Framebuffer clear() needs to consider the situation some draw buffers are disabled.

gpu/command_buffer/service/framebuffer_manager.cc

 // 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.
 
 #include "gpu/command_buffer/service/framebuffer_manager.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "gpu/command_buffer/common/gles2_cmd_utils.h"
 #include "gpu/command_buffer/service/renderbuffer_manager.h"
 #include "gpu/command_buffer/service/texture_manager.h"
@@ skipping 342 matching lines @@
     GLenum attachment) const {
   AttachmentMap::const_iterator it =
       attachments_.find(attachment);
   if (it != attachments_.end()) {
     const Attachment* attachment = it->second.get();
     return !attachment->cleared();
   }
   return false;
 }
 
+bool Framebuffer::HasUnclearedColorAttachments() const {
+  for (AttachmentMap::const_iterator it = attachments_.begin();
+       it != attachments_.end(); ++it) {
+    if (it->first >= GL_COLOR_ATTACHMENT0 &&
+        it->first < GL_COLOR_ATTACHMENT0 + manager_->max_draw_buffers_) {
+      const Attachment* attachment = it->second.get();
+      if (!attachment->cleared())
+        return true;
+    }
+  }
+  return false;
+}
+
+void Framebuffer::ChangeDrawBuffersHelper(bool recover) const {
+  scoped_ptr<GLenum[]> buffers(new GLenum[manager_->max_draw_buffers_]);
+  for (uint32 i = 0; i < manager_->max_draw_buffers_; ++i)
+    buffers[i] = GL_NONE;
+  for (AttachmentMap::const_iterator it = attachments_.begin();
+       it != attachments_.end(); ++it) {
+    if (it->first >= GL_COLOR_ATTACHMENT0 &&
+        it->first < GL_COLOR_ATTACHMENT0 + manager_->max_draw_buffers_) {
+      buffers[it->first - GL_COLOR_ATTACHMENT0] = it->first;
+    }
+  }
+  bool different = false;
+  for (uint32 i = 0; i < manager_->max_draw_buffers_; ++i) {
+    if (buffers[i] != draw_buffers_[i]) {
+      different = true;
+      break;
+    }
+  }
+  if (different) {
+    if (recover)
+      glDrawBuffersARB(manager_->max_draw_buffers_, draw_buffers_.get());
+    else
+      glDrawBuffersARB(manager_->max_draw_buffers_, buffers.get());
+  }
+}
+
+void Framebuffer::PrepareDrawBuffersForClear() const {
+  bool recover = false;
+  ChangeDrawBuffersHelper(recover);
+}
+
+void Framebuffer::RestoreDrawBuffersAfterClear() const {
+  bool recover = true;
+  ChangeDrawBuffersHelper(recover);
+}
+
 void Framebuffer::MarkAttachmentAsCleared(
       RenderbufferManager* renderbuffer_manager,
       TextureManager* texture_manager,
       GLenum attachment,
       bool cleared) {
   AttachmentMap::iterator it = attachments_.find(attachment);
   if (it != attachments_.end()) {
     Attachment* a = it->second.get();
     if (a->cleared() != cleared) {
       a->SetCleared(renderbuffer_manager,
@@ skipping 136 matching lines @@
         index < static_cast<GLsizei>(manager_->max_draw_buffers_));
   return draw_buffers_[index];
 }
 
 void Framebuffer::SetDrawBuffers(GLsizei n, const GLenum* bufs) {
   DCHECK(n <= static_cast<GLsizei>(manager_->max_draw_buffers_));
   for (GLsizei i = 0; i < n; ++i)
     draw_buffers_[i] = bufs[i];
 }
 
+
+
 bool Framebuffer::HasAlphaMRT() const {
   for (uint32 i = 0; i < manager_->max_draw_buffers_; ++i) {
     if (draw_buffers_[i] != GL_NONE) {
       const Attachment* attachment = GetAttachment(draw_buffers_[i]);
       if (!attachment)
         continue;
       if ((GLES2Util::GetChannelsForFormat(
                attachment->internal_format()) & 0x0008) != 0)
         return true;
     }
@@ skipping 155 matching lines @@
        ++it) {
     TextureDetachObserver* observer = *it;
     observer->OnTextureRefDetachedFromFramebuffer(texture);
   }
 }
 
 }  // namespace gles2
 }  // namespace gpu