draw priority is unstable in gl js

[samanpwbb]

I wish I could find better examples of this problem, but:

• Sometimes labels from one layer show up at the exact location on one refresh, and are gone on the next refresh.
• Sometimes layers lower in the order seem to have draw priority above layers higher in the stack.

[jfirebaugh]

Yeah, we're going to need examples for this to be actionable.

[samanpwbb]

The stylesheets and the views are the same here:

I know this isn't much better. I'll work on isolating the problem.

[samanpwbb]

Same map style, two different loads:

Could it have something to do with setStyle calls happening and changing up the draw priority.

[peterqliu]

I've run into this often with Emerald, starting with v8. I can't discern a pattern, though. A page refresh usually fixes the problem.

[Phrogz]

In case it's related, for me Emerald always fails to draw the ocean/rivers/continental borders, at all zoom levels:

^{Chrome Version 45.0.2454.101 m and Firefox v40.0.3
Windows 7x64
GeForce GTX 670 (Driver v355.82, released 2015-Aug-31)}

I'm seeing the same results in Mapbox Studio beta when editing a style that is based off of Emerald as well.

I get the same results on Chrome and Firefox. I (and everyone in my office) previously had a different problem with background colors changing across tiles, that was also the same across Chrome and Firefox. Updating the graphics card drivers fixed that problem. Given this cross-browser consistency, I'm guessing it's a GL interaction with the driver.

[Phrogz]

Not sure if you changed code deployed for Mapbox Studio in the last 24 hours, or if my own upgrade to Windows 7 SP1 fixed something internal, but Mapbox Studio no longer exhibits the problem I described above. (And I can't test on the mapbox-gl-styles URL any more, because you have now changed it to redirect to GitHub.)

[jfirebaugh]

(And I can't test on the mapbox-gl-styles URL any more, because you have now changed it to redirect to GitHub.)

Sorry, I actually changed that in response to your last comment and meant to post back here: the styles that were displayed there weren't being kept up to date, and the page was using a bleeding-edge version of mapbox-gl-js. Together, these made it an unreliable way to show off the available styles. Mapbox Studio has a built-in style picker, and we'll have something similar in our documentation soon.

We haven't changed anything intentionally to fix the rendering issues described here, so I suspect they disappeared for you for other reasons.

[amyleew]

Removed previous comment. Layer order was wrong... higher layers take priority over lower layers for labels.

[amyleew]

Fixed ordering but still running into some inconsistency here with the layer order. Where place-label (lrg) should take priority over place-label (med) and place-label (sm)

[lucaswoj]

I theorize this is a race condition having to do with labels that are too close to tile boundaries. Maybe #1727 will help.

[samanpwbb]

@lucaswoj it's not just borders. I have a style with two symbol layers. Whichever I edit first and apply with a smartsetstyle gets draw priority. The end result is that the things you edit end up on top, and the things you haven't edited in a while drop to the bottom.

Here's a style that should demonstrate this: https://gist.github.com/samanpwbb/0119c53b427a85ce24ef