Hello everyone, I have a question about calculatin...

# compose-android

[sk eat]

Hello everyone, I have a question about calculating the absolute position of a composable on the screen.

I’m trying to determine how many dp a specific composable is positioned from the bottom of the screen. I’ve attempted using positionInWindow(), but it didn’t quite meet my requirements.
If anyone knows the correct approach or can provide guidance, I would greatly appreciate it! 😊

[Stylianos Gakis]

Does this https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/layout/OnGloballyPositionedModifier.kt;l=43?q=onGloball&sq= give you the info you need?

[Stylianos Gakis]

Or this https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/layout/OnLayoutRectChangedModifier.kt;l=56?q=onRectChanged perhaps, which is newer and is supposed to be more efficient, but I'm not sure if it suits your needs

[Stylianos Gakis]

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/spatial/RelativeLayoutBounds.kt;l=47
Looks like yes

[Alex Vanyo]

There’s positionOnScreen(), but I’d be suspicious of most cases of calculating things relative to the overall screen dimension versus calculating within your window

[sk eat]

@Stylianos Gakis @Alex Vanyo Using the coordinates obtained from positionInWindow() and subtracting the screen size and navigation bar height, I was able to implement the solution successfully. It turned out that the issue was caused by not considering the navigation bar size earlier. Thank you for your response!

Code:

fun Modifier.calculateDistanceFromBottom(
    onDistanceCalculated: (Dp) -> Unit
): Modifier = composed {
    val density = LocalDensity.current
    val view = LocalView.current
    val context = LocalContext.current

    val windowHeightDp = with(density) { view.rootView.height.toDp() }
    val systemBottomPadding = context.getBottomNavigationBarHeight()

    var lastDistanceCache by remember { mutableStateOf<Dp?>(null) }

    this.onGloballyPositioned { layoutCoordinates ->
        val viewWindowPositionDp = with(density) { layoutCoordinates.positionInWindow().y.toDp() }
        val viewHeightDp = with(density) { layoutCoordinates.size.height.toDp() }
        val viewBottomPositionDp = viewWindowPositionDp + viewHeightDp
        val bottomDistanceDp = windowHeightDp - viewBottomPositionDp - systemBottomPadding

        if (lastDistanceCache != bottomDistanceDp) {
            lastDistanceCache = bottomDistanceDp
            onDistanceCalculated(bottomDistanceDp)
        }
    }
}