A choropleth's points and lines now draw in their wash, as its doc
says, while its areas keep the page's color at their edges. The legend
moves to the top left, so the attribution a license asks for stays clear
at any width. A key given twice fails. WorldMap's keying by ISO code,
its Natural Earth credit and its acceptance of the bundle's codes, as
Kosovo's XK, each have a test; so does an endless value.
ChoroplethLayer washes each area by its value, keyed by its id or a
property's text or number, on one hue's scale from its faintest at the
least value to its strongest at the most; an area without a value reads
as no data. ChoroplethMap lays it on the owner's map, with or without
tiles, and puts a legend of the scale and of no data in the corner; a
value that matches no area is logged once. WorldMap washes Natural
Earth's 110m countries, bundled trimmed by scripts/countries.py, by ISO
3166 alpha-2 code, and fails on a key that is no code. A shape now
paints as one fill and one edge path per world in view.
ZacharyZhang-NY