#include <X11/Xlib.h>

#include <stdio.h>
#include <stdlib.h>		
#include <unistd.h>		

#define GOOD	1
#define BIG_REQ	2
#define TOO_LONG	3

static Display	*display;
static Drawable	d;
static GC		gc;
static Window	win;
static int screen_num;
static XPoint	*points;
static int		npoints;
static int		mode;

unsigned int display_width, display_height;	
unsigned int win_width, win_height;	

void prepare_points(int npoints)
{
	int i, x, y;

	x = y = 10; 

	points = (XPoint *)malloc(sizeof(XPoint)*npoints);
	if (points == NULL)
	{
		fprintf(stderr, "cannot allocate memory of %d XPoint\n", npoints);
		exit (1);
	}

	for (i = 0; i < npoints; i++)
	{
		(points+i)->x = x;
		(points+i)->y = y;

		x += 10;
		y += 10;

		if (x >= win_width)
		{
			x = 10;
		}

		if (y >= win_height)
		{
			y = 10;
		}
	}
}

void drawlines(Display* display, Window win, GC gc, int mode)
{
  switch (mode) {
    case GOOD:
		npoints = (XMaxRequestSize(display) - 3)/2;

		prepare_points(npoints);

		break;
	case BIG_REQ:
		npoints = XExtendedMaxRequestSize(display);

	    if (npoints)
	    {
	      npoints = ((npoints - 3) >> 2 ) << 2;
		  prepare_points(npoints);
	    }
		else
	    {
			fprintf(stderr, "the server cannot support bigrequest extension\n");
			return; 
		}
		break;
	case TOO_LONG:
		npoints = XExtendedMaxRequestSize(display);

	    if (npoints)
	    {
	      npoints = ((npoints + 3) >> 2 ) << 2;
		  prepare_points(npoints);
	    }
		else
	    {
			fprintf(stderr, "the server cannot support bigrequest extension\n");
			return; 
		}
	    break;  
	}

  XDrawLines(display, win, gc, points, npoints, CoordModeOrigin);

  free(points);
}

void
main(int argc, char* argv[])
{
  unsigned long valuemask = 0; 
  XGCValues values;	
  int win_border_width = 2;
  int mode = 0;
  char *display_name = getenv("DISPLAY");  

  display = XOpenDisplay(display_name);
  if (display == NULL) {
    fprintf(stderr, "%s: cannot connect to X server '%s'\n",
            argv[0], display_name);
    exit(1);
  }

  screen_num = DefaultScreen(display);
  display_width = DisplayWidth(display, screen_num);
  display_height = DisplayHeight(display, screen_num);

  win_width = (display_width / 2);
  win_height = (display_height / 2);

  printf("window width - '%d'; height - '%d'\n", win_width, win_height);

  win = XCreateSimpleWindow(display, RootWindow(display, screen_num),
                            0, 0, win_width, win_height, win_border_width,
                            BlackPixel(display, screen_num),
                            WhitePixel(display, screen_num));
  XMapWindow(display, win);

  XFlush(display);

  gc = XCreateGC(display, win, valuemask, &values);
  if (gc < 0) {
	fprintf(stderr, "XCreateGC: \n");
  }

  XSetForeground(display, gc, BlackPixel(display, screen_num));
  XSetBackground(display, gc, WhitePixel(display, screen_num));

  XSync(display, False);


  for (mode = GOOD; mode <= TOO_LONG; mode++)
  {
	drawlines(display, win, gc, mode);
  
    XFlush(display);

    sleep(5);

	XClearWindow(display, win);
  }

  XCloseDisplay(display);
}