// 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_TREES_SWAP_PROMISE_MONITOR_H_
#define CC_TREES_SWAP_PROMISE_MONITOR_H_

#include "cc/base/cc_export.h"

namespace cc {

class LayerTreeHost;
class LayerTreeHostImpl;

// A SwapPromiseMonitor is used to monitor compositor state change that
// should be associated with a SwapPromise, e.g. SetNeedsCommit() is
// called on main thread or SetNeedsRedraw() is called on impl thread.
// Creating a SwapPromiseMonitor will insert itself into a LayerTreeHost
// or LayerTreeHostImpl. You must provide a pointer to the appropriate
// structure to the monitor (and only one of the two). Notification of
// compositor state change will be sent through OnSetNeedsCommitOnMain()
// or OnSetNeedsRedrawOnImpl(). When SwapPromiseMonitor is destroyed, it
// will unregister itself from LayerTreeHost or LayerTreeHostImpl.
class CC_EXPORT SwapPromiseMonitor {
 public:
  // If the monitor lives on the main thread, pass in layer_tree_host
  // and set layer_tree_host_impl to nullptr.
  // If the monitor lives on the impl thread, pass in layer_tree_host_impl
  // and set layer_tree_host to nullptr.
  SwapPromiseMonitor(LayerTreeHost* layer_tree_host,
                     LayerTreeHostImpl* layer_tree_host_impl);
  virtual ~SwapPromiseMonitor();

  virtual void OnSetNeedsCommitOnMain() = 0;
  virtual void OnSetNeedsRedrawOnImpl() = 0;
  virtual void OnForwardScrollUpdateToMainThreadOnImpl() = 0;

 protected:
  LayerTreeHost* layer_tree_host_;
  LayerTreeHostImpl* layer_tree_host_impl_;
};

}  // namespace cc

#endif  // CC_TREES_SWAP_PROMISE_MONITOR_H_