[GTK3] StyledText reports wrong text typing Chinese letters with Pinyin

[tmssngr]

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Describe the bug If a selection in the StyledText is replaced with a Chinese letter entered using Chinese (Pinyin), no (replaced) text is reported by the SWT.ExtendedModify event.

To Reproduce

• install Pinyin keyboard:
  • Ubuntu: sudo apt install ibus-pinyin, Manjaro: sudo pacman -S ibus-pinyin
  • reboot the machine
  • in the GTK preferences, page Keyboard, add the Chinese (Pinyin) keyboard layout
• Run this snippet:

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ST;
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 PinyinTest {
    public static void main(String[] args) {
        final Display display = new Display();
        final Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        final StyledText st = new StyledText(shell, SWT.BORDER);
        st.addListener(ST.ExtendedModify, event -> {
            System.out.printf("%d %d, '%s'(%d)\n", event.start, event.end - event.start, event.text, event.text.length());
        });

        shell.setSize(400, 300);
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }
}

• keep the keyboard layout at en
• type abc
• select b
• type d (replacing b)
• you will see on the console

  0 1, ''(0)
  1 1, ''(0)
  2 1, ''(0)
  1 1, 'b'(1)
  

• select d
• change the keyboard layout to Chinese (Pinyin)
• type d1 (replacing d)
• you will see on the console

  0 1, ''(0)
  1 1, ''(0)
  2 1, ''(0)
  1 1, 'b'(1)
  1 1, ''(0)
  

-> although d has been replaced, it was not reported in event.text this time

Expected behavior Replacing with a Chinese character also should report the replaced character(s).

Environment:

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

• • [ ] All OS
• • [ ] Windows
• • [x] Linux
• • [ ] macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc) Tried with Ubuntu 22.04 and Manjaro/Gnome (latest)

[tmssngr]

Even worse: at the time when the first edit related event SWT.Verify occurs, the selected character already has been magically replaced (st.getText() does not contain it any more). This looks like a serious bug of the StyledText control with Chinese (Pinyin) keyboard layout.

[tmssngr]

Workaround: use StyledTextContent's TextChangeListener instead of SWT.Verify, SWT.Modify or SWT.ExtendedModify if you want to get access to the replaced text, e.g. for implementing an undo-feature.