text: // Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2013
  // Google Inc. All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //    * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //    * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //    * Neither the name of Google Inc. nor the name Chromium Embedded
  // Framework nor the names of its contributors may be used to endorse
  // or promote products derived from this software without specific prior
  // written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #ifndef CEF_INCLUDE_BASE_CEF_CALLBACK_LIST_H_
  #define CEF_INCLUDE_BASE_CEF_CALLBACK_LIST_H_
  #pragma once
  
  #if defined(BASE_CALLBACK_LIST_H_)
  // Do nothing if the Chromium header has already been included.
  // This can happen in cases where Chromium code is used directly by the
  // client application. When using Chromium code directly always include
  // the Chromium header first to avoid type conflicts.
  #elif defined(USING_CHROMIUM_INCLUDES)
  // When building CEF include the Chromium header directly.
  #include "base/callback_list.h"
  #else  // !USING_CHROMIUM_INCLUDES
  // The following is substantially similar to the Chromium implementation.
  // If the Chromium implementation diverges the below implementation should be
  // updated to match.
  
  #include <list>
  
  #include "include/base/cef_basictypes.h"
  #include "include/base/cef_build.h"
  #include "include/base/cef_callback.h"
  #include "include/base/cef_logging.h"
  #include "include/base/cef_macros.h"
  #include "include/base/cef_scoped_ptr.h"
  #include "include/base/internal/cef_callback_internal.h"
  
  // OVERVIEW:
  //
  // A container for a list of callbacks.  Unlike a normal STL vector or list,
  // this container can be modified during iteration without invalidating the
  // iterator. It safely handles the case of a callback removing itself
  // or another callback from the list while callbacks are being run.
  //
  // TYPICAL USAGE:
  //
  // class MyWidget {
  //  public:
  //   ...
  //
  //   typedef base::Callback<void(const Foo&)> OnFooCallback;
  //
  //   scoped_ptr<base::CallbackList<void(const Foo&)>::Subscription>
  //   RegisterCallback(const OnFooCallback& cb) {
  //     return callback_list_.Add(cb);
  //   }
  //
  //  private:
  //   void NotifyFoo(const Foo& foo) {
  //      callback_list_.Notify(foo);
  //   }
  //
  //   base::CallbackList<void(const Foo&)> callback_list_;
  //
  //   DISALLOW_COPY_AND_ASSIGN(MyWidget);
  // };
  //
  //
  // class MyWidgetListener {
  //  public:
  //   MyWidgetListener::MyWidgetListener() {
  //     foo_subscription_ = MyWidget::GetCurrent()->RegisterCallback(
  //             base::Bind(&MyWidgetListener::OnFoo, this)));
  //   }
  //
  //   MyWidgetListener::~MyWidgetListener() {
  //      // Subscription gets deleted automatically and will deregister
  //      // the callback in the process.
  //   }
  //
  //  private:
  //   void OnFoo(const Foo& foo) {
  //     // Do something.
  //   }
  //
  //   scoped_ptr<base::CallbackList<void(const Foo&)>::Subscription>
  //       foo_subscription_;
  //
  //   DISALLOW_COPY_AND_ASSIGN(MyWidgetListener);
  // };
  
  namespace base {
  
  namespace cef_internal {
  
  template <typename CallbackType>
  class CallbackListBase {
   public:
    class Subscription {
     public:
      Subscription(CallbackListBase<CallbackType>* list,
                   typename std::list<CallbackType>::iterator iter)
          : list_(list), iter_(iter) {}
  
      ~Subscription() {
        if (list_->active_iterator_count_) {
          iter_->Reset();
        } else {
          list_->callbacks_.erase(iter_);
          if (!list_->removal_callback_.is_null())
            list_->removal_callback_.Run();
        }
      }
  
     private:
      CallbackListBase<CallbackType>* list_;
      typename std::list<CallbackType>::iterator iter_;
  
      DISALLOW_COPY_AND_ASSIGN(Subscription);
    };
  
