Implement EXT_draw_buffers WebGL extention support in command buffer.

gpu/command_buffer/service/framebuffer_manager.h

 // Copyright (c) 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.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_MANAGER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_MANAGER_H_
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
@@ skipping 96 matching lines @@
   // not mean the real OpenGL will consider it framebuffer complete. It just
   // means it passed our tests.
   GLenum IsPossiblyComplete() const;
 
   // Implements optimized glGetFramebufferStatus.
   GLenum GetStatus(TextureManager* texture_manager, GLenum target) const;
 
   // Check all attachments are cleared
   bool IsCleared() const;
 
+  GLenum GetDrawBuffer(GLenum draw_buffer) const;
+
+  void SetDrawBuffers(GLsizei n, const GLenum* bufs);
+
   static void ClearFramebufferCompleteComboMap();
 
  private:
   friend class FramebufferManager;
   friend class base::RefCounted<Framebuffer>;
 
   ~Framebuffer();
 
   void MarkAsDeleted();
 
@@ skipping 26 matching lines @@
 
   // A map of attachments.
   typedef base::hash_map<GLenum, scoped_refptr<Attachment> > AttachmentMap;
   AttachmentMap attachments_;
 
   // A map of successful frame buffer combos. If it's in the map
   // it should be FRAMEBUFFER_COMPLETE.
   typedef base::hash_map<std::string, bool> FramebufferComboCompleteMap;
   static FramebufferComboCompleteMap* framebuffer_combo_complete_map_;
 
+  // Hardwired to 16. Might be expanded in the future.
+  // This is not the max drawbuffers supported by the hardware, but the number
+  // of defined GL_DRAW_BUFFER*_ARB enum.
+  static const GLsizei kMaxDrawBuffers = 16;

[greggman, 2013/03/08 21:48:28]

We don't do this for textures, why do it for draw buffers?

In other words, texture units are limited to glGetInteger(GL_MAX_TEXTURE_UNITS)
not GL_TEXTURE31 which is way lower than many current GPUs.

[Zhenyao Mo, 2013/03/13 01:22:02]

Done.

+  GLenum draw_buffers_[kMaxDrawBuffers];
+
   DISALLOW_COPY_AND_ASSIGN(Framebuffer);
 };
 
 // This class keeps track of the frambebuffers and their attached renderbuffers
 // so we can correctly clear them.
 class GPU_EXPORT FramebufferManager {
  public:
   FramebufferManager();
   ~FramebufferManager();
 
@@ skipping 48 matching lines @@
 
   bool have_context_;
 
   DISALLOW_COPY_AND_ASSIGN(FramebufferManager);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_MANAGER_H_