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// 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.
*/
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