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Re: linux XF86 X visuals, IDL 16-bit blues

George McCabe wrote:

> there have been quite a few posts to do with IDL and the X device.
> thanks to (especially dave fanning and liam gumley) i'm beginning to
> understand IDL's use of X, but not enough to be able to configure it
> (satisfactorally) in linux6.
> my video hardware (laptop) supports 64K colors.  the linux Xserver
> installs with the TrueColor, depth 16 visual.  as i've been told ,IDL
> just won't work with 16 bit visuals, but RSINC is unable to tell me how
> to add IDL compatible visuals to X.  is there any XF86 expertise here.
> i would be happy limiting IDL to 8 bits but i don't want to run the
> whole system with only 256 colors.


I think the best approach is to start a second X session in 8-bit mode.
Here is some advice I received from our local Linux guru:

---begin quote---
Okay, here's the simple 2-minute recipe for starting a second X session,
using a different window manager, without exiting your original

Assuming 'fvwm95' is the window manager you want to use for your second
X: In your .Xclients, you add near the top

if [ $DISPLAY == :1 ]; then
   exec fvwm95

This causes startx to branch into the alternate window manager for :1,
to prevent gnome or KDE palette-sucking (as well as to prevent two
simultaneous desktops from clobbering each others' settings).

You'll probably want to use FVWM2 or FVWM95, which can be found at
contrib.redhat.com as RPMS. (I recommend grabbing the Source RPM and
using rpm --rebuild to make proper binaries for your OS version. The
binary RPM will land in /usr/src/redhat/RPMS/i386.) It shouldn't be a
problem to have two simultaneous FVWM sessions, since it's not really a
'desktop environment' level of complexity (i.e. it doesn't maintain its
own configuration files).

Then, provided that your XF86Config file indicates properly that your
hardware is capable of 8 bit modes, you should be able to

startx -- :1 -bpp 8

from anywhere, including xterms in :0. X should merrily startup on the
second virtual graphics console. You can then swap between the two X's
with CTRL-ALT-F7 (:0) and CTRL-ALT-F8 (:1) .

When you're done, you can dump out of the second X by properly exiting
that window manager, or by using ctrl-alt-backspace to kill it.
---end quote---

Please let me know if you have to modify the recipe.


Liam E. Gumley
Space Science and Engineering Center, University of Wisconsin-Madison