SymbolLayer.textVariableAnchorOffset can't be set to any value but nil()

[sargunv]

related: maplibre/maplibre-native#2358

this doesn't seem to be possible to set with the JSON expression converter at all in Native right now.

It crashes on iOS and logs an error on Android. Both with the same error message: Error setting property: text-variable-anchor-offset anchor offset must have two numbers

investigation copied from Slack thread:

Details

Does anyone have insight into setting textVariableAnchorOffset programmatically on a symbol layer? I’m trying to get this working with MapLibre Compose, but I just get: “Error setting property: text-variable-anchor-offset anchor offset must have two numbers” on both iOS and Android.

Here’s some sample code on Android:

layer.setProperties(
  PropertyFactory.textVariableAnchorOffset(
    Expression.Converter.convert(
      JsonArray().apply {
        add("top")
        add(JsonArray().apply {
          add(0)
          add(1)
        })
        add("bottom")
        add(JsonArray().apply {
          add(0)
          add(-2)
        })
      })
  )
)

(edited)
4 replies

sargunv
27 minutes ago
Setting it with a regular Array instead of via an Expression works fine, but I want to support expressions

layer.setProperties(
  PropertyFactory.textVariableAnchorOffset(
    arrayOf(
      "top",
      arrayOf(0, 1),
      "bottom",
      arrayOf(0, -2)
    )
  )
)

sargunv
15 minutes ago
relevant C++ code: https://github.com/maplibre/maplibre-native/blob/c94864f1a9a742d09d4619ec6aa786bb46824cb0/src/mbgl/style/conversion/constant.cpp#L176
nothing jumps out as an obvious cause here; my value seems to be meeting the conditions presented there but it’s still erroring

sargunv
5 minutes ago
Interestingly, this works:

layer.setProperties(
  PropertyFactory.textVariableAnchorOffset(
    Expression.literal(
      arrayOf(
        "top",
        arrayOf(0, 1),
        "bottom",
        arrayOf(0, -2)
      )
    )
  )
)

So it needs to be a literal array, and expressions within the array aren’t supported. That makes this pretty rough to use (edited)
11:01
extra interestingly, doing the same literal construct with the JSON converter presents an error: “Nested literal arrays are not supported.”
but we see above that nested literal arrays aren’t just supported, they’re required by this property. Feels like a bug to me

layer.setProperties(
  PropertyFactory.textVariableAnchorOffset(
    Expression.Converter.convert(
      JsonArray().apply {
        add("literal")
        add(JsonArray().apply {
          add("top")
          add(JsonArray().apply {
            add(0)
            add(1)
          })
          add("bottom")
          add(JsonArray().apply {
            add(0)
            add(-2)
          })
        })
      })
  )
)

[sargunv]

Blocked by maplibre/maplibre-native#3100