cc/base/swap_promise.h

   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
  41   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_