X Toolkit Intrinsics

[citation needed] The low-level library Xlib is the client-side implementation of the X11 protocol.

It communicates with an X server, but does not provide any function for implementing graphical control elements ("widgets"), such as buttons or menus.

Since the graphical user interface of applications typically requires a number of widget types, most developers were reluctant to write their own, and instead prefer to use libraries such as Xaw, Motif and OLIT that provide a set of widgets.

Xt programs had a notorious problem of being unusable if the "app-defaults Xrm database", a text file describing all the widgets, could not be found.

[citation needed] Most modern, widely-used toolkits such as GTK and Qt do not use the Xt library.