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 ==

• ...?