I think in this specific case the function is volatile; and was returning
the "last user interaction". Wonder if this would be represented as
an environment variable of some sort? it is a description of something that
is happening in the environment the style is being executed in.
Jody
On Thu, Jun 30, 2011 at 4:40 PM, Andrea Aime
<andrea.a...@geo-solutions.it>wrote:
> On Thu, Jun 30, 2011 at 3:54 AM, Michael Bedward
> <michael.bedw...@gmail.com> wrote:
> > On 30 June 2011 00:36, Jody Garnett <jody.garn...@gmail.com> wrote:
> >> Micheal I think we will need to mark selection lab as broken and open a
> bug
> >> report on this one; personally I would make a new Filter each time the
> >> selection changes (it is how I handle it in uDig). But that is just me
> ...
> >
> > Hi Jody, Sergey,
> >
> > I've been trying to follow this thread but must admit I'm lost. I'm
> > not familiar (= clueless) about the change to the way that styles are
> > handled, but if it means that filter functions can no longer be
> > created and used on the fly programmatically it seems that we've made
> > life harder for users (?).
>
> Style cloning has been there for a while for a variety of reasons
> (dpi, uom, simplify),
> if a function is not registered in SPI it won't be cloneable, won't be
> usable from
> CQL, SLD and so on.
>
> The tutorial at
> http://docs.geotools.org/latest/userguide/tutorial/advanced/function.html
> is way overkill though, in order to add a function all one has to do
> is to create
> the function implementation and register it in
> META-INF/services/org.opengis.filter.expression.Function
> and GeoTools will pick it up and make it cloneable.
>
> Now, if the results of the function are not stable (calling it twice
> in a row with
> the same parameters does not lead to the same result) then it also has to
> implement the VolatileFunction marker interface, but there are very few
> functions that need to do that
>
> Cheers
> Andrea
>
>
> --
> -------------------------------------------------------
> Ing. Andrea Aime
> GeoSolutions S.A.S.
> Tech lead
>
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
>
> phone: +39 0584 962313
> fax: +39 0584 962313
>
> http://www.geo-solutions.it
> http://geo-solutions.blogspot.com/
> http://www.youtube.com/user/GeoSolutionsIT
> http://www.linkedin.com/in/andreaaime
> http://twitter.com/geowolf
>
> -------------------------------------------------------
>
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