can contain %{} items that will be evaluated too.
	Note that the "%!" expression is evaluated in the context of the
	current window and buffer, while %{} items are evaluated in the
	context of the window that the statusline belongs to.

	When there is error while evaluating the option then it will be made
	empty to avoid further errors.  Otherwise screen updating would loop.
	When the result contains unprintable characters the result is
	unpredictable.

	Note that the only effect of 'ruler' when this option is set (and
	'laststatus' is 2 or 3) is controlling the output of |CTRL-G|.

	field	    meaning ~
	-	    Left justify the item.  The default is right justified
		    when minwid is larger than the length of the item.
	0	    Leading zeroes in numeric items.  Overridden by "-".
	minwid	    Minimum width of the item, padding as set by "-" & "0".
		    Value must be 50 or less.
	maxwid	    Maximum width of the item.  Truncation occurs with a "<"
		    on the left for text items.  Numeric items will be
		    shifted down to maxwid-2 digits followed by ">"number
		    where number is the amount of missing digits, much like
		    an exponential notation.
	item	    A one letter code as described below.

	Following is a description of the possible statusline items.  The
	second character in "item" is the type:
		N for number
		S for string
		F for flags as described below
		- not applicable

	item  meaning ~
	f S   Path to the file in the buffer, as typed or relative to current
	      directory.
	F S   Full path to the file in the buffer.
	t S   File name (tail) of file in the buffer.
	m F   Modified flag, text is "[+]"; "[-]" if 'modifiable' is off.
	M F   Modified flag, text is ",+" or ",-".
	r F   Readonly flag, text is "[RO]".
	R F   Readonly flag, text is ",RO".
	h F   Help buffer flag, text is "[help]".
	H F   Help buffer flag, text is ",HLP".
	w F   Preview window flag, text is "[Preview]".
	W F   Preview window flag, text is ",PRV".
	y F   Type of file in the buffer, e.g., "[vim]".  See 'filetype'.
	Y F   Type of file in the buffer, e.g., ",VIM".  See 'filetype'.
	q S   "[Quickfix List]", "[Location List]" or empty.
	k S   Value of "b:keymap_name" or 'keymap' when |:lmap| mappings are
	      being used: "<keymap>"
	n N   Buffer number.
	b N   Value of character under cursor.
	B N   As above, in hexadecimal.
	o N   Byte number in file of byte under cursor, first byte is 1.
	      Mnemonic: Offset from start of file (with one added)
	O N   As above, in hexadecimal.
	l N   Line number.
	L N   Number of lines in buffer.
	c N   Column number (byte index).
	v N   Virtual column number (screen column).
	V N   Virtual column number as -{num}.  Not displayed if equal to 'c'.
	p N   Percentage through file in lines as in |CTRL-G|.
	P S   Percentage through file of displayed window.  This is like the
	      percentage described for 'ruler'.  Always 3 in length, unless
	      translated.
	S S   'showcmd' content, see 'showcmdloc'.
	a S   Argument list status as in default title.  ({current} of {max})
	      Empty if the argument file count is zero or one.
	{ NF  Evaluate expression between "%{" and "}" and substitute result.
	      Note that there is no "%" before the closing "}".  The
	      expression cannot contain a "}" character, call a function to
	      work around that.  See |stl-%{| below.
	`{%` -  This is almost same as "{" except the result of the expression is
	      re-evaluated as a statusline format string.  Thus if the
	      return value of expr contains "%" items they will get expanded.
	      The expression can contain the "}" character, the end of
	      expression is denoted by "%}".
	      For example: >vim
		func! Stl_filename() abort
		    return "%t"
		endfunc
<	        `stl=%{Stl_filename()}`   results in `"%t"`
	        `stl=%{%Stl_filename()%}` results in `"Name of current file"`
	%} -  End of "{%" expression
	( -   Start of item group.  Can be used for setting the width and
	      alignment of a section.  Must