realtime use of X Windows / svgalib

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From: Tomas Sieger (tomas.sieger@lf1.cuni.cz)
Date: Thu 04 Jan 2001 - 16:59:44 IST


Hello,
i write hard realtime application (under Linux) in which i need 
to use some graphics. No problem with OS load - i plan to use RtLinux.
The problem is that i must ensure that graphics will appear at exact 
times (on order of miliseconds or hunderds of microseconds). 
The question is concentrated on graphics libraries throughput.
Now i study power of X Windows and svgalib. It is clear that svgalib 
is designed in a completely different way, so svgalib reaction time 
could be much less than X Windows' one.
I wonder if it is possible to tell how much time does svgalib / X 
Windows spend processing graphics (i assume no OS load - no other 
apps, no swapping etc., and one station only - no X Windows network 
connection). On X Windows there will be probably need to 'flush' or 
'sync' the screen due to buffering.

Does exist general answer? Specially on i86 platform? Does it depends
on graphics cards / XWin/svgalib versions?

Can X Windows / svgalib wait for vertical retrace?
(there is such function in svgalib - does it work on all platforms / 
graphic cards?; but i'm afraid X Windows are not designed for such use).

Any other suitable graphics libraries?

thanks in advance 
Tomas

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