Fixing labels not appearing when enabling terrain at high zoom

[SnailBones]

Fixes #3454

Before:

broken.webm

After:

fixed.webm

Launch Checklist

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
• Include before/after visuals or gifs if this PR includes visual changes.
• Write tests for all new functionality.
• Add an entry to CHANGELOG.md under the ## main section.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0bb6e69) 85.89% compared to head (2e901eb) 85.90%.
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3545      +/-   ##
==========================================
+ Coverage   85.89%   85.90%   +0.01%     
==========================================
  Files         244      244              
  Lines       48174    48173       -1     
  Branches     5129     5132       +3     
==========================================
+ Hits        41377    41385       +8     
+ Misses       6797     6788       -9     

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[HarelM]

If I understood the fix correctly, the fix is done by reloading the source cache. Can you clarify why reloading the terrain source cache solves this issue?

[SnailBones]

If I understood the fix correctly, the fix is done by reloading the source cache. Can you clarify why reloading the terrain source cache solves this issue?

My understanding of this error is that it's caused by the terrain source cache remaining in an incorrect state when terrain is loaded during rendering.

My fix is to first set painter.terrainFacilitator.dirty = true; so that labels will be redrawn, and then reload tiles in the terrain source cache, which triggers another render loop after terrain is correctly loaded.

Just found a much simpler and faster way to fix the issue: calling sourceCache.reload(); on setTerrain, making the fix a one liner.

[HarelM]

THANKS!

[SnailBones]

Thank you for the fast review @HarelM!