Qt (toolkit)

Qt (toolkit)
Name	Qt
Developer	The Qt Company
Released	1995
Programming language	C++
Operating system	Cross-platform
Platform	x86, x86-64, ARM
Language	English
Genre	Widget toolkit, Application framework
License	GNU Lesser General Public License, commercial

Qt (toolkit) Qt is a cross-platform application framework and widget toolkit for developing graphical user interfaces and cross-platform applications. Qt is widely used in desktop, embedded, and mobile software, providing abstractions for windowing, event handling, graphics, networking, and internationalization. The framework underpins many prominent projects and commercial products across multiple industries.

Overview

Qt provides a comprehensive set of libraries and tools to build native-feeling applications on platforms such as Microsoft Windows, macOS, Linux, Android, and iOS. Qt includes GUI widgets, 2D and 3D graphics, multimedia, database access, and threading primitives. Qt integrates with development environments and build systems like CMake, GNU Compiler Collection, and Microsoft Visual Studio, and is supported by companies and organizations including Nokia, Digia, KDAB, and The Qt Company.

History and development

Qt began in 1991–1995 at the company Trolltech founded by Eirik Chambe-Eng, with early releases adopted by projects such as KDE and various commercial vendors. The licensing and stewardship of Qt involved milestones with entities including Nokia acquiring Trolltech, later divestment to Digia, and formation of The Qt Company. Qt’s roadmap and governance have been influenced by collaborations with firms like Intel, AMD, and standards bodies such as IEEE. Key contributors and maintainers have included developers from KDE e.V., The Free Software Foundation, and companies like BlackBerry Limited and Automotive Grade Linux partners.

Architecture and components

Qt’s modular architecture comprises libraries such as QtCore, QtGui, QtWidgets, QtQuick, and QtNetwork. QtCore supplies core non-GUI facilities used by projects like Apache HTTP Server integrations, while QtGui and QtWidgets provide traditional widget-based UI elements used in applications like Dolphin (file manager) and KDE Plasma. QtQuick and QML enable declarative UI design similar in role to frameworks used by Apple Inc. technologies and Google mobile interfaces. The graphics stack interacts with system graphics APIs including OpenGL, Vulkan, and platform compositors such as Wayland and X.Org Server. Qt’s meta-object system supports signals and slots for event-driven programming and integrates with compilers like Clang and GCC.

Programming language bindings and APIs

Qt is implemented in C++ and exposes primary APIs in that language; it also provides official and third-party bindings for languages such as Python via PyQt and PySide, JavaScript via QML, and bindings for Rust, C#, and Go. Tooling ecosystems include IDEs and editors like Qt Creator, KDevelop, JetBrains CLion, and Visual Studio Code. The framework interoperates with databases including SQLite, PostgreSQL, and MySQL through QtSql, and with web engines like Chromium and WebKit for embedded browsing experiences.

Licensing and commercial editions

Qt has historically been available under multiple licenses: open-source options such as the GNU Lesser General Public License and commercial licensing from The Qt Company. Licensing changes involved stakeholders including Nokia and community organizations like KDE e.V. and prompted responses from entities such as Canonical (company) and Red Hat. Commercial editions provide additional services, long-term support, and proprietary modules often used by corporations like Siemens, Bosch, and Volvo Group.

Platforms and deployment

Qt targets desktop, embedded, and mobile platforms. Desktop deployments include distributions such as Ubuntu, Debian, and Fedora; embedded targets include boards using processors from ARM and vendors like NVIDIA and Raspberry Pi. Qt’s deployment tools assist cross-compilation and packaging for formats like AppImage, Flatpak, and Microsoft Store packages. Embedded Qt variants are used in automotive stacks alongside initiatives such as GENIVI and Automotive Grade Linux, and in consumer electronics produced by companies like LG Electronics and Panasonic Corporation.

Notable applications and adoption

Qt is used by a wide range of applications and organizations. Desktop environments and suites include KDE Plasma, Krita, KDevelop, and file managers like Konqueror. Commercial and industrial users include Adobe Systems, Spotify Technology, Autodesk, Siemens, Ericsson, and Siemens Healthineers. Scientific and engineering tools such as QGIS, OpenFOAM, and ParaView use Qt for UI and visualization. Qt also appears in consumer products and embedded systems from Samsung Electronics, LG Electronics, Siemens AG, and Bosch. Major open-source projects and vendors integrating Qt encompass Blender (software), FreeBSD, Canonical (company), and Valve Corporation through Steam client components.

Category:Widget toolkits