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 namespace test {
  26 class PlatformEventSourceTestAPI;
  27 }
  28
  29 // PlatformEventSource receives events from a source and dispatches the events
  30 // to the appropriate dispatchers.
  31 class EVENTS_EXPORT PlatformEventSource {
  32  public:
  33   virtual ~PlatformEventSource();
  34
  35   static PlatformEventSource* GetInstance();
  36
  37   // Adds a dispatcher to the dispatcher list. If a dispatcher is added during
  38   // dispatching an event, then the newly added dispatcher also receives that
  39   // event.
  40   void AddPlatformEventDispatcher(PlatformEventDispatcher* dispatcher);
  41
  42   // Removes a dispatcher from the dispatcher list. Dispatchers can safely be
  43   // removed from the dispatcher list during an event is being dispatched,
  44   // without affecting the dispatch of the event to other existing dispatchers.
  45   void RemovePlatformEventDispatcher(PlatformEventDispatcher* dispatcher);
  46
  47   // Installs a PlatformEventDispatcher that receives all the events. The
  48   // dispatcher can process the event, or request that the default dispatchers
  49   // be invoked by setting |POST_DISPATCH_PERFORM_DEFAULT| flag from the
  50   // |DispatchEvent()| override.
  51   // The returned |ScopedEventDispatcher| object is a handler for the overridden
  52   // dispatcher. When this handler is destroyed, it removes the overridden
  53   // dispatcher, and restores the previous override-dispatcher (or NULL if there
  54   // wasn't any).
  55   scoped_ptr<ScopedEventDispatcher> OverrideDispatcher(
  56       PlatformEventDispatcher* dispatcher);
  57
  58   // Called to indicate that the source should stop dispatching the current
  59   // stream of events and wait until the next iteration of the message-loop to
  60   // dispatch the rest of the events.
  61   virtual void StopCurrentEventStream();
  62
  63   void AddPlatformEventObserver(PlatformEventObserver* observer);
  64   void RemovePlatformEventObserver(PlatformEventObserver* observer);
  65
  66   static scoped_ptr<PlatformEventSource> CreateDefault();
  67
  68  protected:
  69   PlatformEventSource();
  70
  71   // Dispatches |platform_event| to the dispatchers. If there is an override
  72   // dispatcher installed using |OverrideDispatcher()|, then that dispatcher
  73   // receives the event first. |POST_DISPATCH_QUIT_LOOP| flag is set in the
  74   // returned value if the event-source should stop dispatching events at the
  75   // current message-loop iteration.
  76   virtual uint32_t DispatchEvent(PlatformEvent platform_event);
  77
  78  private:
  79   friend class ScopedEventDispatcher;
  80   friend class test::PlatformEventSourceTestAPI;
  81
  82   static PlatformEventSource* instance_;
  83
  84   // This is invoked when the list of dispatchers changes (i.e. a new dispatcher
  85   // is added, or a dispatcher is removed).
  86   virtual void OnDispatcherListChanged();
  87
  88   void OnOverriddenDispatcherRestored();
  89
  90   // Use an base::ObserverList<> instead of an std::vector<> to store the list
  91   // of
  92   // dispatchers, so that adding/removing dispatchers during an event dispatch
  93   // is well-defined.
  94   typedef base::ObserverList<PlatformEventDispatcher>
  95       PlatformEventDispatcherList;
  96   PlatformEventDispatcherList dispatchers_;
  97   PlatformEventDispatcher* overridden_dispatcher_;
  98
  99   // Used to keep track of whether the current override-dispatcher has been
 100   // reset and a previous override-dispatcher has been restored.
 101   bool overridden_dispatcher_restored_;
 102
 103   base::ObserverList<PlatformEventObserver> observers_;
 104
 105   DISALLOW_COPY_AND_ASSIGN(PlatformEventSource);
 106 };
 107
 108 }  // namespace ui
 109
 110 #endif  // UI_EVENTS_PLATFORM_PLATFORM_EVENT_SOURCE_H_