IssueTracker

Jetpack Compose version: 1.7.6, 1.8.0-alpha03

Jetpack Compose component(s) used: Layout list overload

Kotlin version: 2.1.0

Code:

MaterialTheme {

    Column {

        val initialList = remember { listOf(0, 1, 2, 3, 4) }
        val movedList = remember { listOf(0, 2, 1, 4, 3) }
        var list by remember { mutableStateOf(initialList) }

        Button(onClick = {
            list = if (list == initialList) movedList else initialList
        }) {
            Text("Move")
        }

        Layout(
            contents = listOf(
                @Composable {

                    println(list.joinToString())
                    list.forEach {

                        key(it) {

                            Text(
                                modifier = Modifier.clickable { println("Text $it") },
                                text = "Text $it",
                            )
                        }
                    }
                }
            )
        ) { (measurables), constraints ->

            println("Measuring")

            var currentWidth = 0
            var totalWidth = 0
            val placeables = measurables.fastMap { it.measure(constraints) }
            val widthOffsets = placeables.fastMap {
                val height = currentWidth
                currentWidth += it.width
                totalWidth = currentWidth
                height
            }
            val height = placeables.fastMaxOfOrNull { it.height } ?: 0

            layout(totalWidth, height) {

                println("Placing")

                placeables.fastForEachIndexed { index, placeable ->
                    placeable.place(widthOffsets[index], 0)
                }
            }
        }
    }
}

Pressing 'Move' will re-order the list and recompose. This does not trigger the Measure and Placement passes as expected.

Logs:

0, 1, 2, 3, 4
Measuring
Placing
0, 2, 1, 4, 3
0, 1, 2, 3, 4

Changing the layout composable to the regular one will behave as expected and call the Measure and Placement passes every-time the list changes.

Layout(
    content = {

        println(list.joinToString())

        list.forEach {

            key(it) {

                Text(
                    modifier = Modifier.clickable { println("Text $it") },
                    text = "Text $it",
                )
            }
        }
    }
) { measurables, constraints ->

Logs:

0, 1, 2, 3, 4
Measuring
Placing
0, 2, 1, 4, 3
Measuring
Placing
0, 1, 2, 3, 4
Measuring
Placing