Display boundaries and borders

[bchapuis]

Description: Openstreetmap contains tags for boundaries and borders and we should properly display them at low and high zoom levels. We currently display borders at level 13 and greater. This change probably requires to do some line work and simplifications in the database and possibly in the java code as well (for handling complex multipolygons).

Tag:
https://wiki.openstreetmap.org/wiki/Key:boundary

Attachements:

Files:
https://github.com/apache/incubator-baremaps/tree/main/basemap/layers/boundary

[YongGoose]

@bchapuis

This issue looks interesting.
Would it be okay if I take it on?

I’d like to resolve the issue below and start working on it right away.

• Update Maplibre to version 5 #924 (comment)

[bchapuis]

Great, I left a comment in the other PR. Do not hesitate to reach out if you have difficulties entering the code for the basemap or the java code.

[YongGoose]

@bchapuis

Can I ask which part of the Java code is handling the multi-polygons?

[bchapuis]

Sure, here is the class that créâtes the multiplepolygons:

incubator-baremaps/baremaps-openstreetmap/src/main/java/org/apache/baremaps/openstreetmap/function/RelationMultiPolygonBuilder.java

Line 41 in 96cf335

public class RelationMultiPolygonBuilder implements Consumer<Entity> {

[bchapuis]

The most important test for osm data is located here:

incubator-baremaps/baremaps-openstreetmap/src/test/java/org/apache/baremaps/openstreetmap/OsmDataTest.java

Line 49 in 96cf335

class OsmDataTest {

It uses the examples and corner cases listed in:
https://osmcode.org/osm-testdata/

[YongGoose]

@bchapuis

Thank you! I’ll start working on it after I get off work. 😊