The X Input Subsystem

The X Input Subsystem

While X mandates that every X server support a keyboard and mouse, there is no standard system interface for accessing such devices on UNIX systems. This means each vendor has its own input subsystem for its X server. SGI's input subsystem not only meets the basic requirement to support a keyboard and mouse but also has the following features:

A shared memory input queue is supported for high performance
A wide variety of input devices is supported, including 3D devices such as the Spaceball
Input devices are supported abstractly; knowledge of specific input devices is isolated to modular kernel-level device drivers
Hardware cursor tracking is supported in the kernel

These features provide a more functional, responsive input subsystem than that available in the MIT Sample Server.

The programming interface to the input subsystem from the X client API is covered in the X11 Input Extension Library Specification, an online book that is distributed with the IRIX Developer's Option.

Note: Numerous code examples demonstrating the X input system are available in the X developer component (x_dev component) of the IRIX Developer Option. Source for STREAMS modules to integrate a Spaceball, a dial-and-button box, and other devices can be found in subdirectories of /usr/share/src/X.