xvkbd is a virtual (graphical) keyboard program for X Window System which
provides facility to enter characters onto other clients (softwares) by
clicking on a keyboard displayed on the screen. This may be used for systems
without a hardware keyboard such as kiosk terminals or handheld devices.

This program also has facility to send characters specified as the command
line option to another client, which can help when one wants to fully utilize
some modern mice with multiple buttons.