Decoupling backbuffer allocation suggestion from frontbuffer allocation suggestion.

content/common/gpu/image_transport_surface_win.cc

Index: content/common/gpu/image_transport_surface_win.cc
diff --git a/content/common/gpu/image_transport_surface_win.cc b/content/common/gpu/image_transport_surface_win.cc
index 32e9d8a45b69b51c30135856dbbe3e53ad0dad61..358e12575ca5fc89d954f263ea3d406b80254d6c 100644
--- a/content/common/gpu/image_transport_surface_win.cc
+++ b/content/common/gpu/image_transport_surface_win.cc
@@ -40,7 +40,8 @@ class PbufferImageTransportSurface
   virtual bool SwapBuffers() OVERRIDE;
   virtual bool PostSubBuffer(int x, int y, int width, int height) OVERRIDE;
   virtual std::string GetExtensions() OVERRIDE;
-  virtual void SetBufferAllocation(BufferAllocationState state) OVERRIDE;
+  virtual void SetBackbufferAllocation(bool allocated) OVERRIDE;
+  virtual void SetFrontbufferAllocation(bool allocated) OVERRIDE;
 
  protected:
   // ImageTransportSurface implementation
@@ -55,9 +56,11 @@ class PbufferImageTransportSurface
   virtual ~PbufferImageTransportSurface();
   void SendBuffersSwapped();
   void DestroySurface();
+  void AdjustBufferAllocations();
 
   // Tracks the current buffer allocation state.
-  BufferAllocationState buffer_allocation_state_;
+  bool backbuffer_suggested_allocation_;
+  bool frontbuffer_suggested_allocation_;
 
   // Size to resize to when the surface becomes visible.
   gfx::Size visible_size_;
@@ -71,7 +74,8 @@ PbufferImageTransportSurface::PbufferImageTransportSurface(
     GpuChannelManager* manager,
     GpuCommandBufferStub* stub)
     : GLSurfaceAdapter(new gfx::PbufferGLSurfaceEGL(false, gfx::Size(1, 1))),
-      buffer_allocation_state_(BUFFER_ALLOCATION_FRONT_AND_BACK) {
+      backbuffer_suggested_allocation_(true),
+      frontbuffer_suggested_allocation_(true) {
   helper_.reset(new ImageTransportHelper(this,
                                          manager,
                                          stub,
@@ -122,28 +126,27 @@ bool PbufferImageTransportSurface::PostSubBuffer(
   return false;
 }
 
-void PbufferImageTransportSurface::SetBufferAllocation(
-    BufferAllocationState state) {
-  if (buffer_allocation_state_ == state)
+void PbufferImageTransportSurface::SetBackbufferAllocation(bool allocation) {
+  if (backbuffer_suggested_allocation_ == allocation)
     return;
-  buffer_allocation_state_ = state;
-
-  switch (state) {
-    case BUFFER_ALLOCATION_FRONT_AND_BACK:
-      Resize(visible_size_);
-      break;
+  backbuffer_suggested_allocation_ = allocation;
+  AdjustBufferAllocations();
+}
 
-    case BUFFER_ALLOCATION_FRONT_ONLY:
-      Resize(gfx::Size(1, 1));
-      break;
+void PbufferImageTransportSurface::SetFrontbufferAllocation(bool allocation) {
+  if (frontbuffer_suggested_allocation_ == allocation)
+    return;
+  frontbuffer_suggested_allocation_ = allocation;
+  AdjustBufferAllocations();
+}
 
-    case BUFFER_ALLOCATION_NONE:
-      Resize(gfx::Size(1, 1));
+void PbufferImageTransportSurface::AdjustBufferAllocations() {
+  if (backbuffer_suggested_allocation_) {
+    Resize(visible_size_);

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

DCHECK that we should have a front buffer?

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

Again, I don't think so.
Previously we would set BUFFER_ALLOCATION_FRONT_AND_BACK whenever suggest
backbuffer == true, regardless of frontbuffer suggestion.  Now that the two are
decoupled, we shouldn't assume/necessitate front == true when back == true.
On 2012/05/09 18:13:01, jonathan.backer wrote:

+  } else {
+    Resize(gfx::Size(1, 1));
+    if (!frontbuffer_suggested_allocation_)
       helper_->Suspend();
-      break;
-
-    default:
-      NOTREACHED();
   }
   DestroySurface();
 }
@@ -188,7 +191,7 @@ void PbufferImageTransportSurface::OnResizeViewACK() {
 }
 
 void PbufferImageTransportSurface::OnResize(gfx::Size size) {
-  if (buffer_allocation_state_ == BUFFER_ALLOCATION_FRONT_AND_BACK)
+  if (backbuffer_suggested_allocation_ && frontbuffer_suggested_allocation_)

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

I think that it may make more sense to DCHECK that we have
frontbuffer_suggested_allocation_ here. I don't that what we want to drop this.

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

Fair enough.  Shouldn't we DCHECK for both?
Will we ever send resize message when not visible?

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

[jonathan.backer, 2012/05/10 21:37:48]

AFAIK, we shouldn't resize when not visible. I think that resize is meant for
the backbuffer. So it would be strange to do so. 

     Resize(size);
 
   DestroySurface();