Compose for Desktop: Window party tricks

Just a random collection of window tricks I've accumulated while trying to build a desktop app.

1. Size the window to your content

Sometimes you just want your window to match the size of your content. I've found this to be true for settings windows for example. Simply use:

val state = rememberWindowState(
    size = DpSize(Dp.Unspecified, Dp.Unspecified)
)

Make sure your root layouts don't have fillMaxSize() or else this won't work. You can optionally also make the Window non-resizable via resizable = false on the Window.

If you need the window size to adjust to your content size, checkout https://gist.github.com/ColtonIdle/df23e3dc8e72569a28a4c64197bed14c

More info: https://kotlinlang.slack.com/archives/C01D6HTPATV/p1740892851067859

2. Start with the window centered

Use:

Window(
state = rememberWindowState(position = WindowPosition(Alignment.Center))

(Barely) More info: https://kotlinlang.slack.com/archives/C01D6HTPATV/p1739326963488559

3. Remove title bar

Use:

fun main() = application {
    Window(
        onCloseRequest = ::exitApplication,
        title = ""
    ) {
        Box(Modifier.fillMaxSize().background(Color.Red))
        LaunchedEffect(window.rootPane) {
            with(window.rootPane) {
                putClientProperty("apple.awt.transparentTitleBar", true)
                putClientProperty("apple.awt.fullWindowContent", true)
            }
        }
    }
}

More info:
https://kotlinlang.slack.com/archives/C01D6HTPATV/p1739449034315049

4. Bring window to front and into focus

If you need to bring it to the foreground and focussed

Desktop.getDesktop().requestForeground(true)

More info:
https://github.com/JetBrains/compose-multiplatform/issues/4231#issuecomment-1952205605
and
https://kotlinlang.slack.com/archives/C01D6HTPATV/p1739152698052949

5. Customize UI stuff on Java/macOS: https://developer.apple.com/library/archive/technotes/tn2007/tn2196.html

Source: https://kotlinlang.slack.com/archives/C01D6HTPATV/p1741607313291729

6. Custom title bar

Apparently some stuff changed in later JDK versions?

See: https://gist.github.com/adrientetar/b039998a0752261d2ee7db9ade3e7c15