Currently, opacity applies both to the fill and to the stroke simultaneously. Vegalite has the option to divert opacity into a 'strokeOpacity' and 'fillOpacity' encoding. For other writers, we may be able to apply the opacity to either the stroke or fill ourselves. We should have a think about how to expose this to users, if at all. In #142, we divert the opacity to 'fillOpacity' for layers that have the 'fill' aesthetic.
Currently, opacity applies both to the fill and to the stroke simultaneously. Vegalite has the option to divert opacity into a 'strokeOpacity' and 'fillOpacity' encoding. For other writers, we may be able to apply the opacity to either the stroke or fill ourselves. We should have a think about how to expose this to users, if at all. In #142, we divert the opacity to 'fillOpacity' for layers that have the 'fill' aesthetic.