Using gecko offscreen

[Jeremias Reith]

What should I do to use gecko offscreen?

As far as I know the easiest way is to create a hiddenWindow, access its 
 docshell and doing what ever wanted (no better way?).

Is there a XP way in doing that?

I tried this:

int main (int argc, char **argv)
{
  nsresult rv;
  rv = NS_InitEmbedding(nsnull, nsnull);
  if(NS_FAILED(rv)) {
    NS_ERROR("Could not init embedding");
    NS_TermEmbedding();
    return rv;
  }
  nsCOMPtr<nsIAppShellService> 
appShellService(do_GetService("@mozilla.org/appshell/appShellService;1", 
&rv));
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);

  nsCOMPtr<nsICmdLineService> 
cmdLineArgs(do_GetService("@mozilla.org/appshell/commandLineService;1", 
&rv));
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);

  cmdLineArgs->Initialize(argc, argv);

  rv=appShellService->Initialize(cmdLineArgs, nsnull);
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
  appShellService->CreateHiddenWindow();
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
  nsCOMPtr<nsIXULWindow> hiddenWindow;
  appShellService->GetHiddenWindow(getter_AddRefs(hiddenWindow));
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
  nsCOMPtr<nsIDocShellTreeItem> item;
  rv=hiddenWindow->GetPrimaryContentShell(getter_AddRefs(item));
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
  nsCOMPtr<nsIDocShell> docshell(do_QueryInterface(item, &rv));
  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
  ...
}
But the window has no content shell (GetPrimaryContentShell returns 
null) and using the XULWindow's top level docshell (tried a loadURI(...) 
to mozilla.org) loads the page (checked with tcpdump) but the the DOM 
does not contain the loaded document.

Any ideas?

Regards
/Jeremias Reith