int xosd_set_vertical_offset (xosd* osd, int offset);
changes the number of pixels the XOSD window is offset from the top or
bottom of the screen.
This is normally set to a value such as 48 to avoid desktop-panels,
such as those provided by GNOME or KDE.
The on-screen display object to act on.
Offset from the top or bottom of the screen, in pixels.
On success, a zero is returned.
On error, -1 is returned.