ui/events/event_targeter.h

   1 // Copyright (c) 2013 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_EVENT_TARGETER_H_
   6 #define UI_EVENTS_EVENT_TARGETER_H_
   7
   8 #include "base/compiler_specific.h"
   9 #include "ui/events/event.h"
  10 #include "ui/events/events_export.h"
  11
  12 namespace ui {
  13
  14 class Event;
  15 class EventTarget;
  16 class LocatedEvent;
  17
  18 class EVENTS_EXPORT EventTargeter {
  19  public:
  20   virtual ~EventTargeter();
  21
  22   // Returns the target |event| should be dispatched to. If there is no such
  23   // target, this should return NULL.
  24   virtual EventTarget* FindTargetForEvent(EventTarget* root,
  25                                           Event* event);
  26
  27   // Same as FindTargetForEvent(), but used for positional events. The location
  28   // etc. of |event| are in |root|'s coordinate system. When finding the target
  29   // for the event, the targeter can mutate the |event| (e.g. chnage the
  30   // coordinate to be in the returned target's coordinate sustem) so that it can
  31   // be dispatched to the target without any farther modification.
  32   virtual EventTarget* FindTargetForLocatedEvent(EventTarget* root,
  33                                                  LocatedEvent* event);
  34
  35   // Returns true of |target| or one of its descendants can be a target of
  36   // |event|. Note that the location etc. of |event| is in |target|'s parent's
  37   // coordinate system.
  38   virtual bool SubtreeShouldBeExploredForEvent(EventTarget* target,
  39                                                const LocatedEvent& event);
  40 };
  41
  42 }  // namespace ui
  43
  44 #endif  // UI_EVENTS_EVENT_TARGETER_H_