juce_ListenerList.h

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/*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
template <class ListenerClass,
          class ArrayType = Array<ListenerClass*>>
class ListenerList
{
public:
    //==============================================================================
    ListenerList() = default;

    ~ListenerList()
    {
        WrappedIterator::forEach (activeIterators, [&] (auto& iter)
        {
            iter.invalidate();
        });
    }
 
    //==============================================================================
    void add (ListenerClass* listenerToAdd)
    {
        if (listenerToAdd != nullptr)
            listeners.addIfNotAlreadyThere (listenerToAdd);
        else
            jassertfalse;  // Listeners can't be null pointers!
    }

    void remove (ListenerClass* listenerToRemove)
    {
        jassert (listenerToRemove != nullptr); // Listeners can't be null pointers!
 
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        const auto index = listeners.removeFirstMatchingValue (listenerToRemove);
 
        WrappedIterator::forEach (activeIterators, [&] (auto& iter)
        {
            if (0 <= index && index < iter.get().index)
                --iter.get().index;
        });
    }

    int size() const noexcept                                { return listeners.size(); }

    bool isEmpty() const noexcept                            { return listeners.isEmpty(); }

    void clear()                                             { listeners.clear(); }

    bool contains (ListenerClass* listener) const noexcept   { return listeners.contains (listener); }

    const ArrayType& getListeners() const noexcept           { return listeners; }
 
    //==============================================================================
    template <typename Callback>
    void call (Callback&& callback)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (WrappedIterator iter (*this, activeIterators); iter.get().next();)
            callback (*iter.get().getListener());
    }

    template <typename Callback>
    void callExcluding (ListenerClass* listenerToExclude, Callback&& callback)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (WrappedIterator iter (*this, activeIterators); iter.get().next();)
        {
            auto* l = iter.get().getListener();
 
            if (l != listenerToExclude)
                callback (*l);
        }
    }

    template <typename Callback, typename BailOutCheckerType>
    void callChecked (const BailOutCheckerType& bailOutChecker, Callback&& callback)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (WrappedIterator iter (*this, activeIterators); iter.get().next (bailOutChecker);)
        {
            callback (*iter.get().getListener());
        }
    }

    template <typename Callback, typename BailOutCheckerType>
    void callCheckedExcluding (ListenerClass* listenerToExclude,
                               const BailOutCheckerType& bailOutChecker,
                               Callback&& callback)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (WrappedIterator iter (*this, activeIterators); iter.get().next (bailOutChecker);)
        {
            auto* l = iter.get().getListener();
 
            if (l != listenerToExclude)
                callback (*l);
        }
    }
 
    //==============================================================================
    struct DummyBailOutChecker
    {
        bool shouldBailOut() const noexcept                 { return false; }
    };
 
    using ThisType      = ListenerList<ListenerClass, ArrayType>;
    using ListenerType  = ListenerClass;
 
    //==============================================================================
    struct Iterator
    {
        explicit Iterator (const ListenerList& listToIterate) noexcept
            : list (listToIterate), index (listToIterate.size())
        {}
 
        //==============================================================================
        bool next() noexcept
        {
            if (index <= 0)
                return false;
 
            auto listSize = list.size();
 
            if (--index < listSize)
                return true;
 
            index = listSize - 1;
            return index >= 0;
        }
 
        template <class BailOutCheckerType>
        bool next (const BailOutCheckerType& bailOutChecker) noexcept
        {
            return (! bailOutChecker.shouldBailOut()) && next();
        }
 
        ListenerClass* getListener() const noexcept
        {
            return list.getListeners().getUnchecked (index);
        }
 
    private:
        const ListenerList& list;
        int index;
 
        friend ListenerList;
 
        JUCE_DECLARE_NON_COPYABLE (Iterator)
    };
 
