Original author(s)
Haavard Nord and Eirik Chambe-Eng[1]
- Trolltech (1991–2008)
- Nokia (2008–2011)
- Qt Project (2011–present)
- Digia (2012–2014)
- The Qt Company (2014–present)
20 May 1995[1]
/ 2 April 2024
Qt (software)
Qt (pronounced "cute"[7][8] or as an initialism) is cross-platform application development framework 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.
For the company formerly known as Qt Software, see The Qt Company.$_$_$DEEZ_NUTS#1__titleDEEZ_NUTS$_$_$
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Purposes and abilities[edit]
Qt is used for developing graphical user interfaces (GUIs) and multi-platform applications that run on all major desktop platforms and 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.[13]
Qt supports various C++ compilers, including the GCC and Clang C++ compilers and the Visual Studio suite. It supports other languages with bindings or extensions, such as Python via Python bindings[14] and PHP via an extension for PHP5,[15] and has extensive internationalization support. Qt also provides Qt Quick, that includes a declarative scripting language called QML that allows using JavaScript to provide the logic. With Qt Quick, rapid application development for mobile devices became possible, while logic can still be written with native code as well to achieve the best possible performance.
Other features include SQL database access, XML parsing, JSON parsing, thread management and network support.
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History of Qt[edit]
Early developments[edit]
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.[1][115] 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.[1]
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.[1]
The first two versions of Qt had only two flavors: Qt/X11 for Unix and Qt/Windows for Windows.
On 20 May 1995 Trolltech publicly released Qt 0.90 for X11/Linux with the source code under the Qt Free Edition License.[116][117][118] 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.
Becoming free software–friendly[edit]
With the release of version 2.0 of the toolkit in mid-1999, 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,[119] which guarantees that Qt would fall under a BSD-style license should no free/open source version of Qt be released during 12 months.[120][121]
In 2000, Qt/X11 2.2 was released under the GPL v2,[122] 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.[123] 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.[124][125] 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.[126] Qt 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[127] 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.
Acquisition by Nokia[edit]
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.[128] 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,[129] to make Qt more attractive for both non-GPL open source projects and closed applications.[130]
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).[131] 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.
Merging and demerging with Digia[edit]
In March 2011, Nokia sold the commercial licensing part of Qt to Digia, creating Qt Commercial.[132] In August 2012, Digia announced that it would acquire Qt from Nokia.[133] The Qt team at Digia started their work in September 2012.[134] 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 brands[135] related to Qt. In May 2016, Digia and Qt demerged completely into two independent companies.[136]
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