gl_setscreenoffset man page
gl_setscreenoffset — set a memory offset for copyscreen
void gl_setscreenoffset(int o);
Set the offset in pixels into video memory for copyscreen(3) and copyboxtocontext(3), copyboxfromcontext(3) and thus allows for page-flipping. Must be a multiple of the scanline width in bytes. It is reset to zero after the completion of copyscreen(3).
svgalib(7), vgagl(7), svgalib.conf(5), threedkit(7), testgl(1), gl_copyboxfromcontext(3), gl_copyboxtocontext(3), gl_copyscreen(3), gl_enablepageflipping(3).
This manual page was edited by Michael Weller <email@example.com>. The exact source of the referenced demo as well as of the original documentation is unknown.
It is very likely that both are at least to some extent are due to Harm Hanemaayer <H.Hanemaayer@inter.nl.net>.
Occasionally this might be wrong. I hereby asked to be excused by the original author and will happily accept any additions or corrections to this first version of the svgalib manual.