Thoughts on a shared location component for MapLibre Compose Multiplatform

[TonyGnk]

First, I want to express my gratitude to all the maintainers - your work on MapLibre for Compose Multiplatform is truly impressive and greatly appreciated!

I've been thinking about location handling across platforms while using the library. I understand you're juggling many priorities right now and have a roadmap of your own, but I'd love to start a conversation about a potential shared location component.

Having worked with MapLibre on Android, I've seen the challenges with location implementation, and I imagine it becomes even more complex when considering iOS, Desktop, and Web platforms - each with their own permission models and location APIs. Then there's the question of fused location providers and various accuracy levels that different use cases might require.

I'm wondering if others in the community have been thinking about this too? Perhaps a simple approach could be allowing a location component to be passed in the MapLibreMap constructor?

What are your thoughts on this? Is this something on your radar, or are there technical challenges I'm not considering?

[Vichy97]

I implemented location using Compass library and it was pretty straightforward. I can share code snippets for how I displayed it if you are interested

[TonyGnk]

Really? Yes. If you’re open to sharing some code snippets, I’d be interested in seeing how you handled it

[Vichy97]

if (displayCurrentLocation && deviceLocation != null) {
      val locationSource = rememberGeoJsonSource(
        id = "location",
        data = Point(
          Position(
            latitude = deviceLocation.latitude,
            longitude = deviceLocation.longitude,
          ),
        ),
      )
      LocationPuck(
        locationSource = locationSource,
        accuracy = deviceLocation.accuracy,
        metersPerDp = cameraState.metersPerDpAtTarget,
      )
    }
    
    @Composable
  private fun LocationPuck(
    locationSource: Source,
    accuracy: Double,
    metersPerDp: Double,
  ) {
    val isLocationAccurate = accuracy <= ACCURACY_THRESHOLD
    CircleLayer(
      id = "location-accuracy",
      visible = isLocationAccurate,
      source = locationSource,
      radius = const((accuracy / metersPerDp).dp),
      opacity = const(.5f),
      color = const(locationPuckColor),
      strokeColor = const(locationPuckColor),
      strokeWidth = const(1.dp),
    )
  
    CircleLayer(
      id = "location-puck-shadow",
      source = locationSource,
      radius = const(12.dp),
      blur = const(.5f),
      color = const(locationPuckShadowColor),
    )
    CircleLayer(
      id = "location-puck",
      source = locationSource,
      radius = const(5.dp),
      strokeWidth = const(3.dp),
      strokeColor = const(Color.White),
      color = const(if (isLocationAccurate) locationPuckColor else locationPuckDisabledColor),
    )
  }

This gives a solid puck with a semi-transparent ring to indicate the accuracy as long as the accuracy isn't wildly off (I think my threshold is 100 meters). I set it to grey if the location is inaccurate or out of date. I'm using the accuracy and lat/lng from the Compass library

[Vichy97]

This effect is very similar to what the google maps location puck looks like. It could use some improvements, but it's good enough for my project and should be a good starting point for you

[TonyGnk]

Thank you! Looks good. Could you try integrating the fused Google Play location engine in android source set?

[Vichy97]

Compass is working fine for me. I'm not sure if they use the fused service under the hood, but it would be easy enough to integrate that and use this same puck for displaying it on the map

[sargunv]

Some more context here: #27

I'd love to have a shared location component for this library, ideally as a separate, optional, module. But since it's not that hard to do on the library's public API already, it's not a priority for me to develop myself.

Exposing the location component already included in the iOS/Android MapLibre SDK is an alternative approach, but there's no such component available on other platforms, and with #218 we'd lose that code on Android/iOS too. So IMO the best approach is to build a new, multiplatform, location component.

[sargunv]

Something that got brought up in #402: the Compass library uses Google Play Services to get location. Ideally, we should aim to be compatible with Android devices without Google services available (anything in China, GrapheneOS, Amazon Fire, specialized devices like Boox and Meta Quest, etc) so, in our geolocation module, would need to either:

• continue wrapping Compass but provide a custom Locator implementation
• continue wrapping Compass but convince them to move off of Google services
  • let's open an issue now, if one doesn't already exist, and see what they say
• build our own geolocation module with only Android APIs
  • Fused location provider requires Android SDK >= 31