Delay resize of the front buffer until the swap for offscreen buffers.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 1b96d2befa39865268bfef3127fb2e50cc2d2169..923cfae5f351823f358d3b6832ae914e7614a532 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?

[Ken Russell (switch to Gerrit), 2011/08/30 22:47:13]

I'm quite sure it is -- if the offscreen color texture has increased in width or
height then the copy from the frame buffer will not cover it all, so we must
prevent garbage from showing up in the other regions.

+      {
+        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()) {