Is it correct to call `invoke` on composable funct...

# compose-desktop

[v79]

Is it correct to call invoke on composable functions? I'm creating a desktop status bar row like this...

@Composable
fun StatusBar(
    left: @Composable (() -> Unit)? = null,
    centre: @Composable (() -> Unit)? = null,
    right: @Composable (() -> Unit)? = null
) {
    Row(
        Modifier.fillMaxWidth().padding(2.dp).border(1.dp, Color.Gray),
        horizontalArrangement = Arrangement.SpaceBetween
    ) {
        Box(Modifier.padding(start = 2.dp)) { left?.invoke() }
        Box { centre?.invoke() }
        Box(Modifier.padding(end = 2.dp)) { right?.invoke() }
    }
}

I can't find an example of implementing the built in RowScope or ColumnScope or whatever functions, which is what I think I need. But not sure.

[v79]

I find I really don't know what to google for with compose!

[s3rius]

Not exactly sure what you're going for, but you propagate RowScope like this:

fun StatusBar(content: RowScope.() -> Unit) {
    Row(...) { content() } // content() can only be called inside Row because it's providing a RowScope 
}

[v79]

Maybe mentioning RowScope wasn't helpful. The StatusBar I've built above is working, but is it doing it the compose way?

[v79]

Maybe I'm supposed to be creating a rememberStatusBar type function and a MutableStateOf<StatusBarContent>?

[s3rius]

Ah, so creating a new state for your composable only really makes sense if the composable itself holds stateful content. Your composable is more like a layout which usually doesn't have state. See Box, Row, etc.
Usually it's good practice that the first optional parameter is a Modifier which is passed to the immediate child. In your case it would be your Row. You can see that with almost every composable.
invoke() on composables is fine. Depending on the effect you want, you might want to avoid creating the Box if a param is null if (left != null) Box { left() }. But in your case I think you need the boxes that the layout looks as you expect it to.

[s3rius]

If you integrate into Material you probably also want to use a Theme color instead of Color.Gray.

[v79]

I'd have to pass the theme object in then?

[s3rius]

You'd use an appropriate color inside the composable, such as border(1.dp, Theme.colorScheme.outline) for Material3.
Or you can also pass it as a parameter into the composable borderColor: Color = ... if you want to make it easier modifiable.
If you don't want to tie it to Material2/3 then you would also pass it in as a parameter but probably just not provide a default value, so the caller would have to provide it.