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

[thomas bonfort]

just a couple of remarks:

* GEOMETRYTRANSFORM seems to me to be a better keyword than
geometryexpression, as the expression keyword is used to express
filtering in mapserver-land

* I think adding this keyword to the *layer* level poses a few
problems regarding the layer/geometry type (eg layer type geometry
with a "centroid" transform creates a point layer), that would have to
be carefully checked, as the layer type is used in a few places after
layergetshape.

thomas

On Thu, Nov 6, 2008 at 00:36, Tamas Szekeres <szekerest at gmail.com> wrote:
> 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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>