If I have a `Row` and if a sum width of all of its children is less than `screenWidth` I want to use...

# compose

[dimsuz]

If I have a Row and if a sum width of all of its children is less than screenWidth I want to use .weight(1) for them.
Otherwise I want to use .horizontalScroll() on the Row.

Is there a nice way to achieve this?
I thought about SubcomposeLayout instead of Row but I'm not sure, because I need to also manipulate Modifier in this case (for scrolling)

[Filip Wiesner]

If you add weight to all children and put them in a scrolling container at the same time, wouldn't that achieve this behavior? 🤔 Not sure, just a thought

[dimsuz]

No, in this case they will be measured with Constraint.Infinite and this will result in "wrap content" measurement, weight(1) will have no effect.

[Filip Wiesner]

I just saw weight working in scrollable Column so I thought this would work

[dimsuz]

Hmm, I'll recheck.

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

If that works I'll be surprised. It would have to measure the items once to find out if they can fit, and if they do, measure them again with the weight, which is 2 measurements which isn't allowed.

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

I think you could do something like this:

var viewportSize by remember { mutableStateOf(Size.Unspecified) }

Layout(
  content = content,
  modifier = modifier
    .onSizeChanged { viewportSize = it }
    .verticalScroll(…)
) { m, c ->
  // Use intrinsics to determine if items will fit inside viewportSize. 
  // If they do, measure with equal fixed constraints. 
  // If not, measure with unbounded constraints.
  …
}

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

That should work as long as onSizeChanged is called before the verticalScroll measures its contents, which I'm not sure will happen. Actually I don't think it can.

So you can replace onSizeChanged with a custom pass through layout modifier that stores the max constraints from before the verticalScroll in that state.

[Filip Wiesner]

I was surprised too. I'll try to remember tomorrow to look at the place where I saw it.

[Filip Wiesner]

Yeah, I didn't read the question properly, sorry. I thought you meant you want to have bunch of items with space between them using weight. And it would start scrolling when the size of the spaces would reach zero.

[dimsuz]

Thanks, Zach! That solution about storing in the state and doing this in 2 stages crossed my mind, but I thought maybe there's a more "elegant" solution.

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

Doing everything in a single layout pass is a lot more elegant than using subcomposition at least.