[mkgmap-dev] New branch is-in for experiments on style function is_in

Mon Dec 30 13:16:21 GMT 2019

Hi Gerd,

is the function still invoked with —is-in-hook=landuse…,  as before?
Or is it now just to be defined in the Style?
And which are the three parameters you mentioned?

Jan

> Am 30.12.2019 um 11:47 schrieb Gerd Petermann <gpetermann_muenchen at hotmail.com>:
> 
> Hi all,
> 
> with the help of Ticker I see a way to implement an is_in style function 
> I've created branch is-in to experiment with this. Sorry for the different spelling is-in in the branch name!
> 
> Unfortunately I got no response regarding the contents of the file is-in-hook-samples-v2.osm  posted here:
> http://gis.19327.n8.nabble.com/Test-cases-for-possible-is-in-hook-tp5954103.html
> So, Ticker and I have to guess what the function should do when a way or polygon crosses or touches the boundary of
> a polygon with the given attribute.
> 
> The code in r4400 implements a function is_in with three parameters which returns either true or false.
> It allows a rule like this in the lines file:
> highway=* & bicycle!=* & (is_in(landuse,cemetery,all) = true | is_in(amenity,grave_yard,all) = true) {add bicycle=dismount}
> 
> or this one in the polygons file:
> # render building only when completely outside of a residential area
> building=* & building!=no & is_in(landuse,residential,any)=false [0x13 resolution 24]
> 
> A BIG question mark is the handling of rules which change the tags of polygons. 
> Assume you have a rule like this in polygons:
> landuse=residential | landuse=commercial {set mylanduse=xyz}
> and somewhere else
> building=* & building!=no & is_in(mylanduse,xyz,any)=false [0x13 resolution 24]
> 
> It might not be obvious but this could produce more or less unpredictable results as it depends on the 
> order in which elements are processed. 
> 
> So, Ticker suggested to say "results of the is_in function are undefined when tags of polygons are changed".
> I hope we can change this to something like "changing tags of polygons in the style rules has no effect on the results of the is_in function"
> by creating copies of elements before the style rules are applied.
> 
> Gerd
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