Describe the bug

SWT on GTK4 does not dispose the native resources allocated by the Shell.

To Reproduce

Run the below example with a process monitor running

package org.eclipse.swt.snippets;

import org.eclipse.swt.internal.gtk.*;
import org.eclipse.swt.widgets.*;

public class Snippet1 {

	public static void main(String[] args) {
		System.out.println("GTK4: " + GTK.GTK4);
		int i = 0;
		while (i++ < 2500000) {
			System.out.println(i);
			final Display display = new Display();
			Shell shell = new Shell(display);
			shell.open(); // only needed on wayland
			while (display.readAndDispatch()) {
			}
			display.dispose();
			System.gc();
		}
	}
}

Expected behavior

No memory or thread growth after first few iterations - the GTK3 version achieves this.

Screenshots

(apologies for the picture of my screen, while tests were running I couldn't get screenshots working)

Image shows, the following java processes. The snippet above was running for about 3 minutes, or about 600 iterations.

1. My IDE
2. GTK4 x11 of above snippet
3. GTK3 x11 of above snippet
4. GTK4 wayland of above snippet

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)

Ubuntu 25.10

In addition to the obvious problem of a memory leak, this is one of the blockers for getting #2714 complete because the test java process keeps running out of memory and the GitHub runner gets killed for trying to allocate too much memory.