ui/events/event_processor.h

   1 // Copyright 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_PROCESSOR_H_
   6 #define UI_EVENTS_EVENT_PROCESSOR_H_
   7
   8 #include "ui/events/event_dispatcher.h"
   9 #include "ui/events/event_source.h"
  10
  11 namespace ui {
  12
  13 // EventProcessor receives an event from an EventSource and dispatches it to a
  14 // tree of EventTargets.
  15 class EVENTS_EXPORT EventProcessor : public EventDispatcherDelegate {
  16  public:
  17   virtual ~EventProcessor() {}
  18
  19   // Returns the root of the tree this event processor owns.
  20   virtual EventTarget* GetRootTarget() = 0;
  21
  22   // Dispatches an event received from the EventSource to the tree of
  23   // EventTargets (whose root is returned by GetRootTarget()).  The co-ordinate
  24   // space of the source must be the same as the root target, except that the
  25   // target may have a high-dpi scale applied.
  26   virtual EventDispatchDetails OnEventFromSource(Event* event)
  27       WARN_UNUSED_RESULT;
  28
  29  protected:
  30   // Prepares the event so that it can be dispatched. This is invoked before
  31   // an EventTargeter is used to find the target of the event. So this can be
  32   // used to update the event so that the targeter can operate correctly (e.g.
  33   // it can be used to updated the location of the event when disptaching from
  34   // an EventSource in high-DPI).
  35   virtual void PrepareEventForDispatch(Event* event);
  36 };
  37
  38 }  // namespace ui
  39
  40 #endif  // UI_EVENTS_EVENT_PROCESSOR_H_