main() function cannot be @Composable - Window title as a mutable state

[damien79github]

Hello,

I'm trying to get started with Compose for Desktop. I love Kotlin and it's fantastic to have Compose for Desktop.
I would like to have the title of a Window a mutable state. But trying to do so :

var text by remember { mutableStateOf("Title") }
@composable
fun main() = Window(title = text) {

I run into 2 errors :

@composable invocations can only happen from the context of a @composable function
@composable main functions are not currently supported

Window() is a top function call. How can I make the title of a Window a mutable state ?

That would be the necessary for instance to make an editor app the the Window title is the path of the file opened in the editor.

Thanks a lot for your help.

[jimgoog]

You don't need the remember, you can just have var text by mutableStateof("Title").

[jimgoog]

remember is a composable function, mutableStateOf is not, and can thus be used from outside of composables.

[damien79github]

Thanks for your answer. I have adapted my code accordingly :

private var title by mutableStateOf("Title")
fun main() = Window(title = title) {
Button(onClick = {
title = "Title " + LocalTime.now()
}) {
Text("Button")
}
}

There is no runtime error but the title of the Window does not refresh when the button is clicked. What's missing for the UI to be updated with the mutable state title var ?

[lhwdev]

I think wrapping Window call with application will work, like

fun main() = application {
    Window(...) { ... }
}

[lhwdev]

All composable functions track state reads, but in your situation reading title is tracked nowhere.