#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <cairo/cairo-xlib.h>
 
int main(void) {
   Display *d;
   Window w;
   XEvent e;
   cairo_surface_t *surface;
   cairo_t *cr;
   int s;
 
   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, 100, 100, 1,
                           BlackPixel(d, s), WhitePixel(d, s));
   XSelectInput(d, w, ExposureMask | KeyPressMask);
   XMapWindow(d, w);

   surface = cairo_xlib_surface_create(d, w, DefaultVisual(d, s), 100, 100);
   cr = cairo_create(surface);
 
   while (1) {
      XNextEvent(d, &e);
      if (e.type == ConfigureNotify) {
	      cairo_xlib_surface_set_size(surface, e.xconfigure.width, e.xconfigure.height);
      }
      if (e.type == Expose) {
		cairo_set_source_rgb(cr, 1, 1, 1);
		cairo_paint(cr);

		cairo_set_source_rgba(cr, 0, 0, 0, 0.2);

		cairo_rectangle(cr, 10, 10, 80, 80);
		cairo_fill(cr);

		cairo_rectangle(cr, 20, 20, 60, 60);
		cairo_fill(cr);

		cairo_rectangle(cr, 30, 30, 40, 40);
		cairo_fill(cr);

		cairo_rectangle(cr, 40, 40, 20, 20);
		cairo_fill(cr);

	 cairo_surface_flush(surface);
      }
      if (e.type == KeyPress)
         break;
   }
 
   cairo_destroy(cr);
   cairo_surface_destroy(surface);
   XCloseDisplay(d);
   return 0;
}