Pro CleanPlot, silent=silent, ShowOnly = showonly ;Reset System  Variables 
;+
; NAME:
;       CLEANPLOT
; PURPOSE:
;       Reset all plotting system variables (!P,!X,!Y,!Z) to their default values
; EXPLANATION:
;       Reset all system variables (!P,!X,!Y,!Z) which are set by the user
;       and which affect plotting to their default values.
;
; CALLING SEQUENCE:
;       Cleanplot, [ /Silent, /ShowOnly]
;
; INPUTS:       
;       None
;
; OPTIONAL KEYWORD INPUT:
;       /SHOWONLY - If set, then CLEANPLOT will display the plotting system
;                 variables with nondefault values, but it will not reset them.
;               
;       /SILENT - If set, then CLEANPLOT will not display a message giving the 
;                 the system variables tags being reset.    One cannot set 
;                  both /SILENT and /SHOWONLY
; OUTPUTS:      
;       None
;
; SIDE EFFECTS: 
;       The system variables that concern plotting are reset to their default
;       values.  A message is output for each variable changed.
;       The !P.CLIP and CRANGE, S, WINDOW, and REGION fields of the
;       !X, !Y, and !Z system variables are not checked since these are
;       set by the graphics device and not by the user.   
;
; PROCEDURE:
;       This does NOT reset the plotting device.
;       This does not change any system variables that don't control plotting.
;
; RESTRICTIONS:
;       If user default values for !P, !X, !Y and !Z are different from
;       the defaults adopted below, user should change P_old etc accordingly
;
; MODIFICATION HISTORY:
;       Written IDL Version 2.3.0  W. Landsman & K. Venkatakrishna May '92
;       Handle new system variables in V3.0.0     W. Landsman   Dec 92
;       Assume user has at least V3.0.0           W. Landsman   August 95
;       V5.0 has 60 instead of 30 TICKV values    W. Landsman   Sep. 97
;       Change !D.N_COLORS to !D.TABLE_SIZE for 24 bit displays
;               W. Landsman  April 1998
;       Added silent keyword to supress output & modified X_old to
;       handle the new !X and !Y tags in IDL 5.4   S. Penton     July 2000
;       Test for visual depth if > V5.1   W. Landsman     July 2000
;       Macs can report a visual depth of 32  W. Landsman  March 2001
;       Call device,get_visual_depth only for device which allow it 
;                W. Landsman  June 2001
;       Default !P.color is 16777215 for 16 bit systems 
;                       W. Landsman/M. Hadfield   November 2001 
;       Added ShowOnly keyword   W. Landsman      April 2002
;       
;-
 if not keyword_set(silent) then silent=0B

 On_error,2
 if keyword_set(showonly) then begin
     print,'Current Plotting System Variables with non-default Values'
     clearing = ''
     oldvalue = ' '
     reset = 0
 endif else begin
     clearing = 'Clearing '
     oldvalue = ', old value '
     reset = 1
 end
; For !X, !Y, and !Z we will assume that the default values except for MARGIN are 
; either 0 or '', while for !P we explicitly write all default values in P_old

 P_old = { BACKGROUND: 0L,CHARSIZE:0.0, CHARTHICK:0.0,  $
          CLIP:[0L,0,639,511,0,0], $                      ;Not used
          COLOR : !D.TABLE_SIZE-1, FONT: -1L, LINESTYLE: 0L, MULTI:lonarr(5),$
          NOCLIP: 0L, NOERASE: 0L, NSUM: 0L, POSITION: fltarr(4),$
          PSYM: 0L, REGION: fltarr(4), SUBTITLE:'', SYMSIZE:0.0, T:fltarr(4,4),$
          T3D:0L, THICK: 0.0, TITLE:'', TICKLEN:0.02, CHANNEL:0L }
 
 X_old=!X
for i=0,n_tags(!X)-1 do $
    if size(!X.(i),/type) eq 7 then X_old.(i)= '' else X_old.(i) = 0

 X_old.MARGIN = [10.0,3.0]
 
 Y_old = X_old
 Y_old.MARGIN = [4.0, 2.0]

 Z_old = X_old
 Z_old.MARGIN = [0.0, 0.0]

 P_var = tag_names(!P)

 if !D.NAME EQ 'PS' then begin 
          P_old.background = 255
          P_old.color = 0 
 endif else if  ( (!D.NAME EQ 'X') or (!D.NAME EQ 'MAC') or $
                  (!D.NAME EQ 'WIN') ) then begin
          device,get_visual_depth = depth  
          if depth GT 8 then P_old.color = 16777215 else $
                             P_old.color = 256L^(depth/8) - 1
 endif
 
; Reset !P to its default value except for !P.CLIP
       
   for i=0, N_elements(P_var)-1 do begin
     if i NE 3 then begin 
     n = N_elements(!P.(i))
     if ( total( (!P.(i) EQ P_old.(i))) NE n ) then Begin
         if not silent then $
            Print,clearing +  '!P.'+P_var[i]+ oldvalue +'=',!P.(i)
        if reset then !P.(i) = P_old.(i)
        EndIf
    endif
 endfor
;                               Reset !X !Y and !Z to their default values
 X_var = tag_names(!X)
 Y_var = tag_names(!Y)
 Z_var = tag_names(!Z)

 for i = 0, n_tags(!X)-1 do begin
   if total( i EQ [7,8,11,12] ) EQ 0 then begin  ;Skip S,CRANGE,WINDOW,REGION
       n = N_elements(!X.(i))

       if ( total( (!X.(i) EQ X_old.(i))) NE n ) then Begin
       if not silent then $
          Print,clearing + '!X.'+X_var[i]+ oldvalue + '=', !X.(i)
       if reset then !X.(i) = X_old.(i)
       EndIf
 
       if (total( (!Y.(i) EQ Y_old.(i))) NE n ) then Begin
       if not silent then $
          Print,clearing + '!Y.'+Y_var[i]+ oldvalue + '=', !Y.(i)
       if reset then !Y.(i) = Y_old.(i)
       EndIf

       if (total( (!Z.(i) EQ Z_old.(i))) NE n) then Begin
       if not silent then $
          Print,clearing +'!Z.'+Z_var[i]+ oldvalue + '=',!Z.(i)
       if reset then !Z.(i) = Z_old.(i)
       EndIf
   endif
endfor

Return                                  ;Completed
End