nsIWebBrowserPrint

Hi!
I use JavaXPCOM to embed gecko into an awt canvas. A print button
should print the content.
If I compile and run the java class found below, wait for mozilla.org
to be rendered inside the canvas and then press the print button,
nothing is printed.
Sometimes (not always), a print dialog opens (but nothing happens
after pressing "ok")
Sometimes (not always) an exception is thrown:
 org.mozilla.xpcom.XPCOMException: The function "print" returned an
error condition  (0x80040111)

Can anyone tell me what's wrong?
Thanks in advance!
hs
-------------------------------------------
package bugs;

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Canvas;
import java.awt.Frame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;

import org.mozilla.xpcom.GREVersionRange;
import org.mozilla.xpcom.IAppFileLocProvider;
import org.mozilla.xpcom.Mozilla;
import org.mozilla.xpcom.nsIAppStartup;
import org.mozilla.xpcom.nsIBaseWindow;
import org.mozilla.xpcom.nsIEventQueue;
import org.mozilla.xpcom.nsIEventQueueService;
import org.mozilla.xpcom.nsIInterfaceRequestor;
import org.mozilla.xpcom.nsIProxyObjectManager;
import org.mozilla.xpcom.nsIServiceManager;
import org.mozilla.xpcom.nsIWebBrowser;
import org.mozilla.xpcom.nsIWebBrowserPrint;
import org.mozilla.xpcom.nsIWebNavigation;

public class PrintTest extends Canvas {

  private nsIWebBrowser webBrowser;

  // used if no gre can be located automatically
  public static String FALLBACK_GRE_PATH = "/path/to/xulrunner";


  public static void main(String[] args) throws Exception {
    // init gtk
    // this line removes the warnings, but not the crash
    // sun.awt.X11.XToolkit.checkGTK();

    final PrintTest pt = new PrintTest();
    Button bt = new Button("print");
    bt.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        pt.print();
      }
    });
    Frame frame = new Frame("PrintTest");
    frame.setLayout(new BorderLayout());
    frame.add(bt, BorderLayout.NORTH);
    frame.add(pt, BorderLayout.CENTER);
    frame.setBounds(100, 100, 400, 400);
    frame.setVisible(true);
    Thread.sleep(2000);
    System.out.println("starting test...");
    pt.test();
  }


  public void test() throws Exception {

    Mozilla mozilla = Mozilla.getInstance();
    GREVersionRange[] range = new GREVersionRange[1];
    range[0] = new GREVersionRange("1.8.0", true, "1.9", false);

    File grePath = Mozilla.getGREPathWithProperties(range, null);
    if (null == grePath) grePath = new File(FALLBACK_GRE_PATH);
    LocationProvider locProvider = new LocationProvider(grePath);
    mozilla.initEmbedding(grePath, grePath, locProvider);

    Mozilla moz = Mozilla.getInstance();

    nsIServiceManager serviceManager = moz.getServiceManager();
    nsIAppStartup appStartup = (nsIAppStartup)
serviceManager.getServiceByContractID(
      "@mozilla.org/toolkit/app-startup;1",
nsIAppStartup.NS_IAPPSTARTUP_IID);

    String NS_IWEBBROWSER_CID = "F1EAC761-87E9-11d3-
AF80-00A024FFC08C"; //$NON-NLS-1$
    this.webBrowser = (nsIWebBrowser)
moz.getComponentManager().createInstance(NS_IWEBBROWSER_CID, null,
      nsIWebBrowser.NS_IWEBBROWSER_IID);

    nsIBaseWindow baseWindow = (nsIBaseWindow)
webBrowser.queryInterface(nsIBaseWindow.NS_IBASEWINDOW_IID);

    // long windowHandle = ((sun.awt.X11.XComponentPeer)
getPeer()).getWindow();
    long windowHandle = ((sun.awt.windows.WComponentPeer)
getPeer()).getHWnd();

    System.out.println("windowHandle " + windowHandle);
    baseWindow.initWindow(windowHandle, 0, 0, 0, getWidth(),
getHeight());
    System.out.println("inited");
    baseWindow.create();
    System.out.println("created");
    baseWindow.setVisibility(true);
    nsIWebNavigation webNavigation = (nsIWebNavigation) webBrowser
      .queryInterface(nsIWebNavigation.NS_IWEBNAVIGATION_IID);
    webNavigation.loadURI("http://www.mozilla.org",
nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE, null, null,
      null);

    appStartup.run();

  }


  public void print() {
    Mozilla moz = Mozilla.getInstance();
    nsIInterfaceRequestor ir = (nsIInterfaceRequestor) webBrowser
      .queryInterface(nsIInterfaceRequestor.NS_IINTERFACEREQUESTOR_IID);
    nsIWebBrowserPrint print = (nsIWebBrowserPrint) ir
      .getInterface(nsIWebBrowserPrint.NS_IWEBBROWSERPRINT_IID);

    nsIEventQueueService eventQueueServive = (nsIEventQueueService)
moz.getServiceManager()
      .getServiceByContractID("@mozilla.org/event-queue-service;1",
        nsIEventQueueService.NS_IEVENTQUEUESERVICE_IID);
    nsIEventQueue eventQueue = eventQueueServive
      .getSpecialEventQueue(nsIEventQueueService.UI_THREAD_EVENT_QUEUE);
    nsIProxyObjectManager proxyManager = (nsIProxyObjectManager)
moz.getComponentManager()
      .createInstanceByContractID("@mozilla.org/xpcomproxy;1", null,
        nsIProxyObjectManager.NS_IPROXYOBJECTMANAGER_IID);
    nsIWebBrowserPrint printProxy = (nsIWebBrowserPrint)
proxyManager.getProxyForObject(eventQueue,
      nsIWebBrowserPrint.NS_IWEBBROWSERPRINT_IID, print,
nsIProxyObjectManager.INVOKE_SYNC);
    printProxy.print(null, null);
  }

  public static class LocationProvider implements IAppFileLocProvider
{
    private final File libXULPath;
    int counter = 0;


    public LocationProvider(File grePath) {
      this.libXULPath = grePath;
    }


    public File getFile(String aProp, boolean[] aPersistent) {
      File file = null;
      if (aProp.equals("GreD") || aProp.equals("GreComsD")) {
        file = libXULPath;
        if (aProp.equals("GreComsD")) {
          file = new File(file, "components");
        }
      } else if (aProp.equals("MozBinD") || aProp.equals("CurProcD")
|| aProp.equals("ComsD")
        || aProp.equals("ProfD")) {
        file = libXULPath;
        if (aProp.equals("ComsD")) {
          file = new File(file, "components");
        }
      }
      return file;
    }


    public File[] getFiles(String aProp) {
      File[] files = null;
      if (aProp.equals("APluginsDL")) {
        files = new File[1];
        files[0] = new File(libXULPath, "plugins");
      }
      return files;
    }
  }
}