Hi,
as you may know in GeoServer we have a community module allowing
to style maps using a CSS syntax:
http://docs.geoserver.org/latest/en/user/extensions/css/index.html
The module uses a Scala based parser which eventually translates the
style into an equivalent SLD form.
The scala parser has been source of some issues:
* The module is not actively developed (last commit is 8 months old), and
some
pull requests have been waiting to be accepted for months
* The number of developers proficient with Scala is quite limited
(proficient as in,
someone that can go and write changes to the module straight away)
* There has been some complaint about the CSS->SLD translation performance
A few months ago Jody was suggesting to fork the module and rewrite it in
Java
to get a larger potential maintaner base (
http://osgeo-org.1560.x6.nabble.com/GeoTools-GeoServer-Meeting-2013-12-10-td5093533.html#a5093665).
..
which is what I did in the last couple of weekends, initial results here:
https://github.com/aaime/geotools/tree/css
For the moment I have a (supposedly) complete parser for the syntax
currently
used by GeoServer based on the parbolied parser library
https://github.com/sirthias/parboiled/wiki
This library was suggested originally by David Winslow as we were talking
about
the possibility of a Java rewrite some months ago.
The plan is to move forward and create a CSS->SLD translator in the next
few weeks,
trying to pay attention to performance, and see if some of the issues in
the existing
Scala version can be solved too, e.g., creationg of a line and polygon
symbolizer
when a single polygon symbolizer would do, and no use of ElseFilter for the
rules matching "everything else".
I'll probably have to pimp up the SimplifyingFilterVisitor a bit to
recognize filters
that match everything, or nothing, to do the above, which in the end will be
of benefit also for all other users of the class above (e.g., stores
translating filters
into some sql/xml format)
Feedback welcomed
Cheers
Andrea
--
==
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Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
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Italy
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