base/message_pump_observer.h

   1 // Copyright (c) 2012 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 BASE_MESSAGE_PUMP_OBSERVER_H
   6 #define BASE_MESSAGE_PUMP_OBSERVER_H
   7 #pragma once
   8
   9 #include "base/event_types.h"
  10
  11 namespace base {
  12
  13 enum EventStatus {
  14   EVENT_CONTINUE,    // The event should be dispatched as normal.
  15 #if defined(USE_X11)
  16   EVENT_HANDLED      // The event should not be processed any farther.
  17 #endif
  18 };
  19
  20 // A MessagePumpObserver is an object that receives global
  21 // notifications from the UI MessageLoop with MessagePumpWin or
  22 // MessagePumpAuraX11.
  23 //
  24 // NOTE: An Observer implementation should be extremely fast!
  25 //
  26 // For use with MessagePumpAuraX11, please see message_pump_glib.h for more
  27 // info about how this is invoked in this environment.
  28 class BASE_EXPORT MessagePumpObserver {
  29  public:
  30   // This method is called before processing a NativeEvent. If the
  31   // method returns EVENT_HANDLED, it indicates the event has already
  32   // been handled, so the event is not processed any farther. If the
  33   // method returns EVENT_CONTINUE, the event dispatching proceeds as
  34   // normal.
  35   virtual EventStatus WillProcessEvent(const NativeEvent& event) = 0;
  36
  37   // This method is called after processing a message. This method
  38   // will not be called if WillProcessEvent returns EVENT_HANDLED.
  39   virtual void DidProcessEvent(const NativeEvent& event) = 0;
  40
  41  protected:
  42   virtual ~MessagePumpObserver() {}
  43 };
  44
  45 }  // namespace base
  46
  47 #endif  // BASE_MESSAGE_PUMP_OBSERVER_VIEWS_H