|Original author(s)||Haavard Nord and Eirik Chambe-Eng|
|Initial release||20 May 1995|
|Stable release||6.1 (6 May 2021 )|
|Operating system||Android, iOS, Linux (embedded, Wayland, X11), macOS, Microsoft Windows, WebAssembly, ...|
|Type||Widget toolkit and Application framework|
Qt (pronounced "cute") is a widget toolkit for creating graphical user interfaces as well as cross-platform applications that run on various software and hardware platforms such as Linux, Windows, macOS, Android or embedded systems with little or no change in the underlying codebase while still being a native application with native capabilities and speed.
Qt is currently being developed by The Qt Company, a publicly listed company, and the Qt Project under open-source governance, involving individual developers and organizations working to advance Qt.Qt is available under both commercial licenses and open-source GPL 2.0, GPL 3.0, and LGPL 3.0 licenses.
Qt is used for developing graphical user interfaces (GUIs) and multi-platform applications that run on all major desktop platforms and most mobile or embedded platforms. Most GUI programs created with Qt have a native-looking interface, in which case Qt is classified as a widget toolkit . Non-GUI programs can also be developed, such as command-line tools and consoles for servers. An example of such a non-GUI program using Qt is the Cutelyst web framework.
Other features include SQL database access, XML parsing, JSON parsing, thread management and network support.
The latest version is Qt 6.0, which was released on 8 December 2020.
The current long-term support (LTS) version is Qt 5.15 LTS. The Qt Company is moving Qt 5.15 To Its Commercial-Only LTS Phase starting on Jan 5th 2021.
Also Qt 5.12 is LTS versionActual Version is 5.12.10.
The initial release of Qt software was on 20 May 1995.
In 2017, the Qt Company estimated a community of about 1 million developers worldwidein over 70 industries.
Graphical user-interfaces and desktop environments that utilize Qt/QML as widget toolkit:
Many notable open-source or proprietary cross-platform software are using Qt or QML:
Qt is utilized by a wide range of companies and organizations such as
Qt is built on these key concepts:
Starting with Qt 4.0 the framework was split into individual modules.With Qt 5.0 the architecture was modularized even further. Qt is now split into essential and add-on modules.
|Qt Core||The only required Qt module, containing classes used by other modules, including the meta-object system, concurrency and threading, containers, event system, plugins and I/O facilities.|
|Qt GUI||The central GUI module. In Qt 5 this module now depends on OpenGL, but no longer contains any widget classes.|
|Qt Widgets||Contains classes for classic widget based GUI applications and the QSceneGraph classes. Was split off from QtGui in Qt 5.|
|Qt Quick||The module for GUI application written using QML2.|
|Qt Quick Controls||Widget like controls for Qt Quick intended mainly for desktop applications.|
|Qt Quick Layouts||Layouts for arranging items in Qt Quick.|
|Qt Network||Network abstraction layer. Complete with support for TCP, UDP, HTTP, TLS, SSL (in Qt 4) and SPDY (since Qt 5.3).|
|Qt Multimedia||Classes for audio, video, radio and camera functionality.|
|Qt Multimedia Widgets||The widgets from Qt Multimedia.|
|Qt SQL||Contains classes for database integration using SQL.|
|Qt WebEngine||A new set of Qt Widget and QML webview APIs based on Chromium.|
|Qt Test||Classes for unit testing Qt applications and libraries.|
|Active Qt||Classes for applications which use ActiveX.|
|Qt Bluetooth||Classes accessing Bluetooth hardware.|
|Qt D-Bus||Classes for IPC using the D-Bus protocol.|
|Qt NFC||Classes accessing NFC hardware. Only officially supported on BlackBerry hardware so far (or N9 in the MeeGo port).|
|Qt OpenGL||Legacy module containing the OpenGL classes from Qt 4. In Qt 5 the similar functionality in Qt GUI is recommended.|
|Qt Location||Classes for accessing GPS and other location services and for mapping and navigation. Split off from the Qt 4 Mobility module of Qt Location. Supported on Android, BlackBerry, iOS, Linux (using GeoClue), Windows and Sailfish OS.|
|Qt Sensors||Classes for accessing various mobile hardware sensors. Used to be part of Qt Mobile in Qt 4. Supported on Android, BlackBerry, iOS, WinRT, Mer and Linux.|
|Qt Serial Port||Classes for access to hardware and virtual serial ports. Supported on Windows, Linux and macOS.|
|Qt WebChannel||Provides access to Qt objects to HTML/Js over WebSockets.|
|Qt WebKit||Qt's WebKit implementation and API.|
|Qt WebKit Widgets||The widget API for Qt WebKit|
|Qt WebSockets||Provides a WebSocket implementation.|
|Qt XML||Legacy module containing classes for SAX and DOM style XML APIs. Replaced with QXmlStreamReader and QXmlStreamWriter classes in Qt Core.|
|Qt XML Patterns||Support for XPath, XQuery, XSLT and XML Schema validation.|
There are four editions of Qt available: Community, Indie Mobile, Professional and Enterprise.The Community version is under the open source licenses, while the Indie Mobile, Professional and Enterprise versions, which contain additional functionality and libraries, e.g. Enterprise Controls are commercially sold by The Qt Company.
