Description Alexander Nyßen 2011-01-04 02:36:13 EST

Executing the snippet given below, typing any character to issue an SWT.Verify event, one can observe the following console output on GTK (Ubuntu 10.04 LTS):

focus gained FocusEvent{Text {} time=211143 data=null}
verify: Event {type=25 Text {} time=212689 data=null x=0 y=0 width=0 height=0 detail=0}
focus lost FocusEvent{Text {} time=212689 data=null}

(SWT:1510): Gtk-CRITICAL **: gtk_editable_get_selection_bounds: assertion `GTK_IS_EDITABLE (editable)' failed

(SWT:1510): GLib-GObject-WARNING **: invalid (NULL) pointer instance

(SWT:1510): GLib-GObject-CRITICAL **: g_signal_stop_emission_by_name: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

On Windows XP and Mac Cocoa the snippet executes with no problem and delivers the following console output:

focus gained FocusEvent{Text {} time=131471052 data=null}
verify: Event {type=25 Text {} time=131472551 data=null x=0 y=0 width=0 height=0 detail=0}
focus lost FocusEvent{Text {} time=131472551 data=null}
org.eclipse.swt.widgets.Display@7b479feb

Here is the snippet to reproduce:

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.FocusEvent;
import org.eclipse.swt.events.FocusListener;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class Snippet {
	public static void main(String[] args) {
		final Display display = new Display();
		Shell shell = new Shell();
		shell.setLayout(new GridLayout());
		final Text text = new Text(shell, SWT.SINGLE);
		text.addListener(SWT.Verify, new Listener() {

			public void handleEvent(Event event) {
				System.out.println("verify: " + event);
				text.setVisible(false);
				text.dispose();
			}
		});
		text.addFocusListener(new FocusListener() {

			public void focusLost(FocusEvent e) {
				System.out.println("focus lost " + e);
				System.out.println(text.getDisplay());
			}

			public void focusGained(FocusEvent e) {
				System.out.println("focus gained " + e);
			}
		});
		shell.setSize(300, 300);
		shell.open();
		text.setFocus();

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

I ran into this when trying to investigate the SWT issue behind bug #318959, which seems to be causes by a similar problem (the listener receives an SWT.Verify event after the Text widget has already be disposed).