Decoupling backbuffer allocation suggestion from frontbuffer allocation suggestion.

content/common/gpu/texture_image_transport_surface.cc

Index: content/common/gpu/texture_image_transport_surface.cc
diff --git a/content/common/gpu/texture_image_transport_surface.cc b/content/common/gpu/texture_image_transport_surface.cc
index a19a743a7994295ff728c07803b42bb759224392..dd55326b54b03bd92b31839c66aa7d1ecd369d69 100644
--- a/content/common/gpu/texture_image_transport_surface.cc
+++ b/content/common/gpu/texture_image_transport_surface.cc
@@ -65,6 +65,8 @@ TextureImageTransportSurface::TextureImageTransportSurface(
       : fbo_id_(0),
         front_(0),
         stub_destroyed_(false),
+        backbuffer_suggested_allocation_(true),
+        frontbuffer_suggested_allocation_(true),
         parent_stub_(NULL) {
   GpuChannel* parent_channel = manager->LookupChannel(handle.parent_client_id);
   DCHECK(parent_channel);
@@ -155,19 +157,24 @@ unsigned int TextureImageTransportSurface::GetBackingFrameBufferObject() {
   return fbo_id_;
 }
 
-void TextureImageTransportSurface::SetBufferAllocation(
-    BufferAllocationState state) {
+void TextureImageTransportSurface::SetBackbufferAllocation(bool allocation) {
+  if (backbuffer_suggested_allocation_ == allocation)
+     return;
+  backbuffer_suggested_allocation_ = allocation;
+
   if (!helper_->MakeCurrent())
     return;
-  switch (state) {
-    case BUFFER_ALLOCATION_FRONT_AND_BACK:
-      CreateBackTexture(textures_[back()].size);
-      break;
-    case BUFFER_ALLOCATION_FRONT_ONLY:
-    case BUFFER_ALLOCATION_NONE:
-      ReleaseBackTexture();
-      break;
-  };
+
+  if (backbuffer_suggested_allocation_)
+    CreateBackTexture(textures_[back()].size);
+  else
+    ReleaseBackTexture();
+}
+
+void TextureImageTransportSurface::SetFrontbufferAllocation(bool allocation) {
+  if (frontbuffer_suggested_allocation_ == allocation)
+    return;
+  frontbuffer_suggested_allocation_ = allocation;
 }
 
 void* TextureImageTransportSurface::GetShareHandle() {
@@ -203,6 +210,7 @@ void TextureImageTransportSurface::OnWillDestroyStub(
 }
 
 bool TextureImageTransportSurface::SwapBuffers() {
+  DCHECK(backbuffer_suggested_allocation_);

[jonathan.backer, 2012/05/15 15:53:31]

Why not exit early if no frontbuffer (I realize it would NOOP because we aren't
dropping front buffers yet, but you've done this for EGL as well, even though we
aren't dropping those front buffers). If you do add it (your call), the comments
for the EGL path hold.

[mmocny, 2012/05/15 20:02:28]

Fair point, I prefer to add it here than remove it there.

On 2012/05/15 15:53:31, jonathan.backer wrote:

   if (!parent_stub_) {
     LOG(ERROR) << "SwapBuffers failed because no parent stub.";
     return false;
@@ -223,6 +231,7 @@ bool TextureImageTransportSurface::SwapBuffers() {
 
 bool TextureImageTransportSurface::PostSubBuffer(
     int x, int y, int width, int height) {
+  DCHECK(backbuffer_suggested_allocation_);

[jonathan.backer, 2012/05/15 15:53:31]

Same as above.

   if (!parent_stub_) {
     LOG(ERROR) << "PostSubBuffer failed because no parent stub.";
     return false;