ui/events/event_target.h

   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:
  27     explicit DispatcherApi(EventTarget* target) : target_(target) {}
  28
  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   ~EventTarget() override;
  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   void set_target_handler(EventHandler* handler) {
  81     target_handler_ = handler;
  82   }
  83
  84  protected:
  85   EventHandler* target_handler() { return target_handler_; }
  86
  87   // Overridden from EventHandler:
  88   void OnEvent(Event* event) override;
  89   void OnKeyEvent(KeyEvent* event) override;
  90   void OnMouseEvent(MouseEvent* event) override;
  91   void OnScrollEvent(ScrollEvent* event) override;
  92   void OnTouchEvent(TouchEvent* event) override;
  93   void OnGestureEvent(GestureEvent* event) override;
  94
  95  private:
  96   friend class EventDispatcher;
  97   friend class EventTargetTestApi;
  98
  99   // Returns the list of handlers that should receive the event before the
 100   // target. The handlers from the outermost target are first in the list, and
 101   // the handlers on |this| are the last in the list.
 102   void GetPreTargetHandlers(EventHandlerList* list);
 103
 104   // Returns the list of handlers that should receive the event after the
 105   // target. The handlers from the outermost target are last in the list, and
 106   // the handlers on |this| are the first in the list.
 107   void GetPostTargetHandlers(EventHandlerList* list);
 108
 109   EventHandlerList pre_target_list_;
 110   EventHandlerList post_target_list_;
 111   EventHandler* target_handler_;
 112
 113   DISALLOW_COPY_AND_ASSIGN(EventTarget);
 114 };
 115
 116 }  // namespace ui
 117
 118 #endif  // UI_EVENTS_EVENT_TARGET_H_