The Qt toolkit (Qt for short) is a free cross platform graphical widget toolkit for the development of GUI programs, and is produced by the Norwegian company Trolltech (formerly Quasar Technologies, consequently Qt was formerly named Quasar Toolkit). Notably used in KDE, a desktop environment for UNIX and UNIX-like systems. It uses an extended version of the C++ programming language, but bindings for Python, C programming language and Perl exist. It runs on all major platforms, and has extensive internationalization support. Non GUI features include SQL database access, XML parsing, and an unified cross-platform API for file handling..
Four flavours of Qt now exist, supporting various platforms, but with varying licenses:
- Qt/X11 - Qt for Unix X Window System - GPL
- Qt/Mac - Qt for Apple Mac OS X - Formerly Proprietary only, now also under GPL
- Qt/Windows - Qt for Microsoft Windows - Proprietary (obsolete version free)
- Qt/Embedded (designed for PDAs and Embedded Linux) - GPL
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Current
Trolltech is currently developing QSA - Qt Script for Applications. QSA will let Qt developers make their applications scriptable. QSA is based on ECMAScript (aka JavaScript).
History
Development of the tool kit began in 1992, two years before the formation of Trolltech.
Controversy erupted around 1997 when it became clear that KDE was going to become one of the leading desktop environments for GNU/Linux. Based on the Qt Toolkit, which was then under the Q Public License (QPL), many people in the open source and free software movements were worried that an essential piece of one of their major operating systems would be under commercial control.
This gave rise to two efforts: the Harmony toolkit which sought to duplicate the Qt Toolkit under a free software license and the GNOME desktop that was meant to supplant KDE entirely. The GNOME Desktop used the Gtk+ toolkit which was written for the GIMP, and mainly uses the C programming language. Gtk+ endeavors to have the same cross-platform capabilities as Qt.
Compromises were sought between KDE and Trolltech wherein 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 did not satisfy all the critics, and finally, on September 4, 2000, Trolltech announced that the upcoming Qt 2.2 release will be licensed under the GPL. Qt 2.2 was released on September 6, 2000, KDE 2.0 followed on October 23, 2000.
Subsequent releases of Qt/X11 have also been released under the GPL.
