Decoupling backbuffer allocation suggestion from frontbuffer allocation suggestion.

content/common/gpu/image_transport_surface_mac.cc

Index: content/common/gpu/image_transport_surface_mac.cc
diff --git a/content/common/gpu/image_transport_surface_mac.cc b/content/common/gpu/image_transport_surface_mac.cc
index 5223ce14b76bae380fbff0e042efa9f443de3df1..8b1e8bc3a8015768f82732be8dc70ba37156b646 100644
--- a/content/common/gpu/image_transport_surface_mac.cc
+++ b/content/common/gpu/image_transport_surface_mac.cc
@@ -37,7 +37,8 @@ class IOSurfaceImageTransportSurface : public gfx::NoOpGLSurfaceCGL,
   virtual gfx::Size GetSize() OVERRIDE;
   virtual bool OnMakeCurrent(gfx::GLContext* context) OVERRIDE;
   virtual unsigned int GetBackingFrameBufferObject() OVERRIDE;
-  virtual void SetBufferAllocation(BufferAllocationState state) OVERRIDE;
+  virtual void SetBackbufferAllocation(bool allocated) OVERRIDE;
+  virtual void SetFrontbufferAllocation(bool allocated) OVERRIDE;
 
  protected:
   // ImageTransportSurface implementation
@@ -53,8 +54,11 @@ class IOSurfaceImageTransportSurface : public gfx::NoOpGLSurfaceCGL,
 
   void UnrefIOSurface();
   void CreateIOSurface();
+  void AdjustBufferAllocations();
 
-  BufferAllocationState buffer_allocation_state_;
+  // Tracks the current buffer allocation state.
+  bool backbuffer_suggested_allocation_;
+  bool frontbuffer_suggested_allocation_;
 
   uint32 fbo_id_;
   GLuint texture_id_;
@@ -97,7 +101,8 @@ IOSurfaceImageTransportSurface::IOSurfaceImageTransportSurface(
     GpuCommandBufferStub* stub,
     gfx::PluginWindowHandle handle)
     : gfx::NoOpGLSurfaceCGL(gfx::Size(1, 1)),
-      buffer_allocation_state_(BUFFER_ALLOCATION_FRONT_AND_BACK),
+      backbuffer_suggested_allocation_(true),
+      frontbuffer_suggested_allocation_(true),
       fbo_id_(0),
       texture_id_(0),
       io_surface_handle_(0),
@@ -158,27 +163,26 @@ unsigned int IOSurfaceImageTransportSurface::GetBackingFrameBufferObject() {
   return fbo_id_;
 }
 
-void IOSurfaceImageTransportSurface::SetBufferAllocation(
-    BufferAllocationState state) {
-  if (buffer_allocation_state_ == state)
+void IOSurfaceImageTransportSurface::SetBackbufferAllocation(bool allocation) {
+  if (backbuffer_suggested_allocation_ == allocation)
     return;
-  buffer_allocation_state_ = state;
-
-  switch (state) {
-    case BUFFER_ALLOCATION_FRONT_AND_BACK:
-      CreateIOSurface();
-      break;
-
-    case BUFFER_ALLOCATION_FRONT_ONLY:
-      break;
+  backbuffer_suggested_allocation_ = allocation;
+  AdjustBufferAllocations();
+}
 
-    case BUFFER_ALLOCATION_NONE:
-      UnrefIOSurface();
-      helper_->Suspend();
-      break;
+void IOSurfaceImageTransportSurface::SetFrontbufferAllocation(bool allocation) {
+  if (frontbuffer_suggested_allocation_ == allocation)
+    return;
+  frontbuffer_suggested_allocation_ = allocation;
+  AdjustBufferAllocations();
+}
 
-    default:
-      NOTREACHED();
+void IOSurfaceImageTransportSurface::AdjustBufferAllocations() {
+  if (backbuffer_suggested_allocation_) {
+    CreateIOSurface();

[jonathan.backer, 2012/05/09 18:13:01]

Should we DCHECK that we have a front buffer? Not sure, but it's in the spirit
of the original code.

[mmocny, 2012/05/09 18:59:15]

I don't think so.  Since this is the minimum we can do to create a backbuffer,
even if we are suggested to not have a frontbuffer, we still have to do this. 
The renderer doesn't care what you frontbuffer suggestion is, but when it calls
ensureBackbuffer, it better be there.

On 2012/05/09 18:13:01, jonathan.backer wrote:

+  } else if (!frontbuffer_suggested_allocation_) {
+    UnrefIOSurface();
+    helper_->Suspend();
   }
 }