLC(m_context, m_context->vertexAttribPointer(triangleIndexAttribLocation(), 1, GL_FLOAT, false, 6 * sizeof(float), 5 * sizeof(float)));
     GLC(m_context, m_context->enableVertexAttribArray(positionAttribLocation()));
     GLC(m_context, m_context->enableVertexAttribArray(texCoordAttribLocation()));
     GLC(m_context, m_context->enableVertexAttribArray(triangleIndexAttribLocation()));
 }
 
 }  // namespace cc