Map Types

[dcooley]

Add custom MapTypes - https://developers.google.com/maps/documentation/javascript/maptypes

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There's a proof-of-concept on branch issue25 . The tricky bit is how to add Map Type buttons to the control panel:

window[map_id + 'map'].setOptions({
  mapTypeControlOptions: { mapTypeIds: ["image","satellite"]}
});

Do we overwrite the "Map" one, or keep it? How do we let the user chose?