wn_select_rectangle_c

	status.i4.v = wn_select_rectangle_c(window_id.i4.v, color.i4.v,
					    options.u4.v, x.r4.v, y.r4.v,
					    x2.r4.r, y2.r4.r)

	This routine allows the user to select a rectangular portion
	of a graphics window.

	window_id	window ID (use WN_BACKGROUND for background window)
	color		color with which to draw the rubberband rectangle
	options		routine options (not used)
	x, y		initial coordinates
	x2, y2		returned coordinates (These coordinates should be
			initialized by the caller to establish the initial
			rectangle.)

	This function returns ACNET status values as follows:

	OK			success
	CBS_INVARG		invalid ID or coordinates specified
	CBS_INVID		this window does not exist

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	wn_view(_c), wn_world(_c), wn_active(_c), wn_get_active, wn_color(_c),
	wn_draw_mode(_c), wn_box(_c), wn_cursor_init(_c), wn_cursor_disable,
	wn_cursor_update, intro_graphics_windows

	C/C++ usage:

	int	status;
	int	window_id;
	int	color = YELLOW;
	unsigned int	options = 0;
	float	x = 1.0;
	float	y = 1.0;
	float	x2 = 1.0;
	float	y2 = 1.0;

	status = wn_select_rectangle_c(window_id,color,options,x,y,&x2,&y2);