Support defining a custom style layer from iOS Swift

[christian-boks]

I wanted to use a custom style layer in a Swift app on iOS, but discovered that the typedef struct MLNBackendResource structure used to expose the backend wasn't visible in Swift, so I converted it to an Objective-c interface.

And I've also converted the Objective-c example to Swift and added it to the Swift example app, to show how to use it.

[louwers]

Thanks this is awesome!

Got it to compile with the OpenGL backend too.

We're not really supporting that anymore, but I guess it doesn't hurt.

This example doesn't work when I rotate the map. But that can be addressed in a follow-up PR.

I think this is technically a breaking change, but since custom style layers are a somewhat experimental feature I think it is acceptable.

[christian-boks]

Thanks this is awesome!

Got it to compile with the OpenGL backend too.

We're not really supporting that anymore, but I guess it doesn't hurt.

It looks like there is a CI step that still compiles the code without the --//:renderer=metal option tough.

This example doesn't work when I rotate the map. But that can be addressed in a follow-up PR.

I see what you mean, I had just tested it on the simulator before. I guess I need to rotate the matrix too, not just scale it.

I think this is technically a breaking change, but since custom style layers are a somewhat experimental feature I think it is acceptable.

👍

[louwers]

It looks like there is a CI step that still compiles the code without the --//:renderer=metal option tough.

Oh wow, that is an oversight. I will fix that.

[stefankarschti]

This example doesn't work when I rotate the map. But that can be addressed in a follow-up PR

I think that's fine, the original example didn't implement the projection matrix either.

[github-actions]

Bloaty Results (iOS) 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.0% +2.46Ki  [ = ]       0    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results-ios/pr-3154-compared-to-main.txt