Elongated, black triangles on random streets

[1ec5]

As of 7a43f8b on master, I’m seeing some occasional artifacting in the form of elongated, black triangles at either endpoint of a street. For example, here’s a screenshot of the 12/1171/1566 tile in Mapbox Streets v9 on iOS 9.3 on an iPhone 6 after choosing Add 100 Point Annotations from the menu:

Here are some more examples in the 11/585/783 tile:

/cc @jfirebaugh @kkaefer

[jfirebaugh]

Can you bisect this?

[1ec5]

A bisect implicates a43940a, part of #4839. 27baa34 is unaffected by this bug.

[1ec5]

Also worth noting that this issue affects iPhone 6 but not any iOS simulator and not the OS X SDK.

[jfirebaugh]

Thanks, the bisect helped hugely. I was able to reproduce the issue, and found that reverting the default for line-round-limit to 1 resolved the issue.

a43940a changed the default to 1.05 because 1.05 is the correct value according to the style-spec. Apparently that value triggers latent bugs in gl-native however.

[jfirebaugh]

Followups to #5258.