Question

I need one hidden iframe for all opened Firefox windows.

For now I’m creating iframe inside XUL overlay, so it is created for each browser window.

I think i should use XPCOM component to have single iframe instance for all browser windows, but i can’t find way how to create XUL elements from it.

Is it possible?

Answer 1

You can create a frame inside the hidden window:

var hiddenWindow = Components.classes["@mozilla.org/appshell/appShellService;1"]
                             .getService(Components.interfaces.nsIAppShellService)
                             .hiddenDOMWindow;
var frame = hiddenWindow.document.getElementById("myExtensionFrame");
if (!frame)
{
  var XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
  frame = hiddenWindow.document.createElementNS(XUL_NS, "iframe");
  frame.setAttribute("id", "myExtensionFrame");
  frame.setAttribute("src", "...");
  hiddenWindow.document.documentElement.appendChild(frame);
}

However, if all you need is a place to run your global code then there are better ways – like JavaScript code modules.