WebGL 2: add read/write framebuffer binding points to related APIs

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 83 matching lines @@
 
     static PassRefPtr<DrawingBuffer> create(PassOwnPtr<WebGraphicsContext3D>, const IntSize&, PreserveDrawingBuffer, WebGraphicsContext3D::Attributes requestedAttributes);
 
     virtual ~DrawingBuffer();
 
     // Destruction will be completed after all mailboxes are released.
     void beginDestruction();
 
     // Issues a glClear() on all framebuffers associated with this DrawingBuffer. The caller is responsible for
     // making the context current and setting the clear values and masks. Modifies the framebuffer binding.
-    void clearFramebuffers(GLbitfield clearMask);
+    void clearFramebuffers(GLbitfield clearMask, GLenum target = GL_FRAMEBUFFER);
 
     // Given the desired buffer size, provides the largest dimensions that will fit in the pixel budget.
     static IntSize adjustSize(const IntSize& desiredSize, const IntSize& curSize, int maxTextureSize);
     bool reset(const IntSize&);
     void bind(GLenum target = GL_FRAMEBUFFER);
     IntSize size() const { return m_size; }
 
     // Copies the multisample color buffer to the normal color buffer and leaves m_fbo bound.
-    void commit();
+    void commit(GLenum target = GL_FRAMEBUFFER);
 
     // commit should copy the full multisample buffer, and not respect the
     // current scissor bounds. Track the state of the scissor test so that it
     // can be disabled during calls to commit.
     void setScissorEnabled(bool scissorEnabled) { m_scissorEnabled = scissorEnabled; }
 
     // The DrawingBuffer needs to track the texture bound to texture unit 0.
     // The bound texture is tracked to avoid costly queries during rendering.
     void setTexture2DBinding(Platform3DObject texture) { m_texture2DBinding = texture; }
 
     // The DrawingBuffer needs to track the currently bound framebuffer so it
     // restore the binding when needed.
-    void setFramebufferBinding(Platform3DObject fbo) { m_framebufferBinding = fbo; }
+    void setFramebufferBinding(Platform3DObject fbo, GLenum target = GL_FRAMEBUFFER)
+    {
+        if (target == GL_READ_FRAMEBUFFER)
+            m_readFramebufferBinding = fbo;
+        else
+            m_framebufferBinding = fbo;
+    }
 
     // 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;
 
     Platform3DObject framebuffer() const;
 
     bool discardFramebufferSupported() const { return m_discardFramebufferSupported; }
@@ skipping 43 matching lines @@
 private:
     void mailboxReleasedWithoutRecycling(const WebExternalTextureMailbox&);
 
     unsigned createColorTexture();
     // Create the depth/stencil and multisample buffers, if needed.
     void createSecondaryBuffers();
     bool resizeFramebuffer(const IntSize&);
     bool resizeMultisampleFramebuffer(const IntSize&);
     void resizeDepthStencil(const IntSize&);
 
-    // Bind to the m_framebufferBinding if it's not 0. Otherwise, bind to the default FBO.
-    void restoreFramebufferBinding();
+    // Bind to m_framebufferBinding or m_readFramebufferBinding if it's not 0.
+    // Otherwise, bind to the default FBO.
+    void restoreFramebufferBinding(GLenum target = GL_FRAMEBUFFER);
 
     void clearPlatformLayer();
 
     PassRefPtr<MailboxInfo> recycledMailbox();
     PassRefPtr<MailboxInfo> createNewMailbox(const TextureInfo&);
     void deleteMailbox(const WebExternalTextureMailbox&);
     void freeRecycledMailboxes();
 
     // Updates the current size of the buffer, ensuring that s_currentResourceUsePixels is updated.
     void setSize(const IntSize& size);
@@ skipping 17 matching lines @@
     // 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 allocateTextureMemory(TextureInfo*, const IntSize&);
     void deleteChromiumImageForTexture(TextureInfo*);
 
     PreserveDrawingBuffer m_preserveDrawingBuffer;
     bool m_scissorEnabled;
     Platform3DObject m_texture2DBinding;
     Platform3DObject m_framebufferBinding;
+    Platform3DObject m_readFramebufferBinding;
     GLenum m_activeTextureUnit;
 
     OwnPtr<WebGraphicsContext3D> m_context;
     OwnPtr<Extensions3DUtil> m_extensionsUtil;
     IntSize m_size;
     WebGraphicsContext3D::Attributes m_requestedAttributes;
     bool m_multisampleExtensionSupported;
     bool m_packedDepthStencilExtensionSupported;
     bool m_discardFramebufferSupported;
     Platform3DObject m_fbo;
@@ skipping 56 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