[Maps] Repeated labels for vector tile layers

[jsanz]

Kibana version: main

Elasticsearch version: main

Server OS version: Ubuntu 20.04

Browser version: Version 1.37.116 Chromium: 100.0.4896.127 (Official Build) (64-bit)

Browser OS version: Ubuntu 20.04

Original install method: from source

Describe the bug:

Data rendered from Elasticsearch as vector layers with multiple geometries get a label on each geometry.

Steps to reproduce:

1. Index world_countries GeoJSON file from https://maps.elastic.co/#file/world_countries
2. Add it as a layer
3. Label the iso2 field
4. Switch between scaling methods Use Vector Tiles and Limit results to 10.000

Expected behavior:

The labeling should be similar between scaling methods.

This repeated labels issue is also present when using Hexagon grids.

Screenshots (if relevant):

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[nreese]

There are 2 things going on in this issue

For the first case where there are multiple labels per world country: this occurs because maplibre adds a label to each polygon and line in MultiPolygon and MultiLineString. When using GeoJSON, the problem is resolved by creating a single label location. For MultiPolygon, the label location is the centroid of the largest polygon. For MultiLineString, the label location is the centroid of the longest line. This workaround is not available when using vector tiles and another solution is needed.

For the second case where there are multiple labels for a hexagon, this occurs when a hexagon crosses a tile boundary and maplibre labels the feature in both tiles.

[jsanz]

For the second case where there are multiple labels for a hexagon, this occurs when a hexagon crosses a tile boundary and maplibre labels the feature in both tiles.

This is a known issue for mapboxgl-js mapbox/mapbox-gl-js#5583 and suggested workarounds seem go in the direction of creating a full new layer for the labeling.

[nreese]

Elasticsearch is going to need to provide label features to resolve this issue. I created elastic/elasticsearch#86044 in Elasticsearch repo to track the issue

[nreese]

unblocked with elastic/elasticsearch#86458