I tried to migrate from 0.3.2 to 0.4.0 and it seems that the SwingPanel doesn't have the same behavior anymore. In the 0.4.0, the JPanel doesn't follow the modifier rules anymore. When the JFrame is big, the JPanel is too small, when the JFrame is small, the JPanel is too big and it overlaps Compose components. Is this a bug ?

This snippet shows that JPanel still fits into the parent

Box

🤔:

import androidx.compose.desktop.SwingPanel
import androidx.compose.desktop.Window
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.requiredSize
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import java.awt.Color
import javax.swing.JPanel

fun main() = Window {
    Box(Modifier.requiredSize(400.dp, 100.dp)) {
        SwingPanel(
            factory = {
                JPanel().apply {
                    background = Color.RED
                }
            },
            modifier = Modifier.fillMaxSize()
        )
    }
}

Can you check if you replace

SwingPanel

by just

Box

- will

Box

have the right size?

I replaced a SwingPanel by a Box. The Box worked as intented and followed the Modifier rules.

If it works with the usual

Box

and doesn't work with

SwingPanel

then probably it is a bug. I reproduced a simlar issue. If we fix it, then your issue also will be fixed (probably).

Thank you for the answer! I will wait for the fix

As a temporary fix you can probably wrap your SwingPanel into Box and move Modifier from SwingPanel to this Box

Thank you very much for your help. It worked