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 89 matching lines @@
     // 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);
 
     // 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);
+    void bind(GLenum target);
     IntSize size() const { return m_size; }
 
     // Copies the multisample color buffer to the normal color buffer and leaves m_fbo bound.
     void commit();
 
     // 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(GLenum target, Platform3DObject fbo)
+    {
+        switch (target) {
+        case GL_FRAMEBUFFER:
+            m_drawFramebufferBinding = fbo;
+            m_readFramebufferBinding = fbo;
+            break;
+        case GL_DRAW_FRAMEBUFFER:
+            m_drawFramebufferBinding = fbo;
+            break;
+        case GL_READ_FRAMEBUFFER:
+            m_readFramebufferBinding = fbo;
+            break;
+        default:
+            ASSERT(0);
+        }
+    }
 
     // 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 21 matching lines @@
         GLenum destType, GLint level, bool premultiplyAlpha, bool flipY, SourceDrawingBuffer);
 
     void setPackAlignment(GLint param);
 
     void paintRenderingResultsToCanvas(ImageBuffer*);
     bool paintRenderingResultsToImageData(int&, int&, SourceDrawingBuffer, WTF::ArrayBufferContents&);
 
     int sampleCount() const { return m_sampleCount; }
     bool explicitResolveOfMultisampleData() const { return m_multisampleMode == ExplicitResolve; };
 
+    // Bind to m_drawFramebufferBinding or m_readFramebufferBinding if it's not 0.
+    // Otherwise, bind to the default FBO.
+    void restoreFramebufferBindings();
+
 protected: // For unittests
     DrawingBuffer(
         PassOwnPtr<WebGraphicsContext3D>,
         PassOwnPtr<Extensions3DUtil>,
         bool multisampleExtensionSupported,
         bool packedDepthStencilExtensionSupported,
         bool discardFramebufferSupported,
         PreserveDrawingBuffer,
         WebGraphicsContext3D::Attributes requestedAttributes);
 
     bool initialize(const IntSize&);
 
 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();
-
     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 15 matching lines @@
     // 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 allocateTextureMemory(TextureInfo*, const IntSize&);
     void deleteChromiumImageForTexture(TextureInfo*);
 
     PreserveDrawingBuffer m_preserveDrawingBuffer;
     bool m_scissorEnabled;
     Platform3DObject m_texture2DBinding;
-    Platform3DObject m_framebufferBinding;
+    Platform3DObject m_drawFramebufferBinding;
+    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