The region fills did not paint under MapLibre, and three ticks of
instrumenting addLayer() found nothing because the failure never travels
through addLayer's return path. Listening to the map's own `error` EVENT --
the only place it surfaces -- gave it in one run:
layers.regions-fill.paint.fill-emissive-strength: unknown property
layers.regions-border.paint.line-emissive-strength: unknown property
*-emissive-strength is a Mapbox GL v3 lighting property. MapLibre rejects a
layer whose paint carries an unknown property and DROPS THE WHOLE LAYER:
addLayer() accepts the call, emits an error event, and silently omits the
layer. getLayer() then returns undefined and the map renders without it, so
it reads as "the fills do not paint" rather than as a failure.
★ THE REPO ALREADY KNEW THIS, FOR CIRCLES ONLY. useMapProvider.emissivePaint()
exists and its own docstring says "the whole layer is dropped -> invisible
pins" -- but it was hardcoded to 'circle', while the fill, line and
clustering layers still wrote the literal and kept being dropped for exactly
the documented reason. Generalised to emissivePaint(map, kind) and applied
at all five literal sites: useMapLayers x3, useCountryOutline,
useMapClustering. One helper, one rule, no sixth copy.
A second defect was hiding behind the first: regions-border still declared
'source-layer' on the geojson source ("Source layer country_boundaries does
not exist on source"), which only became visible once the paint error
stopped masking it. Fixed the same way as regions-fill.
MEASURED on the built tree: 0 error events, both layers present, and the
screenshot shows the WAGF fills painting under MapLibre -- green, blue,
purple, red, orange -- matching the Mapbox control, which is itself
re-shot and unchanged. Provider sweep 15/17 (the 2 render no map at all),
gates:pre 0, gates:post 17/18 with only the pre-existing
verify/tables-complete failure.
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