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 15 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);
-
-  // TODO(fsamuel): ReadbackBitmap API would be useful here.
 };
 
 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.
   DidReceiveCompositorFrameAck();
 
   // Notification for the client to generate a CompositorFrame.
   OnBeginFrame(BeginFrameArgs args);
 
   // Returns resources sent to SubmitCompositorFrame to be reused or freed.
   ReclaimResources(ReturnedResourceArray resources);
 
   // Called when surface is being scheduled for a draw.
   WillDrawSurface();
 };
 
 // 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);
+
+  // Requests that the renderer send back a copy of the surface that this
+  // CompositorFrameSink submits to. The result can be in form of a bitmap
+  // or a texture. See cc::CopyOutputRequest and cc::CopyOutputResult.
+  RequestCopyOfSurface(cc.mojom.CopyOutputRequest request)
+      => (cc.mojom.CopyOutputResult result);
+
+  // If the copy returned by RequestCopyOfSurface is a texture, this method

[danakj, 2017/02/06 23:02:12]

This might be off-topic but what if it's a bitmap, do we use shared memory or do
we now ship a lot of pixels over ipc? What does
https://cs.chromium.org/chromium/src/cc/ipc/copy_output_result.mojom?rcl=5fdb...
do? Should that be a SharedBitmap?

[Saman Sami, 2017/02/06 23:09:54]

We serialize the bitmap and send it over IPC. I'm not sure how to use shared
bitmap. CopyOutputResult only has a SkBitmap. That might need to change I guess?

[danakj, 2017/02/06 23:24:07]

Yeh it would have to. We should do that cuz copying pixels is slow.

[Saman Sami, 2017/02/13 23:07:37]

I agree. I created a new bug to track this issue. https://crbug.com/691070

+  // must be used to release it.
+  ReleaseCopyOfSurface(gpu.mojom.Mailbox mailbox,
+                       gpu.mojom.SyncToken sync_token, bool is_lost);
 };