WebGL GL_RGB emulation to support IOSurfaces on Mac.

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 123 matching lines @@
             m_drawFramebufferBinding = fbo;
             break;
         case GL_READ_FRAMEBUFFER:
             m_readFramebufferBinding = fbo;
             break;
         default:
             ASSERT(0);
         }
     }
 
+    // The DrawingBuffer needs to track the color mask and clear color so that
+    // it can restore it when needed.
+    void setClearColor(GLfloat* clearColor)
+    {
+        memcpy(m_clearColor, clearColor, 4 * sizeof(GLfloat));
+    }
+
+    void setColorMask(GLboolean* colorMask)
+    {
+        memcpy(m_colorMask, colorMask, 4 * sizeof(GLboolean));
+    }
+
+    // The DrawingBuffer needs to track the currently bound renderbuffer so it
+    // restore the binding when needed.
+    void setRenderbufferBinding(GLuint renderbuffer)
+    {
+        m_renderbufferBinding = renderbuffer;
+    }
+
     // Track the currently active texture unit. Texture unit 0 is used as host for a scratch
     // texture.
     void setActiveTextureUnit(GLint textureUnit) { m_activeTextureUnit = textureUnit; }
 
     bool multisample() const;
 
     GLuint framebuffer() const;
 
     bool discardFramebufferSupported() const { return m_discardFramebufferSupported; }
 
     void markContentsChanged();
     void setBufferClearNeeded(bool);
     bool bufferClearNeeded() const;
     void setIsHidden(bool);
     void setFilterQuality(SkFilterQuality);
 
+    // Indicates that the currently bound framebuffer has internalformat
+    // GL_RGBA, but is emulating GL_RGB. This happens to the backbuffer when the
+    // client requests alpha:False, but GL_RGB textures are unusable because of
+    // driver bugs.
+    bool requiresRGBEmulation();
+
     WebLayer* platformLayer();
 
     gpu::gles2::GLES2Interface* contextGL();
     WebGraphicsContext3DProvider* contextProvider();
 
     // WebExternalTextureLayerClient implementation.
     bool prepareMailbox(WebExternalTextureMailbox*, WebExternalBitmap*) override;
     void mailboxReleased(const WebExternalTextureMailbox&, bool lostResource = false) override;
 
     // Destroys the TEXTURE_2D binding for the owned context
@@ skipping 22 matching lines @@
         bool premultipliedAlpha,
         PreserveDrawingBuffer);
 
     bool initialize(const IntSize&, bool wantDepthBuffer, bool wantStencilBuffer, bool useMultisampling);
 
 private:
     struct TextureParameters {
         DISALLOW_NEW();
         GLenum target;
         GLenum internalColorFormat;
+
+        // The internal color format used when allocating storage for the
+        // texture. This may be different from internalColorFormat if RGB
+        // emulation is required.
+        GLenum creationInternalColorFormat;
         GLenum colorFormat;
         GLenum internalRenderbufferFormat;
 
         TextureParameters()
             : target(0)
             , internalColorFormat(0)
+            , creationInternalColorFormat(0)
             , colorFormat(0)
             , internalRenderbufferFormat(0)
         {
         }
     };
 
     // If we used CHROMIUM_image as the backing storage for our buffers,
     // we need to know the mapping from texture id to image.
     struct TextureInfo {
         DISALLOW_NEW();
@@ skipping 65 matching lines @@
 
     // Helper function to flip a bitmap vertically.
     void flipVertically(uint8_t* data, int width, int height);
 
     // Helper to texImage2D with pixel==0 case: pixels are initialized to 0.
     // By default, alignment is 4, the OpenGL default setting.
     void texImage2DResourceSafe(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, GLint alignment = 4);
     // Allocate buffer storage to be sent to compositor using either texImage2D or CHROMIUM_image based on available support.
     void deleteChromiumImageForTexture(TextureInfo*);
 
+    // If RGB emulation is required, then the CHROMIUM image's alpha channel
+    // must be immediately cleared after it is bound to a texture. Nothing
+    // should be allowed to change the alpha channel after this.
+    void clearChromiumImageAlpha(const TextureInfo&);
+
     // Tries to create a CHROMIUM_image backed texture if
     // RuntimeEnabledFeatures::webGLImageChromiumEnabled() is true. On failure,
     // or if the flag is false, creates a default texture.
     TextureInfo createTextureAndAllocateMemory(const IntSize&);
 
     // Creates and allocates space for a default texture.
     TextureInfo createDefaultTextureAndAllocateMemory(const IntSize&);
 
     void resizeTextureMemory(TextureInfo*, const IntSize&);
 
     void attachColorBufferToCurrentFBO();
 
     const PreserveDrawingBuffer m_preserveDrawingBuffer;
     bool m_scissorEnabled;
     GLuint m_texture2DBinding;
     GLuint m_drawFramebufferBinding;
     GLuint m_readFramebufferBinding;
+    GLuint m_renderbufferBinding;
     GLenum m_activeTextureUnit;
+    GLfloat m_clearColor[4];
+    GLboolean m_colorMask[4];
 
     OwnPtr<WebGraphicsContext3DProvider> m_contextProvider;
     // Lifetime is tied to the m_contextProvider.
     gpu::gles2::GLES2Interface* m_gl;
     OwnPtr<Extensions3DUtil> m_extensionsUtil;
     IntSize m_size;
     const bool m_discardFramebufferSupported;
     const bool m_wantAlphaChannel;
     const bool m_premultipliedAlpha;
     bool m_hasImplicitStencilBuffer;
     GLuint m_fbo;
     // DrawingBuffer's output is double-buffered. m_colorBuffer is the back buffer.
     TextureInfo m_colorBuffer;
     struct FrontBufferInfo {
         TextureInfo texInfo;
         WebExternalTextureMailbox mailbox;
     };
     FrontBufferInfo m_frontColorBuffer;
 
     OwnPtr<SameThreadClosure> m_newMailboxCallback;
 
     // This is used when the user requests either a depth or stencil buffer.
     GLuint m_depthStencilBuffer;
 
     // For multisampling.
     GLuint m_multisampleFBO;
+    GLuint m_intermediateFBO;
+    GLuint m_intermediateRenderbuffer;
     GLuint m_multisampleColorBuffer;
 
     // True if our contents have been modified since the last presentation of this buffer.
     bool m_contentsChanged;
 
     // True if commit() has been called since the last time markContentsChanged() had been called.
     bool m_contentsChangeCommitted;
     bool m_bufferClearNeeded;
 
     enum AntialiasingMode {
@@ skipping 26 matching lines @@
     // used to resize the Canvas.
     SkBitmap m_resizingBitmap;
 
     // Used to flip a bitmap vertically.
     Vector<uint8_t> m_scanline;
 };
 
 } // namespace blink
 
 #endif // DrawingBuffer_h