Re: [platform-swt-dev] MessageBox blocks display thread on linux

[Rainer.Stransky@xxxxxxxxxx]

I tested with Eclipse 3.1.2 and 3.2 with exactly the same behaviour. So its
hard to believe, this simple and basic behaviour is a bug on both major
releases !?

I will send a bug report in parallel.


Here the code to reproduce:

---- snipped ---
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.MessageBox;
import org.eclipse.swt.widgets.Shell;

/*
 * This test class open a shell with a button and a label
 * The label is refreshed by a Thread each second and shows a counter
incrementing
 * A click on the button will open a MessageBox, waiting for a user input.
 * While waiting for the user input the refresh of the label using
asyncExec() is blocked on Linux/GTK.
 * Closing the MessageBox will de-block the thread and the refresh events
are processed.
 *
 * On Windows the behavior is different/better. The refresh of the label is
done also while wating for the
 * user input of the MessageBox.open() call.
 *
 */
public class TestSnipped {

  static int ourCnt = 1;

  public static void main(String[] args) {

    final Display display = new Display();
    Shell shell = new Shell(display);
    shell.setLayout(new FillLayout());
    final Label time = new Label(shell, SWT.BORDER);
    time.setText("" + ourCnt);
    time.pack();
    Button dialog = new Button(shell, SWT.PUSH);
    dialog.addSelectionListener(new SelectionListener() {
        public void widgetDefaultSelected(SelectionEvent arg0) {}
        public void widgetSelected(SelectionEvent arg0) {
            MessageBox mb = new MessageBox(new Shell(display), SWT.OK|
SWT.CANCEL|SWT.SYSTEM_MODAL);
            mb.open();
        }
    });
    dialog.setText("Start Messagebox");
    shell.pack();
    shell.setSize(200, 200);
    shell.open();
    new Thread() {
      public void run() {
        while (true) {
          try {
            sleep(1000);
          } catch (InterruptedException e) {
            e.printStackTrace();
          }
          display.asyncExec(new Runnable() {
            public void run() {
              ourCnt++;
              time.setText("" + ourCnt);
            }
          });
        }
      }
    }.start();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}