    /**
     * The FocusManager is responsible for globally:
     *
     * 1. Managing component focus
     * 2. Providing basic keyboard navigation
     * 3. (optional) Provide a visual cue for focused components, in the form of a focus ring/frame.
     *
     * To activate the FocusManager, simply call `Ext.FocusManager.enable();`. In turn, you may
     * deactivate the FocusManager by subsequently calling `Ext.FocusManager.disable();`.  The
     * FocusManager is disabled by default.
     *
     * To enable the optional focus frame, pass `true` or `{focusFrame: true}` to {@link #method-enable}.
     *
     * Another feature of the FocusManager is to provide basic keyboard focus navigation scoped to any {@link Ext.container.Container}
     * that would like to have navigation between its child {@link Ext.Component}'s.
     *
     * @author Jarred Nicholls <jarred@sencha.com>
     * @docauthor Jarred Nicholls <jarred@sencha.com>
     */
    Ext.define('Ext.FocusManager', {
        singleton: true,
        alternateClassName: ['Ext.FocusMgr' ],

        mixins: {
            observable: 'Ext.util.Observable'
        },

        requires: [
            'Ext.AbstractComponent',
            'Ext.Component',
            'Ext.ComponentManager',
            'Ext.ComponentQuery',
            'Ext.util.HashMap',
            'Ext.util.KeyNav'
        ],

        /**
         * @property {Boolean} enabled
         * Whether or not the FocusManager is currently enabled
         */
        enabled: false,

        /**
         * @property {Ext.Component} focusedCmp
         * The currently focused component.
         */

        focusElementCls: Ext.baseCSSPrefix + 'focus-element',

        focusFrameCls: Ext.baseCSSPrefix + 'focus-frame',

        /**
         * @property {String[]} whitelist
         * A list of xtypes that should ignore certain navigation input keys and
         * allow for the default browser event/behavior. These input keys include:
         *
         * 1. Backspace
         * 2. Delete
         * 3. Left
         * 4. Right
         * 5. Up
         * 6. Down
         *
         * The FocusManager will not attempt to navigate when a component is an xtype (or descendents thereof)
         * that belongs to this whitelist. E.g., an {@link Ext.form.field.Text} should allow
         * the user to move the input cursor left and right, and to delete characters, etc.
         */
        whitelist: [
            'textfield'
        ],

        constructor: function(config) {
            var me = this,
                CQ = Ext.ComponentQuery;

            me.mixins.observable.constructor.call(me, config);

            me.addEvents(
                /**
                 * @event beforecomponentfocus
                 * Fires before a component becomes focused. Return `false` to prevent
                 * the component from gaining focus.
                 * @param {Ext.FocusManager} fm A reference to the FocusManager singleton
                 * @param {Ext.Component} cmp The component that is being focused
                 * @param {Ext.Component} previousCmp The component that was previously focused,
                 * or `undefined` if there was no previously focused component.
                 */
                'beforecomponentfocus',

                /**
                 * @event componentfocus
                 * Fires after a component becomes focused.
                 * @param {Ext.FocusManager} fm A reference to the FocusManager singleton
                 * @param {Ext.Component} cmp The component that has been focused
                 * @param {Ext.Component} previousCmp The component that was previously focused,
                 * or `undefined` if there was no previously focused component.
                 */
                'componentfocus',

                /**
                 * @event disable
                 * Fires when the FocusManager is disabled
                 * @param {Ext.FocusManager} fm A reference to the FocusManager singleton
                 */
                'disable',

                /**
                 * @event enable
                 * Fires when the FocusManager is enabled
                 * @param {Ext.FocusManager} fm A reference to the FocusManager singleton
                 */
                'enable'
            );

            me.focusTask = new Ext.util.DelayedTask(me.handleComponentFocus, me);

            // Gain control on Component focus, blur, hide and destroy
            Ext.override(Ext.AbstractComponent, {
                onFocus: function() {
                    this.callParent(arguments);
                    if (me.enabled && this.hasFocus) {
                        Array.prototype.unshift.call(arguments, this);
                        me.onComponentFocus.apply(me, arguments);
                    }
                },
                onBlur: function() {
                    this.callParent(arguments);
                    if (me.enabled && !this.hasFocus) {
                        Array.prototype.unshift.call(arguments, this);
                        me.onComponentBlur.apply(me, arguments);
                    }
                },
                onDestroy: function() {
                    this.callParent(arguments);
                    if (me.enabled) {
                        Array.prototype.unshift.call(arguments, this);
                        me.onComponentDestroy.apply(me, arguments);
                    }
                }
            });
            Ext.override(Ext.Component, {
                afterHide: function() {
                    this.callParent(arguments);
                    if (me.enabled) {
                        Array.prototype.unshift.call(arguments, this);
                        me.onComponentHide.apply(me, arguments);
                    }
                }
            });
            // Setup KeyNav that's bound to document to catch all
            // unhandled/bubbled key events for navigation
            me.keyNav = new Ext.util.KeyNav(Ext.getDoc(), {
                disabled: true,
                scope: me,

                backspace: me.focusLast,
                enter: me.navigateIn,
                esc: me.navigateOut,
                tab: me.navigateSiblings,
                space: me.navigateIn,
                del: me.focusLast,
                left: me.navigateSiblings,
                right: me.navigateSiblings,
                down: me.navigateSiblings,
                up: me.navigateSiblings
            });

            me.focusData = {};
            me.subscribers = new Ext.util.HashMap();
            me.focusChain = {};

