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From: kent@gnomee.pa.dec.com (Christopher A. Kent)
Newsgroups: comp.windows.x
Subject: Re: Colormaps (was ...and Visuals)
Message-ID: <1890@bacchus.dec.com>
Date: 4 Oct 89 22:55:21 GMT
References: <8909210815.AA26154@Larry.McRCIM.McGill.EDU>
Sender: news@decwrl.dec.com
Lines: 49

I had the same problem, and came up with the following code. It's not pretty, and it doesn't leave the cells sharable, but it works.

static Bool
_AllocContiguousCells(dpy, cmap, pixels, npixels)
Display *dpy;
Colormap cmap;
unsigned long *pixels;          /* filled in by routine */
int npixels;
{
    unsigned long *waste = (unsigned long *)NULL;
    int nwaste = 0;
    Bool contig = False;
    int status, i;
    unsigned long masks = NULL;

    while (!contig) {
        status = XAllocColorCells(dpy, cmap, False, &masks, 0, pixels,
                npixels);
        if (!status)
            break;   /* can't get enough contiguous cells */
        for (i=0; i < (npixels-1); i++) {
            if (pixels[i] + 1 != pixels[i+1]) {
                /* isn't contiguous, keep trying */
                XFreeColors(dpy, cmap, &pixels[i+1], npixels - (i+1), 0);
                if (!waste)
                    waste = (unsigned long *)malloc((i + 1) *
                                sizeof(unsigned long));
                else
                    waste = (unsigned long *)realloc(waste, (nwaste +
                                (i + 1)) * sizeof(unsigned long));
                bcopy(pixels, waste+nwaste, (i+1) * sizeof(unsigned long));
                nwaste += (i+1);
                break;
            }
        }
        if (i == (npixels-1))
            contig = True;
    }
    /* clean up and return 'contig' */
    if (nwaste) {
        XFreeColors(dpy, cmap, waste, nwaste, 0);
        free(waste);
    }
    return (contig);
}


Chris Kent	Western Software Laboratory	Digital Equipment Corporation
kent@decwrl.dec.com	decwrl!kent			(415) 853-6639