Struggling with very basic

[zell-mbc]

I am trying to migrate one of my Android apps from OsmDroid (deprecated) to Map-libre. And given that I am already using Compose I thought I might as well go with maplibre-compose (v0.10.1) and potentially gain platform independence in the future.
The requirements of my app are fairly basic I think: I need a map on which I draw various (clickable) icons representing nodes and their types which I pull out of OSM via overpass.

But after spending quite a bit of time I am not getting anywhere when it comes to adding icons to the map. Been trying with SymbolLayer() but can't get that one to work. Nothing will show on the map.

Tried to follow another a post here from last month, #477, with a similar issue but can't get that one to work either.
The proposal in #477 for rememberGeoJsonSource() shows "id" and "data" as parameters, but given that the code didn't compile I looked at the documentation of rememberGeoJsonSource() and there is no id any longer?

public fun rememberGeoJsonSource(
    data: GeoJsonData,
    options: GeoJsonOptions = GeoJsonOptions()
): GeoJsonSource

Now the Amtrac example https://maplibre.org/maplibre-compose/layers/#sources-and-layers in the docs seems to follow the "no id" for rememberGeoJsonSource, but still got the id in the LineLayer?

val amtrakRoutes =  rememberGeoJsonSource(GeoJsonData.Uri(Res.getUri("files/data/amtrak_routes.geojson")))
LineLayer(
  id = "amtrak-routes",
  source = amtrakRoutes,
  color = const(Color.Blue),
  width = const(4.dp),
)

If I blend #477 and the Amtrak example I end up with the below, but the expected blue circle doesn't show on my map

val source2 = rememberGeoJsonSource(
    data = GeoJsonData.Features(Point(Position(48.061515, 9.661092))),
    options = GeoJsonOptions()
)
CircleLayer(
  id = "example",
  source = source2,
  color = const(Color.Blue),
  radius = const(200.dp)
)

I would really appreciate if anyone could point out where I am going wrong here?

[sargunv]

Which platform are you testing on?

[zell-mbc]

Right now it's all Android and Android Studio as dev platform.

[zell-mbc]

Thanks for confirming @sargunv. That is really strange? Given this, I think I will start all over with a clean project and then add in my apps content piece by piece. I'll get back to you...

[sargunv]

Before that, do share your logcat output. For example, when I ran it with your sample code, my logs included this:

2025-07-21 23:03:01.647  9606-9606  maplibre-compose        dev.sargunv.maplibrecompose.demoapp  I  Queuing layer example for addition at anchor Top, index 0
2025-07-21 23:03:01.659  9606-9606  maplibre-compose        dev.sargunv.maplibrecompose.demoapp  I  Initializing anchor Top with layer example
2025-07-21 23:03:01.660  9606-9606  maplibre-compose        dev.sargunv.maplibrecompose.demoapp  I  Adding source __MAPLIBRE_COMPOSE_source_0

This shows the library's style manager applying your style composition to the underlying map style.

[zell-mbc]

Oh well, your confirmation that my code example should work and the hint regarding the logs made it clear that something was in fact drawing, just not in the place I expected it. Typical case of not seeing the wood for the trees, I mixed up latitude and longitude 🙄
Got my circle now, which is handy, because I'll need it in some other place anyway. :-)

Does that mean that the "id", parameter in CircleLayer and SymbolLayer hasn't got any relevance any longer?
SymbolLayer(id = "marker-layer",…)

Edit:
Found the issue with my icons, the Overpass Json to GeoJsonData converter I use GeoJsonData.JsonString() isn't producing the required format. I probably need to write a parser of sorts.
With that out of the way, one last question regarding the icons if I may: The app supports ~10 different artwork types, each with it's own icon. With OSMDroid I created individual markers for each artwork and assigned each marker an icon based on the type of artwork.
With maplibre-compose I don't think I can do that, so I am considering to group the overpass result by artwork type and then create one SymbolLayer per artwork type. Each SymbolLayer with it's own icon. Is that the correct way to handle this situation?

[sargunv]

Does that mean that the "id", parameter in CircleLayer and SymbolLayer hasn't got any relevance any longer?
SymbolLayer(id = "marker-layer",…)

It's relevant in that's the ID of the layer when it's added to the MapLibre style, and layer IDs are not allowed to conflict. It's also the ID you'll see in the logs. Someday we may make the layer ID generated internally (like we now do for layers), which'll make the logs slightly less useful but make the API cleaner and safer.

With maplibre-compose I don't think I can do that, so I am considering to group the overpass result by artwork type and then create one SymbolLayer per artwork type. Each SymbolLayer with it's own icon. Is that the correct way to handle this situation?

You can add them all to the same Source and Layer combo. In the source, you'd include the artwork type in the feature properties. In the layer, you'd select the icon based on the feature property using an Expression.

It'd be good to read up on how expressions work in the JSON style spec, and then the corresponding expression DSL in Kotlin.

You can, if you want, create ten different sources and layers, and that'll work just fine, though it's less efficient (but doesn't really matter at ~10 layers).

[sargunv]

Here's an example of an expression to select a color based on a building type:

switch(
  input = feature["building_type"].convertToString(),
  case(
    label = "residential",
    output = const(Color.Cyan),
  ),
  case(
    label = listOf("commercial", "industrial"),
    output = const(Color.Yellow),
  ),
  fallback = const(Color.Red),
)

Your expression to select an icon based on artwork type would work similarly.

[zell-mbc]

Cool! Everything is working now!
Thank you very much for helping me over the initial hurdles, and of course as well as for providing this project. The resulting code is a lot simpler than what I used to have. I am glad I made the switch.

In case you are maintaining a list of apps using your project, you can add this one https://gitlab.com/toz12/PublicArtExplorer pretty soon :-)

[sargunv]

That's a good idea, we should maintain such a list. Will file an issue

[sargunv]

given that the code didn't compile I looked at the documentation of rememberGeoJsonSource() and there is no id any longer?
...
Now the Amtrac example maplibre.org/maplibre-compose/layers#sources-and-layers in the docs seems to follow the "no id" for rememberGeoJsonSource, but still got the id in the LineLayer?

Yeah, this was a change in v0.10.0. The library now internally manages source IDs in order to avoid some crashes with order of operations when modifying styles.

We may internally manage layer IDs in the future too for consistency; for now they still have the v0.9-and-below style API.