OnDrawHardware() implementation with async messages

content/browser/android/synchronous_compositor_host.cc

Index: content/browser/android/synchronous_compositor_host.cc
diff --git a/content/browser/android/synchronous_compositor_host.cc b/content/browser/android/synchronous_compositor_host.cc
index 288bb586a276132d8520c5c41dcbafc021aa2b33..7a84626e87220025d47d7a225b9f0b522db9cd1f 100644
--- a/content/browser/android/synchronous_compositor_host.cc
+++ b/content/browser/android/synchronous_compositor_host.cc
@@ -91,11 +91,23 @@ bool SynchronousCompositorHost::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(SyncCompositorHostMsg_OutputSurfaceCreated,
                         OutputSurfaceCreated)
     IPC_MESSAGE_HANDLER(SyncCompositorHostMsg_UpdateState, ProcessCommonParams)
+    IPC_MESSAGE_HANDLER(SyncCompositorHostMsg_ReturnFrame,
+                        DemandDrawHwReceiveFrame)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
+void SynchronousCompositorHost::DemandDrawHwAsync(
+    const gfx::Size& viewport_size,
+    const gfx::Rect& viewport_rect_for_tile_priority,
+    const gfx::Transform& transform_for_tile_priority) {
+  SyncCompositorDemandDrawHwParams params(viewport_size,
+                                          viewport_rect_for_tile_priority,
+                                          transform_for_tile_priority);
+  sender_->Send(new SyncCompositorMsg_DemandDrawHwAsync(routing_id_, params));
+}
+
 SynchronousCompositor::Frame SynchronousCompositorHost::DemandDrawHw(
     const gfx::Size& viewport_size,
     const gfx::Rect& viewport_rect_for_tile_priority,
@@ -103,15 +115,35 @@ SynchronousCompositor::Frame SynchronousCompositorHost::DemandDrawHw(
   SyncCompositorDemandDrawHwParams params(viewport_size,
                                           viewport_rect_for_tile_priority,
                                           transform_for_tile_priority);
-  SynchronousCompositor::Frame frame;
-  frame.frame.reset(new cc::CompositorFrame);
+  uint32_t output_surface_id;
+  cc::CompositorFrame compositor_frame;
   SyncCompositorCommonRendererParams common_renderer_params;
+
   if (!sender_->Send(new SyncCompositorMsg_DemandDrawHw(
-          routing_id_, params, &common_renderer_params,
-          &frame.output_surface_id, frame.frame.get()))) {
+          routing_id_, params, &common_renderer_params, &output_surface_id,
+          &compositor_frame))) {
     return SynchronousCompositor::Frame();
   }
+
   ProcessCommonParams(common_renderer_params);
+
+  return ProcessHardwareFrame(output_surface_id, compositor_frame);
+}
+
+void SynchronousCompositorHost::DemandDrawHwReceiveFrame(
+    uint32_t output_surface_id,
+    const cc::CompositorFrame& compositor_frame) {
+  client_->OnDrawHardwareProcessFrame(
+      ProcessHardwareFrame(output_surface_id, compositor_frame));
+}
+
+SynchronousCompositor::Frame SynchronousCompositorHost::ProcessHardwareFrame(
+    uint32_t output_surface_id,
+    const cc::CompositorFrame& compositor_frame) {
+  SynchronousCompositor::Frame frame;
+  frame.frame.reset(new cc::CompositorFrame);
+  frame.output_surface_id = output_surface_id;
+  *frame.frame = std::move(const_cast<cc::CompositorFrame&>(compositor_frame));

[dcheng, 2016/08/31 18:06:44]

Hmm...

I wonder if we can try to make this better, this seems pretty sketchy.

Can we use some type traits in the IPC code to determine when to pass by const
ref / copy vs move?

[boliu, 2016/08/31 18:23:53]

So uhh, for this, I think we'll just copy what chrome does with
RenderWidgetHostImpl::OnSwapCompositorFrame. It just reads the message.


But I am curious what would it take to teach IPC about movable types. So some
questions that's more for me learning this..

I imagine it would be something like ParamTrain::IsMovable that's then
specialized for the type? And then ipc would do a std::move when it calls
handlers. The type in the handler method would simply be cc::CompositorFrame (ie
by value)?

[boliu, 2016/08/31 18:25:45]

Does that involve updating all ParamTraits though?

[ojars, 2016/09/02 01:29:56]

Done.

   if (!frame.frame->delegated_frame_data) {
     // This can happen if compositor did not swap in this draw.
     frame.frame.reset();