Metal: Incorrect reuse of sprites for line-pattern

[chchrn]

Describe the bug

In our product we use a style with line-pattern. In versions that use MetalKit for map rendering we noticed a problem with filling lines with pattern.

I have prepared a test project demonstrating the problem (attached).

The project style is available in style.json file or at https://api.npoint.io/7dac9318bfb95b18a9dc.

The example uses a simple geojson with two lines, one should be filled with a black dashed line and the other with yellow icons.

On a small zoom everything shows up as it should, but if you zoom in on the map you can see that the styles get mixed up.
The yellow line starts to appear as a black dashed line and vice versa.

The problem seems to be the reuse of sprites.

We have only noticed this problem for the line-pattern property.

Before using the pre-metalKit version, we had no problems. The problem persists on the latest version 6.5.4 , and is also definitely present on 6.5.0

MlnPatterBug.zip

Screenshots

Platform information (please complete the following information):

• OS: iOS
• Platform: iOS
• Version: 6.5.4

[louwers]

Thanks for the bug report. I'll have a look if I can create a render test for this.

[moodstubos]

We have the same problem with current Android release: android-v11.1.0

[sjg-wdw]

@alexcristici see if you can fix this and ideally create a test for it.

[chchrn]

@alexcristici how can I help with finding the bug? Do you have any idea what the bug might be?

[alexcristici]

@chchrn I'm investigating the pattern_from and pattern_to data driven attribute buffers.

[iwo]

This issue is probably a root cause of #2621

It can easily be reproduced on Android (both real device and emulator) using the minimalistic sample style provided above.

@TimSylvester I see you recently worked on LineLayerTweaker, maybe you could help with this bug?

[TimSylvester]

I don't think it's just the pattern coordinates getting mixed up, the geometry seems to be wrong. Somehow a drawable is ending up with positions, and their matching texture coordinates, from both lines. I think that points to a problem in the bucket.

Scratch that, it seems to be normal to add geometry outside the tile and rely on stencil clipping to draw the right part in each tile.

[iwo]

Great! The fix resolved our issues 🎉

@louwers what's your release schedule i.e. when will the fix go live?

[louwers]

@iwo Nice. 🙂 I can make a release today.

[iwo]

Hi @louwers, I see you made a release of Android v10 branch but I don't see android-v11.5.2. Are you planning to make it soon? Is there some there some problem with making this release?

[louwers]

There is no problem, releases can be made on request. Happy to make a release for Android with this fix as well.

[iwo]

It would be great if you could make it then :-)
We keep getting reports from prod users about this issue.

[louwers]

Will be released later today.

[iwo]

Hey @louwers, any update on the release?

[louwers]

There was an issue with the release @iwo, but it is out now.