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1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef CC_BASE_SWAP_PROMISE_H_
6 #define CC_BASE_SWAP_PROMISE_H_
7 
8 #include "cc/output/compositor_frame_metadata.h"
9 
10 namespace cc {
11 
12 const unsigned int kMaxQueuedSwapPromiseNumber = 100;
13 
14 // When a change to the compositor's state/invalidation/whatever happens, a
15 // Swap Promise can be inserted into LayerTreeHost/LayerTreeImpl, to track
16 // whether the compositor's reply to the new state/invaliadtion/whatever is
17 // completed in the compositor, i.e. the compositor knows it has been sent
18 // to its output or not.
19 //
20 // If the new compositor state is sent to the output, SwapPromise::DidSwap()
21 // will be called, and if the compositor fails to send its new state to the
22 // output, SwapPromise::DidNotSwap() will be called.
23 //
24 // Client wishes to use SwapPromise should have a subclass that defines
25 // the behavior of DidSwap() and DidNotSwap(). Notice that the promise can
26 // be broken at either main or impl thread, e.g. commit fails on main thread,
27 // new frame data has no actual damage so LayerTreeHostImpl::SwapBuffers()
28 // bails out early on impl thread, so don't assume that DidSwap() and
29 // DidNotSwap() are called at a particular thread. It is better to let the
30 // subclass carry thread-safe member data and operate on that member data in
31 // DidSwap() and DidNotSwap().
32 class CC_EXPORT SwapPromise {
33  public:
34   enum DidNotSwapReason {
35     DID_NOT_SWAP_UNKNOWN,
36     SWAP_FAILS,
37     COMMIT_FAILS,
38     SWAP_PROMISE_LIST_OVERFLOW,
39   };
40 
SwapPromise()41   SwapPromise() {}
~SwapPromise()42   virtual ~SwapPromise() {}
43 
44   virtual void DidSwap(CompositorFrameMetadata* metadata) = 0;
45   virtual void DidNotSwap(DidNotSwapReason reason) = 0;
46 };
47 
48 }  // namespace cc
49 
50 #endif  // CC_BASE_SWAP_PROMISE_H_
51