#
#define MAXUSERS 4
#include <X11/Xlib.h>
#include <stdio.h>
#include <X11/StringDefs.h>
#include <X11/cursorfont.h>
#define TRUE 1
#define FALSE 0

main(argc,argv)
int argc;
char **argv;
{
  Display *display[MAXUSERS];
  Window root[MAXUSERS], window[MAXUSERS];
  long fgcolor, bgcolor;
  int screen;
  int eventmask = KeyPressMask|ExposureMask|ButtonMotionMask|ButtonPressMask|ButtonReleaseMask;
long gcmask = GCForeground | GCBackground | GCLineWidth | GCCapStyle |
GCJoinStyle;

  XEvent event;
  XGCValues gcval;
  GC draw[MAXUSERS];
  int NC;
  int i, j;

  int oldx, oldy, curx, cury;
  if (argc == 1) NC = argc;
  else NC = argc-1;

  for (i=0; i< NC; i++){
    if (!(display[i] = XOpenDisplay(argv[i+1]))) {
      perror("XOpenDisplay");
      exit(1);
    }

    root[i] = RootWindow(display[i],screen = DefaultScreen(display[i]));
    fgcolor = BlackPixel(display[i],screen);
    bgcolor = WhitePixel(display[i],screen);

    window[i] = XCreateSimpleWindow(display[i],root[i],0,0,200,200,2,
        fgcolor,bgcolor);

/*
    XSetWindowBackgroundPixmap(display[i],window[i],NULL);
*/

    gcval.foreground = fgcolor;
    gcval.background = bgcolor;
   gcval.line_width  = 7;
   gcval.cap_style = CapRound;
   gcval.join_style = JoinRound;

    draw[i] = XCreateGC(display[i],window[i], gcmask,&gcval);

    XMapWindow(display[i],window[i]);
    XFlush(display[i]);
    XGrabButton(display[i], AnyButton, AnyModifier,
               window[i], TRUE,
               ButtonPressMask | ButtonMotionMask |
               ButtonReleaseMask, 
               GrabModeAsync, GrabModeAsync,
               window[i],
               XCreateFontCursor(display[i],
                                 XC_crosshair));


               XSelectInput(display[i],window[i],eventmask);
  }

  for (;;) {
    for(j=0; j < NC; j++) {

    if (XCheckWindowEvent(display[j],window[j],eventmask,&event))
    switch (event.type) {
    case ButtonPress:
	oldx=event.xbutton.x;
        oldy= event.xbutton.y;

 
    case MotionNotify:
        for (i=0; i<NC; i++) 
           XDrawLine(display[i],window[i],draw[i],oldx,oldy,
                     curx=event.xmotion.x, cury=event.xmotion.y);
           oldx=curx;
           oldy=cury;
        for (i=0; i<NC; i++)
           XFlush(display[i]);
        break;
    case KeyPress:
      for (i=1; i<NC; i++)
        XDestroyWindow(display[i], window[i]);
      exit(0);
    default:
      fprintf(stderr,"Unexpected event: %d\n",event.type);
    }
  } 
  }
}