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/frame_sink_id.mojom";
import "cc/ipc/local_frame_id.mojom";
import "cc/ipc/returned_resource.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);

  // Submits a CompositorFrame to the display compositor that will be presented
  // to screen the next time frames from all CompositorFrameSinks are aggregated
  // to produce a display CompositorFrame. If a client wishes to allocate a new
  // surface (e.g. during resize), then it can simply allocate a new
  // |local_frame_id|.
  // For successful swaps, the implementation must call
  // DidReceiveCompositorFrameAck() asynchronously when the frame has been
  // processed in order to unthrottle the next frame.
  SubmitCompositorFrame(cc.mojom.LocalFrameId local_frame_id,
                        cc.mojom.CompositorFrame frame);

  // 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);
};

// 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);
};