Run the following code and popup the combo (you will get an exception in setVisible()):


package bugs;

import javafx.collections.FXCollections;
import javafx.embed.swt.FXCanvas;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.layout.GridPane;

import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;

public class RT30307_Combo {
     private static void openTestShell(final boolean useSwtGroup,
             final boolean useSwtCanvas) {
          Display display = new Display();
          Shell shell = new Shell(display);
          //shell.setLayout(new FillLayout());
          Composite parent = shell;
          if (useSwtGroup) {
             Group group = new Group(parent, SWT.NONE);
             group.setText("Group");
             //group.setLayout(new GridLayout(1, true));
             parent = group;
          }
          if (useSwtCanvas) {
             Canvas swtCanvas = new Canvas(parent, SWT.NONE);
             //swtCanvas.setLayout(new FillLayout());
             parent = swtCanvas;
          }
    
          FXCanvas canvas = new FXCanvas(parent, SWT.BORDER);
          canvas.setBounds(25, 50, 200, 200);
    
          GridPane gridPane = new GridPane();
          Scene scene;
          scene = new Scene(gridPane);
          canvas.setScene(scene);
          ComboBox<String> myCombo = new ComboBox<String>();
          myCombo
                .setItems(FXCollections.observableArrayList("One", "Two", "Three"));
          gridPane.add(myCombo, 0, 0);
          
          parent.pack();
          shell.pack();
          shell.open();

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

    public static void main(String[] args) {
        openTestShell(true, false);
    }
}