Qt works on many different platforms; the following are officially supported:
|X11||Qt for X Window System (Linux); FreeBSD, NetBSD, OpenBSD, and DragonFly BSD have community support.|
|Wayland||Qt applications can switch between graphical backends like X and Wayland at load time with the -platform command line option. This allows a seamless transition of Qt applications from X11 to Wayland. SailfishOS uses Wayland only as it doesn't have X11.|
|Android||Qt for Android (formerly known as Necessitas).|
|Embedded Linux||Qt for embedded platforms: personal digital assistant, smartphone, etc. Exists as multiple platforms depending on display technology. DirectFB, LinuxFB and EGLFS (EGL Full Screen).|
|Windows||Qt for Microsoft Windows 7, 8 and 10|
|Windows RT||Support for WinRT-based Windows 10 Mobile apps and Windows 10 IoT|
|macOS||Qt for Apple macOS; supports applications on Cocoa|
|iOS||Qt for iOS platforms (iPhone, iPad)|
|Other embedded platforms|
|Integrity||Qt for Integrity|
|QNX||Qt for QNX|
|VxWorks||Qt for VxWorks. Only available under a proprietary (commercial) license. Qt 5.5.|
After Nokia opened the Qt source code to the community on Gitorious, various ports appeared. There are also some ports of Qt that may be available, but are not supported anymore. These platforms are listed in List of platforms supported by Qt. See also there for current community support for other lesser known platforms, such as SailfishOS.
Qt is available under the following free software licenses:GPL 2.0, GPL 3.0, LGPL 3.0 and LGPL 2.1 (with Qt special exception). Note that some modules are available only under a GPL license, which means that applications which link to these modules need to comply with that license.
In addition, Qt has always been available under a commercial license, like the Qt Commercial License,that allows developing proprietary applications with no restrictions on licensing.
Qt comes with its own set of tools to ease cross-platform development, which can otherwise be cumbersome due to different set of development tools.
Qt Creator is a cross-platform IDE for C++ and QML. Qt Designer's GUI layout/design functionality is integrated into the IDE, although Qt Designer can still be started as a standalone tool.
In addition to Qt Creator, Qt provides qmake, a cross-platform build script generation tool that automates the generation of Makefiles for development projects across different platforms. There are other tools available in Qt, including the Qt Designer interface builder and the Qt Assistant help browser (which are both embedded in Qt Creator), the Qt Linguist translation tool, uic (user interface compiler), and moc (Meta-Object Compiler).
In the summer of 1990, Haavard Nord and Eirik Chambe-Eng (the original developers of Qt and the CEO and President, respectively, of Trolltech) were working together on a database application for ultrasound images written in C++ and running on Mac OS, Unix, and Microsoft Windows.They began development of "Qt" in 1991, three years before the company was incorporated as Quasar Technologies, then changed the name to Troll Tech and then to Trolltech.
The toolkit was called Qt because the letter Q looked appealing in Haavard's Emacs typeface, and "t" was inspired by Xt, the X toolkit.
The first two versions of Qt had only two flavors: Qt/X11 for Unix and Qt/Windows for Windows.
On 20 May 1995 Troll Tech publicly released Qt 0.90 for X11/Linux with the source code under the Qt Free Edition License.This license was viewed as not compliant with the free software definition by Free Software Foundation because, while the source was available, it did not allow the redistribution of modified versions. Trolltech used this license until version 1.45. Controversy erupted around 1998 when it became clear that the K Desktop Environment was going to become one of the leading desktop environments for Linux. As it was based on Qt, many people in the free software movement worried that an essential piece of one of their major operating systems would be proprietary.
The Windows platform was available only under a proprietary license, which meant free/open source applications written in Qt for X11 could not be ported to Windows without purchasing the proprietary edition.
With the release of version 2.0 of the toolkit, the license was changed to the Q Public License (QPL), a free software license, but one regarded by the Free Software Foundation as incompatible with the GPL. Compromises were sought between KDE and Trolltech whereby Qt would not be able to fall under a more restrictive license than the QPL, even if Trolltech was bought out or went bankrupt. This led to the creation of the KDE Free Qt foundation,which guarantees that Qt would fall under a BSD-style license should no free/open source version of Qt be released during 12 months.
