Update patch set 2
Patch Set 2:
Wow, this looks great! Although I don't think a new hidden input is
> the best way to store this data on the page, because it won't work
> if there's more than one map in the form. Better would be one or
> more additional attributes on an existing part of the map input -
> the attribute name(s) should start with "data-". (https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/data-*)
That's a good point. Thanks.