Hidden iframe Firefox add-on using WebExtensions

Question

I need to create a hidden iframe in a Firefox add-on using WebExtensions.

This is what I'm trying to do (as suggested here: Load multiple pages in a hidden iframe from a xul-based firefox extension):

var hiddenWindow = Components.classes["@mozilla.org/appshell/appShellService;1"].
                   getService(Components.interfaces.nsIAppShellService).
                   hiddenDOMWindow;

I get the error "Components.classes is undefined", and can't seem to work around it.

Help is appreciated. Thank you.

Noitidart · Accepted Answer · 2016-06-14T12:58:33.173

Don't do this. In WEAPI this isn't even possible, you can't run code like this in that scope.

WEAPI

If you are using webextensions use a background page and you don't have to worry about this - https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Anatomy_of_a_WebExtension#Background_scripts

Bootstrap

In bootstrap you can do this, but don't. In bootstrap use the same tech used by WEAPI which is windowless browsers which are supported since Firefox 23 -

 var webnav = Services.appShell.createWindowlessBrowser(true);
 var docshell = webnav.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDocShell);
 var systemPrincipal = Cc["@mozilla.org/systemprincipal;1"].createInstance(Ci.nsIPrincipal);
 docshell.createAboutBlankContentViewer(systemPrincipal);
 var contentWindow = docshell.contentViewer.DOMDocument.defaultView;

 // when you are done with it, destroy it
 if (webnav.close) { webnav.close() }; // only available in Firefox 46+, and is needed for good measure
 webnav = null; // in Firefox <= 45 setting to null will cause it to get GC'ed which will destroy it

Here's another example, this is how webextenions use this code above:

let chromeWebNav = Services.appShell.createWindowlessBrowser(true);
this.chromeWebNav = chromeWebNav;

let url;
if (this.page) {
  url = this.extension.baseURI.resolve(this.page);
} else {
  // TODO: Chrome uses "_generated_background_page.html" for this.
  url = this.extension.baseURI.resolve("_blank.html");
}

if (!this.extension.isExtensionURL(url)) {
  this.extension.manifestError("Background page must be a file within the extension");
  url = this.extension.baseURI.resolve("_blank.html");
}

let system = Services.scriptSecurityManager.getSystemPrincipal();

let chromeShell = chromeWebNav.QueryInterface(Ci.nsIInterfaceRequestor)
                              .getInterface(Ci.nsIDocShell);
chromeShell.createAboutBlankContentViewer(system);

let chromeDoc = chromeWebNav.document;
const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
let browser = chromeDoc.createElementNS(XUL_NS, "browser");
browser.setAttribute("type", "content");
browser.setAttribute("disableglobalhistory", "true");
browser.setAttribute("webextension-view-type", "background");
chromeDoc.body.appendChild(browser);

let frameLoader = browser.QueryInterface(Ci.nsIFrameLoaderOwner).frameLoader;
let docShell = frameLoader.docShell;

let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
this.webNav = webNav;

webNav.loadURI(url, 0, null, null, null);

let window = webNav.document.defaultView;
this.contentWindow = window;

https://dxr.mozilla.org/mozilla-central/source/toolkit/components/extensions/ext-backgroundPage.js#25-64

Hidden iframe Firefox add-on using WebExtensions

1 Answers1

WEAPI

Bootstrap