Fix boundary_labels

Use shape file because Tilemaker does not have a PointOnSurface
function.

boundary_labels_shape_file.md

@@ -0,0 +1,48 @@
+# Boundary Labels Shape File
+
+The *boundary_labels* layer uses a shape file of labelling points for administrative polygons as data source
+because Tilemaker offers a centroid but no PointOnSurface function. This file explains how to create the shape file.
+
+## Content of the Shape File
+
+The shape file must have the following fields:
+
+* `admin_leve`: value of OSM `admin_level=*` tag
+* `name`: value of OSM `name=*` tag
+* `name_de`: value of OSM `name:de=*` tag
+* `name_en`: value of OSM `name:en=*` tag
+* `way_area`: polygon area in ha in Web Mercator projection
+
+The features must be sorted by `way_area` in descending order.
+
+The shape file must contain features with `admin_level=2` and `admin_level=4` only.
+
+## Create Shape File with Osmium, Osm2pgsql and PostGIS
+
+You can create the shape file with Osmium, Osm2pgsql and PostGIS:
+
+Filter the planet dump using Osmium:
+
+```sh
+osmium tags-filter -o admin.osm.pbf planet-latest.osm.pbf r/admin_level=2 r/admin_level=4
+```
+
+Create database and enable PostGIS and Hstore support (you might have to create the database superuser using `createuser` first):
+
+```sh
+createdb -E utf8 -O $USER adminpolygons
+psql -d adminpolygons -c "CREATE EXTENSION postgis;"
+psql -d adminpolygons -c "CREATE EXTENSION hstore;"
+```
+
+Import filtered planet dump:
+
+```sh
+osm2pgsql -d adminpolygons --hstore --multi-geometry --latlong admin.osm.pbf
+```
+
+Export shape file:
+
+```sh
+pgsql2shp -f admin-points.shp adminpolygons "SELECT admin_level, name, tags->'name:de' AS name_de, tags->'name:en' AS name_en, ST_Area(ST_Transform(way, 3857)) / 10000 AS way_area, ST_PointOnSurface(way) AS geom FROM planet_osm_polygon WHERE osm_id < 0 AND boundary = 'administrative' AND admin_level IN ('2', '4') ORDER BY way_area DESC;"
+```

config.json

@@ -14,7 +14,9 @@
         },
         "boundary_labels": {
             "minzoom": 2,
-            "maxzoom": 14
+            "maxzoom": 14,
+            "source": "data/admin-points-4326/admin_points.shp",
+	    "source_columns": true
         },
         "addresses": {
             "minzoom": 14,

process.lua

@@ -757,9 +757,6 @@ function way_function(way)
 	end
 
 	-- Layer boundaries
-	if way:Find("boundary") == "administrative" then
-		process_boundary_labels(way)
-	end
 	process_boundary_lines(way)
 
 	-- Layer streets, street_labels
@@ -824,5 +821,21 @@ function attribute_function(attr, layer)
 		attributes["y"] = 0
 		return attributes
 	end
+	if layer == "boundary_labels" then
+		attributes = {}
+		attributes["admin_level"] = attr["admin_leve"]
+		if attributes["admin_level"] == nil then
+			attributes["admin_level"] = attr["ADMIN_LEVE"]
+		end
+		keys = {"name", "name_de", "name_en", "way_area"}
+		for index, value in ipairs(keys) do
+			if attr[value] == nil then
+				attributes[value] = attr[string.upper(value)]
+			else
+				attributes[value] = attr[value]
+			end
+		end
+		return attributes
+	end
 	return attr
 end