Decoupling backbuffer allocation suggestion from frontbuffer allocation suggestion.

content/common/gpu/image_transport_surface_mac.cc

 // Copyright (c) 2012 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.
 
 #if defined(ENABLE_GPU)
 
 #include "content/common/gpu/image_transport_surface.h"
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 19 matching lines @@
   // GLSurface implementation
   virtual bool Initialize() OVERRIDE;
   virtual void Destroy() OVERRIDE;
   virtual bool IsOffscreen() OVERRIDE;
   virtual bool SwapBuffers() OVERRIDE;
   virtual bool PostSubBuffer(int x, int y, int width, int height) OVERRIDE;
   virtual std::string GetExtensions() OVERRIDE;
   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
   virtual void OnNewSurfaceACK(uint64 surface_handle,
                                TransportDIB::Handle shm_handle) OVERRIDE;
   virtual void OnBuffersSwappedACK() OVERRIDE;
   virtual void OnPostSubBufferACK() OVERRIDE;
   virtual void OnResizeViewACK() OVERRIDE;
   virtual void OnResize(gfx::Size size) OVERRIDE;
 
  private:
   virtual ~IOSurfaceImageTransportSurface() OVERRIDE;
 
   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_;
 
   base::mac::ScopedCFTypeRef<CFTypeRef> io_surface_;
 
   // The id of |io_surface_| or 0 if that's NULL.
   uint64 io_surface_handle_;
 
   // Weak pointer to the context that this was last made current to.
@@ skipping 22 matching lines @@
   base::mac::ScopedCFTypeRef<CFNumberRef> number(
       CFNumberCreate(NULL, kCFNumberSInt32Type, &value));
   CFDictionaryAddValue(dictionary, key, number.get());
 }
 
 IOSurfaceImageTransportSurface::IOSurfaceImageTransportSurface(
     GpuChannelManager* manager,
     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),
       context_(NULL),
       made_current_(false) {
   helper_.reset(new ImageTransportHelper(this, manager, stub, handle));
 }
 
 IOSurfaceImageTransportSurface::~IOSurfaceImageTransportSurface() {
   Destroy();
@@ skipping 40 matching lines @@
   OnResize(gfx::Size(1, 1));
 
   made_current_ = true;
   return true;
 }
 
 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;
+  backbuffer_suggested_allocation_ = allocation;
+  AdjustBufferAllocations();
+}
 
-  switch (state) {
-    case BUFFER_ALLOCATION_FRONT_AND_BACK:
-      CreateIOSurface();
-      break;
+void IOSurfaceImageTransportSurface::SetFrontbufferAllocation(bool allocation) {
+  if (frontbuffer_suggested_allocation_ == allocation)
+    return;
+  frontbuffer_suggested_allocation_ = allocation;
+  AdjustBufferAllocations();
+}
 
-    case BUFFER_ALLOCATION_FRONT_ONLY:
-      break;
-
-    case BUFFER_ALLOCATION_NONE:
-      UnrefIOSurface();
-      helper_->Suspend();
-      break;
-
-    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();
   }
 }
 
 bool IOSurfaceImageTransportSurface::SwapBuffers() {
   glFlush();
 
   GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params params;
   params.surface_handle = io_surface_handle_;
   helper_->SendAcceleratedSurfaceBuffersSwapped(params);
 
@@ skipping 174 matching lines @@
       NOTREACHED();
       return NULL;
   }
   if (surface->Initialize())
     return surface;
   else
     return NULL;
 }
 
 #endif  // defined(USE_GPU)