Streets: Fluvial administrative boundaries look like roads

[1ec5]

Administrative boundaries have a translucent, grayish casing. It’s a good choice, but it blends in too easily with some landcover and ends up looking like a road or pier when the boundary runs over water. It’s obvious that it’s part of a boundary, but at middle zoom levels, it can make a river look like a series of disjointed lakes:

The casing should be made more transparent. Ideally, the outer edges of the casing should fade away slightly.

[nickidlugash]

@1ec5 ideally these would be more transparent, but we can't style them this way unless we have per-layer opacity, which is probably not going to happen soon. I'll investigate ways to improve this styling without opacity.

[1ec5]

A color operation could be helpful here (mapbox/mapbox-gl-style-spec#38). After all, the casing of an administrative boundary is essentially a halo. On the mapbox-gl-js side, color operations appear to have been implemented via mapbox/mapbox-gl-js#1158 and mapbox/color-ops. On the native front, there’s the https://github.com/mapbox/mapbox-gl-native/tree/color_operations branch.

[samanpwbb]

I'd be interested in switching to black dashed line with semi-transparent white halo. Better contrast with roads, and just feels more understandable.

[nickidlugash]

Black is too strong, and makes it more difficult to read text labels. I've made the line much more desaturated, and lighter. White is also too strong, since we can't implement light semi-transparencies well. I've added a line blur to the background layers, although I'm not sure what performance impact this has.

[samanpwbb]

This is in better shape now.