juce_ListenerList.h

/*
  ==============================================================================
 
   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() { clear(); }
 
    //==============================================================================
    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!
 
        const ScopedLockType lock (listeners->getLock());
 
        if (const auto index = listeners->removeFirstMatchingValue (listenerToRemove); index >= 0)
        {
            for (auto* it : *iterators)
            {
                --it->end;
 
                if (index <= it->index)
                    --it->index;
            }
        }
    }

    ErasedScopeGuard addScoped (ListenerClass& listenerToAdd)
    {
        add (&listenerToAdd);
        return ErasedScopeGuard { [this, &listenerToAdd] { remove (&listenerToAdd); } };
    }

    int size() const noexcept                                { return listeners->size(); }

    bool isEmpty() const noexcept                            { return listeners->isEmpty(); }

    void clear()
    {
        const ScopedLockType lock (listeners->getLock());
 
        listeners->clear();
 
        for (auto* it : *iterators)
            it->end = 0;
    }

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

    const ArrayType& getListeners() const noexcept           { return *listeners; }
 
    //==============================================================================
    template <typename Callback>
    void call (Callback&& callback)
    {
        callCheckedExcluding (nullptr,
                              DummyBailOutChecker{},
                              std::forward<Callback> (callback));
    }

    template <typename Callback>
    void callExcluding (ListenerClass* listenerToExclude, Callback&& callback)
    {
        callCheckedExcluding (listenerToExclude,
                              DummyBailOutChecker{},
                              std::forward<Callback> (callback));
 
    }

    template <typename Callback, typename BailOutCheckerType>
    void callChecked (const BailOutCheckerType& bailOutChecker, Callback&& callback)
    {
        callCheckedExcluding (nullptr,
                              bailOutChecker,
                              std::forward<Callback> (callback));
    }

    template <typename Callback, typename BailOutCheckerType>
    void callCheckedExcluding (ListenerClass* listenerToExclude,
                               const BailOutCheckerType& bailOutChecker,
                               Callback&& callback)
    {
        const auto localListeners = listeners;
        const ScopedLockType lock { localListeners->getLock() };
 
        Iterator it{};
        it.end = localListeners->size();
 
        iterators->push_back (&it);
 
        const ScopeGuard scope { [i = iterators, &it]
        {
            i->erase (std::remove (i->begin(), i->end(), &it), i->end());
        } };
 
        for (; it.index < it.end; ++it.index)
        {
            if (bailOutChecker.shouldBailOut())
                return;
 
            auto* listener = localListeners->getUnchecked (it.index);
 
            if (listener == listenerToExclude)
                continue;
 
            callback (*listener);
        }
    }
 
    //==============================================================================
    template <typename... MethodArgs, typename... Args>
    void call (void (ListenerClass::*callbackFunction) (MethodArgs...), Args&&... args)
    {
        callCheckedExcluding (nullptr,
                              DummyBailOutChecker{},
                              callbackFunction,
                              std::forward<Args> (args)...);
    }

    template <typename... MethodArgs, typename... Args>
    void callExcluding (ListenerClass* listenerToExclude,
                        void (ListenerClass::*callbackFunction) (MethodArgs...),
                        Args&&... args)
    {
        callCheckedExcluding (listenerToExclude,
                              DummyBailOutChecker{},
                              callbackFunction,
                              std::forward<Args> (args)...);
    }

    template <typename BailOutCheckerType, typename... MethodArgs, typename... Args>
    void callChecked (const BailOutCheckerType& bailOutChecker,
                      void (ListenerClass::*callbackFunction) (MethodArgs...),
                      Args&&... args)
    {
        callCheckedExcluding (nullptr,
                              bailOutChecker,
                              callbackFunction,
                              std::forward<Args> (args)...);
    }

    template <typename BailOutCheckerType, typename... MethodArgs, typename... Args>
    void callCheckedExcluding (ListenerClass* listenerToExclude,
                               const BailOutCheckerType& bailOutChecker,
                               void (ListenerClass::*callbackFunction) (MethodArgs...),
                               Args&&... args)
    {
        callCheckedExcluding (listenerToExclude, bailOutChecker, [&] (ListenerClass& l)
        {
            (l.*callbackFunction) (args...);
        });
    }
 
    //==============================================================================
    struct DummyBailOutChecker
    {
        constexpr bool shouldBailOut() const noexcept { return false; }
    };
 
    //==============================================================================
    using ThisType      = ListenerList<ListenerClass, ArrayType>;
    using ListenerType  = ListenerClass;
 
private:
    //==============================================================================
    using ScopedLockType = typename ArrayType::ScopedLockType;
 
    //==============================================================================
    using SharedListeners = std::shared_ptr<ArrayType>;
    const SharedListeners listeners = std::make_shared<ArrayType>();
 
    struct Iterator
    {
        int index{};
        int end{};
    };
 
    using SafeIterators = std::vector<Iterator*>;
    using SharedIterators = std::shared_ptr<SafeIterators>;
    const SharedIterators iterators = std::make_shared<SafeIterators>();
 
    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE (ListenerList)
};
 
} // namespace juce