/****** w9.C ******/
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xos.h>
#include <X11/keysymdef.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
int I=0;
Display *disp;
Window win;
void Invalidate(Display *disp, Window win, int SetClear);
void OnSignal(int v){v=v;Invalidate(disp, win, 1);}

int main()
{
 int ScrNum;
 GC prGC;
 XEvent Evnt;
 int ix,iy;
 
 if ( (disp = XOpenDisplay (NULL)) == NULL)
  {
    printf("\n====1");
    exit(1);
  }
 
 ScrNum = DefaultScreen( disp );
 
 win = XCreateSimpleWindow( disp, RootWindow( disp, ScrNum), 0, 0, 500, 500, 2, 
                                  BlackPixel(  disp, ScrNum), WhitePixel(  disp, ScrNum) );

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

 XMapWindow (disp,win);
//----------------------------------------------------------
// set reaction  on timer signal: 
 signal(SIGALRM, OnSignal);
// timer signal should be sent one time per 0.003 sec :
 itimerval tval,ovalue;
 tval.it_value.tv_sec=0; tval.it_value.tv_usec=3000;
 tval.it_interval.tv_sec=0; tval.it_interval.tv_usec=3000;
 setitimer(ITIMER_REAL, &tval, &ovalue);
//----------------------------------------------------------

 while( 1 )
  {
    XNextEvent( disp, &Evnt);
    switch (Evnt.type)
     {
      case ButtonPress:
       break;
      case Expose:
        if ( Evnt.xexpose.count!=0 ) break;
         prGC = XCreateGC( disp, win, 0, NULL );
         XSetForeground( disp, prGC, BlackPixel(disp, 0) );
          if(I>400){ix=800-I; iy=400-(I-800)*(400-I)/400;} else {ix=I; iy=400-I*(400-I)/400;}
           XDrawArc(disp, win, prGC, ix+5, iy+5, 10, 10, 0, 360*64);  
           XDrawLine(disp, win, prGC, 0+5,400+10+5,400+10+5,400+10+5);
           XDrawLine(disp, win, prGC, 0+5,400+10+5,0+5,0+5);
           XDrawLine(disp, win, prGC, 400+10+5,5+10,400+10+5,400+10+5);
           XDrawString(disp, win, prGC, 5,450,"Press Q to exit",strlen("Press Q to exit"));
         XFreeGC( disp, prGC );
         I++;if(I>800)I=0;
       break;
      case KeyPress:
       KeyCode code=Evnt.xkey.keycode;  KeySym  sym=XKeycodeToKeysym(disp,code,0);
       if(sym==XK_q||sym==XK_Q)
        goto fin;
     }
  } 
fin:
 XCloseDisplay( disp ); 
 return 0;
}
void Invalidate(Display *disp, Window win, int SetClear)
{int left=0,right=1000,top=0,bottom=1000;
//printf("Invalidate:width=%d height=%d\n",right-left,bottom-top);
 if(!SetClear)
 {
 static XEvent ev;
 int width=right-left,height=bottom-top;
 ev.xexpose.type=Expose;
 ev.xexpose.send_event=1;
 ev.xexpose.display=disp;
 ev.xexpose.window=win;
 ev.xexpose.x=ev.xexpose.y=0;ev.xexpose.width=width;ev.xexpose.height=height;ev.xexpose.count=0;
 XSendEvent(disp,win,1,ExposureMask,&ev);
 }
 else
 {
  XClearWindow(disp,win);
 int width=right-left,height=bottom-top;
 static XEvent ev;
 ev.xexpose.type=Expose;
 ev.xexpose.send_event=1;
 ev.xexpose.display=disp;
 ev.xexpose.window=win;
 ev.xexpose.x=ev.xexpose.y=0;ev.xexpose.width=width;ev.xexpose.height=height;ev.xexpose.count=0;
 XSendEvent(disp,win,1,ExposureMask,&ev);
 }
 XFlush(disp);
}