ui/events/platform/scoped_event_dispatcher.h

   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
  12 namespace ui {
  13
  14 class 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.
  23 class 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_