XLib resize problem.

    #include <X11/Xlib.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    int main(void) {
       Display *d;
       Window w, ww;
       XEvent e;
       int s;
       int i;

       int width = 100, height = 100;

       d = XOpenDisplay(NULL);
       if (d == NULL) {
          fprintf(stderr, "Cannot open display\n");
          exit(1);
       }

       s = DefaultScreen(d);
       w = XCreateSimpleWindow(d, RootWindow(d, s), 10, 10, 120, 120, 1,
                                WhitePixel(d, s), BlackPixel(d, s));

       ww = XCreateSimpleWindow(d, w, 10, 10, width, height, 1, BlackPixel(d, s), WhitePixel(d, s));

       XSelectInput(d, w, ExposureMask | KeyPressMask | StructureNotifyMask );
       XSelectInput(d, ww, ExposureMask | KeyPressMask);
       XMapWindow(d, w);
       XMapWindow(d, ww);

       while (1) {
          XNextEvent(d, &e);
          if (e.type == Expose) {
             for (i=0;i<1000;i++) {
               XFillRectangle(d, ww, DefaultGC(d, s), 20, 20, 10, 10);
               XFillRectangle(d, ww, DefaultGC(d, s), width-30, height-30, 10, 10);
               XFillRectangle(d, ww, DefaultGC(d, s), 20, height-30, 10, 10);
               XFillRectangle(d, ww, DefaultGC(d, s), width-30, 20, 10, 10);
             }
          }
          if (e.type == KeyPress)
             break;

          if (e.type == ConfigureNotify) {
            width = e.xconfigure.width - 20;
            if (width < 100) width = 100;
            height = e.xconfigure.height - 20;
            if (height < 100) height = 100;
            XMoveResizeWindow (d, ww, 10, 10, width, height);
          }
       }

       XCloseDisplay(d);
       return 0;
    }