NamedStylesProposal

== Proposed Map File Syntax Example ==

MAP                                                                                                                                                     
  STYLE                                                                                                                                                 
    # define a named style with global visibility                                                                                                       
    NAME "some_style"                                                                                                                                   
    ...                                                                                                                                                 
  END                                                                                                                                                   
  ...                                                                                                                                                   
  LAYER                                                                                                                                                 
    NAME "uses_a_style"                                                                                                                                 
    CLASS                                                                                                                                               
       # a name instead of a block means 'use the named style directly'                                                                                 
       STYLE "some_style"                                                                                                                               
       ...                                                                                                                                              
    END                                                                                                                                                 
  END                                                                                                                                                   
  LAYER                                                                                                                                                 
    NAME "extends_a_style"                                                                                                                              
    CLASS                                                                                                                                               
      STYLE                                                                                                                                             
        # inside a style block, pull in properties from another style                                                                                   
        # then make custom changes for this LAYER/CLASS                                                                                                 
        EXTENDS "some_style"                                                                                                                            
        ...                                                                                                                                             
      END                                                                                                                                               
    END                                                                                                                                                 
  END                                                                                                                                                   
END                                                                                                                                                     

== Mapfile Extensions ==

• Enable STYLE blocks at the top MAP level

  • Add a NAME directive to the STYLE block
  • Top-level STYLE blocks ''must'' be named

• Provide a "named style" declaration in the LAYER block in the form of LAYER "name" (in addition to the existing LAYER ... END syntax)

  • The LAYER object gets instantiated with a ''copy'' of the named style from the top level
  • Referencing a non-existent STYLE by name throws an exception

• Add an EXTENDS "style" directive to the STYLE block

  • Block styles that inherit from a named style are instantied as a copy of the named style before other declarations in the STYLE block are applied

== MapServer StyleObj Extensions ==

• Add a "name" property to styleObj
• Add a "shared" property to styleObj
  • Exporting a map file would emit all styleObjs with style.shared set to true at the top level
  • Programmatic changes to shared styles would affect all classes using that style
  • If you don't want that behavior, use cloneStyle/EXTENDS
• Add a "cloneStyle" function to mapfile.c
  • This would be the programmatic interface for EXTENDS
  • cloneStyle would presumably copy a top-level style and set the new object's shared property to false
• Look at INLINESYMBOLS(?) for exporting styles
• Possibly have the styles cacaded at render time rather than at mapfile parse time and work around the default issues

== MapScript Extensions ==

• ...?