Mac Overlays: Add GPU back-pressure

content/common/gpu/image_transport_surface_overlay_mac.h

Index: content/common/gpu/image_transport_surface_overlay_mac.h
diff --git a/content/common/gpu/image_transport_surface_overlay_mac.h b/content/common/gpu/image_transport_surface_overlay_mac.h
index 66c0591f1ee365618d667be13d0aaefe99e5d24a..32b93c941ecea6b869824dedc8856dbfa3a31259 100644
--- a/content/common/gpu/image_transport_surface_overlay_mac.h
+++ b/content/common/gpu/image_transport_surface_overlay_mac.h
@@ -5,9 +5,12 @@
 #ifndef CONTENT_COMMON_GPU_IMAGE_TRANSPORT_SURFACE_OVERLAY_MAC_H_
 #define CONTENT_COMMON_GPU_IMAGE_TRANSPORT_SURFACE_OVERLAY_MAC_H_
 
+#include <list>
+
 #import "base/mac/scoped_nsobject.h"
 #include "content/common/gpu/gpu_command_buffer_stub.h"
 #include "content/common/gpu/image_transport_surface.h"
+#include "ui/accelerated_widget_mac/display_link_mac.h"
 #include "ui/gl/gl_surface.h"
 
 @class CAContext;
@@ -47,14 +50,29 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
   void WakeUpGpu() override;
 
  private:
+  class PendingSwap;
+
   ~ImageTransportSurfaceOverlayMac() override;
+
+  gfx::SwapResult SwapBuffersInternal(const gfx::Rect& pixel_damage_rect);
+
+  // Check the oldest swap in |pending_swaps_|, and, if its fence has passed,
+  // send the content to the window server by -[CALayer setContents:]. If
+  // |force_immediate_display| is true then skip the fence check and immediately
+  // call -[CALayer setContents:].
+  void CheckAndDisplayPendingSwaps(bool force_immediate_display);
+
+  // Post a call to CheckAndDisplayPendingSwaps at the next midpoint of a
+  // vsync period.
+  void PostCheckAndDisplayPendingSwaps();
+
+  // Force all pending swaps to display immediately.
+  void FinishAllPendingSwaps();
+
   scoped_ptr<ImageTransportHelper> helper_;
   base::scoped_nsobject<CAContext> ca_context_;
   base::scoped_nsobject<CALayer> layer_;
 
-  // A phony NSView handle used to identify this.
-  gfx::AcceleratedWidget widget_;
-
   gfx::Size pixel_size_;
   float scale_factor_;
   std::vector<ui::LatencyInfo> latency_info_;
@@ -63,6 +81,16 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
   // consumed and reset when SwapBuffers is called. For now, only one overlay
   // plane is supported.
   gfx::GLImage* pending_overlay_image_;
+
+  // A queue of all frames that have been created by SwapBuffersInternal but
+  // have not yet been displayed by CheckAndDisplayPendingSwaps.
+  std::list<scoped_refptr<PendingSwap>> pending_swaps_;

[dcheng, 2015/08/07 00:28:37]

How about using linked_ptr instead of refcounting? Once we can use unique_ptr,
it'll be straightforward to programmatically convert it.

[ccameron, 2015/08/07 22:14:16]

Done.

+
+  // The display link used to compute the delay for the posted task in
+  // PostCheckAndDisplayPendingSwaps.
+  scoped_refptr<ui::DisplayLinkMac> display_link_mac_;
+
+  base::WeakPtrFactory<ImageTransportSurfaceOverlayMac> weak_factory_;
 };
 
 }  // namespace content