    // Add a callback to the list. The callback will remain registered until the
    // returned Subscription is destroyed, which must occur before the
    // CallbackList is destroyed.
    scoped_ptr<Subscription> Add(const CallbackType& cb) WARN_UNUSED_RESULT {
      DCHECK(!cb.is_null());
      return scoped_ptr<Subscription>(
          new Subscription(this, callbacks_.insert(callbacks_.end(), cb)));
    }
  
    // Sets a callback which will be run when a subscription list is changed.
    void set_removal_callback(const Closure& callback) {
      removal_callback_ = callback;
    }
  
    // Returns true if there are no subscriptions. This is only valid to call when
    // not looping through the list.
    bool empty() {
      DCHECK_EQ(0, active_iterator_count_);
      return callbacks_.empty();
    }
  
   protected:
    // An iterator class that can be used to access the list of callbacks.
    class Iterator {
     public:
      explicit Iterator(CallbackListBase<CallbackType>* list)
          : list_(list), list_iter_(list_->callbacks_.begin()) {
        ++list_->active_iterator_count_;
      }
  
      Iterator(const Iterator& iter)
          : list_(iter.list_), list_iter_(iter.list_iter_) {
        ++list_->active_iterator_count_;
      }
  
      ~Iterator() {
        if (list_ && --list_->active_iterator_count_ == 0) {
          list_->Compact();
        }
      }
  
      CallbackType* GetNext() {
        while ((list_iter_ != list_->callbacks_.end()) && list_iter_->is_null())
          ++list_iter_;
  
        CallbackType* cb = NULL;
        if (list_iter_ != list_->callbacks_.end()) {
          cb = &(*list_iter_);
          ++list_iter_;
        }
        return cb;
      }
  
     private:
      CallbackListBase<CallbackType>* list_;
      typename std::list<CallbackType>::iterator list_iter_;
    };
  
    CallbackListBase() : active_iterator_count_(0) {}
  
    ~CallbackListBase() {
      DCHECK_EQ(0, active_iterator_count_);
      DCHECK_EQ(0U, callbacks_.size());
    }
  
    // Returns an instance of a CallbackListBase::Iterator which can be used
    // to run callbacks.
    Iterator GetIterator() { return Iterator(this); }
  
    // Compact the list: remove any entries which were NULLed out during
    // iteration.
    void Compact() {
      typename std::list<CallbackType>::iterator it = callbacks_.begin();
      bool updated = false;
      while (it != callbacks_.end()) {
        if ((*it).is_null()) {
          updated = true;
          it = callbacks_.erase(it);
        } else {
          ++it;
        }
  
        if (updated && !removal_callback_.is_null())
          removal_callback_.Run();
      }
    }
  
   private:
    std::list<CallbackType> callbacks_;
    int active_iterator_count_;
    Closure removal_callback_;
  
    DISALLOW_COPY_AND_ASSIGN(CallbackListBase);
  };
  
  }  // namespace cef_internal
  
  template <typename Sig>
  class CallbackList;
  
  template <>
  class CallbackList<void(void)>
      : public cef_internal::CallbackListBase<Callback<void(void)>> {
   public:
    typedef Callback<void(void)> CallbackType;
  