In 2000, Qt/X11 2.2 was released under the GPL v2,ending all controversy regarding GPL compatibility.
At the end of 2001, Trolltech released Qt 3.0, which added support for Mac OS X (now known as macOS). The Mac OS X support was available only in the proprietary license until June 2003, when Trolltech released Qt 3.2 with Mac OS X support available under the GPL.
In 2002, members of the KDE on Cygwin project began porting the GPL licensed Qt/X11 code base to Windows.This was in response to Trolltech's refusal to license Qt/Windows under the GPL on the grounds that Windows was not a free/open source software platform. The project achieved reasonable success although it never reached production quality.
This was resolved when Trolltech released Qt 4.0 also for Windows under the GPL in June 2005. 4 supported the same set of platforms in the free software/open source editions as in the proprietary edition, so it is possible, with Qt 4.0 and later releases, to create GPL-licensed free/open source applications using Qt on all supported platforms. The GPL v3 with special exception was later added as an added licensing option. The GPL exception allows the final application to be licensed under various GPL-incompatible free software/open source licenses such as the Mozilla Public License 1.1.Qt
Nokia acquired Trolltech ASA on 17 June 2008 and changed the name first to Qt Software, then to Qt Development Frameworks.
Nokia focused on turning Qt into the main development platform for its devices, including a port to the Symbian S60 platform. Version 1.0 of the Nokia Qt SDK was released on 23 June 2010.The source code was made available over Gitorious, a community oriented git source code repository, with a goal of creating a broader community using and improving Qt.
On 14 January 2009, Qt version 4.5 added another option, the LGPL,to make Qt more attractive for both non-GPL open source projects and closed applications.
In February 2011, Nokia announced its decision to drop Symbian technologies and base their future smartphones on the Windows Phone platform instead (and since then support for that platform has also been dropped).One month later, Nokia announced the sale of Qt's commercial licensing and professional services to Digia, with the immediate goal of taking Qt support to Android, iOS and Windows 8 platforms, and to continue focusing on desktop and embedded development, although Nokia was to remain the main development force behind the framework at that time.
In March 2011, Nokia sold the commercial licensing part of Qt to Digia, creating Qt Commercial.In August 2012, Digia announced that it would acquire Qt from Nokia. The Qt team at Digia started their work in September 2012. They released Qt 5.0 within a month and newer versions every six months with new features and additional supported platforms.
In September 2014, Digia transferred the Qt business and copyrights to their wholly owned subsidiary, The Qt Company, which owns 25 brandsrelated to Qt. In May 2016, Digia and Qt demerged completely into two independent companies.
Framework development of Qt 5 moved to open governance at qt-project.org, which made it possible for developers outside Digia to submit patches for review.
Aside from The Qt Company, many organizations and individuals using Qt as their development platform participate in the open development of Qt via the Qt Project.
One such Qt contributor is Klarälvdalens Datakonsult AB, a Swedish Qt consulting company.KDAB is involved in many areas, including maintenance of several components.
Together with RIM/BlackBerry, KDAB is maintaining the QNX and BlackBerry 10 ports of Qt.
Another participator is Intel, contributing for example Wayland support.AudioCodes maintains IBM ClearCase support in Qt Creator.
As a heavy user of Qt, the KDE project submits many patches and features from its developer library KDE Frameworks back to Qt.
Qt Wiki provides a comprehensive list of English books about Qt.This is a list of notable books:
The Qt Company is a software company based in Espoo, Finland. It oversees the development of its Qt application framework within the Qt Project. It was formed following the acquisition of Qt by Digia, but was later spun off into a separate, publicly traded company.
The Q Public License (QPL) is a non-copyleft license, created by Trolltech for its free edition of the Qt. It was used until Qt 3.0, as Trolltech toolkit version 4.0 was released under GPL version 2.
In computing, cross-platform software is computer software that is implemented on multiple computing platforms. Cross-platform software may be divided into two types; one requires individual building or compilation for each platform that it supports, and the other one can be directly run on any platform without special preparation, e.g., software written in an interpreted language or pre-compiled portable bytecode for which the interpreters or run-time packages are common or standard components of all platforms.
In computing, Motif refers to both a graphical user interface (GUI) specification and the widget toolkit for building applications that follow that specification under the X Window System on Unix and Unix-like operating systems.
wxWidgets is a widget toolkit and tools library for creating graphical user interfaces (GUIs) for cross-platform applications. wxWidgets enables a program's GUI code to compile and run on several computer platforms with minimal or no code changes. A wide choice of compilers and other tools to use with wxWidgets facilitates development of sophisticated applications. wxWidgets supports a comprehensive range of popular operating systems and graphical libraries, both proprietary and free, and is widely deployed in prominent organizations.
