event_processor.h revision a1401311d1ab56c4ed0a474bd38c108f75cb0cd9
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 11namespace ui { 12 13// EventProcessor receives an event from an EventSource and dispatches it to a 14// tree of EventTargets. 15class 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_ 41