IntrinsicMeasureScope

open val isLookingAhead: Boolean

import androidx.compose.animation.core.Animatable
import androidx.compose.animation.core.AnimationVector2D
import androidx.compose.animation.core.VectorConverter
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.layout.width
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clipToBounds
import androidx.compose.ui.layout.LookaheadScope
import androidx.compose.ui.layout.layout
import androidx.compose.ui.unit.IntSize

var sizeAnim by remember { mutableStateOf<Animatable<IntSize, AnimationVector2D>?>(null) }
var lookaheadSize by remember { mutableStateOf<IntSize?>(null) }
val coroutineScope = rememberCoroutineScope()
LookaheadScope {
    // The Box is in a LookaheadScope. This means there will be a lookahead measure pass
    // before the main measure pass.
    // Here we are creating something similar to the `animateContentSize` modifier.
    Box(
        Modifier.clipToBounds().layout { measurable, constraints ->
            val placeable = measurable.measure(constraints)

            val measuredSize = IntSize(placeable.width, placeable.height)
            val (width, height) =
                if (isLookingAhead) {
                    // Record lookahead size if we are in lookahead pass. This lookahead size
                    // will be used for size animation, such that the main measure pass will
                    // gradually change size until it reaches the lookahead size.
                    lookaheadSize = measuredSize
                    measuredSize
                } else {
                    // Since we are in an explicit lookaheadScope, we know the lookahead pass
                    // is guaranteed to happen, therefore the lookahead size that we recorded is
                    // not null.
                    val target = requireNotNull(lookaheadSize)
                    val anim =
                        sizeAnim?.also { coroutineScope.launch { it.animateTo(target) } }
                            ?: Animatable(target, IntSize.VectorConverter)
                    sizeAnim = anim
                    // By returning the animated size only during main pass, we are allowing
                    // lookahead pass to see the future layout past the animation.
                    anim.value
                }

            layout(width, height) { placeable.place(0, 0) }
        }
    ) {
        // Some content that changes size
    }
}

val layoutDirection: LayoutDirection