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.
5 #ifndef UI_EVENTS_EVENT_DISPATCHER_H_
6 #define UI_EVENTS_EVENT_DISPATCHER_H_
8 #include "base/auto_reset.h"
9 #include "ui/events/event.h"
10 #include "ui/events/event_constants.h"
11 #include "ui/events/event_handler.h"
12 #include "ui/events/events_export.h"
16 class EventDispatcher;
20 struct EventDispatchDetails {
21 EventDispatchDetails()
22 : dispatcher_destroyed(false),
23 target_destroyed(false) {}
24 bool dispatcher_destroyed;
25 bool target_destroyed;
28 class EVENTS_EXPORT EventDispatcherDelegate {
30 EventDispatcherDelegate();
31 virtual ~EventDispatcherDelegate();
33 // Returns whether an event can still be dispatched to a target. (e.g. during
34 // event dispatch, one of the handlers may have destroyed the target, in which
35 // case the event can no longer be dispatched to the target).
36 virtual bool CanDispatchToTarget(EventTarget* target) = 0;
38 // Returns the event being dispatched (or NULL if no event is being
40 Event* current_event();
42 // Dispatches |event| to |target|. This calls |PreDispatchEvent()| before
43 // dispatching the event, and |PostDispatchEvent()| after the event has been
45 EventDispatchDetails DispatchEvent(EventTarget* target, Event* event)
49 // This is called once a target has been determined for an event, right before
50 // the event is dispatched to the target. This function may modify |event| to
51 // prepare it for dispatch (e.g. update event flags, location etc.).
52 virtual EventDispatchDetails PreDispatchEvent(
54 Event* event) WARN_UNUSED_RESULT;
56 // This is called right after the event dispatch is completed.
57 // |target| is NULL if the target was deleted during dispatch.
58 virtual EventDispatchDetails PostDispatchEvent(
60 const Event& event) WARN_UNUSED_RESULT;
63 // Dispatches the event to the target.
64 EventDispatchDetails DispatchEventToTarget(EventTarget* target,
65 Event* event) WARN_UNUSED_RESULT;
67 EventDispatcher* dispatcher_;
69 DISALLOW_COPY_AND_ASSIGN(EventDispatcherDelegate);
72 // Dispatches events to appropriate targets.
73 class EVENTS_EXPORT EventDispatcher {
75 explicit EventDispatcher(EventDispatcherDelegate* delegate);
76 virtual ~EventDispatcher();
78 void ProcessEvent(EventTarget* target, Event* event);
80 const Event* current_event() const { return current_event_; }
81 Event* current_event() { return current_event_; }
83 bool delegate_destroyed() const { return !delegate_; }
85 void OnHandlerDestroyed(EventHandler* handler);
86 void OnDispatcherDelegateDestroyed();
89 void DispatchEventToEventHandlers(EventHandlerList* list, Event* event);
91 // Dispatches an event, and makes sure it sets ER_CONSUMED on the
92 // event-handling result if the dispatcher itself has been destroyed during
93 // dispatching the event to the event handler.
94 void DispatchEvent(EventHandler* handler, Event* event);
96 EventDispatcherDelegate* delegate_;
98 Event* current_event_;
100 EventHandlerList handler_list_;
102 DISALLOW_COPY_AND_ASSIGN(EventDispatcher);
107 #endif // UI_EVENTS_EVENT_DISPATCHER_H_