ui/events/platform/platform_event_source.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_SOURCE_H_
   6 #define UI_EVENTS_PLATFORM_PLATFORM_EVENT_SOURCE_H_
   7
   8 #include <map>
   9 #include <vector>
  10
  11 #include "base/auto_reset.h"
  12 #include "base/macros.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/observer_list.h"
  15 #include "ui/events/events_export.h"
  16 #include "ui/events/platform/platform_event_types.h"
  17
  18 namespace ui {
  19
  20 class Event;
  21 class PlatformEventDispatcher;
  22 class PlatformEventObserver;
  23 class ScopedEventDispatcher;
  24
  25 // PlatformEventSource receives events from a source and dispatches the events
  26 // to the appropriate dispatchers.
  27 class EVENTS_EXPORT PlatformEventSource {
  28  public:
  29   virtual ~PlatformEventSource();
  30
  31   static PlatformEventSource* GetInstance();
  32
  33   // Adds a dispatcher to the dispatcher list. If a dispatcher is added during
  34   // dispatching an event, then the newly added dispatcher also receives that
  35   // event.
  36   void AddPlatformEventDispatcher(PlatformEventDispatcher* dispatcher);
  37
  38   // Removes a dispatcher from the dispatcher list. Dispatchers can safely be
  39   // removed from the dispatcher list during an event is being dispatched,
  40   // without affecting the dispatch of the event to other existing dispatchers.
  41   void RemovePlatformEventDispatcher(PlatformEventDispatcher* dispatcher);
  42
  43   // Installs a PlatformEventDispatcher that receives all the events. The
  44   // dispatcher can process the event, or request that the default dispatchers
  45   // be invoked by setting |POST_DISPATCH_PERFORM_DEFAULT| flag from the
  46   // |DispatchEvent()| override.
  47   // The returned |ScopedEventDispatcher| object is a handler for the overridden
  48   // dispatcher. When this handler is destroyed, it removes the overridden
  49   // dispatcher, and restores the previous override-dispatcher (or NULL if there
  50   // wasn't any).
  51   scoped_ptr<ScopedEventDispatcher> OverrideDispatcher(
  52       PlatformEventDispatcher* dispatcher);
  53
  54   // Called to indicate that the source should stop dispatching the current
  55   // stream of events and wait until the next iteration of the message-loop to
  56   // dispatch the rest of the events.
  57   virtual void StopCurrentEventStream();
  58
  59   void AddPlatformEventObserver(PlatformEventObserver* observer);
  60   void RemovePlatformEventObserver(PlatformEventObserver* observer);
  61
  62   static scoped_ptr<PlatformEventSource> CreateDefault();
  63
  64  protected:
  65   PlatformEventSource();
  66
  67   // Dispatches |platform_event| to the dispatchers. If there is an override
  68   // dispatcher installed using |OverrideDispatcher()|, then that dispatcher
  69   // receives the event first. |POST_DISPATCH_QUIT_LOOP| flag is set in the
  70   // returned value if the event-source should stop dispatching events at the
  71   // current message-loop iteration.
  72   virtual uint32_t DispatchEvent(PlatformEvent platform_event);
  73
  74  private:
  75   friend class ScopedEventDispatcher;
  76   static PlatformEventSource* instance_;
  77
  78   // This is invoked when the list of dispatchers changes (i.e. a new dispatcher
  79   // is added, or a dispatcher is removed).
  80   virtual void OnDispatcherListChanged();
  81
  82   void OnOverriddenDispatcherRestored();
  83
  84   // Use an ObserverList<> instead of an std::vector<> to store the list of
  85   // dispatchers, so that adding/removing dispatchers during an event dispatch
  86   // is well-defined.
  87   typedef ObserverList<PlatformEventDispatcher> PlatformEventDispatcherList;
  88   PlatformEventDispatcherList dispatchers_;
  89   PlatformEventDispatcher* overridden_dispatcher_;
  90
  91   // Used to keep track of whether the current override-dispatcher has been
  92   // reset and a previous override-dispatcher has been restored.
  93   bool overridden_dispatcher_restored_;
  94
  95   ObserverList<PlatformEventObserver> observers_;
  96
  97   DISALLOW_COPY_AND_ASSIGN(PlatformEventSource);
  98 };
  99
 100 }  // namespace ui
 101
 102 #endif  // UI_EVENTS_PLATFORM_PLATFORM_EVENT_SOURCE_H_