/****************************************************************************
**
** Copyright (C) 2004-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the documentation of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** In addition, as a special exception, Trolltech gives you certain
** additional rights. These rights are described in the Trolltech GPL
** Exception version 1.0, which can be found at
** http://www.trolltech.com/products/qt/gplexception/ and in the file
** GPL_EXCEPTION.txt in this package.
**
** In addition, as a special exception, Trolltech, as the sole copyright
** holder for Qt Designer, grants users of the Qt/Eclipse Integration
** plug-in the right for the Qt/Eclipse Integration to link to
** functionality provided by Qt Designer and its related libraries.
**
** Trolltech reserves all rights not expressly granted herein.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

/*!
    \page qt4-threads.html
    \title Thread Support in Qt 4

    \contentspage {What's New in Qt 4}{Home}
    \previouspage The Qt 4 Style API

    Qt 4 makes it easier than ever to write multithreaded
    applications. More classes have been made usable from non-GUI
    threads, and the signals and slots mechanism can now be used to
    communicate between threads.

    \section1 General Overview

    QThread now inherits QObject. It emits signals to indicate that
    the thread started or finished executing, and provides a few
    slots as well.

    Each thread can now have its own event loop. The initial thread
    starts its event loops using QCoreApplication::exec(); other
    threads can start an event loop using QThread::exec(). Like
    QCoreApplication, QThread also provides an
    \l{QThread::exit()}{exit(int)} function and a
    \l{QThread::quit()}{quit()} slot.

    An event loop in a thread makes it possible for the thread to use
    certain non-GUI Qt classes that require the presence of an event
    loop (such as QTimer, QTcpSocket, and QProcess). It also makes it
    possible to connect signals from any threads to slots of a
    specific thread. When a signal is emitted, the slot isn't called
    immediately; instead, it is invoked when control returns to the
    event loop of the thread to which the object belongs. The slot is
    executed in the thread where the receiver object lives. See
    QObject::connect() for details.

    Qt 4 also introduces a new synchronization class: QReadWriteLock.
    It is similar to QMutex, except that it distinguishes between
    "read" and "write" access to shared data and allows multiple
    readers to access the data simultaneously. Using QReadWriteLock
    instead of QMutex when it is possible can make multithreaded
    programs more concurrent.

    Since Qt 4, \l{implicitly shared} classes can safely be copied
    across threads, like any other value classes. They are fully
    reentrant. This is implemented using atomic reference counting
    operations, which are implemented in assembly language for the
    different platforms supported by Qt. Atomic reference counting is
    very fast, much faster than using a mutex.

    See \l{Thread Support in Qt} for more information.

    \section1 Comparison with Qt 3

    Earlier versions of Qt offered an option to build the library
    without thread support. In Qt 4, threads are always enabled.

    Qt 3 had a class called \c QDeepCopy that you could use to take a
    deep copy of an implicitly shared object. In Qt 4, the atomic
    reference counting makes this class superfluous.
*/
