offset.i4.v = window_scroll_offset_c(window_id.i2.v)

	This routine returns the number of lines scrolled off the top
	of the window indicated by "window_id".

	window_id	window ID (use WMNGR_BACKGROUND for background window)

	This function returns status values as follows:

	CBS_INVARG		invalid window ID
	CBS_NO_WINDOW		requested window does not exist
	CBS_MEMFAIL		dynamic memory allocation failure
	otherwise		offset from top of scroll buffer to top line

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	window_scroll(_c), window_query_scroll(_c), window_total_lines_c,
	window_entry_to_row_c, window_row_to_entry_c, window_hscroll_offset_c,

	C/C++ usage:

	short	window_id;
	int	offset;

	offset = window_scroll_offset_c(window_id);