[mkgmap-dev] multipolygons: how to flag role=inner role=outer in Style file?

Sat Feb 27 18:59:16 GMT 2010

Hi Minko,

> Is there a method in the style file to flag ways with role=outer and  
> role=inner from the same multipolygon?

Yes, the relations file can match on role. I have never tried writing  
relations rules for multipolygons, though.

> What I would like to do is something like this:
> >From lake A with type=multipolygon and way A1 {natural=water &
> role=outer} and way A2 {natural=water & role=inner}
> remove the tag natural=water from way A2 (or retag natural=water to
> natural=land?)
> 
> Is this possible?

Something like this (not tested) in the relations file of your style  
should do the trick:

type=multipolygon & natural=water { apply role=inner { set natural=land  
} }

This will assign natural=land to each inner member of multipolygon  
relations.

As far as I understand, it is not possible to write other conditions  
for the apply than role. And you cannot match role by regular  
expression. In this case, you cannot add a condition that you only want  
to set natural=land for those inner members that had natural=water.

I do not know when the custom multipolygon processing kicks in. It  
could be that the style rules are executed after that, and it is too  
late to adjust anything with style rules.

Best regards,

	Marko