Is there a way to set the background color of the native window before content is rendered? There's ...

# compose-desktop

[David W]

Is there a way to set the background color of the native window before content is rendered?
There's a white flash before the app's (dark) content appears. All of the answers I saw for this were specific to Android.

[David W]

I even tried making the window not visible for a second to let the content render, but it still flashed white on making it visible...perhaps content doesn't render while it's invisible.

[Thomas]

Hey, I was wondering did you find a good solution for this?

[David W]

Nope, it's on my "wait and see" pile for Compose 🙂

[Thomas]

Yeah I am trying to fix a few things from that pile

[Thomas]

The JetBrains Toolbox app does not flash white so it should be possible

[David W]

No, it is transparent (but with the OS frame) until everything is drawn, then it appears.

[David W]

good point

[Thomas]

Found the issue, you can set the background color in the Window content using window.background = , but at that point the window is already shown, so its too late.

[Thomas]

Fix is to call it immediately after the ComposeWindow creation, which is a bit difficult: https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/[…]desktop.kt;l=148;drc=c5559f4d2522a059fda3ea5c1d3a7ed6d6e7257c

[Thomas]

The line I linked is where you need to call this.window.background = … which works

[Thomas]

ComposeWindow is actually a JFrame, which has a default background color

[Thomas]

Calling the following before creating a window also works, but not sure what it all affects:

javax.swing.UIManager.getDefaults().apply {
    put("control", javax.swing.plaf.ColorUIResource(java.awt.Color.RED))
}

[Thomas]

I am now using the following workaround. Call it just before the Window function.

@Composable
private fun fixWhiteFlashOnStartup() {
    val background = MaterialTheme.colors.background
    remember(background) {
        UIManager.getDefaults().apply {
            put("control", ColorUIResource(background.toArgb()))
        }
    }
}

[David W]

interestingly, i'm still getting the flash

[David W]

I got it after trying

javax.swing.UIManager.getDefaults().apply {
    put("control", javax.swing.plaf.ColorUIResource(java.awt.Color.RED))
}

too

[Thomas]

Did you call that before Window(onCloseRequest..)?

[Thomas]

It works for me on macOS

[David W]

Windows here.

[Thomas]

Hmm maybe this trick does not work on Windows, will have to try that

[Thomas]

FYI there is a fix here: https://github.com/JetBrains/androidx/pull/182

[David W]

thank you! you're the best