I'm trying to build a simple screen, but I'd want ...

# compose

[Zhelyazko Atanasov]

I'm trying to build a simple screen, but I'd want to restrict the width of a Column to a percentage of the screen width. So I'm using Modifier.fillMaxWidth(0.8f) but the Column is still occupying the max screen width. Is this an expected behaviour and I haven't fully understood the fraction argument or it's some kind of a bug? I'm using beta03

If that matters, the Column is put inside a Surface with fillMaxSize() set.

Column(
        modifier = Modifier
            .fillMaxWidth(0.8f)
            .fillMaxHeight()
            .background(Color.Green)
    ) {
        val (email, setEmail) = remember { mutableStateOf(TextFieldValue()) }
        TextField(
            value = email,
            onValueChange = { setEmail(it) },
            modifier = Modifier
                .align(CenterHorizontally)
        )
    }

[Albert Chang]

Surface always propagates min size constraints to its children. You are setting fillMaxSize() on the surface, so the min width, which is the screen width, is passed to the Column. If you want to use Surface outside, remove the fillMaxSize() modifier or wrap the Column in a Box.

[Zhelyazko Atanasov]

Thanks! But then shouldn't the Column be 80% of the min width? Unless the incoming max width is Infinity... the docs say that the incoming max width is multiplied by the fraction.

[Albert Chang]

Min size is mandatory.