Can someone explain why

LocalConfiguration.current

line exists in

calculateWindowSizeClass(activity: Activity)

? Am I wrong in thinking that it does nothing here? 🤔 https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/[…]ndroidWindowSizeClass.android.kt;l=37?q=calculateWindowSi&sq=

I think it's explained in the comment above:

// Observe view configuration changes and recalculate the size class on each change. We can't
// use Activity#onConfigurationChanged as this will sometimes fail to be called on different
// API levels, hence why this function needs to be @Composable so we can observe the
// ComposeView's configuration changes.

Oh so just calling

LocalConfiguration.current

triggers Recomposition? 🤔

I believe so

Yes, reading this will cause this to recompose when

LocalConfiguration.current

changes. And

LocalConfiguration.current

changes whenever

onConfigurationChanged

is called on the

ComposeView

. So essentially this will recompose everytime

onConfigurationChanged

is called on the view

the same mecanism is used for stringResource() btw !

@Composable
@ReadOnlyComposable
private fun resources(): Resources {
    LocalConfiguration.current
    return LocalContext.current.resources
}

@Composable
@ReadOnlyComposable
fun stringResource(@StringRes id: Int): String {
    val resources = resources()
    return resources.getString(id)
}

Oh you’re right. Well it’s a TIL for me 😃 Thanks all!

But why does

resources

need to call

LocalConfiguration.current

twice?

Even I misread it the first time. The later one is

LocalContext

not config :blob-sweat-smile:

Oh 🤦‍♂️ Thanks 😄

This appears generalizable to any state variable. In one of my projects, I had a really weird edge case where I needed to recalculate something whenever a recomposition occurred, and I needed recomposition to occur when a variable changed, so I just had a line that read the variable with a comment explaining the mechanism and why the variable couldn’t be removed.