addPersistentStyleCustomLayer

open fun addPersistentStyleCustomLayer(layerId: String, layerHost: CustomLayerHost, layerPosition: LayerPosition): Expected<String, None>

Adds a new [style custom layer](https://docs.mapbox.com/mapbox-gl-js/style-spec/#layers). Whenever a new style is being parsed and currently used style has persistent layers, an engine will try to do following: - keep the persistent layer at its relative position - keep the source used by a persistent layer - keep images added through `addStyleImage` method In cases when a new style has the same layer, source or image resource, style's resources would be used instead and `MapLoadingError` event will be emitted.

Return

string describing an error if the operation was not successful, or empty otherwise.

Parameters

layerHost

The `custom layer host`.

layerId

A style layer identifier.

layerPosition

If not empty, the new layer will be positioned according to `layer position` parameters.