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/events_export.h"
  10
  11 namespace ui {
  12
  13 class Event;
  14 class EventTarget;
  15
  16 class EVENTS_EXPORT EventTargeter {
  17  public:
  18   virtual ~EventTargeter() {}
  19
  20   // Returns the target |event| should be dispatched to. If there is no such
  21   // target, return NULL. If |event| is a located event, the location of |event|
  22   // is in the coordinate space of |root|. Furthermore, the targeter can mutate
  23   // the event (e.g., by changing the location of the event to be in the
  24   // returned target's coordinate space) so that it can be dispatched to the
  25   // target without any further modification.
  26   virtual EventTarget* FindTargetForEvent(EventTarget* root, Event* event) = 0;
  27
  28   // Returns the next best target for |event| as compared to |previous_target|.
  29   // |event| is in the local coordinate space of |previous_target|.
  30   // Also mutates |event| so that it can be dispatched to the returned target
  31   // (e.g., by changing |event|'s location to be in the returned target's
  32   // coordinate space).
  33   virtual EventTarget* FindNextBestTarget(EventTarget* previous_target,
  34                                           Event* event) = 0;
  35 };
  36
  37 }  // namespace ui
  38
  39 #endif  // UI_EVENTS_EVENT_TARGETER_H_