MLNStyleLayerDrawingContext not available

[bsudekum]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Checkout the branch MLNCustomStyleLayer + Metal example #2041
2. Import MapLibre into a Swift file
3. Create a simple layer which subclasses MGLOpenGLStyleLayer

final class MyLayer: MLNCustomStyleLayer {
    override func draw(in mapView: MGLMapView, with context: MGLStyleLayerDrawingContext) {
        super.draw(in: mapView, with: context)
        /// do stuff
    }
}

4. Compile
5. An error is thrown

....swift:18:61: error: cannot find type 'MLNStyleLayerDrawingContext' in scope
   override func draw(in mapView: MLNMapView, with context: MLNStyleLayerDrawingContext) {
                                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~
external/MapLibre/MapLibre.xcframework/ios-arm64_x86_64-simulator/MapLibre.framework/Headers/MLNCustomStyleLayer.h:19:16: note: record 'MLNStyleLayerDrawingContext' is not trivial to copy or destroy
typedef struct MLNStyleLayerDrawingContext {
               ^
....swift:18:18: error: method does not override any method from its superclass
   override func draw(in mapView: MLNMapView, with context: MLNStyleLayerDrawingContext) {
   ~~~~~~~~      ^
....swift:19:14: error: value of type 'MLNCustomStyleLayer' has no member 'draw'
       super.draw(in: mapView, with: context)
       ~~~~~ ^~~~
external/MapLibre/MapLibre.xcframework/ios-arm64_x86_64-simulator/MapLibre.framework/Headers/MLNCustomStyleLayer.h:52:1: note: method 'drawInMapView:withContext:' unavailable (cannot import)
- (void)drawInMapView:(MLNMapView *)mapView withContext:(MLNStyleLayerDrawingContext)context;
^
external/MapLibre/MapLibre.xcframework/ios-arm64_x86_64-simulator/MapLibre.framework/Headers/MLNCustomStyleLayer.h:52:58: note: parameter 'context' unavailable (cannot import)
- (void)drawInMapView:(MLNMapView *)mapView withContext:(MLNStyleLayerDrawingContext)context;

I think the note: record... record bit is a good clue. I'm wondering if this is not available in Swift, rendering the whole struct (MLNStyleLayerDrawingContext) invalid:

maplibre-native/platform/darwin/src/MLNCustomStyleLayer.h

Lines 27 to 29 in 6ae0e97

	#if MLN_RENDER_BACKEND_METAL
	id<MTLRenderCommandEncoder> renderEncoder;
	#endif

[louwers]

Note that OpenGL ES is no longer supported on iOS since the 6.0.0 release.

For development of the Metal renderer, OpenGL was kept around, but we'll be moving towards removing it completely from the iOS sources.

[bsudekum]

Understood, I'm compiling with the metal flag here.

[louwers]

Isn't it named MLNCustomStyleLayer on that branch?

[bsudekum]

Sorry, copied old file, updated.

[louwers]

Yeah this might be a limitation of Swift's Objective-C interoperability.

Thanks for trying it out. Could you remove the renderEncoder field from the struct and see if it compiles?

[bsudekum]

@louwers yep that did the trick.

[louwers]

@bsudekum OK maybe @stefankarschti can think of a Swift-compatible interface.

[stefankarschti]

I added renderEncoder as a property. Please retry

[bsudekum]

@stefankarschti it works! thanks for working through this.

[bsudekum]

@stefankarschti found a slight bug. With the above code, there is a pretty massive memory leak if you just simulate the highway drive:

[stefankarschti]

Yep, that's on me 😄
Thanks for testing, please retry now.

[bsudekum]

@stefankarschti cool that worked!

[thothai94]

Understood, I'm compiling with the metal flag here.

Could you please tell me how to set compiling with metal flag in iOS project?
In my case, #if MLN_RENDER_BACKEND_METAL check statement always return false

[louwers]

Please create a new Discussion or Issue for unrelated problems.

@thothai94 But you can generate the Xcode project with:

bazel run //platform/ios:xcodeproj --@rules_xcodeproj//xcodeproj:extra_common_flags="--//:renderer=metal"

https://github.com/maplibre/maplibre-native/blob/main/platform/ios/README.md#developing