[daip] Problems starting XAS server (AIPS 15OCT99)

[Patrick P. Murphy]

On Fri, 10 Mar 2000 20:20:20 +1000 (EST), Scott Gordon
   <gordon at physics.uq.edu.au> said: 

SG> I've compiled the 15OCT99 version of AIPS on an IBM/PC compatible
SG> running RedHat Linux 6.1.

SG> It seems to run fine, except for the XAS server.

SG> The XAS server bombs with a message saying :-

SG> XAS: ***********************************
SG> XAS: **  No TrueColor found
SG> XAS: **  Resorting to PseudoColor
SG> XAS: ***********************************
SG> XAS: No pseudocolor visual - No suitable visual: No such file or directory

See http://www.cv.nrao.edu/aips/aipsmgr/, scroll down to the second item
under "Other Common Questions".  

Short answer: configure your /etc/X11R6/XF86Config file to default to
either 32 or 8 bit depths, depending on what your monitor and graphics
card are capable of handling.

SG> This is obviously due to the fact that the x-windows display (another
SG> Linux PC) uses 16-bit color. XAS works fine in 8-bit color
SG> modes. Changing the color depth is not really an option.

XAS will not run in 16-bit mode.  It runs in 8, 24, or 32 bit depths just
fine.  In 8 bit mode it uses a PseudoColor visual; in the other two it
uses a TrueColor visual.  The latter is better for display fidelity, and
extremely useful for Hue/Intensity (task TVHUI) work, but is less
efficient for altering the brightness/contrast lookup table (TVFIDDLE) as
XAS has to roll its own.  Pseudocolor 8-bit visuals in X11 provide their
own lookup table, so this operation runs faster.

You may want to consider using multiple virtual consoles.  I used to have
gdm/xdm running as usual in virtual console 7 in 8-bit mode (ctrl-alt-f7
to see it), then use one of the others, e.g. #4 (ctrl-alt-f4) to login in
text mode, then do:

     bash$ startx -- :1 -bpp 24

to fire up a second X server (which usually ends up in virtual console 8,
use ctrl-alt-f8 to get to it from the others) with true color enabled.

SG> The display setup on the terminal is a simple XFree86 setup with 16
SG> bit colour and a 1152x864 pixel display, managed by 'xdm'.  XAS should
SG> just be allocating its own 8-bit color map, but can't.

XFree86 version 3 does not support pseudocolor visuals in anything other
than 8-bit mode.  It has nothing to do with XAS.  XFree86 version 4 just
got released this morning but I haven't had a chance to look at the
release notes to see if this has changed.

SG> Every other program which I've ever run on that display works fine, so
SG> XAS is quite an odd one out.

No other program likely has truecolor requirements like XAS.  Remember,
this program was modelled after a now-antique device known as an IIS Model
70!  :-)  The fact that it still works so well after a dozen years, with
relatively few modifications, is in some ways remarkable.

				- Pat
-- 
  Patrick P. Murphy, Ph.D.            Division Head, Charlottesville Computing
  (804) 296-0372, 296-0236                National Radio Astronomy Observatory
  Home: http://www.goof.com/~pmurphy/   Work: http://www.cv.nrao.edu/~pmurphy/
   "Linux is Inevitable."  "Why?"  "Because it's alive!" - John MadDog Hall