Use base::ScopedTypeRef for CGL types

content/browser/renderer_host/compositing_iosurface_layer_mac.mm

 // Copyright 2013 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 "content/browser/renderer_host/compositing_iosurface_layer_mac.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #include <OpenGL/gl.h>
 
 #include "base/mac/sdk_forward_declarations.h"
@@ skipping 83 matching lines @@
   }
 
   // Cache a copy of renderWidgetHostView_ because it may be reset if
   // a software frame is received in GetBackingStore.
   content::RenderWidgetHostViewMac* cached_view = renderWidgetHostView_;
 
   // If a resize is in progress then GetBackingStore request a frame of the
   // current window size and block until a frame of the right size comes in.
   // This makes the window content not lag behind the resize (at the cost of
   // blocking on the browser's main thread).
   if (cached_view->render_widget_host_) {

[ccameron, 2014/02/07 07:17:24]

Hopefully this comment clears up some of the terror regarding this function. I'm
going to try moving this block around in future changes, to see if I can avoid
the nested run loop in this callback (but, in the future).

-    cached_view->about_to_validate_and_paint_ = true;
-    (void)cached_view->render_widget_host_->GetBackingStore(true);
-    cached_view->about_to_validate_and_paint_ = false;
-    CGLSetCurrentContext(glContext);
+    // Note that GetBackingStore can potentially spawn a nested run loop, which
+    // may change the current GL context, or, because the GL contexts are
+    // shared, may change the currently-bound FBO. Ensure that, when the run
+    // loop returns, the original GL context remain current, and the original
+    // FBO remain bound.
+    // TODO(ccameron): This is far too fragile a mechanism to rely on. Find
+    // a way to avoid doing this.
+    GLuint previous_framebuffer = 0;
+    glGetIntegerv(GL_FRAMEBUFFER_BINDING,
+                  reinterpret_cast<GLint*>(&previous_framebuffer));
+    CHECK(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
+    {
+      gfx::ScopedCGLSetCurrentContext scoped_set_current_context(NULL);
+      cached_view->about_to_validate_and_paint_ = true;
+      (void)cached_view->render_widget_host_->GetBackingStore(true);
+      cached_view->about_to_validate_and_paint_ = false;
+    }
+    DCHECK_EQ(CGLGetCurrentContext(), glContext)
+        << "original GL context failed to re-bind, browser crash is imminent.";
+    glBindFramebuffer(GL_FRAMEBUFFER, previous_framebuffer);
   }
 
   // If a transition to software mode has occurred, this layer should be
   // removed from the heirarchy now, so don't draw anything.
   if (!renderWidgetHostView_)
     return;
 
   gfx::Rect window_rect([self frame]);
   float window_scale_factor = 1.f;
   if ([self respondsToSelector:(@selector(contentsScale))])
     window_scale_factor = [self contentsScale];
 
   if (!renderWidgetHostView_->compositing_iosurface_->DrawIOSurface(
         context_,
         window_rect,
         window_scale_factor,
         false)) {
     renderWidgetHostView_->GotAcceleratedCompositingError();
     return;
   }
 
   renderWidgetHostView_->SendPendingLatencyInfoToHost();
 }
 
 @end