/****** w4.C ******/
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xos.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main()
{
 Display *disp;
 int ScrNum;
 GC prGC;
 XEvent Evnt;
 Window win;
 int i=0,n_call=0,x,y;
 char str[100]="Hello world!";//,s[100]="*";

 if ( (disp = XOpenDisplay (NULL)) == NULL)
  {
    printf("\n====1");
    exit(1);
  }

 ScrNum = DefaultScreen( disp );

 win = XCreateSimpleWindow( disp, RootWindow( disp, ScrNum), 0, 0, 100, 100, 2,
                                  BlackPixel(  disp, ScrNum), WhitePixel(  disp, ScrNum) );

 XSelectInput( disp, win, ExposureMask | KeyPressMask | ButtonPressMask);

 XMapWindow (disp,win);

 while( 1 )
  {
    XNextEvent( disp, &Evnt);
    switch (Evnt.type)
     {
      case ButtonPress:
        prGC = XCreateGC( disp, win, 0, NULL );
        XSetForeground( disp, prGC, BlackPixel(disp, 0) );
         XDrawLine(disp, win, prGC, i*10,i*i, (i+1)*10,(i+1)*(i+1) );
        XFreeGC( disp, prGC );
        x=Evnt.xbutton.x;
        y=Evnt.xbutton.y;
printf("\nx=%d y=%d\n",x,y);
        i++;
       break;
      case Expose:
        if ( Evnt.xexpose.count!=0 ) break;
         prGC = XCreateGC( disp, win, 0, NULL );
         XSetForeground( disp, prGC, BlackPixel(disp, 0) );
         XDrawString( disp, win, prGC, 10,50, str, strlen(str) );
         XFreeGC( disp, prGC );
         n_call++;
         sprintf(str,"Hello... %d",n_call);
       break;
      case KeyPress:
       goto fin;
     }
  }
fin:
 XCloseDisplay( disp );
 return 0;
}