A not correctly working implementation of a master-detail user interface with compose desktop 0.1.0-m1-build62

App.kt

import androidx.compose.foundation.background
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.width
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp

data class Item(val name: String, val value: String)

@Composable
fun App() {
    val items = remember {
        mutableStateListOf(Item("First", "one"), Item("Second", "two"), Item("Third", "three"))
    }
    var selectedItemIndex by remember { mutableStateOf(0) }

    MaterialTheme {
        Row {
            ItemsList(items, selectedItemIndex, modifier = Modifier.width(150.dp)) {
                selectedItemIndex = it
            }
            ItemForm(items[selectedItemIndex]) {
                items[selectedItemIndex] = it
            }
        }
    }
}

@Composable
fun ItemForm(item: Item, saveAction: (Item) -> Unit) {
    var tempItem by remember(item) { mutableStateOf(item) }

    Column {
        TextField(
                value = tempItem.name,
                label = { Text("Name") },
                onValueChange = {
                    tempItem = tempItem.copy(name = it)
                }
        )
        TextField(
                value = tempItem.value,
                label = { Text("Value") },
                onValueChange = {
                    tempItem = tempItem.copy(value = it)
                }
        )
        Button(onClick = { saveAction(tempItem) }) {
            Text("Save")
        }
    }
}

@Composable
fun ItemsList(listItems: List<Item>, selectedIndex: Int, modifier: Modifier = Modifier, selectAction: (Int) -> Unit) {
    Column(modifier) {
        listItems.forEachIndexed { index, item ->
            val m = if (selectedIndex == index) {
                Modifier.background(MaterialTheme.colors.secondary)
            } else {
                Modifier.background(MaterialTheme.colors.background)
            }
            ListItem(modifier = m.clickable { selectAction(index) }) {
                Text(item.name)
            }
        }
    }
}