// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \page concurrent-changes-qt6.html
    \title Changes to Qt Concurrent
    \ingroup changes-qt-5-to-6
    \brief Improved to work with a variable number of arguments.

    Qt 6 is a result of the conscious effort to make the framework more
    efficient and easy to use.

    We try to maintain binary and source compatibility for all the public
    APIs in each release. But some changes were inevitable in an effort to
    make Qt a better framework.

    In this topic we summarize those changes in Qt Concurrent, and provide
    guidance to handle them.

    \section1 QtConcurrent::run()

    QtConcurrent::run() has been improved to work with a variable number
    of arguments, so the signatures are changed to:

    \code
    // run
    template <typename T>
    QFuture<T> run(Function &&f, Args &&...args)

    // run with a QThreadPool argument
    template <typename T>
    QFuture<T> run(QThreadPool *pool, Function &&f, Args &&...args)
    \endcode

    As a side effect, if \c f is a pointer to a member function, the first
    argument of \c args should be the object for which that member is defined
    (or a reference, or a pointer to it). So instead of writing:

    \code
    QImage image = ...;
    QFuture<void> future = QtConcurrent::run(&image, &QImage::invertPixels, QImage::InvertRgba);
    \endcode

    You have to write:

    \code
    QFuture<void> future = QtConcurrent::run(&QImage::invertPixels, &image, QImage::InvertRgba);
    \endcode

    Another side effect is that \c QtConcurrent::run() will not work with
    overloaded functions anymore. For example, the code below won't compile:

    \include qtconcurrentrun.cpp run-with-overload-calls

    Other methods of QtConcurrent have no behavioral changes and do not introduce
    source compatibility breaks.
*/