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Re: Force 8bit display ? [message #47275 is a reply to message #47262]

Wed, 01 February 2006 10:14

Karl Schultz
Messages: 341
Registered: October 1999

Senior Member

On Wed, 01 Feb 2006 10:47:44 -0700, David Fanning wrote:

> Karl Schultz writes:
>
>> Right. The 8-bit PseudoColor visual was almost a de facto standard on
>> early X servers because it was very efficient on the hardware available at
>> the time. Today's hardware handles the TrueColor 24-bit model well
>> and you don't see the 8-bit stuff as much anymore. Some SUN X servers
>> provide both 8 and 24 bit Visuals.
>
> I'm going to regret saying this, I know, but you
> *might* try asking for a 24-bit DirectColor visual.
> This normally won't work worth a damn, but I have heard
> of an undocumented keyword that is *suppose* to fix
> the problem. After setting to 24-bit direct color,
> try issuing this statement:
>
> DEVICE, /INSTALL_COLORMAP
>
> Now if you change color tables, you graphics window *might*
> change, too. Let us know. :-)
>

Right. If I do:

DEVICE, direct_color=24, /install_colormap
LOADCT, 5
TVSCL, dist(400)

I'll get the correct colors when I move my mouse over the IDL graphics
window. Of course, the rest the screen gets false colors, but it works,
at least on Fedora Core 2.

I can then do subsequent LOADCT commands to change the colors immediately
if I leave colormap focus on the graphics window and keyboard focus in the
xterm.

The reason why /INSTALL_COLORMAP is needed is because SOME of the window
managers in the newer desktops either purposely or accidentially do not
install private colormaps themselves when colormap focus changes. So, the
application (IDL) needs to watch for the focus change and (un)install the
colormap itself. This is considered evil from an ICCCM point of view, and
that's why it is a keyword. I've filed bugs with these components, and
the response was along the lines of "we look forward to your patch".

Karl

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[Message index]

		Re: Force 8bit display ? By: Nigel Wade on Thu, 02 February 2006 01:49
		Re: Force 8bit display ? By: Karl Schultz on Wed, 01 February 2006 10:14
		Re: Force 8bit display ? By: David Fanning on Wed, 01 February 2006 09:47
		Re: Force 8bit display ? By: Karl Schultz on Wed, 01 February 2006 09:39
		Re: Force 8bit display ? By: David Fanning on Wed, 01 February 2006 08:13
		Re: Force 8bit display ? By: L. Testut on Wed, 01 February 2006 07:51
		Re: Force 8bit display ? By: David Fanning on Wed, 01 February 2006 06:21
		Re: Force 8bit display ? By: peter.albert@gmx.de on Wed, 01 February 2006 05:18

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