[Mac] StyledText: backspaces deletes too much while IME is active #2412

Describe the bug
A Korean user of our SWT-based application reports following problem. When typing Korean characters, pressing backspace will delete two characters instead of the last entered one.

To Reproduce
Please launch this simple snippet

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class StyledTextTest {

    public static void main(String[] args) {
        final Display display = new Display();

        final Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());

        new StyledText(shell, SWT.BORDER);

        shell.setSize(400, 300);
        shell.open();

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

        display.dispose();
    }
}

on MacOS and select the "2-Set Korean" keyboard layout (there are different Korean keyboard layouts, I've only tried this one). Now type (assuming you are using a US keyboard) the characters h e l l o. This will produce following output (mind the last, blue underlined character):

Now press backspace and it will not just remove the underlined character, but also the previous one:

Expected behavior
I would think, if there is a character in composition, pressing backspace should just abort the composition.

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)
   Tried on MacOS 14.7.3.