Fast Light Toolkit is a cross-platform widget library for graphical user interfaces (GUIs), developed by Bill Spitzak and others. Made to accommodate 3D graphics programming, it has an interface to OpenGL, but it is also suitable for general GUI programming.
PyQt is a Python binding of the cross-platform GUI toolkit Qt, implemented as a Python plug-in. PyQt is free software developed by the British firm Riverbank Computing. It is available under similar terms to Qt versions older than 4.5; this means a variety of licenses including GNU General Public License (GPL) and commercial license, but not the GNU Lesser General Public License (LGPL). PyQt supports Microsoft Windows as well as various flavours of UNIX, including Linux and MacOS.
The FOX toolkit is an open-source, cross-platform widget toolkit, i.e. a library of basic elements for building a graphical user interface (GUI). FOX stands for Free Objects for X.
KDE Software Compilation 4 was the only series of the so-called KDE Software Compilation, first released in January 2008 and the last release being 4.14.3 released in November 2014. It was the follow-up to K Desktop Environment 3. Following KDE SC 4, the compilation was broken up into basic framework libraries, desktop environment and applications, which are termed KDE Frameworks 5, KDE Plasma 5 and KDE Applications, respectively.
Maemo is a software platform originally developed by Nokia, now developed by the community, for smartphones and Internet tablets. The platform comprises both the Maemo operating system and SDK. Maemo played a key role in Nokia's strategy to compete with Apple and Android, and that strategy failed due to over-funding.
fpGUI, the Free Pascal GUI toolkit, is a cross-platform graphical user interface toolkit developed by Graeme Geldenhuys. fpGUI is open source and free software, licensed under a Modified LGPL license. The toolkit has been implemented using the Free Pascal compiler, meaning it is written in the Object Pascal language.
A software widget is a relatively simple and easy-to-use software application or component made for one or more different software platforms.
Ultimate++, also known as U++ and Upp - is a C++ rapid application development framework which aims to reduce the code complexity of typical desktop applications by extensively exploiting C++ features. Programs created with it can work on multiple operating systems and hardware architectures without the need to write platform specific code.
PySide is a Python binding of the cross-platform GUI toolkit Qt developed by The Qt Company, as part of the Qt for Python project. It is one of the alternatives to the standard library package Tkinter. Like Qt, PySide is free software. PySide supports Linux/X11, macOS, and Microsoft Windows.
The KDE Software Compilation was an umbrella term for the desktop environment plus a range of included applications produced by KDE. From its 1.0 release in July 1998 until the release of version 4.4 in February 2010, the Software Compilation was simply known as KDE, which stood for K Desktop Environment until the rebrand. The then called KDE SC was used from 4.4 onward until the final release 4.14 in July 2014. It consisted of the KDE Plasma 4 desktop and those KDE applications, whose development teams chose to follow the Software Compilation's release schedule. After that, the KDE SC was split into three separate product entities: KDE Plasma, KDE Frameworks and KDE Applications, each with their own independent release schedules.
mpv is free and open-source media player software based on MPlayer, mplayer2 and FFmpeg. It runs on several operating systems, including the Unix-like operating systems and the non-Unix Microsoft Windows, along with having an Android port called mpv-android. It is cross-platform, running on ARM, PowerPC, x86/IA-32, x86-64, and MIPS architecture.
The Qt Project is an open collaboration effort to coordinate the development of the Qt software framework. Initially founded by Nokia in 2011, the project is now led by The Qt Company.
KDE Projects are projects maintained by the KDE community, a group of people developing and advocating free software for everyday use, for example KDE Plasma and KDE Frameworks or applications such as Amarok, Krita or Digikam. There are also non-coding projects like designing the Breeze desktop theme and iconset, which is coordinated by KDE's VisualDesignGroup. Even non-Qt applications like GCompris, which started as a GTK-based application, or web-based projects like WikiToLearn are officially part of KDE.
The Deepin desktop environment has been refactored in the latest Qt GUI toolkit, replacing the HTML5 and WebKit frameworks, while Go is still used for the backend.
3ds Max 2018 now uses Qt 5.6.2, and plug-ins can build UIs in Qt using the standard GPL Qt 5.6.2 distribution, and the Visual Studio 2015 Qt add-on
the whole QGIS code depends on Qt libraries
Qt uses the native graphics APIs of each platform it supports, taking full advantage of system resources and ensuring that applications have native look and feel.
|Wikimedia Commons has media related to Qt .|
|Wikibooks has a book on the topic of: Qt|