/****** w7.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>
void Invalidate(Display *disp, Window win, int SetClear);
int main()
{
 Display *disp;
 int ScrNum;
 GC prGC;
 XEvent Evnt;
 Window win;
 int n_call=0,ix,iy,d=20;
 char str[100]="";//,s[100]="*";
 char s2[3]=" ";
 
 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);

 while( 1 )
  {
    XNextEvent( disp, &Evnt);
    switch (Evnt.type)
     {
      case ButtonPress:
         for(int i=0;i<10;i++)
         {
          ix=i%3; iy=i/3;
          if(Evnt.xbutton.x>d+d*ix*2 && Evnt.xbutton.x<d+d*(1+ix*2) && Evnt.xbutton.y>d+d*iy*2 && Evnt.xbutton.y<d+d*(1+iy*2))
          {s2[0]='0'+i; strcat(str,s2);  Invalidate(disp, win, 1); break;}
         }
       
       break;
      case Expose:
        if ( Evnt.xexpose.count!=0 ) break;
         prGC = XCreateGC( disp, win, 0, NULL );
         XSetForeground( disp, prGC, BlackPixel(disp, 0) );
         for(int i=0;i<10;i++)
         {
          ix=i%3; iy=i/3;
          XDrawLine(disp,win,prGC, d+d*ix*2,d+d*iy*2,d+d*(ix*2+1),d+d*iy*2);          XDrawLine(disp,win,prGC, d+d*ix*2,d+d*iy*2,d+d*ix*2,d+d*(iy*2+1));
          XDrawLine(disp,win,prGC, d+d*(1+ix*2),d+d*(1+iy*2),d+d*(ix*2+1),d+d*iy*2);  XDrawLine(disp,win,prGC, d+d*(1+ix*2),d+d*(1+iy*2),d+d*ix*2,d+d*(iy*2+1));
          s2[0]='0'+i;
          XDrawString(disp,win,prGC,d+d*(ix*2)+d/3,d+d*(1+iy*2)-d/3,s2,1);
         }
         XDrawString(disp,win,prGC,d,d+d*(2+iy*2)-d/3,str,strlen(str));
         XDrawString(disp,win,prGC,d,d+d*(3+iy*2)-d/3,"Press Q to exit",strlen("Press Q to exit"));
         XFreeGC( disp, prGC );
         n_call++;
       break;
      case KeyPress:
       KeyCode code=Evnt.xkey.keycode;  KeySym  sym=XKeycodeToKeysym(disp,code,0);
       if(sym==XK_q||sym==XK_Q)
        goto fin;
       {
        strcat(str,(sym==XK_0?"0":sym==XK_1?"1":sym==XK_2?"2":sym==XK_3?"3":sym==XK_4?"4":sym==XK_5?"5":sym==XK_6?"6":sym==XK_7?"7":sym==XK_8?"8":sym==XK_9?"9":"_"));
        Invalidate(disp, win, 1); break;
       }
     }
  } 
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);
}