IBUs

IBus, or Intelligent Input Bus, is an open-source input method framework for Linux and other Unix-like systems. It provides a unified interface for multiple input methods (IMEs) and routes keyboard input to language-specific engines. The system runs as a per-user daemon and integrates with GTK and Qt frontends, enabling desktop environments such as GNOME and KDE to switch between languages.

The core component is the ibus-daemon, which manages engine selection, input events, and the preedit area. Engines are implemented as separate modules (ibus-engine-*) that provide the logic for specific languages and input methods. The frontend communicates with the daemon via a standard protocol, and libraries such as libibus support integration into GTK and Qt applications.

Engines and languages: A wide range of engines exist for Chinese, Japanese, Korean, Indic languages, Vietnamese, and other scripts. Users can install additional engines and switch among them at runtime through keyboard shortcuts or the IBus preference panel.

Features and workflow: As users type, the engine builds a preedit string and presents candidate completions. The user can accept a candidate to commit the corresponding characters. IBus supports dead keys, Unicode composition, and complex scripts, as well as layout switching and language selection. It integrates with GNOME, KDE and other desktops and provides indicators and panels to manage input methods.

History and usage: IBus was developed as a modern, modular alternative to older input-method frameworks. It is widely used on Linux desktops and is included in major distributions, often alongside GNOME or KDE integrations. It competes with other frameworks such as Fcitx and SCIM, and continues to receive contributions from the open-source community.