Question

How to check if a given window is open in Xul?

I would like to check if a window is already openned in my desktop app. So if it is, I’ll not open it again.

— my attempt

I’m trying to accomplish this using the window title, so I get the list of windows from windowManager and check the title, but the getAttribute is not from an interface that I can query, it’s from element, what interface should I use?

var windowManager = Components.classes['@mozilla.org/appshell/window-mediator;1'].getService(Components.interfaces.nsIWindowMediator);
var enum = windowManager.getXULWindowEnumerator(null);
while(enum.hasMoreElements()) {
    var win = enum.getNext().QueryInterface(Components.interfaces[" WHICH INTERFACE TO PUT HERE? "]);
    write("WINDOW TITLE = " + win.getAttribute("title"));
}

Answer 1

var windowManager = Components.classes['@mozilla.org/appshell/window-mediator;1'].getService(Components.interfaces.nsIWindowMediator);
var enum = windowManager.getEnumerator(null);
while(enum.hasMoreElements()) {
  var win = enum.getNext().QueryInterface( Components.interfaces.nsIDOMChromeWindow );
  write("WINDOW TITLE = " + win.document.documentElement.getAttribute("title") );
}

if you are using getXULWindowEnumerator you should use Components.interfaces.nsIXULWindow

you probably could use the nsIDOMWindow attribute name if you open the windows your self because you set the name of the window in the open function. This is not visible to the user so you have a little more flexibility

var win = window.open( "chrome://myextension/content/about.xul", 
                          "windowName", "chrome,centerscreen" );

write( "WINDOW NAME: " + win.name ); // Should now give  WINDOW NAME: windowName

If you are leaving the window name blank it will open a new window every time. If you however use a window name (something else than “” ) it will create it if it does not exists, or load the new content in the already existing window with the name you have specified.

Which seems like almost what you want. Butt you could use name attribute to avoid the reload if you have to.

var openNewWindow = true;
var windowManager = Components.classes['@mozilla.org/appshell/window-mediator;1'].getService(Components.interfaces.nsIWindowMediator);
var enum = windowManager.getEnumerator(null);

while(enum.hasMoreElements()) {
  var win = enum.getNext().QueryInterface( Components.interfaces.nsIDOMChromeWindow );
  if( win.name == "windowName" ) {
    openNewWindow = false;
  }
}

if( openNewWindow ) {
  var win = window.open( "chrome://myextension/content/about.xul", 
                      "windowName", "chrome" );
}