Qt

Qt is a cross-platform application framework primarily for C++. It provides a comprehensive set of libraries and tools for developing graphical user interfaces as well as non-GUI functionality such as networking, threading, and data persistence. Qt supports desktop, embedded, and mobile platforms including Windows, macOS, Linux, Android, and iOS.

At its core, Qt uses a metaobject system based on signals and slots for communication between objects, and relies on the moc preprocessor. The core modules include Qt Core, Qt GUI, and Qt Widgets; Qt Quick and QML provide a modern declarative UI approach. The toolchain includes Qt Creator IDE, Qt Designer, and a set of utilities; building applications often uses CMake or qmake. Licensing is dual: LGPLv3 (or GPLv2) for open-source use, and a commercial license for proprietary development.

History and development: The framework originated at Trolltech in Norway in 1995. Trolltech was acquired by Nokia in 2008, then by Digia in 2012, and later reorganized as The Qt Company in 2016. Qt has evolved through major releases such as Qt 5 and Qt 6, with ongoing development and long-term support. Qt 6 introduced a refreshed rendering stack and modular architecture to better support modern hardware and platforms.

Ecosystem and bindings: Bindings exist for languages other than C++, notably Python via PyQt and PySide; Qt for Python provides official bindings. Qt is used in a wide range of applications, from KDE software to many commercial products, and is a common choice for cross-platform desktop and embedded applications.