function sunsymbol, FONT=font
;+
; NAME:
;	SUNSYMBOL
; PURPOSE:
;	Return the Sun symbol as a subscripted postscript character string
; EXPLANATION:
;	Returns the Sun symbol (circle with a dot in the middle) as a 
;	(subscripted) postscript character string.    Needed because although 
;	the Sun symbol	is available using the vector fonts as the string 
;	'!9n', it is not in the standard postscript set.   
;
; CALLING SEQUENCE:
;	result = SUNSYMBOL([FONT= ])
;
; INPUTS:
;	None
;
; OPTIONAL INPUT KEYWORDS:
;       font = scalar font graphics keyword (-1,0 or 1) for text.   Note that
;              this keyword is useful for printing text with XYOUTS but *not*
;              e.g. the XTIT keyword to PLOT where the font call to PLOT takes
;              precedence.
;
; OUTPUTS:
;	result - a scalar string representing the Sun symbol.   A different
;		string is output depending (1) the device is postscript and
;		hardware fonts are used (!P.FONT=0), (2) vector fonts are used,
;		or (3) hardware fonts are used on a non-postscript device.
;		For case (3), SUNSYMBOL simply outputs the 3 character string
;		'Sun'
;
; EXAMPLE:
;	To make the X-axis of a plot read  M/M_Sun
;	IDL>  cgplot,indgen(10),xtit = 'M / M' + sunsymbol()
;
; RESTRICTIONS:
;	(1) The postscript output does not have the dot perfectly centered in 
;		the circle.   For a better symbol, consider postprocessing with
;               psfrag (see http://www.astrobetter.com/idl-psfrag/ ).
;	(2) SUNSYMBOL() includes subscript output positioning commands in the 
;		output string.
;       (3) For true-type fonts(Font=1) and IDL Versions prior to V8.2,
;           you must first use the SET_FONT keyword to Device to use a font
;           that includes the Sun Symbol, e.g. "arial Unicode MS" or
;           the Apple Symbols font.
;           http://www.idlcoyote.com/misc_tips/sun_symbol.html
;           In V8.2 and later, SUNSYMBOL() will automatically convert to the
;           DejaVuSans font to create a Sun symbol (and then return to the 
;           input font).
;       (4) Also look at CGSYMBOL http://www.idlcoyote.com/programs/cgsymbol.pro
;           which includes 'sun' as one if the symbols.
; REVISION HISTORY:
;	Written,  W. Landsman,    HSTX          April, 1997
;       Allow font keyword to be passed.  T. Robishaw Apr. 2006
;       Since IDL8.2 a Sun symbol is available for true-type fonts Feb 2013
;-
 On_error,2
 compile_opt idl2

 if N_elements(font) eq 0 then font = !p.font
 if (font EQ -1) then return,'!D!9n!N!X' else $
 if (!D.NAME NE 'PS')  then return,'!DSun!N' else begin

;Since 8.2 we can use !10 to select DejaVuSans font and then use the 
;unicode Sun symbol
 if FONT EQ 1 then $ 
     if (!VERSION.RELEASE GE '8.2') then return,'!10!D!Z(2609)!X!N' else $
     return,'!D!Z(2609)!X!N'
;Want to use /AVANTGARDE,/BOOK which is the default font 17, but to make sure
;that ISOLATIN encoding is turned off, we'll define our own font.

   device,/AVANTGARDE,/BOOK,ISOLATIN=0,FONT_INDEX = 20

   return, '!20!S!DO!R!I ' + string(183b) + '!X!N'
 endelse
 end