From: Matan Ziv-Av (matan@svgalib.org)
Date: Fri 21 Dec 2001 - 22:56:17 IST
On Fri, 21 Dec 2001, Frank H. Baker wrote:
> After a lapse, I am back to my interest of exploring the use of SVGAlib
> in a multi-monitor system.Your email responding to my inquiry of some
> months ago (many thanks) has encouraged me to pursue that path, but I
> have questions about the implementation.
>
> -- It is not clear how the programmer designates the adapter being
> written to.While I've not looked much into the 1.9.12 source (I'm not
> currently a SVGAlib user), I have scanned src/ and looked for likely
> calls in vga.h. Is there an example program in the distribution that
> demonstrates the usage of two monitors, or could you send me an example?
There is actually no true multi monitor support in svgalib. A single
process that uses svgalib can only access one video card. Which card is
used by svgalib is decided when vga_init() is called, by the value of
some config parameters (chipset, pcistart). The way I use this is by
having different config file for each card (libvga.config.nv3,
libvga.config.g450, etc.), and setting the environment variable
SVGALIB_CARD according to the card I want to use, before running the
program. If this variable exists, svgalib uses the config file
libvga.config.$SVGALIB_CARD, instead of libvga.config. If you wan't to
write a single program to use two monitors, you'll need to fork the
program into two processes before running vga_init(), call the correct
setenv("SVGALIB_CARD",cardname,1) in each process and then call
vga_init(). Of course, then the processes need to use some IPC method to
cooperate.
> -- Am I correct in assuming from your response to my inquiry that there
> is no problem driving two displays with SVGAlib while X handles athird
> display?
Yes. I actually do exactly that quite often.
--
Matan Ziv-Av. matan@svgalib.org
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