Description Greg Watson 2012-02-06 18:05:26 EST

We see different behavior for combo listeners on different platforms. Is this expected?

The issue is shown in the following example. On Mac/Windows, clicking on the Update button results in:

update combo
modify event

On Linux, the same code produces:

update combo
modify event
modify event
modify event
fire event that should not happen!

It seems that on Linux there is an extra event generated by the system after the button listener has finished. Are we doing something wrong? If a bug, can you suggest a workaround? 

Thanks!

----------------------------

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.ModifyEvent;
import org.eclipse.swt.events.ModifyListener;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;

public class ComboEventTest {

	private static Combo combo;
	private static boolean initializing = false;
	private static String[] languages = new String[] { "Java" };

	public ComboEventTest() {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new GridLayout(2, true));

		combo = new Combo(shell, SWT.READ_ONLY | SWT.DROP_DOWN);

		for (int i = 0; i < languages.length; i++) {
			combo.add(languages[i]);
			combo.setData(Integer.toString(i), languages[i]);
		}

		combo.select(0);
		combo.addModifyListener(new ModifyListener() {

			public void modifyText(ModifyEvent e) {
				System.out.println("modify event");
				if (!initializing) {
					System.out.println("fire event that should not happen!");
				}
			}

		});
		Button b = new Button(shell, SWT.PUSH);
		b.setText("Update");
		b.addListener(SWT.Selection, new Listener() {
			public void handleEvent(Event event) {
				updateComboSelection();
			}
		});

		shell.pack();
		shell.open();

		// Set up the event loop.
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) {
				// If no more entries in event queue
				display.sleep();
			}
		}

		display.dispose();
	}

	private static void updateComboSelection() {
		initializing = true;
		System.out.println("update combo");
		combo.removeAll();
		for (int i = 0; i < languages.length; i++) {
			combo.add(languages[i]);
			combo.setData(Integer.toString(i), languages[i]);
		}

		combo.select(0);

		combo.getParent().layout(true);
		initializing = false;
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		new ComboEventTest();
	}

}