Path: utzoo!news-server.csri.toronto.edu!rutgers!bellcore!uunet!mcsun!corton!inria!seti!fantasia!mamou
From: mamou@bdblues.altair.fr (Jean Claude Mamou)
Newsgroups: comp.windows.x
Subject: read/write colorcells problem
Message-ID: <1991Mar13.154106@fantasia.altair.fr>
Date: 13 Mar 91 14:41:06 GMT
Sender: news@seti.inria.fr
Reply-To: mamou@bdblues.altair.fr
Organization: GIP Altair - BP 105 - 78153 Le Chesnay Cedex
Lines: 76


Hello,

I have a problem to allocate read/write colorcells in a colormap. If I
create a new virtual colormap with XCopyColrormapAndFree after a failure 
of XAllocColorCells, one of the extra allocation requests returns a
bad pixel value (e.g. 256) that is out of range of the colormap. I give below
an example of code producing that problem.

Does someone know about that, and is it a known way of doing such a thing ?

Thanks.

-----------------------------------------------------------------------------
Jean-Claude Mamou                       |   tel : +33 (1) 39.63.58.20    
GIP ALTAIR                              |   fax : +33 (1) 39.63.58.90
Domaine de Voluceau                     |   email : mamou@bdblues.altair.fr
BP 105, 78153 Le Chesnay Cedex, FRANCE  |
-----------------------------------------------------------------------------




#include <X11/Xlib.h>
#include <X11/X.h>
#include <stdio.h>
main (argc,argv)
int   argc;
char *argv[];
{
  int i,j,numcols, alloccols,theScreen;
  Colormap cmap, theCmap,LocalCmap;
  XColor   defs[256];
  char * display;
  Display *theDisp;
  unsigned char r[256],g[256],b[256];
  
  display = NULL; LocalCmap =0;
  if ((theDisp = XOpenDisplay(display)) == NULL) {
    printf(stderr, "%s: Can't open display\n",argv[0]);
    exit(1);}
  theScreen = DefaultScreen(theDisp);
  theCmap = DefaultColormap(theDisp, theScreen);
  cmap = theCmap;
  XSynchronize(theDisp, True);
 
/* Allocate one pixel */
  defs[0].pixel = 2;
  XAllocColor(theDisp, cmap, &defs[0]);

  alloccols = 0; numcols = 256;
  
  for (i=0; i<numcols; i++) {
    unsigned long pmr[1], pix[1];
    if (XAllocColorCells(theDisp, cmap, False, pmr, 0, pix, 1)) {
      printf("%d%s%d\n",i, " : XAllocColorcells returns pix = ", pix[0]);
      defs[i].pixel = pix[0];
      defs[i].red   = r[i]<<8;
      defs[i].green = g[i]<<8;
      defs[i].blue  = b[i]<<8;
      defs[i].flags = DoRed | DoGreen | DoBlue;
      alloccols++;
    }
    else if (!LocalCmap) 
      {
	printf("%s%d\n","Creation of a new colormap for i = ", i);
	LocalCmap = XCopyColormapAndFree(theDisp,theCmap);
        cmap = LocalCmap;
	i--;	  
      }
    else printf("%s\n", "Color non allocated");
  }
  printf("%s%d\n","Allocated colors = ", alloccols);
  fflush(stdout);
  for (i=0; i<alloccols; i++) XStoreColor(theDisp, cmap, &defs[i]);
  }