Use Case: Offline maps

[prushforth]

This issue is for discussion of the use case “Save map content for offline use”, its examples & list of required capabilities.

---

I believe that service workers goes a long way towards enabling this use case, but in Canada, for instance the location I am writing this from, there are large areas that are poorly connected to the internet.

So having the ability either built-in or provided by the author, to download and cache map content for offline use would be important.

If we agree on a declarative vocabulary for map content, it should even be possible to make this a feature of the map widget even without the author doing work to enable it.

[AmeliaBR]

This is definitely an important use case!

How it would look in practice depends on a lot of other implementation decisions. E.g., can the user save map data / open a map in a stand-alone tab? If so, does this pre-fetch extra tiles/content not currently displayed? If so, how would the user specify how much data to pre-fetch (e.g., from a tileset that might cover the entire world at many resolution levels)?