Add support for "mapnik-geometry-type" in filters

[strk]

This is a simple implementation of support for mapnik-geometry-type use in filters.
See #180

I'm probably missing something about the use of variables (ie: should we allow a variable to expand to "mapnik-gemetry-type" ? I suppose that part isn't implemented).

Also, this implementation doesn' t use any support of mapnik-reference

[strk]

We've been using this in staging for these 3 weeks and it works fine. Anything I could do to help merging this in ?

[springmeyer]

I'd prefer to rename this in mapnik to something that will work long term rather than embed compatibility in the carto code. Ideally mapnik-reference could be used to declare the name of this magic word across mapnik versions (once/if we rename).

[strk]

We're using mapnik-geometry-type in production on cartodb.com already, do you think it'll be feasible to have that kind of interface or what did you have in mind ?

[strk]

any news about this ?

[springmeyer]

sorry, no news. lost track of this. Each time I have a moment to work on exposing it in mapnik-reference I see the need for other fixes. I'll put this back on my list though.

[tmcw]

Isn't this patch just adding a shorthand of ["mapnik-geometry-type"=foo] for ["mapnik::geometry-type"=foo]?

[strk]

So it looks, but the consequence is you can use mapnik-geometry-type with no quotes, as suggested by @artemp here: #180 (comment)

We've been using [mapnik-geometry-type=<num>] constructor for a long time now.

[tmcw]

That ticket seems to think mapnik-geometry-type would be implemented in mapnik, not aliased in Carto, right?

[strk]

I don't now if it'll ever be implemented in mapnik, given mapnik already exposes the pseudo-attribute mapnik::geometry_type -- it was you suggesting to support the mapnik-geometry-type naming (comment above artemp's). To me it sounds cleaner (for mapnik) to use the :: syntax

[strk]

@springmeyer any chance to look at this ?

[springmeyer]

no chance yet, need some time to thing about the big picture of this.

[strk]

Everyone happy about using "mapnik::geometry_type" ? We may decide to automatically convert our custom mapnik-geometry-type back to "mapnik::geometry_type" when upgrading to mapnik-2.2.x if that's the final decision...

[tmcw]

Closing; everyone is on board for "mapnik::geometry_type"