ui/events/platform/platform_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_PLATFORM_EVENT_DISPATCHER_H_
   6 #define UI_EVENTS_PLATFORM_PLATFORM_EVENT_DISPATCHER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "ui/events/events_export.h"
  10 #include "ui/events/platform/platform_event_types.h"
  11
  12 namespace ui {
  13
  14 // See documentation for |PlatformEventDispatcher::DispatchEvent()| for
  15 // explanation of the meaning of the flags.
  16 enum PostDispatchAction {
  17   POST_DISPATCH_NONE = 0x0,
  18   POST_DISPATCH_QUIT_LOOP = 0x1,
  19   POST_DISPATCH_PERFORM_DEFAULT = 0x2,
  20   POST_DISPATCH_STOP_PROPAGATION = 0x4,
  21 };
  22
  23 // PlatformEventDispatcher receives events from a PlatformEventSource and
  24 // dispatches them.
  25 class EVENTS_EXPORT PlatformEventDispatcher {
  26  public:
  27   // Returns whether this dispatcher wants to dispatch |event|.
  28   virtual bool CanDispatchEvent(const PlatformEvent& event) = 0;
  29
  30   // Dispatches |event|. If this is not the default dispatcher, then the
  31   // dispatcher can request that the default dispatcher gets a chance to
  32   // dispatch the event by setting POST_DISPATCH_PERFORM_DEFAULT to the return
  33   // value. If a nested message-loop is active, then the dispatcher can signal
  34   // that the nested message-loop should be terminated by setting
  35   // POST_DISPATCH_QUIT_LOOP flag on the return value. If the dispatcher has
  36   // processed the event, and no other dispatcher should be allowed to dispatch
  37   // the event, then the dispatcher should set POST_DISPATCH_STOP_PROPAGATION
  38   // flag on the return value.
  39   virtual uint32_t DispatchEvent(const PlatformEvent& event) = 0;
  40
  41  protected:
  42   virtual ~PlatformEventDispatcher() {}
  43 };
  44
  45 }  // namespace ui
  46
  47 #endif  // UI_EVENTS_PLATFORM_PLATFORM_EVENT_DISPATCHER_H_