animateContentSize

val (width, height) = animateTo(measuredSize)
return layout(width, height) {

val (_, height) = animateTo(measuredSize)
return layout(measuredSize.width, height) {

fun Modifier.animateContentHeight(
  animationSpec: FiniteAnimationSpec<IntSize> = spring(),
  finishedListener: ((initialValue: IntSize, targetValue: IntSize) -> Unit)? = null,
): Modifier = composed(
  inspectorInfo = debugInspectorInfo {
    name = "animateContentSize"
    properties["animationSpec"] = animationSpec
    properties["finishedListener"] = finishedListener
  },
) {
  val scope = rememberCoroutineScope()
  val animModifier = remember(scope) {
    HeightAnimationModifier(animationSpec, scope)
  }
  animModifier.listener = finishedListener
  this.clipToBounds().then(animModifier)
}

private class HeightAnimationModifier(
  val animSpec: AnimationSpec<IntSize>,
  val scope: CoroutineScope,
) : LayoutModifierWithPassThroughIntrinsics() {
  var listener: ((startSize: IntSize, endSize: IntSize) -> Unit)? = null

  data class AnimData(
    val anim: Animatable<IntSize, AnimationVector2D>,
    var startSize: IntSize,
  )

  var animData: AnimData? by mutableStateOf(null)

  override fun MeasureScope.measure(
    measurable: Measurable,
    constraints: Constraints,
  ): MeasureResult {
    val placeable = measurable.measure(constraints)

    val measuredSize = IntSize(placeable.width, placeable.height)

    val (_, height) = animateTo(measuredSize)
    return layout(measuredSize.width, height) {
      placeable.placeRelative(0, 0)
    }
  }

  fun animateTo(targetSize: IntSize): IntSize {
    val data = animData?.apply {
      if (targetSize != anim.targetValue) {
        startSize = anim.value
        scope.launch {
          val result = anim.animateTo(targetSize, animSpec)
          if (result.endReason == AnimationEndReason.Finished) {
            listener?.invoke(startSize, result.endState.value)
          }
        }
      }
    } ?: AnimData(
      Animatable(
        targetSize,
        IntSize.VectorConverter,
        IntSize(1, 1),
      ),
      targetSize,
    )

    animData = data
    return data.anim.value
  }
}

private abstract class LayoutModifierWithPassThroughIntrinsics : LayoutModifier {
  final override fun IntrinsicMeasureScope.minIntrinsicWidth(
    measurable: IntrinsicMeasurable,
    height: Int,
  ) = measurable.minIntrinsicWidth(height)

  final override fun IntrinsicMeasureScope.minIntrinsicHeight(
    measurable: IntrinsicMeasurable,
    width: Int,
  ) = measurable.minIntrinsicHeight(width)

  final override fun IntrinsicMeasureScope.maxIntrinsicWidth(
    measurable: IntrinsicMeasurable,
    height: Int,
  ) = measurable.maxIntrinsicWidth(height)

  final override fun IntrinsicMeasureScope.maxIntrinsicHeight(
    measurable: IntrinsicMeasurable,
    width: Int,
  ) = measurable.maxIntrinsicHeight(width)
}