ui/events/event_target_iterator.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_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   ~EventTargetIteratorImpl() override {}
  32
  33   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_