(keybUtils => {
    var btn = this;
    var listener = {
        handleEvent(e) {
            if(e.target != btn)
                return;
            e.preventDefault();
            e.stopPropagation();
            this.switch();
        },
        switch() {
            var br = document.activeElement;
            br && br.localName == "browser" && br.isRemoteBrowser
                ? br.messageManager.loadFrameScript(this.url, false)
                : this.keybUtils.switchSelKeybLayout();
        },
        get url() {
            delete this.url;
            return this.url = `data:;charset=utf-8,(${
                encodeURIComponent(keybUtils)
            }).switchSelKeybLayout()`;
        },
        get keybUtils() {
            delete this.keybUtils;
            var url = "data:;charset=utf-8,this.keybUtils = " + encodeURIComponent(keybUtils);
            Services.scriptloader.loadSubScript(url, this);
            this.keybUtils.button = btn;
            this.keybUtils.getFocusedElement = function(_subCall, _focusFixed) {
                if(
                    !_focusFixed
                    && "closeMenus" in window
                    && document.commandDispatcher.focusedElement == this.button
                ) {
                    closeMenus(this.button);
                    setTimeout(function(_this) {
                        _this.switchSelKeybLayout(_subCall, true);
                    }, 0, this);
                    return;
                }
                return document.commandDispatcher.focusedElement;
            }
            return this.keybUtils;
        }
    };
    if(btn instanceof XULElement && addEventListener.length > 3) {
        addEventListener("command", listener, true, this.parentNode);
    }
    listener.switch();
})(`{
    //== Options
    noSelBehavior: { // Shift+Home
        ctrlKey:  false,
        altKey:   false,
        shiftKey: true,
        metaKey:  false,
        keyCode:  KeyEvent.DOM_VK_HOME,
        charCode: 0
    },
    // 0 - do nothing
    // 1 - convert all text
    // Or use object like following to simulate "keypress" event:
    /*
    noSelBehavior: { // Ctrl+Shift+Left
        ctrlKey:  true,
        altKey:   false,
        shiftKey: true,
        metaKey:  false,
        keyCode:  KeyEvent.DOM_VK_LEFT,
        charCode: 0
    }
    */
    convTableForward: { // ru -> en
        "\\"": "@",
        ":": "^",
        ";": "$",
        "?": "&",
        ",": "?",
        "/": "|",
        ".": "/",
        "э": "'",
        "б": ",",
        "ю": ".",
        "Ж": ":",
        "ж": ";",
        "Б": "<",
        "Ю": ">",
        "Э": "\\"",
        "х": "[",
        "ъ": "]",
        "ё": "\`",
        "Х": "{",
        "Ъ": "}",
        "Ё": "~",
        "№": "#",
        "Ф": "A",
        "ф": "a",
        "И": "B",
        "и": "b",
        "С": "C",
        "с": "c",
        "В": "D",
        "в": "d",
        "У": "E",
        "у": "e",
        "А": "F",
        "а": "f",
        "П": "G",
        "п": "g",
        "Р": "H",
        "р": "h",
        "Ш": "I",
        "ш": "i",
        "О": "J",
        "о": "j",
        "Л": "K",
        "л": "k",
        "Д": "L",
        "д": "l",
        "Ь": "M",
        "ь": "m",
        "Т": "N",
        "т": "n",
        "Щ": "O",
        "щ": "o",
        "З": "P",
        "з": "p",
        "Й": "Q",
        "й": "q",
        "К": "R",
        "к": "r",
        "Ы": "S",
        "ы": "s",
        "Е": "T",
        "е": "t",
        "Г": "U",
        "г": "u",
        "М": "V",
        "м": "v",
        "Ц": "W",
        "ц": "w",
        "Ч": "X",
        "ч": "x",
        "Н": "Y",
        "н": "y",
        "Я": "Z",
        "я": "z",
        __proto__: null
    },
    //== End of options

