/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
\page topics-core.html
\title Core Internals
\brief Qt's core topics

Qt contains a rich set of fundamental enablers, mainly from the \l{Qt Core}
module. Qt uses these enablers to provide higher-level UI and application
development components. The following topics explain the most important enablers
and show how to use them to implement specialized functionality not already
provided by Qt.

\section1 Objects, Properties, and Events

The QObject class forms the foundation of Qt's object model and is the
parent class of many Qt classes. The object model introduces many mechanisms
such as a meta-object system which allows run-time introspection, manipulation,
and invocation of properties and methods in the object. It also serves as the
basis for Qt's event system, which is a low-level way of communicating between
QObject-based objects. Another high-level form of communication is provided in
Qt's signals and slots mechanism.

These features can also be used in combination
with the State Machine Framework which provides a formally defined and
predictable way of managing the states of your application.
An alternative way of implementing state machines is using the
\l{Qt SCXML Overview}{Qt SCXML} add-on module to create them from State Chart
XML (SCXML) files.

In addition, QObject
provides a simple timing mechanism with \l QObject::startTimer(). Alternatively,
the QTimer class provides a high-level interface for timers.

\list
\li \l{Object Model}
\li \l{The Meta-Object System}
\li \l{The Property System}
\li \l{The Event System}
\li \l{Signals & Slots}
    \list
    \li \l{Differences between String-Based and Functor-Based Connections}
    \endlist
\li \l{The State Machine Framework}
\li \l{Timers}
\endlist

\section1 Container Classes

A \e container is a data structure whose instances are collections of other
objects. Some examples of containers are: dynamic arrays, queues, linked
lists, and associative arrays. Qt provides a set of general purpose,
template-based container classes for structuring data in memory.

See the full list of \l [QtCore]{The Container Classes}{Container Classes} for
more details.

\section1 Internationalization

Qt uses Unicode for the encoding of displayable text strings. Unicode provides
support for all commonly used writing systems in the world and is ideal for
cross-platform development. Applications can also be written to support any
number of different languages with one code base using Qt's powerful
internationalization system.

\list
\li \l{Unicode in Qt}
\li \l{Internationalization with Qt}
\endlist

\section1 Inter-Process Communication

Qt provides several classes to support communication between processes. You can
also launch and manage external processes using the QProcess class.

\list
\li \l{Inter-Process Communication in Qt}
\endlist

\section1 Threading

Qt provides functionality to manage threads and parallelized code in a safe and
platform-independent way.

\list
\li \l{Threading Basics}
\li \l{Thread Support in Qt}
\endlist

\section1 Platform Support

Qt allows you to write platform-independent code, where the same code base can
be compiled for and deployed on different platforms without any changes. In
cases where you need to use platform-specific features and integrate with system
libraries, Qt also provides solutions for this.

Qt integrates with the windowing system on the target platform using Qt
Platform Abstraction (QPA). QPA is an abstraction of a windowing system which
makes porting Qt to new platforms simple and quick. One such system is the
Wayland protocol. Qt can be used together with Wayland as a light-weight
windowing system on embedded hardware to support a multi-process graphical user
interface.

The Qt Platform Abstraction uses Qt's plugin system. This plugin system provides
APIs to extend Qt in specific areas (such as adding support for new image
formats, database drivers, and so on) and also for writing your own extensible
Qt applications which support third-party plugins.

\list
\li \l{Qt Platform Abstraction}
\li \l{Implementing Atomic Operations} - for new architectures
\li \l{How to Create Qt Plugins}
\li \l{Endian Conversion Functions} - functions for handling endianness from the QtEndian header
\endlist
*/