    CallbackList() {}
  
    void Notify() {
      cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run();
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1>
  class CallbackList<void(A1)>
      : public cef_internal::CallbackListBase<Callback<void(A1)>> {
   public:
    typedef Callback<void(A1)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1, typename A2>
  class CallbackList<void(A1, A2)>
      : public cef_internal::CallbackListBase<Callback<void(A1, A2)>> {
   public:
    typedef Callback<void(A1, A2)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1,
                typename cef_internal::CallbackParamTraits<A2>::ForwardType a2) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1, a2);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1, typename A2, typename A3>
  class CallbackList<void(A1, A2, A3)>
      : public cef_internal::CallbackListBase<Callback<void(A1, A2, A3)>> {
   public:
    typedef Callback<void(A1, A2, A3)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1,
                typename cef_internal::CallbackParamTraits<A2>::ForwardType a2,
                typename cef_internal::CallbackParamTraits<A3>::ForwardType a3) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1, a2, a3);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1, typename A2, typename A3, typename A4>
  class CallbackList<void(A1, A2, A3, A4)>
      : public cef_internal::CallbackListBase<Callback<void(A1, A2, A3, A4)>> {
   public:
    typedef Callback<void(A1, A2, A3, A4)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1,
                typename cef_internal::CallbackParamTraits<A2>::ForwardType a2,
                typename cef_internal::CallbackParamTraits<A3>::ForwardType a3,
                typename cef_internal::CallbackParamTraits<A4>::ForwardType a4) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1, a2, a3, a4);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1, typename A2, typename A3, typename A4, typename A5>
  class CallbackList<void(A1, A2, A3, A4, A5)>
      : public cef_internal::CallbackListBase<
            Callback<void(A1, A2, A3, A4, A5)>> {
   public:
    typedef Callback<void(A1, A2, A3, A4, A5)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1,
                typename cef_internal::CallbackParamTraits<A2>::ForwardType a2,
                typename cef_internal::CallbackParamTraits<A3>::ForwardType a3,
                typename cef_internal::CallbackParamTraits<A4>::ForwardType a4,
                typename cef_internal::CallbackParamTraits<A5>::ForwardType a5) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1, a2, a3, a4, a5);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1,
            typename A2,
            typename A3,
            typename A4,
            typename A5,
            typename A6>
  class CallbackList<void(A1, A2, A3, A4, A5, A6)>
      : public cef_internal::CallbackListBase<
            Callback<void(A1, A2, A3, A4, A5, A6)>> {
   public:
    typedef Callback<void(A1, A2, A3, A4, A5, A6)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1,
                typename cef_internal::CallbackParamTraits<A2>::ForwardType a2,
                typename cef_internal::CallbackParamTraits<A3>::ForwardType a3,
                typename cef_internal::CallbackParamTraits<A4>::ForwardType a4,
                typename cef_internal::CallbackParamTraits<A5>::ForwardType a5,
                typename cef_internal::CallbackParamTraits<A6>::ForwardType a6) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1, a2, a3, a4, a5, a6);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  template <typename A1,
            typename A2,
            typename A3,
            typename A4,
            typename A5,
            typename A6,
            typename A7>
  class CallbackList<void(A1, A2, A3, A4, A5, A6, A7)>
      : public cef_internal::CallbackListBase<
            Callback<void(A1, A2, A3, A4, A5, A6, A7)>> {
   public:
    typedef Callback<void(A1, A2, A3, A4, A5, A6, A7)> CallbackType;
  
    CallbackList() {}
  
    void Notify(typename cef_internal::CallbackParamTraits<A1>::ForwardType a1,
                typename cef_internal::CallbackParamTraits<A2>::ForwardType a2,
                typename cef_internal::CallbackParamTraits<A3>::ForwardType a3,
                typename cef_internal::CallbackParamTraits<A4>::ForwardType a4,
                typename cef_internal::CallbackParamTraits<A5>::ForwardType a5,
                typename cef_internal::CallbackParamTraits<A6>::ForwardType a6,
                typename cef_internal::CallbackParamTraits<A7>::ForwardType a7) {
      typename cef_internal::CallbackListBase<CallbackType>::Iterator it =
          this->GetIterator();
      CallbackType* cb;
      while ((cb = it.GetNext()) != NULL) {
        cb->Run(a1, a2, a3, a4, a5, a6, a7);
      }
    }
  
   private:
    DISALLOW_COPY_AND_ASSIGN(CallbackList);
  };
  
  }  // namespace base
  
  #endif  // !USING_CHROMIUM_INCLUDES
  
  #endif  // CEF_INCLUDE_BASE_CEF_CALLBACK_LIST_H_
  