SAOimage on 16(or more)-bit Displays

For those people running Linux and who normally use a 16-bit or higher display, there is a possible workaround for the nuisance of having to start an 8-bit XServer whenever they want to use SAOtng (or XImtool). The IRAF FAQ suggests using XNest to start a nested XServer which runs inside your 16-bit display, but is itself an 8-bit display. Ideally, it would be possible to run an SAOtng within this nested XServer while still using various 'colour-intensive' applications, such as netscape, in the 16-bit Xserver. The unfortunate reality is that many video cards don't support multiple display depths: you can use XNest, but it has to run at the same depth as the main XServer....

Under Linux it is possible to use one of the virtual terminals (Ctrl-Alt-F1..12) as a second display. Normally when you start Xwindows, your display (usually :0.0) starts up on the virtual terminal accessed through Ctrl-Alt-F7. If you were to start second Xsession (called, say, :1.0) it would start under a different virtual terminal (usually Ctrl-Alt-F8). Here's what I do, which is probably not the most elegant solution:

• Start Xwindows normally, e.g.

       startx -- -bpp 16
  

  using the following .xinitrc:

      #!/bin/csh
      xrdb -load $HOME/.Xdefaults
      xset c off s 600
  
      xterm -ls -T ${HOST} -display :0.0 -cr red -g 80x24+0+0 -fg black -bg white &
      sleep 2
      xload -display :0.0 -update 2  -g 150x80-135-0 &
      sleep 2
      xbiff  -display :1.0 -g -5+0 &
  
      xsetroot -gray
      fvwm  -display :0.0
  

  This starts an Xwindows session on the virtual terminal F7.

• Go to virtual terminal F2 (Ctr-Alt-F2 -- the usual login screen is F1) and login.

• Start the second Xserver with

      startx ~/.xinitrc.2 -- :1 -bpp 8
  

  where .xinitrc.2 is:

  #!/bin/csh
      xrdb -load $HOME/.Xdefaults
      xset c off s 600
  
      xterm -ls -T ${HOST} -display :1.0 -cr red -g 80x24+0+0 -fg black -bg white &
      sleep 2
      xload -display :1.0 -update 2  -g 150x80-135-0 &
      sleep 2
      xbiff  -display :1.0 -g -5+0 &
  
      xsetroot -gray
      fvwm  -display :1.0
  

  This starts an Xwindows session on the virutal terminal F8

• The two Xsessions can be switched between using Ctrl-Alt-F7 (the 16-bit session) and Ctrl-Alt-F8 (the 8-bit session)

I have no idea if the XServers for Solaris, SunOs, Alphas, etc. allow virtual terminals, but it may be that XNest will work on their video cards.
John Ouellette