What is an idiomatic way to write "slot-based" custom layouts? For example I want to have 3 slots: ...

# compose

[dimsuz]

What is an idiomatic way to write "slot-based" custom layouts?

For example I want to have 3 slots:

Layout(content = { leftSlot(); centerSlot(); rightSlot(); }) { measurables, constraints -> ... }

And layout logic is based on the assumption that I'll have 3 measureables: for example I want to always expand centerSlot. But I've found that if a centerSlot() composable will not emit any UI (return Unit), I'll have measurables.size == 2 , and also I won't know which one of them is missing.

For now I solved this by wrapping each slot in a box (e.g. Box { leftSlot() }), but I'm not sure if this is the best way.

[Rob Meeuwisse]

Have a look at the androidx.compose.material.TextField code. If you go down the rabbit hole enough levels you end up in private fun IconsWithTextFieldLayout, which does a call to layout(). Please notice that it passes a variable set of composables in the content argument. But they have a Modifier.layoutId(SomeId) so that they can be found again inside the measurePolicy block.

[dimsuz]

Oh, layoutId is the thing I've unsuccessfully tried to remember yesterday 🙂 Thank you, will look into this example you've suggested.

[Adam Powell]

If you want to treat the contents of each slot as single units like that then yes, you'll want to call each one in an appropriate sub-layout and work with those groups.