What do minzoom and maxzoom do in Mapbox-GL-JS exactly?

Question

What exactly do the minzoom and maxzoom properties on vector tile sources, and vector-based layers do in Mapbox-GL-JS styles? The documentation is a bit short.

Cunctation

Answer 1

In a vector tile source

Let's take this example:

"mytiles": {
    "type": "vector",
    "tiles": ["http://localhost/tiles/{z}/{x}/{y}.pbf"],
    "minzoom": 7,
    "maxzoom": 12
}

This means:

• If there is a TileJSON file available at http://localhost/tiles/tiles.json (I think), ignore its minzoom and maxzoom properties.
• Never attempt to fetch any tile outside the range 7-12.
• If a tile is needed at, say, zoom 13, then fetch the equivalent tile at zoom 12, and overzoom it instead.
• If a tile is needed at, say, zoom, 6, then don't display a tile at all. Underzooming never occurs.

If minzoom and/or maxzoom properties are not defined on the source, the equivalent properties are used from a TileJSON if available. Otherwise, tiles are assumed to be available at any zoom level requested, and no overzooming occurs. (If tiles aren't actually available, they just don't display.)

In a vector layer

Let's take this example, referring to the source above:

{
    "id": "mylayer",
    "source": "mytiles",
    "source-layer": "mytiles-layer",
    "type": "fill",
    "minzoom": 10,
    "maxzoom": 14
}

This means:

• Never display this layer at zooms less than 10, even though there are tiles available.
• Attempt to display this layer at zooms 10.0-13.9, overzooming tiles between 13.0 and 13.9 as required.
• Never display this layer at zooms 14+

If minzoom/maxzoom properties are not defined, then the layer will attempt to display at any given zoom within the source's zoom range.

On the map object

For completeness: When instantiating the Map object:

   const map = new mapboxgl.Map({
     container: 'map,
     style,
     minZoom: 8, // note the camel-case
     maxZoom: 15
   });

This means:

• Don't allow the user to zoom out less than 8, or in more than 15.

Cunctation

That sounds pretty much it, except the last bit mylayer should display at 13.9 but not 14, at least that's how it works with my testing. map.setZoom(14) hides the layer. – Smalley