From 1fb8c48b658c3d4422f806d012f51b250446a748 Mon Sep 17 00:00:00 2001
From: "piman@chromium.org"
 <piman@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Wed, 31 Aug 2011 01:01:53 +0000
Subject: Delay resize of the front buffer until the swap for offscreen
 buffers.

Previous code was resizing, and clearing the front buffer as soon as the back
buffer was resized. It can lead to race conditions where the compositor draws a
black texture if it triggers between the resize and the swap.

BUG=None
TEST=Pepper Flash


Review URL: http://codereview.chromium.org/7795015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98905 0039d316-1c4b-4281-b951-d872f2087c98
---
 gpu/command_buffer/service/gles2_cmd_decoder.cc | 89 +++++++++++++------------
 1 file changed, 46 insertions(+), 43 deletions(-)

diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 1b96d2b..923cfae 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2534,49 +2534,6 @@ bool GLES2DecoderImpl::ResizeOffscreenFrameBuffer(const gfx::Size& size) {
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
     RestoreClearState();
   }
-
-  // Workaround for NVIDIA driver bug on OS X; crbug.com/89557,
-  // crbug.com/94103. TODO(kbr): figure out reproduction so Apple will
-  // fix this.
-  if (needs_mac_nvidia_driver_workaround_) {
-    offscreen_saved_frame_buffer_->Create();
-    glFinish();
-  }
-
-  // Allocate the offscreen saved color texture.
-  DCHECK(offscreen_saved_color_format_);
-  offscreen_saved_color_texture_->AllocateStorage(
-      offscreen_size_, offscreen_saved_color_format_);
-
-  offscreen_saved_frame_buffer_->AttachRenderTexture(
-      offscreen_saved_color_texture_.get());
-  if (offscreen_saved_frame_buffer_->CheckStatus() !=
-      GL_FRAMEBUFFER_COMPLETE) {
-    LOG(ERROR) << "GLES2DecoderImpl::ResizeOffscreenFrameBuffer failed "
-               << "because offscreen saved FBO was incomplete.";
-    return false;
-  }
-
-  // Destroy the offscreen resolved framebuffers.
-  if (offscreen_resolved_frame_buffer_.get())
-    offscreen_resolved_frame_buffer_->Destroy();
-  if (offscreen_resolved_color_texture_.get())
-    offscreen_resolved_color_texture_->Destroy();
-  offscreen_resolved_color_texture_.reset();
-  offscreen_resolved_frame_buffer_.reset();
-
-  // Clear the offscreen color texture.
-  {
-    ScopedFrameBufferBinder binder(this, offscreen_saved_frame_buffer_->id());
-    glClearColor(0, 0, 0, 0);
-    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
-    glDisable(GL_SCISSOR_TEST);
-    glClear(GL_COLOR_BUFFER_BIT);
-    RestoreClearState();
-  }
-
-  UpdateParentTextureInfo();
-
   return true;
 }
 
@@ -6582,6 +6539,52 @@ error::Error GLES2DecoderImpl::HandleSwapBuffers(
   // If offscreen then don't actually SwapBuffers to the display. Just copy
   // the rendered frame to another frame buffer.
   if (is_offscreen) {
+    if (offscreen_size_ != offscreen_saved_color_texture_->size()) {
+      // Workaround for NVIDIA driver bug on OS X; crbug.com/89557,
+      // crbug.com/94163. TODO(kbr): figure out reproduction so Apple will
+      // fix this.
+      if (needs_mac_nvidia_driver_workaround_) {
+        offscreen_saved_frame_buffer_->Create();
+        glFinish();
+      }
+
+      // Allocate the offscreen saved color texture.
+      DCHECK(offscreen_saved_color_format_);
+      offscreen_saved_color_texture_->AllocateStorage(
+          offscreen_size_, offscreen_saved_color_format_);
+
+      offscreen_saved_frame_buffer_->AttachRenderTexture(
+          offscreen_saved_color_texture_.get());
+      if (offscreen_saved_frame_buffer_->CheckStatus() !=
+          GL_FRAMEBUFFER_COMPLETE) {
+        LOG(ERROR) << "GLES2DecoderImpl::ResizeOffscreenFrameBuffer failed "
+                   << "because offscreen saved FBO was incomplete.";
+        return error::kLostContext;
+      }
+
+      // Destroy the offscreen resolved framebuffers.
+      if (offscreen_resolved_frame_buffer_.get())
+        offscreen_resolved_frame_buffer_->Destroy();
+      if (offscreen_resolved_color_texture_.get())
+        offscreen_resolved_color_texture_->Destroy();
+      offscreen_resolved_color_texture_.reset();
+      offscreen_resolved_frame_buffer_.reset();
+
+      // Clear the offscreen color texture.
+      // TODO(piman): Is this still necessary?
+      {
+        ScopedFrameBufferBinder binder(this,
+                                       offscreen_saved_frame_buffer_->id());
+        glClearColor(0, 0, 0, 0);
+        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+        glDisable(GL_SCISSOR_TEST);
+        glClear(GL_COLOR_BUFFER_BIT);
+        RestoreClearState();
+      }
+
+      UpdateParentTextureInfo();
+    }
+
     ScopedGLErrorSuppressor suppressor(this);
 
     if (IsOffscreenBufferMultisampled()) {
-- 
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