base/message_loop/message_pump_dispatcher.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_LOOP_MESSAGE_PUMP_DISPATCHER_H_
   6 #define BASE_MESSAGE_LOOP_MESSAGE_PUMP_DISPATCHER_H_
   7
   8 #include <stdint.h>
   9
  10 #include "base/base_export.h"
  11 #include "base/event_types.h"
  12
  13 namespace base {
  14
  15 // Dispatcher is used during a nested invocation of Run to dispatch events when
  16 // |RunLoop(dispatcher).Run()| is used.  If |RunLoop().Run()| is invoked,
  17 // MessageLoop does not dispatch events (or invoke TranslateMessage), rather
  18 // every message is passed to Dispatcher's Dispatch method for dispatch. It is
  19 // up to the Dispatcher whether or not to dispatch the event.
  20 //
  21 // The nested loop is exited by either posting a quit, or setting the
  22 // POST_DISPATCH_QUIT_LOOP flag on the return value from Dispatch.
  23 class BASE_EXPORT MessagePumpDispatcher {
  24  public:
  25   enum PostDispatchAction {
  26     POST_DISPATCH_NONE = 0x0,
  27     POST_DISPATCH_QUIT_LOOP = 0x1,
  28     POST_DISPATCH_PERFORM_DEFAULT = 0x2,
  29   };
  30
  31   virtual ~MessagePumpDispatcher() {}
  32
  33   // Dispatches the event. The return value can have more than one
  34   // PostDispatchAction flags OR'ed together. If POST_DISPATCH_PERFORM_DEFAULT
  35   // is set in the returned value, then the message-pump performs the default
  36   // action. If POST_DISPATCH_QUIT_LOOP is set, in the return value, then the
  37   // nested loop exits immediately.
  38   virtual uint32_t Dispatch(const NativeEvent& event) = 0;
  39 };
  40
  41 }  // namespace base
  42
  43 #endif  // BASE_MESSAGE_LOOP_MESSAGE_PUMP_DISPATCHER_H_