    //==============================================================================
   #ifndef DOXYGEN
    void call (void (ListenerClass::*callbackFunction) ())
    {
        call ([=] (ListenerClass& l) { (l.*callbackFunction)(); });
    }
 
    void callExcluding (ListenerClass* listenerToExclude, void (ListenerClass::*callbackFunction) ())
    {
        callExcluding (listenerToExclude, [=] (ListenerClass& l) { (l.*callbackFunction)(); });
    }
 
    template <class BailOutCheckerType>
    void callChecked (const BailOutCheckerType& bailOutChecker, void (ListenerClass::*callbackFunction) ())
    {
        callChecked (bailOutChecker, [=] (ListenerClass& l) { (l.*callbackFunction)(); });
    }
 
    template <class BailOutCheckerType>
    void callCheckedExcluding (ListenerClass* listenerToExclude,
                               const BailOutCheckerType& bailOutChecker,
                               void (ListenerClass::*callbackFunction) ())
    {
        callCheckedExcluding (listenerToExclude, bailOutChecker, [=] (ListenerClass& l) { (l.*callbackFunction)(); });
    }
 
    template <typename... MethodArgs, typename... Args>
    void call (void (ListenerClass::*callbackFunction) (MethodArgs...), Args&&... args)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (Iterator iter (*this); iter.next();)
            (iter.getListener()->*callbackFunction) (static_cast<typename TypeHelpers::ParameterType<Args>::type> (args)...);
    }
 
    template <typename... MethodArgs, typename... Args>
    void callExcluding (ListenerClass* listenerToExclude,
                        void (ListenerClass::*callbackFunction) (MethodArgs...),
                        Args&&... args)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (Iterator iter (*this); iter.next();)
            if (iter.getListener() != listenerToExclude)
                (iter.getListener()->*callbackFunction) (static_cast<typename TypeHelpers::ParameterType<Args>::type> (args)...);
    }
 
    template <typename BailOutCheckerType, typename... MethodArgs, typename... Args>
    void callChecked (const BailOutCheckerType& bailOutChecker,
                      void (ListenerClass::*callbackFunction) (MethodArgs...),
                      Args&&... args)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (Iterator iter (*this); iter.next (bailOutChecker);)
            (iter.getListener()->*callbackFunction) (static_cast<typename TypeHelpers::ParameterType<Args>::type> (args)...);
    }
 
    template <typename BailOutCheckerType, typename... MethodArgs, typename... Args>
    void callCheckedExcluding (ListenerClass* listenerToExclude,
                               const BailOutCheckerType& bailOutChecker,
                               void (ListenerClass::*callbackFunction) (MethodArgs...),
                               Args&&... args)
    {
        typename ArrayType::ScopedLockType lock (listeners.getLock());
 
        for (Iterator iter (*this); iter.next (bailOutChecker);)
            if (iter.getListener() != listenerToExclude)
                (iter.getListener()->*callbackFunction) (static_cast<typename TypeHelpers::ParameterType<Args>::type> (args)...);
    }
   #endif
 
private:
    class WrappedIterator
    {
    public:
        WrappedIterator (const ListenerList& listToIterate, WrappedIterator*& listHeadIn)
            : it (listToIterate), listHead (listHeadIn), next (listHead)
        {
            listHead = this;
        }
 
        ~WrappedIterator()
        {
            if (valid)
                listHead = next;
        }
 
        auto& get() noexcept { return it; }
 
        template <typename Callback>
        static void forEach (WrappedIterator* wrapped, Callback&& cb)
        {
            for (auto* p = wrapped; p != nullptr; p = p->next)
                cb (*p);
        }
 
        void invalidate() noexcept { valid = false; }
 
    private:
        Iterator it;
        WrappedIterator*& listHead;
        WrappedIterator* next = nullptr;
        bool valid = true;
    };
 
    //==============================================================================
    ArrayType listeners;
    WrappedIterator* activeIterators = nullptr;
 
    JUCE_DECLARE_NON_COPYABLE (ListenerList)
};
 
} // namespace juce