PrismLauncher/launcher/MTPixmapCache.h

#pragma once

#include <QCoreApplication>
#include <QDebug>
#include <QPixmapCache>
#include <QThread>
#include <QTime>
#include <limits>

#define GET_TYPE()                                                          \
    Qt::ConnectionType type;                                                \
    if (QThread::currentThread() != QCoreApplication::instance()->thread()) \
        type = Qt::BlockingQueuedConnection;                                \
    else                                                                    \
        type = Qt::DirectConnection;

#define DEFINE_FUNC_NO_PARAM(NAME, RET_TYPE, RET_DEF)                                        \
    static RET_TYPE NAME()                                                                   \
    {                                                                                        \
        RET_TYPE ret = RET_DEF;                                                              \
        GET_TYPE()                                                                           \
        QMetaObject::invokeMethod(s_instance, "_" #NAME, type, Q_RETURN_ARG(RET_TYPE, ret)); \
        return ret;                                                                          \
    }
#define DEFINE_FUNC_ONE_PARAM(NAME, RET_TYPE, RET_DEF, PARAM_1_TYPE)                                                  \
    static RET_TYPE NAME(PARAM_1_TYPE p1)                                                                             \
    {                                                                                                                 \
        RET_TYPE ret = RET_DEF;                                                                                       \
        GET_TYPE()                                                                                                    \
        QMetaObject::invokeMethod(s_instance, "_" #NAME, type, Q_RETURN_ARG(RET_TYPE, ret), Q_ARG(PARAM_1_TYPE, p1)); \
        return ret;                                                                                                   \
    }
#define DEFINE_FUNC_TWO_PARAM(NAME, RET_TYPE, RET_DEF, PARAM_1_TYPE, PARAM_2_TYPE)                                   \
    static RET_TYPE NAME(PARAM_1_TYPE p1, PARAM_2_TYPE p2)                                                           \
    {                                                                                                                \
        RET_TYPE ret = RET_DEF;                                                                                      \
        GET_TYPE()                                                                                                   \
        QMetaObject::invokeMethod(s_instance, "_" #NAME, type, Q_RETURN_ARG(RET_TYPE, ret), Q_ARG(PARAM_1_TYPE, p1), \
                                  Q_ARG(PARAM_2_TYPE, p2));                                                          \
        return ret;                                                                                                  \
    }

/** A wrapper around QPixmapCache with thread affinity with the main thread.
 */
class PixmapCache final : public QObject {
    Q_OBJECT

   public:
    PixmapCache(QObject* parent) : QObject(parent) {}
    ~PixmapCache() override = default;

    static PixmapCache& instance() { return *s_instance; }
    static void setInstance(PixmapCache* i) { s_instance = i; }

   public:
    DEFINE_FUNC_NO_PARAM(cacheLimit, int, -1)
    DEFINE_FUNC_NO_PARAM(clear, bool, false)
    DEFINE_FUNC_TWO_PARAM(find, bool, false, const QString&, QPixmap*)
    DEFINE_FUNC_TWO_PARAM(find, bool, false, const QPixmapCache::Key&, QPixmap*)
    DEFINE_FUNC_TWO_PARAM(insert, bool, false, const QString&, const QPixmap&)
    DEFINE_FUNC_ONE_PARAM(insert, QPixmapCache::Key, {}, const QPixmap&)
    DEFINE_FUNC_ONE_PARAM(remove, bool, false, const QString&)
    DEFINE_FUNC_ONE_PARAM(remove, bool, false, const QPixmapCache::Key&)
    DEFINE_FUNC_TWO_PARAM(replace, bool, false, const QPixmapCache::Key&, const QPixmap&)
    DEFINE_FUNC_ONE_PARAM(setCacheLimit, bool, false, int)
    DEFINE_FUNC_NO_PARAM(markCacheMissByEviciton, bool, false)
    DEFINE_FUNC_ONE_PARAM(setFastEvictionThreshold, bool, false, int)

    // NOTE: Every function returns something non-void to simplify the macros.
   private slots:
    int _cacheLimit() { return QPixmapCache::cacheLimit(); }
    bool _clear()
    {
        QPixmapCache::clear();
        return true;
    }
    bool _find(const QString& key, QPixmap* pixmap) { return QPixmapCache::find(key, pixmap); }
    bool _find(const QPixmapCache::Key& key, QPixmap* pixmap) { return QPixmapCache::find(key, pixmap); }
    bool _insert(const QString& key, const QPixmap& pixmap) { return QPixmapCache::insert(key, pixmap); }
    QPixmapCache::Key _insert(const QPixmap& pixmap) { return QPixmapCache::insert(pixmap); }
    bool _remove(const QString& key)
    {
        QPixmapCache::remove(key);
        return true;
    }
    bool _remove(const QPixmapCache::Key& key)
    {
        QPixmapCache::remove(key);
        return true;
    }
    bool _replace(const QPixmapCache::Key& key, const QPixmap& pixmap) { return QPixmapCache::replace(key, pixmap); }
    bool _setCacheLimit(int n)
    {
        QPixmapCache::setCacheLimit(n);
        return true;
    }

    /**
     *  Mark that a cache miss occurred because of a eviction if too many of these occur too fast the cache size is increased
     * @return if the cache size was increased
     */
    bool _markCacheMissByEviciton()
    {
        static constexpr uint maxCache = static_cast<uint>(std::numeric_limits<int>::max()) / 4;
        static constexpr uint step = 10240;
        static constexpr int oneSecond = 1000;

        auto now = QTime::currentTime();
        if (!m_last_cache_miss_by_eviciton.isNull()) {
            auto diff = m_last_cache_miss_by_eviciton.msecsTo(now);
            if (diff < oneSecond) {  // less than a second ago
                ++m_consecutive_fast_evicitons;
            } else {
                m_consecutive_fast_evicitons = 0;
            }
        }
        m_last_cache_miss_by_eviciton = now;
        if (m_consecutive_fast_evicitons >= m_consecutive_fast_evicitons_threshold) {
            // increase the cache size
            uint newSize = _cacheLimit() + step;
            if (newSize >= maxCache) {  // increase it until you overflow :D
                newSize = maxCache;
                qDebug() << m_consecutive_fast_evicitons
                         << tr("pixmap cache misses by eviction happened too fast, doing nothing as the cache size reached it's limit");
            } else {
                qDebug() << m_consecutive_fast_evicitons
                         << tr("pixmap cache misses by eviction happened too fast, increasing cache size to") << static_cast<int>(newSize);
            }
            _setCacheLimit(static_cast<int>(newSize));
            m_consecutive_fast_evicitons = 0;
            return true;
        }
        return false;
    }

    bool _setFastEvictionThreshold(int threshold)
    {
        m_consecutive_fast_evicitons_threshold = threshold;
        return true;
    }

   private:
    static PixmapCache* s_instance;
    QTime m_last_cache_miss_by_eviciton;
    int m_consecutive_fast_evicitons = 0;
    int m_consecutive_fast_evicitons_threshold = 15;
};