Supplements a font with ligatures of country and US state shapes. E.g. type "stateCA" -> California shape, "countryCA" -> Canada shape.

geo_ligatures.py

import fontforge
import json

from shapely.geometry import shape, MultiPolygon
from shapely.affinity import translate

font = fontforge.open("Arial.ttf") # font to edit
font.fullname = "Geo Ligatures"
font.familyname = "Geo Ligatures"
font.fontname = "GEO_LIGATURES"
font.version = "1.0"
font.addLookup('ligatures','gsub_ligature', (),[['rlig',[['latn',['dflt']]]]])
font.addLookupSubtable('ligatures', 'ligatureshi')

glyph_w = 1000
glyph_h = 800

def scaled_xy(x, y, minx, miny, maxx, maxy):
    scaled_x = (x - minx)/(maxx - minx)
    scaled_y = (y - miny)/(maxy - miny)
    return (scaled_x * glyph_w, scaled_y * glyph_h)

def create_ligature(geo_file, code_col, ligature_prefix):
    with open(geo_file, "r") as f:
        features = json.load(f)["features"]

    for i, feature in enumerate(features):
        first_char = feature["properties"][code_col][0]
        second_char = feature["properties"][code_col][1]
        ligature_name = f"{ligature_prefix}_{first_char}_{second_char}"
        ligature_glyph = font.createChar(-1, ligature_name)

        ligature_tuple = tuple(list(ligature_prefix) + [first_char, second_char])
        ligature_glyph.addPosSub('ligatureshi', ligature_tuple)
        pen = ligature_glyph.glyphPen()

        mpoly = shape(feature["geometry"])

        if mpoly.geom_type == "Polygon":
            mpoly = MultiPolygon([mpoly])

        new_geoms = []
        for part in mpoly.geoms: # handle features that straddle antimeridian
            if part.centroid.x < 0:
                new_geoms.append(translate(part, xoff=360.0, yoff=0.0, zoff=0.0))
            else:
                new_geoms.append(part)
        mpoly = MultiPolygon(new_geoms)

        bnds = mpoly.bounds

        for j, part in enumerate(mpoly.geoms):
            coords = scaled_xy(*part.exterior.coords[0], *bnds)
            pen.moveTo(coords)

            for coords in part.exterior.coords[1:]:
                pen.lineTo(scaled_xy(*coords, *bnds))

            pen.closePath()
        
        pen = None

        ligature_glyph.width = 1000
        ligature_glyph.autoInstr()

create_ligature("states.geojson", "postal", "state")
create_ligature("countries.geojson", "ISO_A2", "country")

font.generate("./geo-ligatures.ttf") # output font
font.save()