I feel like am missing something fundamental from my mental model of how compose works 😅, could anyone point me to the right direction? I am trying to use a value from LocalConfiguration in a heavy-ish calculation like this:

val calculationResult by remember { derivedStateOf {
    val primaryLocale = LocalConfiguration.current.locales.get(0) // error
    // Some filtering, calculations, etc.
} }

Obviously this doesn't work, since CompositionLocal.current is @Composable and results in an error. If I store the Configuration outside of the derivedStateOf block, it won't work either since it doesn't observe that State is being read and won't update.

val configuration = LocalConfiguration.current
val calculationResult by remember { derivedStateOf {
    val primaryLocale = configuration.locales.get(0)
    // Some filtering, calculations, etc.
} }
// Doesn't update

What would be an idiomatic/correct way to achieve what I'm trying to do here?

It doesn’t observe that State, because you

remember

it without key, which means once calculated it will not change till Composable leaves the composition. Either remove

remember

, or add

configuration

as a

key

, so that the whole

remember

content will be recalculated when

configuration

changes:

val configuration = LocalConfiguration.current
val calculationResult by remember(configuration) { derivedStateOf {
    val primaryLocale = configuration.locales.get(0)
    // Some filtering, calculations, etc.
} }

whetever you read any captured variables in a remember block, you probably need to add them to key

Thank you for the answers! Adding configuration to the key of remember definitely works, but won't it then recompose every time

configuration

changes? (Opposed to recomposition only when the result of the calculation changes)

rememberUpdatedState should give you the object you're looking for in that case