Is there any tutorial/manual/samples/docs on lazy components, like how

LazyVerticalGrid

works internally. I want to implement

LazyTileMap

(a big table of cells into which one looks through a small viewport, I need it for a game-like experience) which would only compose tiles that are visible and will allow scrolling and (optionally) zooming. But I’m currently lost in all these layout stuff, subcomposition, measurements, etc. What is the best guide into this? I’ve read Custom layouts section, but it seems it’s a tiny fraction of the underlying machinery.

Na, I think that's mostly it. There are a few external blogs that have explored the topic of custom layouts (eg. https://jorgecastillo.dev/jetpack-compose-withconstraints) but I think the code is authoritative here. Just start by looking at the source code of simpler layouts and work your way up to the more complex ones, and if you have specific layout questions where you're banging your head against the wall then ask in the #compose channel.

Huh, the example on the docs page is no longer valid:

@Composable
fun MyOwnColumn(
    modifier: Modifier = Modifier,
    content: @Composable() () -> Unit
) {
    Layout(
        modifier = modifier,
        children = content
    ) { measurables, constraints ->
        // measure and position children given constraints logic here
    }
}

The signature of

Layout

function is very different now