#include <cairo.h>
#include <cairo-xlib.h>
#include <math.h>       /* fuer die Berechnung der Ballhoehe */
#ifndef PI
#define PI 3.14159265358979323846
#endif

int main(int argc, char *argv[])
{
  /* Variablen fuer X11 */
  Display *display;
  int screen;
  Window win;
  GC gc;
  int width, height;
  float x,y,t;
  width = 400;
  height = 200;
  /* Variablen fuer Cairo */
  cairo_surface_t *surface;
  cairo_surface_t *imagesurface; /* Puffer */
  cairo_t *cr;
  cairo_t *crimage; /* Drawing context fuer Puffer */
  /* X11-Fenster oeffnen */
  display = XOpenDisplay(0);
  screen = DefaultScreen(display);
  win = XCreateSimpleWindow(display, DefaultRootWindow(display), 0, 0, width, height, 0, WhitePixel(display, screen), WhitePixel(display, screen));
  XMapWindow(display, win);
  /* Cairo Surface in X11 oeffnen: */
  XClearWindow(display, win);
  surface = cairo_xlib_surface_create(display, win, DefaultVisual(display, DefaultScreen(display)), width, height);
  /* Jetzt den Hintergrund-Puffer einrichten: */
  imagesurface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width, height);
  /* Drawing Context holen */
  cr = cairo_create(surface);
  crimage = cairo_create(imagesurface);
  /* Zeichnen */
  for (t=0; t<6*PI; t=t+(0.01))
    {
    x = 50;
    /* hier wird die aktuelle Hoehe berechnet */
    y = 100-(100*exp((-t)*0.3)*fabs(cos(t)));
    /* Schwarze Farbe waehlen */
    cairo_set_source_rgb(crimage, 0, 0, 0);
    /* Grundlinie malen */
    cairo_move_to(crimage, 0,120);
    cairo_line_to(crimage, 400,120);
    cairo_stroke(crimage);
    /* kopiere Ball an seine Position */
    cairo_arc(crimage, x, y, 20, 0, 2*M_PI );
    cairo_fill(crimage);
    /* Und das vorbereitete Image in das Fenster kopieren */
    cairo_set_source_surface(cr, imagesurface, 0, 0);
    cairo_paint(cr);
    /* Hintergrund-Puffer loeschen */
    cairo_set_source_rgb(crimage, 1, 1, 1);
    cairo_rectangle(crimage, 0,0,width,height);
    cairo_fill(crimage);
    cairo_set_source_rgb(crimage, 0, 0, 0);
  } /*for*/
  /* Cairo aufraeumen */
  cairo_destroy(crimage);
  cairo_destroy(cr);
  cairo_surface_destroy(imagesurface);
  cairo_surface_destroy(surface);
  /* X11 aufraeumen */
  XDestroyWindow(display, win);
  XCloseDisplay(display);
  return 0;
}