libx11-6 6.8.2-10.3 (i386 binary) in ubuntu hoary

 The libX11 library, also known as "Xlib", provides a means of communicating
 with an X server via the X protocol.
 .
 Xlib provides low-level functionality, dealing mostly with the wire protocol
 and in terms of basic operations such as opening and closing the connection
 to the X server, creating graphics contexts, drawing graphics primitives such
 as lines, arcs, and glyphs, handling events, and so forth. A set of
 dynamically-loadable internationalization modules is also part of this
 package, though not in the libX11 shared object itself.
 .
 Application programmers who are new to the X Window System will likely find
 one of the many "Toolkit" libraries far more convenient to program against
 than Xlib directly. Examples of popular toolkit libraries are GTK+, Qt,
 XForms, LessTif, and Athena.
 .
 libx11-6 depends on xlibs-data for locale data and the X error and keysym
 databases.