addProtocol for multiple mbtiles under the same source

[BenOnTrack]

I'm working on a svelte app, that has a maplibre Map and that contains a unique source (I'm using the wrapper maplibre-svelte)

        id="basemap"
        tiles={[
            "mbtiles://./basemap/asia/taiwan/{z}/{x}/{y}",
            "mbtiles://./basemap/asia/japan/{z}/{x}/{y}",
        ]}
        minzoom={8}
        maxzoom={14}
        promoteId={"id"}

According to https://maplibre.org/maplibre-style-spec/sources/, this implementation is correct (as similar to maplibre-streets)

I have locally stored my 2 .mbtiles that contains "basemap" tiles respectively for Taiwan and Japan.
I've added a custom "mbtiles" protocol that fetches the tiles with the addProtocol method.

It works great if I have a unique source, for instance tiles = {["mbtiles://./basemap/asia/taiwan/{z}/{x}/{y}"]} and I'm panning above Taiwan.

If I keep both sources as showed above, then I end up with a glitch where some tiles for Taiwan would be showed and some not (as if they were overlapped by the null tiles fetched from the source Japan). In other words, I expect Japan tiles to return null (since I'm panning over Taiwan) but I would not expect that it overlaps the correct tiles fetched from Taiwan...

So I end up with something like:

where half of the tiles from Taiwan source are properly showed, and half of them seem to be overlapped with blank tiles (or not showed)

I perfectly know that the workaround is to split my vector tile source for each source (something like basemap-taiwan / basemap-japan) and duplicate my 100+ layers style but it is not sustainable if I have multiple sources (let's assume one per country) and it would be a pain to manage dynamically (assume new source once the User download new .mbtiles).

Is there any way this should work ?

[HarelM]

If you are using addProtocol I don't see any value in passing two tile addresses.
Simply write a single address, can be as simple as mbtiles://{z}/{x}/{y}
And inside the addProtocol method decide according to the given tile addresses from which source to fetch.
Wouldn't that solve your problem?

[BenOnTrack]

If I only provide z, x and y in my address, then this is the only information addProtocol can have access to, right ? (via the url)
Hence, how would I be able to guide which source to fetch ?

Today I provide a "source", a "continent" and a "country", so I can target the correct .mbtiles, and its corresponding sql database to fetch the tiles.

Would you be able to provide with some directions on how to do otherwise ? Unless based on z/x/y you compute a bounding box and target the correct .mbtiles ?

[HarelM]

Yes, compute the bbox from x y z and select the right source.

[BenOnTrack]

Thanks. I'll give it a try, Is there a way to retrieve the .mbtiles bounding box from its metadata ?

I'm computing my .mbtiles based on geofabrik .pbf that are split by region. I've always been curious how it would work since their region are not always split by "bounding box" (in other words, those are not rectangle - but geographic region, so they can take any shape) - in that case, mbtiles would end up with overlapping tiles for some z/x/y (if that makes sense) -> for those tiles, i would end up with the sam concern of having to fetch 2 db at the same time.

For instance, take Japan https://download.geofabrik.de/asia/japan.html you can easily see that the .pbf are not defined by bounding box. in other words a z/x/y tile could belong to 2 .mbtiles

Bonus question : why is tiles an array if it does not work for multiple sources ?

[BenOnTrack]

I confirm it's working great! Thanks so much for your support!