// 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. #ifndef CC_BASE_SWAP_PROMISE_H_ #define CC_BASE_SWAP_PROMISE_H_ #include "cc/output/compositor_frame_metadata.h" namespace cc { const unsigned int kMaxQueuedSwapPromiseNumber = 100; // 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 { public: enum DidNotSwapReason { DID_NOT_SWAP_UNKNOWN, SWAP_FAILS, COMMIT_FAILS, SWAP_PROMISE_LIST_OVERFLOW, }; SwapPromise() {} virtual ~SwapPromise() {} virtual void DidSwap(CompositorFrameMetadata* metadata) = 0; virtual void DidNotSwap(DidNotSwapReason reason) = 0; }; } // namespace cc #endif // CC_BASE_SWAP_PROMISE_H_