The functions turn the generation of the video signal on or off. On some video boards, SVGA memory access is faster when no video signal is generated. On the other hand, not all boards allow to disable it (at least not in all modes).
The functions always return 0 (on which you should probably not really rely).
svgalib(7), vgagl(7), libvga.config(5), vga_init(3), vga_setmode(3), vga_clear(3),
This manual page was edited by Michael Weller <email@example.com>. The exact source of the referenced function 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.
The man page vga_screenon(3) is an alias of vga_screenoff(3).