[GTK4] SwtFixed sizing problem on 4.20(or even 4.18) +

[akurtakov]

Running the following snippet

package org.eclipse.swt.snippets;

import org.eclipse.swt.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class Snippet39 {
	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setText("Snippet 39");
		shell.setLayout(new FillLayout());

		Combo combo = new Combo(shell, SWT.NONE);
		combo.setText("text");
		System.out.println(combo.getSize());
		System.out.println(combo.getBounds());


		shell.pack();
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) display.sleep();
		}
		display.dispose();
	}
}

produces only headerbar window like

The output is:

Point {0, 0}
Rectangle {0, 0, 0, 0}

This hasn't been a problem in Gtk 4.16.

[jonahgraham]

It looks correct for me on Ubuntu 25.10 x11:

wayland:

I get all 0s output on GTK3 too with the sysout at that point in the code. If I change it like this (I stuck this snippet in swt tests so I can access SwtTestUtil) then I get sensible sizes printed out.

		shell.pack();
		SwtTestUtil.openShell(shell);
		System.out.println(combo.getSize());
		System.out.println(combo.getBounds());
		while (!shell.isDisposed()) {

I have tried running this in Fedora 43, via Docker (blog post later today on how I did that) and it looks ok there too. Not sure what is different in my dockerized env vs your full install.

PS I assume you came across this problem trying to diagnose #2817?

[akurtakov]

So this is DE/compositor specific - I get the broken behavior on Gnome but the working one on KDE - all with same GTK version on the very same Fedora instance.

[jonahgraham]

Do you see problem on x11 + wayland, or just wayland? Did you have a way of starting the second compositor without having to exit the first? I can do that with x11 (xfce) and wayland, but I don't know how to have two compositors running for wayland at the same time yet.

[jonahgraham]

blog post later today on how I did that

Here: https://kichwacoders.com/2025/11/29/easily-running-swt-on-different-linux-distros/

[akurtakov]

XWayland shows the problem under Gnome wayland. I prefer to logout/in to have pristine settings closer to what users will actually start on thus haven't tried starting nested compositor .