/* diamond.cc */

#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <stdio.h>
#include <math.h>

#define N 16

unsigned long GetColor( Display* dis, char* color_name )
{
  Colormap cmap;
  XColor near_color, true_color;
  
  cmap = DefaultColormap( dis, 0 );
  XAllocNamedColor( dis, cmap, color_name, &near_color, &true_color );
  return( near_color.pixel );
}


int main( void )
{
  Display* dis;
  Window win;
  XSetWindowAttributes att;
  GC gc;
  XEvent ev;
  
  int x[N],y[N];
  int i,j;
  
  dis = XOpenDisplay( NULL );
  win = XCreateSimpleWindow( dis, RootWindow(dis,0), 100, 100,
	    256, 256, 3, WhitePixel(dis,0), BlackPixel(dis,0) );
  
  att.backing_store = WhenMapped;
  XChangeWindowAttributes( dis, win, CWBackingStore, &att );
  
  XSelectInput( dis, win, ExposureMask );
  XMapWindow( dis, win );
  
  do{
    XNextEvent( dis, &ev);
  }while( ev.type != Expose );
  
  gc = XCreateGC( dis, DefaultRootWindow(dis), 0, 0 );
  XSetForeground( dis, gc, GetColor( dis, "green")  );
  
  
  for( i=0 ; i<N ; i++ ){
    x[i] = (int)(128*cos(2*M_PI*i/N))+128;
    y[i] = (int)(128*sin(2*M_PI*i/N))+128;
  }
  
  for( i=0 ; i<N ; i++ ){
    for( j=i+1 ; j<N ; j++ ){
      XDrawLine( dis, win, gc, x[i], y[i], x[j], y[j] );
    }
  }
  
  XFlush( dis );
  
  printf("Push return key.");
  getchar();
  XDestroyWindow( dis , win );
  XCloseDisplay( dis );
  
  return(0);
}