[treee111]

This PR…

• Restores the first GUI combobox to a list of continents. Since [FEAT] Minimalistic raw maps: Download regions instead of countries #275 it also offered countries (germany) and sub-regions of a country (baden-wuerttemberg, bayern, nordrhein-westfalen, england, greater-london, british-columbia, nunavut).
• Keeps the download/processing savings of [FEAT] Minimalistic raw maps: Download regions instead of countries #275 completely intact — see the measurements below.

The cause

#275 changed geofabrik_regions from "the entries without a parent" to "every entry that is a parent of something":

# geofabrik_json.py
geofabrik_regions.add(parent)   # any parent, at any depth

That is exactly right for what #275 needed it for, but the list has a second consumer:

consumer	needs	all levels correct?
geofabrik.py:166,179,323	container maps that must not be downloaded, only their children	✅ yes — baden-wuerttemberg has to be split into its four *-regbez
input.py — first combobox	continents	❌ no — this is the bug

The list grew from 9 entries to 32, and the 7 sub-country entries showed up in the combobox next to the continents.

Considerations and implementations

geofabrik_regions is deliberately not touched — the download logic depends on it having all levels. Instead GeofabrikJson gets a small accessor for what the GUI actually wants:

def get_continents(self):
    return sorted(self.geofabrik_region_overview)

geofabrik_region_overview already holds exactly the entries without a parent, so this is the same list the combobox had up to and including v4.3.0, in the same order:

africa antarctica asia australia-oceania central-america europe north-america russia south-america

The labels go back to "Select continent:" / "Select country:" accordingly.

This does not cost us anything from #275

The minimalistic-maps benefit lives entirely in find_needed_countries and never sees the GUI:

• geofabrik.py:179 — parent in geofabrik_regions and regionname not in geofabrik_regions → border maps are always taken at the deepest available level
• geofabrik.py:166 — regionname not in geofabrik_regions → a selected container map is never downloaded as itself

The second point is the important one: combobox 2 still offers every container map, and selecting one already triggers the split. Pick netherlands and you get its 12 provinces; pick germany and you get the ~38 state/regbez files, never germany-latest.osm.pbf.

Measured by running the selection algorithm with both definitions of geofabrik_regions and summing the actual PBF sizes from geofabrik:

wanted_map = belgium
  before #275 :  6 files   13.616 MB   belgium france germany luxembourg netherlands united-kingdom
  with  #275  : 17 files    2.793 MB   21% — 10,8 GB less

wanted_map = netherlands
  before #275 :  4 files   11.428 MB   belgium france germany netherlands
  with  #275  : 22 files    3.771 MB   33% — 7,7 GB less

The saving comes from the two files that disappear — france-latest.osm.pbf (4.832 MB) and germany-latest.osm.pbf (4.602 MB) were pulled in full just to cover a border strip. Both of these maps are selected from combobox 2, so both keep the full saving after this PR.

What is no longer possible

Creating a map of a sub-country region directly from the GUI — greater-london or freiburg-regbez now require selecting united-kingdom resp. germany. That was the side effect @Ebe66 described in #275:

a possibly desired side effect is that in the GUI you can now select regions of a country to create […] I call it a plus others might disagree

It is a question of selection scope, not of speed, and the mixed-level combobox is not a good way to offer it. The CLI is unaffected — python -m wahoomc cli -co greater-london still works. If we want it in the GUI, a proper continent → country → region cascade on develop is the way, not a release branch.

How to test

1. Start the GUI. The first combobox contains 9 entries, all continents — no baden-wuerttemberg, bayern, england, nunavut, …
2. Select europe → germany → Create map. The log shows the German state/regbez files being downloaded, not germany-latest.osm.pbf.
3. Select europe → belgium → Create map. Border coverage comes from alsace, lorraine, duesseldorf-regbez, koeln-regbez, kent, … and neither france nor germany is downloaded.
4. python -m unittest tests.test_constants_geofabrik — includes the new test_continents_of_geofabrik.

Pull Request Checklist

• Reviewed the Contributing Guidelines
  • Especially the Pull-Requests section
• Commits (and commit-messages) are understandable
• Tested with macOS / Linux
• Tested with Windows

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