Fcitx

Fcitx is a free and open-source input method framework for Linux and other Unix-like systems. It provides a modular architecture that separates the input method logic from the user interface, enabling users to type in many languages using a variety of input methods. The framework consists of a central daemon, a set of backends implementing individual input methods, and frontends for different desktop toolkits.

Backends include popular input methods for various languages and scripts, such as Chinese pinyin and other Chinese input methods via fcitx-libpinyin, as well as support for Japanese kana, Korean Hangul, and many other languages through additional modules. The fcitx core manages input state, candidate windows, and dictionary support, while frontends for GTK and Qt provide the on-screen UI for selecting methods, showing candidate lists, and adjusting settings.

Fcitx integrates with X11 through the X Input Method protocol and can operate under Wayland via XWayland or compatible environments. It is commonly used in desktop environments such as GNOME, KDE, and Xfce, with configuration typically handled by a dedicated configuration tool (fcitx-configtool or fcitx5-configtool) and by setting environment variables such as FCITX_IM_MODULE in applications, along with the corresponding GTK_IM_MODULE and QT_IM_MODULE.

There are two main lines of development: the classic fcitx and the newer fcitx5. Fc itx5 represents a redesign aimed at improved performance, better Wayland support, and a modular backend architecture. Fcitx is developed and maintained by a volunteer community and is distributed under open-source licenses, with packages available across major Linux distributions.

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