SlackBuildsOrg/misc/xbanish

xbanish hides the mouse cursor when you start typing, and shows it again when
the mouse cursor moves or a mouse button is pressed.  This is similar to
xterm's pointerMode setting, but xbanish works globally in the X11 session.

One can easily start this automatically by putting `/usr/bin/xbanish &' to eg.
~/.xinitrc or some other DM specific startup file.