import org.eclipse.swt.SWT;
import org.eclipse.swt.events.MouseEvent;
import org.eclipse.swt.events.MouseListener;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.events.ShellEvent;
import org.eclipse.swt.events.ShellListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.List;
import org.eclipse.swt.widgets.Shell;

public class ComboTest {
    
    MyPopup popup;

    public static void main (String [] args) {
        Display display = new Display();
        Shell shell = new ComboTest().open(display);
        // Event loop
        while (shell != null && ! shell.isDisposed()) {
            if (! display.readAndDispatch()) display.sleep();
        }
        // Cleanup
        display.dispose();

    }
    
    
    public Shell open(Display d){
        Shell shell = new Shell();
        createPartControl(shell);
       
        shell.pack();
        shell.open();
        return shell;
    }
    
    public void createPartControl(final Shell shell){
        GridLayout gl = new GridLayout(2,false);
        gl.marginHeight = 10;
        gl.marginWidth = 10;
        shell.setLayout(gl);
        
        final Label l = new Label(shell,SWT.NONE);
        l.setText("Nothing Selected");
        l.setBackground(Display.getCurrent().getSystemColor(SWT.COLOR_LIST_BACKGROUND));
        
        final Button b = new Button(shell,SWT.ARROW | SWT.DOWN);
    
        
        b.addSelectionListener(new SelectionListener(){
            public void widgetSelected(SelectionEvent arg0) {
                showPopup(shell,l);
            }
            public void widgetDefaultSelected(SelectionEvent arg0) {
            }}
        );
        
    }
    
    public void showPopup(Shell parentShell,Label l){
        if (popup == null){
            popup = new MyPopup(parentShell,l);
        }
        
        popup.show(l);
        
    }
    
    
    private class MyPopup {

        Shell shell;
        List list;
        Shell parentShell;
        Label label;
        
        public MyPopup(Shell arg0,Label arg1) {
            shell = new Shell(arg0,SWT.TOOL);
            
            parentShell = arg0;
            parentShell.addShellListener(new ShellListener(){
                public void shellActivated(ShellEvent arg0) {
                }
                public void shellClosed(ShellEvent arg0) {
                }
                public void shellDeactivated(ShellEvent arg0) {
                    if (!shell.isDisposed())
                        Display.getCurrent().asyncExec(new Runnable(){
                            public void run() {
                                shell.setVisible(false);
                            }}
                        );                        
                }
                public void shellDeiconified(ShellEvent arg0) {
                }
                public void shellIconified(ShellEvent arg0) {
                }}
            );
            
            label = arg1;
            
            shell.setLayout(new FillLayout());
            
            list = new List(shell,SWT.NONE);
            
            list.addMouseListener(new MouseListener(){
                public void mouseDoubleClick(MouseEvent arg0) {
                }
                public void mouseDown(MouseEvent arg0) {
                    list.setCapture(false);
                    parentShell.setActive();
                    if (list.getBounds().contains(arg0.x,arg0.y)){
                        try {
                            Display.getCurrent().getThread().sleep(200);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                        label.setText(list.getSelection()[0]);
                    }
                    shell.setVisible(false);
                }
                public void mouseUp(MouseEvent arg0) {
                }}
            );

            
            list.add("Item 1");
            list.add("Item 2");
            list.add("Item 3");
            list.add("Item 4");
            
            shell.setSize(100,100);
        }
        
        public void show(Label l) {
            shell.setLocation(l.toDisplay(l.getLocation()));            
            shell.setVisible(true);            
            list.setCapture(true);
            
        }
    
    }
}