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      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_TARGET_ITERATOR_H_
      6 #define UI_EVENTS_EVENT_TARGET_ITERATOR_H_
      7 
      8 #include <vector>
      9 
     10 namespace ui {
     11 
     12 class EventTarget;
     13 
     14 // An interface that allows iterating over a set of EventTargets.
     15 class EventTargetIterator {
     16  public:
     17   virtual ~EventTargetIterator() {}
     18   virtual EventTarget* GetNextTarget() = 0;
     19 };
     20 
     21 // Provides an EventTargetIterator implementation for iterating over a list of
     22 // EventTargets. The list is iterated in the reverse order, since typically the
     23 // EventTargets are maintained in increasing z-order in the lists.
     24 template<typename T>
     25 class EventTargetIteratorImpl : public EventTargetIterator {
     26  public:
     27   explicit EventTargetIteratorImpl(const std::vector<T*>& children)
     28       : begin_(children.rbegin()),
     29         end_(children.rend()) {
     30   }
     31   virtual ~EventTargetIteratorImpl() {}
     32 
     33   virtual EventTarget* GetNextTarget() OVERRIDE {
     34     if (begin_ == end_)
     35       return NULL;
     36     EventTarget* target = *(begin_);
     37     ++begin_;
     38     return target;
     39   }
     40 
     41  private:
     42   typename std::vector<T*>::const_reverse_iterator begin_;
     43   typename std::vector<T*>::const_reverse_iterator end_;
     44 };
     45 
     46 }  // namespace ui
     47 
     48 #endif  // UI_EVENTS_EVENT_TARGET_ITERATOR_H_
     49