1// Copyright 2014 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 UI_EVENTS_PLATFORM_SCOPED_EVENT_DISPATCHER_H_
6#define UI_EVENTS_PLATFORM_SCOPED_EVENT_DISPATCHER_H_
7
8#include "base/auto_reset.h"
9#include "base/basictypes.h"
10#include "ui/events/events_export.h"
11
12namespace ui {
13
14class PlatformEventDispatcher;
15
16// A temporary PlatformEventDispatcher can be installed on a
17// PlatformEventSource that overrides all installed event dispatchers, and
18// always gets a chance to dispatch the event first. The PlatformEventSource
19// returns a ScopedEventDispatcher object in such cases. This
20// ScopedEventDispatcher object can be used to dispatch the event to any
21// previous overridden dispatcher. When this object is destroyed, it removes the
22// override-dispatcher, and restores the previous override-dispatcher.
23class EVENTS_EXPORT ScopedEventDispatcher {
24 public:
25  ScopedEventDispatcher(PlatformEventDispatcher** scoped_dispatcher,
26                        PlatformEventDispatcher* new_dispatcher);
27  ~ScopedEventDispatcher();
28
29  operator PlatformEventDispatcher*() const { return original_; }
30
31 private:
32  PlatformEventDispatcher* original_;
33  base::AutoReset<PlatformEventDispatcher*> restore_;
34
35  DISALLOW_COPY_AND_ASSIGN(ScopedEventDispatcher);
36};
37
38}  // namespace ui
39
40#endif  // UI_EVENTS_PLATFORM_SCOPED_EVENT_DISPATCHER_H_
41