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// Copyright 2013 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.
#include "cc/output/compositor_frame_metadata.h"
namespace cc {
// When a change to the compositor's state/invalidation/whatever happens, a
// Swap Promise can be inserted into LayerTreeHost/LayerTreeImpl, to track
// whether the compositor's reply to the new state/invaliadtion/whatever is
// completed in the compositor, i.e. the compositor knows it has been sent
// to its output or not.
// If the new compositor state is sent to the output, SwapPromise::DidSwap()
// will be called, and if the compositor fails to send its new state to the
// output, SwapPromise::DidNotSwap() will be called.
// Client wishes to use SwapPromise should have a subclass that defines
// the behavior of DidSwap() and DidNotSwap(). Notice that the promise can
// be broken at either main or impl thread, e.g. commit fails on main thread,
// new frame data has no actual damage so LayerTreeHostImpl::SwapBuffers()
// bails out early on impl thread, so don't assume that DidSwap() and
// DidNotSwap() are called at a particular thread. It is better to let the
// subclass carry thread-safe member data and operate on that member data in
// DidSwap() and DidNotSwap().
class CC_EXPORT SwapPromise {
enum DidNotSwapReason {
SwapPromise() {}
virtual ~SwapPromise() {}
virtual void DidSwap(CompositorFrameMetadata* metadata) = 0;
virtual void DidNotSwap(DidNotSwapReason reason) = 0;
// A non-zero trace id identifies a trace flow object that is embedded in the
// swap promise. This can be used for registering additional flow steps to
// visualize the object's path through the system.
virtual int64 TraceId() const = 0;
} // namespace cc