X11 Programming - Moving an Object in a GC?

[Iqbal Maraqa <iqbal.maraqa@xxxxxxxxxxxxxxxxxxxx>]

Hi, i'm trying to move a triangel i've drawn with XDrawLine from left to
right. This is the best idea i came up with: i move the coordinates in  
a for-loop and draw on the last ones with white.

int counter=0, x1=0, y1=0, x2=15, y2=15, x3=0, y3=30, start=1;
for (counter; counter < 100; counter++)
{
  if(!start) /* if already drawn */
  {
    /* delete last step -> draw in white */	  
    XSetForeground(display, gc, WhitePixel(display, screen_num));
    XDrawLine(display, win, gc, x1+counter-1, y1, x2+counter-1, y2);
    XDrawLine(display, win, gc, x2+counter-1, y2, x3+counter-1, y3); 
    XDrawLine(display, win, gc, x3+counter-1, y3, x1+counter-1, y1);
   }
   /* draw next step in black */
   XSetForeground(display, gc, BlackPixel(display, screen_num));
   XDrawLine(display, win, gc, x1+counter, y1, x2+counter, y2);
   XDrawLine(display, win, gc, x2+counter, y2, x3+counter, y3);
   XDrawLine(display, win, gc, x3+counter, y3, x1+counter, y1);
   XFlush(display);

   usleep(100000);
   start= 1;
}

Can anyone tell me how to update the GC in order to emulate motion?

Thanks and best regards,
Iqbal
-- 
echo "[q]sa[ln0=aln256%Pln256/snlbx]sb9110849205086363247337574050075\
032905184391195412274100697358608023133864165787933915045683432087129\
472907338347329339706073226139582008068077725378669120069632snlbxq"|dc

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