ATSPI2

AT-SPI 2, commonly written as AT-SPI 2 or ATSPI2, is the second generation of the Assistive Technology Service Provider Interface. It is a Linux accessibility framework that exposes the user interface of applications to assistive technologies such as screen readers, magnifiers, and speech synthesizers. Built on inter-process communication via D-Bus, AT-SPI 2 enables tools to discover, inspect, and interact with UI elements regardless of the toolkit used by the application.

The AT-SPI 2 architecture consists of a registry daemon (at-spi2-registryd) that maintains a live tree of accessible objects across an X1 1/ Wayland session, a core server library (at-spi2-core) that implements the D-Bus interfaces, and a set of client libraries (libatspi) used by assistive technologies to query objects and subscribe to events. Applications export their accessibility information through AT-SPI 2, often via bridges for toolkits such as GTK (AT-SPI via ATK) and Qt. The registry and core communicate via D-Bus, and events propagate to clients when properties or state changes occur.

AT-SPI 2 emphasizes interoperability across desktop environments and toolkits, enabling screen readers like Orca among others to read and interact with UI controls, menus, and dialogs. It is commonly used in Linux environments with GNOME, KDE, and other desktops, and integrates with accessibility toolkits through bridges that translate toolkit-specific accessibility into AT-SPI 2 interfaces.

Developed as a modern rewrite of the original AT-SPI, AT-SPI 2 has been maintained as the standard accessibility framework for many Linux distributions. It continues to evolve with new toolkit support and improvements in performance, event reporting, and security.