Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!think!mintaka!bloom-beacon!EXPO.LCS.MIT.EDU!converse
From: converse@EXPO.LCS.MIT.EDU (Donna Converse)
Newsgroups: comp.windows.x
Subject: Re: Help with colormaps.
Message-ID: <9002261950.AA01703@expo.lcs.mit.edu>
Date: 26 Feb 90 19:50:44 GMT
References: <9002250842.AA02138@dogmatix.cs.uoregon.edu.cs.uoregon.edu>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: X Consortium, MIT Laboratory for Computer Science
Lines: 37


> Constructing the colormap is not a problem.  I can't figure out how to
> use it.  I have tried two things:
> 
> i)  cmap=XCreateColormap(display,window,visual,AllocAll);
> 
> 	Whenever I use AllocAll in this call it does something funky
> 	to display.  The side effect is that it bombs when it hits
> 	XNextEvent(display,&e).  Reason?

Hmmm.... Does something funky to display.... bombs....   hmmm...  my crystal
ball suggests that perhaps you're specifying a visual type that doesn't 
allow read/write allocation. Try reading about visuals, try using the function
XGetVisualInfo or XMatchVisualInfo, try looking for error messages and try using
a debugger.


> ii) cmap=XCreateColormap(display,window,visual,AllocNone);

      with the following (paraphrased by the answerer):
      XAllocColorCells(display, cmap, False, NULL, 0, pixels, ncolors);

> It didn`t seem to work
> for any value of ncolors (I put it in a loop from 256 down to 0).

Maybe the colormap was created with a visual type that doesn't allow read/write
allocation from the colormap.  


> Finally, when I actually do get around to building the virtual colormap
> successfully, do I use XInstallColormap or XSetWindowColormap?

XSetWindowColormap.


Donna Converse
converse@expo.lcs.mit.edu