MojoCompositorFrameSinkPrivate should support copy requests

cc/ipc/mojo_compositor_frame_sink.mojom

 // Copyright 2016 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.
 
 module cc.mojom;
 
 import "cc/ipc/begin_frame_args.mojom";
 import "cc/ipc/compositor_frame.mojom";
+import "cc/ipc/copy_output_request.mojom";
+import "cc/ipc/copy_output_result.mojom";
 import "cc/ipc/frame_sink_id.mojom";
 import "cc/ipc/local_surface_id.mojom";
 import "cc/ipc/surface_reference.mojom";
 import "cc/ipc/returned_resource.mojom";
 import "cc/ipc/surface_sequence.mojom";
+import "gpu/ipc/common/mailbox.mojom";
+import "gpu/ipc/common/sync_token.mojom";
 
 // A MojoCompositorFrameSink is an interface for receiving CompositorFrame
 // structs. A CompositorFrame contains the complete output meant for display.
 // Each time a client has a graphical update, and receives an OnBeginFrame, it
 // is responsible for creating a CompositorFrame to update its portion of the
 // screen.
 interface MojoCompositorFrameSink {
   // Lets the display compositor know that the client wishes to receive the next
   // BeginFrame event.
   SetNeedsBeginFrame(bool needs_begin_frame);
@@ skipping 16 matching lines @@
   // TODO(staraz): Delete Require() and Satisfy() once surface references
   // (CL 2541683004) are ready.
   // Add the provided |sequence| as a destruction dependency of the
   // surface associated with the provided |local_surface_id|.
   Require(cc.mojom.LocalSurfaceId local_surface_id,
           cc.mojom.SurfaceSequence sequence);
 
   // Mark the sequence as satisfied and garbage collect surfaces.
   Satisfy(cc.mojom.SurfaceSequence sequence);
 
+  RequestCopyOfSurface(cc.mojom.CopyOutputRequest request)
+      => (cc.mojom.CopyOutputResult result);
+
+  DeleteMailbox(gpu.mojom.Mailbox mailbox, gpu.mojom.SyncToken sync_token, bool is_lost);

[Fady Samuel, 2017/02/06 17:13:48]

This is way too generic, in my opinion. Why do we need this?

[danakj, 2017/02/06 19:18:51]

Same, CFS can transport resources but it doesn't manage lifetimes. Textures are
deleted/mailboxes are dereffed thru a GL context.

[Fady Samuel, 2017/02/06 19:45:02]

This sync token indicates when it's safe to delete this mailbox, right? Can The
display compositor allocate the synctoken instead and pass it to the client in
CopyOutputResult?

[Saman Sami, 2017/02/06 20:04:00]

Can you explain how it should be? I'm basically trying to mimic how copy
requests work at the moment. The requester has to run a callback to delete the
mailbox (called release_callback_ in CopyOutputResult). Since the callback would
be tricky with mojo, I added a method to the mojo interface which acts like that
callback.

[danakj, 2017/02/06 20:09:15]

I see, just call this ReleaseMailbox then. It doesn't delete, it tells the
service that it is done with it and is releasing ownership of its contents.
Delete implies something else altogether and may be what the service does, or
not.

[danakj, 2017/02/06 20:10:27]

ReleaseMailboxForCopyOutputResult might work too if that is too general as this
is a widely used API. Or can the cc.mojom.CopyOutputResult provide this somehow
to namespace it?

+
   // TODO(fsamuel): ReadbackBitmap API would be useful here.

[Fady Samuel, 2017/02/06 17:13:49]

Delete this?

 };
 
 interface MojoCompositorFrameSinkClient {
   // Notification that the previous CompositorFrame given to
   // SubmitCompositorFrame() has been processed and that another frame
   // can be submitted. This provides backpressure from the display compositor
   // so that frames are submitted only at the rate it can handle them.
   // TODO(fsamuel): This method ought not be necessary with unified BeginFrame.
   // However, there's a fair amount of cleanup and refactoring necessary to get
   // rid of it.
@@ skipping 10 matching lines @@
 };
 
 // MojoCompositorFrameSinkPrivate is used by the display compositor host to set
 // up BeginFrameSource hierarchies.  This API lives in SurfaceManager but is
 // called from here in order to ensure that hierarchy registration does not race
 // CompositorFrameSink creation.
 interface MojoCompositorFrameSinkPrivate {
   AddChildFrameSink(FrameSinkId child_frame_sink_id);
   RemoveChildFrameSink(FrameSinkId child_frame_sink_id);
 };