CLEANPLOT
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
      
       Use V6.0 notation W. Landsman April 2011