guimarac
(Guimarac)
June 14, 2016, 10:09am
1
Hello. I am writing a Firefox addon using WebExtension. I want to create a hidden iframe, so I have the following code:
var hiddenWindow = Components.classes["@mozilla.org/appshell/appShellService;1"].getService(Components.interfaces.nsIAppShellService).hiddenDOMWindow;
I always get the error “Components.classes is undefined”. I had no luck in finding a solution… Hope someone can help me.
Thank you.
noitidart
(Noitidart)
June 14, 2016, 1:00pm
2
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
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