[MapServer Docs] Add note in SLD doc for spatial filtering

[jmckenna@…]

> 
> Having seen your excellent web page on SDL’s 
> (http://mapserver.gis.umn.edu/doc44/sld-howto.html), I wonder if you 
> could advise me on how I can features differently, based upon spatial 
> location. An example would be showing schools as red points within a 
> particular bounding box, whereas outside the bounding box, they would 
> appear black.
> 
>  
> 
> The WMS specification alludes to it, but doesn’t provide a concrete 
> example, that I can see.
> 


Hi There,

 Check at these urls (and the slds) : it will give you an idea on how to acheive
that. Basically you need to do it in 2 separate requests :

   * first request is a regular wms get map request all all elements drawn in
the default way that you want (an sld might me used or not)
   * the second request will use an sld with a filter encoding bbox element that
will only select elements inside a region and draw them accoring to waht is
defined in the sld.



http://www2.dmsolutions.ca/cgi-bin/mswms_world?SERVICE=WMS&VeRsIoN=1.1.1&Request=GetMap&LAYERS=WorldGen_Outline&SLD=http://www2.dmsolutions.ca/msapps/world_testdata/tests/sld_tests/sld_line_simple_spatial.xml

http://www2.dmsolutions.ca/cgi-bin/mswms_world?SERVICE=WMS&VeRsIoN=1.1.1&Request=GetMap&LAYERS=WorldGen_Outline&SLD=http://www2.dmsolutions.ca/msapps/world_testdata/tests/sld_tests/sld_line_simple_spatial2.xml

[jmckenna@…]

reassigning

[jmckenna@…]

added spatial filter to sld doc, in CVS