[mapserver-dev] ms rfc 48: adding a type keyword to the style block

[Tamas Szekeres]

Thomas,

I this is a neat idea, however it seems there are a large number of
options how the geometries could be transformed, therefore it's quite
difficult to maintain these as some pre-definied types at style level.
I'd rather like to see a custom expression to be evaluated here, which
could easily be extended according to the further requirements without
having to introduce new keywords in the mapfile. We could consider for
example something like:

STYLE
  GEOMETRYEXPRESSION  "buffer(geom, 25)"
END

An expression evaluator could easily prepare this, by building up a
hierarchy of structs containing the pointers to the geometry operation
functions along with the constant values and the geometry
placeholders. With this option we could also support complex
expressions like:

GEOMETRYEXPRESSION  "difference(buffer(geom, 25),geom)"


I think we should support this geometry transformation at layer level
as well, since for example we might want to specify labeling options
regarding to the transformed shapes. In this case the geometry
transformer should be hooked into somewhere inside the LayerGetShape
and LayerNextShape calls.


Best regards,

Tamas




2008/11/5 thomas bonfort <thomas.bonfort at gmail.com>:
> hi devs,
>
> RFC48 is Steve's idea about adding a type keyword to style blocks,
> that modifies how mapserver treats the underlying geometry. It can be
> used to draw arrowheads, bboxes, centroids and later on maybe
> convexhulls or buffers.
>
> I've committed a first draft of it here:
> http://trac.osgeo.org/mapserver/browser/trunk/mapserver/rfc/ms-rfc-48.txt
>
> Could those of you having an interest in vector rendering have a look
> and comment ?
> Any other ideas on the usage of the keyword welcome !
>
> cheers,
>
> thomas
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