Re: Midas Problem under Linux?

[Werner Becker <web@mpe-garching.mpg.de>]

On Mon, 14 Sep 1998, Kym M. Hill wrote:

> I am running midas under Linux (Recent version).  If I run X-Windows
> with more than 256 colours (say 16bit since my video card has 2Mb of
> ram and I use 1024x768) , then midas fails to create a display window.
> See output below:
>
>    Midas 001> create/dis
>    OSX: Writing error in 'round_trip', error = 0
>    no. of LUTs has been changed to 1073770848
>
>    OSX: Writing error in 'round_trip', error = 0
>    OSX: Writing error in 'round_trip', error = 0
>    We could not connect to IDIserver
>    OSX: Writing error in 'round_trip', error = -1
>    Midas 002>
>
>
> Is there a solution to this problem?  Every thing works fine if I
> configure X to work in 256 colour mode. I am happy to have a 256
> colour LUT, but would like to have 16bit colour for other applications
> that are running at the same time.
>
> Any hints welcome.
>
> Thanks Kym
>
>

Dear Kym,

 this is a pending problem of MIDAS, which (I think) has been reported
 to ESO many times in the last several years. However, I have not heard
 on any progress in that direction. Probably a man power problem ?!.

 The problem is that MIDAS "needs" a PseudoColor visual. This has
 256 colors. If this color visual does not exist MIDAS fails to
 open/create a display window. I guess that this 'feature' is a relic of
 the days when graphic hardware was very expensive and most X-terminals had
 256 colors only. However, things have changed in the last years and it
 would be great if the maintainer/developer of MIDAS take that problem
 important enough to provide native support of True- and HighColor visuals
 in their next release to keep up-to-date !!.

 To be fair, however, one has to mention that this point depend also a
 bit on the ability of the X-server running on your computer. For example,
 MIDAS runs well on a Silicon Graphics Computer (its X-server provides
 PseudoColor on TrueColor). For Linux there are two commercial X-window
 server available on the market. One is called 'Accelerated-X' and the
 other is Metro-X. At least Accelerated-X (see http://www.xig.com) provides
 a PseudoColor visual as an overlay on a 16, 24 or 32 bit TrueColor visual.
 With this X-server running you provide a TrueColor (or HighColor) visual
 for software which makes use of it (e.g. Netscape, xv, gimp, etc..), but
 if a client software is looking for a PseudoColor visual, it will find
 it, getting 256 colors out of the 24 (or 16 bit) color pool.

 Unfortunately, if you have installed the PseudoColor overlay mode using
 Accelerated-X, also most window manager such like fvwm2, fvwm95, KDE etc..
 take their colors from the 256 PseudoColor room rather than from the 16M
 pool. The result is that there are again only few colors avialble for
 an application like MIDAS. If MIDAS implements his own color map one has
 the effect that all colors on the screen change if one changes the
 active window :-(

 For your information, I copy the screen from the 'Graphic Mode Selection'
 page, provided by the Accelerated-X setup program:


       Resolution            Desktop              Colors
       ----------------------------------------------------------------
       ( ) 640x480           ( ) 640x480          ( ) 256
       ( ) 800x600           ( ) 800x600          ( ) 32K
       ( ) 1024x768          ( ) 1024x768         ( ) 64K
       ( ) 1152x864          ( ) 1152x864         ( ) 16M, Packed
       (*) 1280x1024         ( ) 1280x1024        (*) 16M, Overlays
       ( ) 1600x1200         ( ) 1600x1200
                             (*) Disabled

 There also is a demo program of Accelearted-X available, which allows
 you to install the X-server and to test it. The restriction is in the
 way that you can have only few windows open at the same time. The free
 X-server XFree86 does not provide a PseudoColor visual as an overlay
 on a 16M visual. As long as ESO/MIDAS does not come up with a native
 support of TrueColor visuals, Accelerated-X may provide at least
 something like a 'work-arround'.


 With best regards,

  Werner Becker