    get convTableBackward() {
        var ctb = { __proto__: null };
        var ctf = this.convTableForward;
        for(var c in ctf)
            ctb[ctf[c]] = c;
        delete this.convTableBackward;
        return this.convTableBackward = ctb;
    },
    inPrimaryLayout: function(s) {
        for(var i = 0, l = s.length; i < l; ++i) {
            var c = s.charAt(i);
            if(c in this.convTableForward)
                return true;
            if(c in this.convTableBackward)
                return false;
        }
        return false;
    },
    switchKeybLayout: function(s, convTable) {
        var res = "";
        for(var i = 0, l = s.length; i < l; ++i) {
            var c = s.charAt(i);
            res += c in convTable ? convTable[c] : c;
        }
        return res;
    },
    getFocusedElement: function() {
        return Cc["@mozilla.org/focus-manager;1"].getService(Ci.nsIFocusManager)
            .getFocusedElementForWindow(content, true, {});
    },
    switchSelKeybLayout: function(_subCall, _focusFixed) {
        var fe = this.getFocusedElement(_subCall, _focusFixed);
        if(!fe)
            return;
        if(fe instanceof HTMLInputElement || fe instanceof HTMLTextAreaElement) {
            var ta = fe;
            try {
                var val = ta.value;
                var sel = val.substring(ta.selectionStart, ta.selectionEnd);
            }
            catch(e) { // Non-text HTMLInputElement
                return;
            }
            if(!sel && val && this.noSelBehavior && !_subCall) {
                if(this.noSelBehavior == 1) {
                    ta.selectionStart = 0;
                    ta.selectionEnd = val.length;
                    sel = val;
                }
                else {
                    this.handleNoSel(ta);
                    return;
                }
            }
            if(!sel)
                return;
            var res = this.switchKeybLayout(
                sel,
                this.inPrimaryLayout(sel)
                    ? this.convTableForward
                    : this.convTableBackward
            );
            if(res != sel)
                this.insertText(ta, res);
        }
        else if(fe.contentEditable == "true") {
            var doc = fe.ownerDocument;

            var docURI = doc.documentURI;
            if(
                docURI.substr(0, 5) == "data:"
                && docURI.indexOf("chrome://browser/skin/devtools/") != -1
            ) {
                //~ todo: seems like we only can use paste from clipboard here...
                return;
            }

            var sel = doc.defaultView.getSelection();
            var rng = sel.rangeCount && sel.getRangeAt(0);
            var tmpNode;
            if(!rng || rng.collapsed) {
                if(!this.noSelBehavior || _subCall)
                    return;
                if(this.noSelBehavior == 1) {
                    var r = doc.createRange();
                    r.selectNodeContents(fe);
                    sel.removeAllRanges();
                    sel.addRange(r);
                    tmpNode = fe.cloneNode(true);
                }
                else {
                    this.handleNoSel(fe);
                    return;
                }
            }
            else {
                tmpNode = doc.createElementNS("http://www.w3.org/1999/xhtml", "div");
                tmpNode.appendChild(rng.cloneContents());
            }

            var orig = tmpNode.innerHTML;
            var convTable = this.inPrimaryLayout(tmpNode.textContent)
                ? this.convTableForward
                : this.convTableBackward;

            var _this = this;
            var parseChildNodes = function(node) {
                if(node instanceof Element) {
                    var childNodes = node.childNodes;
                    for(var i = childNodes.length - 1; i >= 0; --i)
                        parseChildNodes(childNodes[i]);
                }
                else if(node.nodeType == node.TEXT_NODE) {
                    var text = node.nodeValue;
                    var newText = _this.switchKeybLayout(node.nodeValue, convTable);
                    if(newText != text)
                        node.parentNode.replaceChild(doc.createTextNode(newText), node);
                }
            }
            parseChildNodes(tmpNode);

            var res = tmpNode.innerHTML;
            if(res != orig)
                doc.execCommand("insertHTML", false, res);
        }
    },
    handleNoSel: function(node) {
        this.select(node);
        this.switchSelKeybLayout(true);
    },
    select: function(node) {
        var e = this.noSelBehavior;
        if(!e || typeof e != "object")
            return;
        var evt = node.ownerDocument.createEvent("KeyboardEvent");
        evt.initKeyEvent(
            "keypress", true /*bubbles*/, true /*cancelable*/, node.ownerDocument.defaultView,
            e.ctrlKey, e.altKey, e.shiftKey, e.metaKey,
            e.keyCode, e.charCode
        );
        node.dispatchEvent(evt);
    },
    insertText: function(ta, text) {
        //var editor = ta.QueryInterface(Components.interfaces.nsIDOMNSEditableElement).editor
        var editor = ta.editor
            .QueryInterface(Components.interfaces.nsIPlaintextEditor);
        if(editor.flags & editor.eEditorReadonlyMask)
            return;

        var sTop = ta.scrollTop;
        var sHeight = ta.scrollHeight;
        var sLeft = ta.scrollLeft;
        // var sWidth = ta.scrollWidth;

        if(text)
            editor.insertText(text);
        else
            editor.deleteSelection(0, 0);

        ta.scrollTop = sTop + (ta.scrollHeight - sHeight);
        ta.scrollLeft = sLeft; // + (ta.scrollWidth - sWidth);
    }
}`);

// Код