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From: jim@EXPO.LCS.MIT.EDU (Jim Fulton)
Newsgroups: comp.windows.x
Subject: Re: Allocating 256 color cells
Message-ID: <8806161417.AA24808@EXPO.LCS.MIT.EDU>
Date: 16 Jun 88 14:17:43 GMT
References: <225@raunvis.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: X Consortium, MIT Laboratory for Computer Science
Lines: 31


Deja vu.

The default colormap will always have at least colors preallocated for
BlackPixel and WhitePixel.  In addition, if you are already running any
applications (such as a couple of xterms, an xclock, an xload, a window
manager, etc.), they will most likely have also allocated some color cells
out of the default colormap.  So, you won't probably won't be able to 
allocate more than NCELLS-10 (or so, where 10 is the number of cells that
existing applications have grabbed already; your mileage may vary).

So, if you want to allocate all of the colormap cells, you'll need to 
create a new colormap.  From last Friday's note:

>        visual = /* select the proper visual if DefaultVisual isn't right */
>        cmap = XCreateColormap (dpy, RootWindow (dpy, scr), visual, All);
>
> The visual determines what sort of colormap should be allocated.  This is 
> necessary for running on displays that provide more than one type of window
> (for example: 24 bit DirectColor and 16 bit PseudoColor, or 8 bit PseudoColor
> and 1 bit StaticGray).

Useful readings:
	Xlib manual, Section 3.1, Visual Types
		     Section 5.1, Colormap Functions
		     Section 9.2, Manipulating Standard Colormaps
	ICCCM

This topic clearly needs to be added to the list of Tutorials to be written....

Jim Fulton
MIT X Consortium