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_TREES_SWAP_PROMISE_H_ 6 #define CC_TREES_SWAP_PROMISE_H_ 7 8 #include <stdint.h> 9 10 #include "cc/cc_export.h" 11 #include "components/viz/common/quads/compositor_frame_metadata.h" 12 13 namespace cc { 14 15 // When a change to the compositor's state/invalidation/whatever happens, a 16 // Swap Promise can be inserted into LayerTreeHost/LayerTreeImpl, to track 17 // whether the compositor's reply to the new state/invaliadtion/whatever is 18 // completed in the compositor, i.e. the compositor knows it has been sent 19 // to its output or not. 20 // 21 // If the commit results in a successful activation of the pending layer tree, 22 // SwapPromise::DidActivate() will be called. 23 // 24 // If the new compositor state is goint to be sent to the output, 25 // SwapPromise::WillSwap() will be called before the swap and 26 // SwapPromise::DidSwap() will be called once the swap is over. 27 // 28 // If the scheduler fails to activate the pending tree, or the compositor 29 // fails to send its new state to the output, SwapPromise::DidNotSwap() will 30 // be called. Note that it is possible to activate, and subsequently not swap. 31 // 32 // Promises complete afer either DidSwap() or DidNotSwap() is called, thus 33 // there are three possible call sequences: 34 // DidNotSwap() 35 // DidActivate() ; WillSwap(); DidSwap() 36 // DidActivate() ; DidNotSwap() 37 // 38 // Clients that wish to use SwapPromise should have a subclass that defines 39 // the behavior of DidActivate(), WillSwap(), DidSwap() and DidNotSwap(). Notice 40 // that the promise can be broken at either main or impl thread, e.g. commit 41 // fails on main thread, new frame data has no actual damage so 42 // LayerTreeHostImpl::SwapBuffers() bails out early on impl thread, so don't 43 // assume that DidNotSwap() method is called at a particular thread. It is 44 // better to let the subclass carry thread-safe member data and operate on that 45 // member data in DidNotSwap(). 46 class CC_EXPORT SwapPromise { 47 public: 48 enum DidNotSwapReason { 49 SWAP_FAILS, 50 COMMIT_FAILS, 51 COMMIT_NO_UPDATE, 52 ACTIVATION_FAILS, 53 }; 54 55 enum class DidNotSwapAction { 56 BREAK_PROMISE, 57 KEEP_ACTIVE, 58 }; 59 SwapPromise()60 SwapPromise() {} ~SwapPromise()61 virtual ~SwapPromise() {} 62 63 virtual void DidActivate() = 0; 64 virtual void WillSwap(viz::CompositorFrameMetadata* metadata) = 0; 65 virtual void DidSwap() = 0; 66 // Return |KEEP_ACTIVE| if this promise should remain active (should not be 67 // broken by the owner). 68 virtual DidNotSwapAction DidNotSwap(DidNotSwapReason reason) = 0; 69 // This is called when the main thread starts a (blocking) commit OnCommit()70 virtual void OnCommit() {} 71 72 // A non-zero trace id identifies a trace flow object that is embedded in the 73 // swap promise. This can be used for registering additional flow steps to 74 // visualize the object's path through the system. 75 virtual int64_t TraceId() const = 0; 76 }; 77 78 } // namespace cc 79 80 #endif // CC_TREES_SWAP_PROMISE_H_ 81