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. 4 5 #ifndef UI_EVENTS_EVENT_TARGET_H_ 6 #define UI_EVENTS_EVENT_TARGET_H_ 7 8 #include <vector> 9 10 #include "base/basictypes.h" 11 #include "base/compiler_specific.h" 12 #include "base/memory/scoped_ptr.h" 13 #include "ui/events/event_handler.h" 14 #include "ui/events/events_export.h" 15 16 namespace ui { 17 18 class EventDispatcher; 19 class EventTargeter; 20 class EventTargetIterator; 21 class LocatedEvent; 22 23 class EVENTS_EXPORT EventTarget : public EventHandler { 24 public: 25 class DispatcherApi { 26 public: DispatcherApi(EventTarget * target)27 explicit DispatcherApi(EventTarget* target) : target_(target) {} 28 pre_target_list()29 const EventHandlerList& pre_target_list() const { 30 return target_->pre_target_list_; 31 } 32 33 private: 34 DispatcherApi(); 35 EventTarget* target_; 36 37 DISALLOW_COPY_AND_ASSIGN(DispatcherApi); 38 }; 39 40 EventTarget(); 41 virtual ~EventTarget(); 42 43 virtual bool CanAcceptEvent(const Event& event) = 0; 44 45 // Returns the parent EventTarget in the event-target tree. 46 virtual EventTarget* GetParentTarget() = 0; 47 48 // Returns an iterator an EventTargeter can use to iterate over the list of 49 // child EventTargets. 50 virtual scoped_ptr<EventTargetIterator> GetChildIterator() const = 0; 51 52 // Returns the EventTargeter that should be used to find the target for an 53 // event in the subtree rooted at this EventTarget. 54 virtual EventTargeter* GetEventTargeter() = 0; 55 56 // Updates the states in |event| (e.g. location) to be suitable for |target|, 57 // so that |event| can be dispatched to |target|. 58 virtual void ConvertEventToTarget(EventTarget* target, 59 LocatedEvent* event); 60 61 // Adds a handler to receive events before the target. The handler must be 62 // explicitly removed from the target before the handler is destroyed. The 63 // EventTarget does not take ownership of the handler. 64 void AddPreTargetHandler(EventHandler* handler); 65 66 // Same as AddPreTargetHandler except that the |handler| is added to the front 67 // of the list so it is the first one to receive events. 68 void PrependPreTargetHandler(EventHandler* handler); 69 void RemovePreTargetHandler(EventHandler* handler); 70 71 // Adds a handler to receive events after the target. The handler must be 72 // explicitly removed from the target before the handler is destroyed. The 73 // EventTarget does not take ownership of the handler. 74 void AddPostTargetHandler(EventHandler* handler); 75 void RemovePostTargetHandler(EventHandler* handler); 76 77 // Returns true if the event pre target list is empty. 78 bool IsPreTargetListEmpty() const; 79 80 protected: set_target_handler(EventHandler * handler)81 void set_target_handler(EventHandler* handler) { 82 target_handler_ = handler; 83 } 84 85 // Overridden from EventHandler: 86 virtual void OnEvent(Event* event) OVERRIDE; 87 virtual void OnKeyEvent(KeyEvent* event) OVERRIDE; 88 virtual void OnMouseEvent(MouseEvent* event) OVERRIDE; 89 virtual void OnScrollEvent(ScrollEvent* event) OVERRIDE; 90 virtual void OnTouchEvent(TouchEvent* event) OVERRIDE; 91 virtual void OnGestureEvent(GestureEvent* event) OVERRIDE; 92 93 private: 94 friend class EventDispatcher; 95 friend class EventTargetTestApi; 96 97 // Returns the list of handlers that should receive the event before the 98 // target. The handlers from the outermost target are first in the list, and 99 // the handlers on |this| are the last in the list. 100 void GetPreTargetHandlers(EventHandlerList* list); 101 102 // Returns the list of handlers that should receive the event after the 103 // target. The handlers from the outermost target are last in the list, and 104 // the handlers on |this| are the first in the list. 105 void GetPostTargetHandlers(EventHandlerList* list); 106 107 EventHandlerList pre_target_list_; 108 EventHandlerList post_target_list_; 109 EventHandler* target_handler_; 110 111 DISALLOW_COPY_AND_ASSIGN(EventTarget); 112 }; 113 114 } // namespace ui 115 116 #endif // UI_EVENTS_EVENT_TARGET_H_ 117