Hello! Is it possible to check if element is compo...

# compose

[PHondogo]

Hello! Is it possible to check if element is composed in scrollable content or not?

[Alexander Zhirkevich]

BoxWithConstraints {
      Text(if (constraints.hasBoundedHeight) "Static" else "Scrollable")
 }

[Zach Klippenstein (he/him) [MOD]]

Absolutely not BoxWithConstraints. If the element isn’t composed, that code won’t run at all, and if it is, it’s super inefficient.

• If you’re in a lazy list, use LazyListLayoutInfo.
• If not a lazy list, you can use a DisposableEffect to keep track of composed items is the simplest way (the effect will start when first composed, and be disposed when removed from composition). If you want to check if an item is visible, use the LayoutCoordinates of the item to get the clipped bounds.
◦ Depending on when you need to check visibility, you can use onPlaced (if you only need to check on demand) or onGloballyPositioned (if you need to check every time the visibility may have changed).

[Alexander Zhirkevich]

I thought the question was not about if element is visible but about if parent is scrollable

[PHondogo]

Yes. It is about how to check if parent is scrollable. BoxWithConstraint is normal solution (i dont check performance yet). But the better will be to use some Locals for that, cause with Box i need to wrap me element with it and pass root modifier to Box. But there is also need to apply modifier to my element.

[Alexander Zhirkevich]

Yep, BoxWithConstraint isn't the most efficient thing, but having a lot of custom locals is not a good practice either

[Zach Klippenstein (he/him) [MOD]]

Ah, ok. If you want to check constraints then it’s much cheaper to do it via a layout modifier:

layout { measurable, constraints ->
  if (constraints.hasBoundedHeight) { … }
  val placeable = measurable.measure(constraints)
  layout(placeable.width, placeable.height) {
    placeable.placeRelative(0, 0)
  }
}