Cannot make undecorated window fullscreen

[mgroth0]

Describe the bug

An undecorated window refuses to go fullscreen.

Affected platforms

• Desktop (macOS)

Versions

• Kotlin version*: 2.0.0-Beta5
• Compose Multiplatform version*: 1.6.1
• OS version(s)* (required for Desktop and iOS issues): macos
• OS architecture (x86 or arm64):arm64
• JDK (for desktop issues): 20

To Reproduce

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.Button
import androidx.compose.material3.Text
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.window.Window
import androidx.compose.ui.window.WindowPlacement.Fullscreen
import androidx.compose.ui.window.WindowState
import androidx.compose.ui.window.application

fun main() {
    val state = WindowState()
    application {
        Window(
            onCloseRequest = ::exitApplication,
            state = state,
            undecorated = true
        ) {
            Box(Modifier.background(Color.DarkGray).fillMaxSize()) {
                Button(
                    onClick = {
                        state.placement = Fullscreen
                    }
                ) {
                    Text("Fullscreen")
                }
            }
        }
    }
}

Expected behavior For the window to go fullscreen

Actual behavior

The window looks like it attempts to go fullscreen, but it refuses to fill the whole screen size. It shows the content of the window surrounded by black space.

Screenshots

Additional context

Note that if the window is decorated, fullscreen works as expected

[okushnikov]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.