            // Setup some ComponentQuery pseudos
            Ext.apply(CQ.pseudos, {
                focusable: function(cmps) {
                    var len = cmps.length,
                        results = [],
                        i = 0,
                        c;

                    for (; i < len; i++) {
                        c = cmps[i];
                        if (c.isFocusable()) {
                            results.push(c);
                        }
                    }

                    return results;
                },

                // Return the single next focusable sibling from the current idx in either direction (step -1 or 1)
                nextFocus: function(cmps, idx, step) {
                    step = step || 1;
                    idx = parseInt(idx, 10);

                    var len = cmps.length,
                        i = idx, c;

                    for (;;) {
                        // Increment index, and loop round if off either end
                        if ((i += step) >= len) {
                            i = 0;
                        } else if (i < 0) {
                            i = len - 1;
                        }

                        // As soon as we loop back to the starting index, give up, there are no focusable siblings.
                        if (i === idx) {
                            return [];
                        }

                        // If we have found a focusable sibling, return it
                        if ((c = cmps[i]).isFocusable()) {
                            return [c];
                        }
                    }

                    return [];
                },

                prevFocus: function(cmps, idx) {
                    return this.nextFocus(cmps, idx, -1);
                },

                root: function(cmps) {
                    var len = cmps.length,
                        results = [],
                        i = 0,
                        c;

                    for (; i < len; i++) {
                        c = cmps[i];
                        if (!c.ownerCt) {
                            results.push(c);
                        }
                    }

                    return results;
                }
            });
        },

        /**
         * Adds the specified xtype to the {@link #whitelist}.
         * @param {String/String[]} xtype Adds the xtype(s) to the {@link #whitelist}.
         */
        addXTypeToWhitelist: function(xtype) {
            var me = this;

            if (Ext.isArray(xtype)) {
                Ext.Array.forEach(xtype, me.addXTypeToWhitelist, me);
                return;
            }

            if (!Ext.Array.contains(me.whitelist, xtype)) {
                me.whitelist.push(xtype);
            }
        },

        clearComponent: function(cmp) {
            clearTimeout(this.cmpFocusDelay);
            if (!cmp.isDestroyed) {
                cmp.blur();
            }
        },

        /**
         * Disables the FocusManager by turning of all automatic focus management and keyboard navigation
         */
        disable: function() {
            var me = this;

            if (!me.enabled) {
                return;
            }

            delete me.options;
            me.enabled = false;

            me.removeDOM();

            // Stop handling key navigation
            me.keyNav.disable();

            me.fireEvent('disable', me);
        },

        /**
         * Enables the FocusManager by turning on all automatic focus management and keyboard navigation
         * @param {Boolean/Object} options Either `true`/`false` to turn on the focus frame, or an object
         * with the following options:
         * @param {Boolean} [focusFrame=false] `true` to show the focus frame around a component when it is focused.
         */
        enable: function(options) {
            var me = this;

            if (options === true) {
                options = { focusFrame: true };
            }
            me.options = options = options || {};

            if (me.enabled) {
                return;
            }

            // When calling addFocusListener on Containers, the FocusManager must be enabled, otherwise it won't do it.
            me.enabled = true;
            me.initDOM(options);

            // Start handling key navigation
            me.keyNav.enable();

            // Finally, let's focus our global focus el so we start fresh
            me.focusEl.focus();
            delete me.focusedCmp;

            me.fireEvent('enable', me);
        },

        focusLast: function(e) {
            var me = this;

            if (me.isWhitelisted(me.focusedCmp)) {
                return true;
            }

            // Go back to last focused item
            if (me.previousFocusedCmp) {
                me.previousFocusedCmp.focus();
            }
        },

        getRootComponents: function() {
            var me = this,
                CQ = Ext.ComponentQuery,
                inline = CQ.query(':focusable:root:not([floating])'),
                floating = CQ.query(':focusable:root[floating]');

            // Floating items should go to the top of our root stack, and be ordered
            // by their z-index (highest first)
            floating.sort(function(a, b) {
                return a.el.getZIndex() > b.el.getZIndex();
            });

            return floating.concat(inline);
        },

        initDOM: function(options) {
            var me = this,
                cls = me.focusFrameCls,
                needListeners = Ext.ComponentQuery.query('{getFocusEl()}:not([focusListenerAdded])'),
                i = 0, len = needListeners.length;

            if (!Ext.isReady) {
                return Ext.onReady(me.initDOM, me);
            }

            // When we are enabled, we must ensure that all Components which return a focusEl that is *not naturally focusable*
            // have focus/blur listeners enabled to then trigger onFocus/onBlur handling so that we get to know about their focus action.
            // These listeners are not added at initialization unless the FocusManager is enabled at that time.
            for (; i < len; i++) {
                needListeners[i].addFocusListener();
            }

            // Make the document body the global focus element
            if (!me.focusEl) {
                me.focusEl = Ext.getBody();
                me.focusEl.dom.tabIndex = -1;
            }

            // Create global focus frame
            if (!me.focusFrame && options.focusFrame) {
                me.focusFrame = Ext.getBody().createChild({
                    cls: cls,
                    children: [
                        { cls: cls + '-top' },
                        { cls: cls + '-bottom' },
                        { cls: cls + '-left' },
                        { cls: cls + '-right' }
                    ],
                    style: 'top: -100px; left: -100px;'
                });
                me.focusFrame.setVisibilityMode(Ext.Element.DISPLAY);
                me.focusFrame.hide().setLeftTop(0, 0);
            }
        },

        isWhitelisted: function(cmp) {
            return cmp && Ext.Array.some(this.whitelist, function(x) {
                return cmp.isXType(x);
            });
        },

        navigateIn: function(e) {
            var me = this,
                focusedCmp = me.focusedCmp,
                defaultRoot,
                firstChild;

            if (me.isWhitelisted(focusedCmp)) {
                return true;
            }

            if (!focusedCmp) {
                // No focus yet, so focus the first root cmp on the page
                defaultRoot = me.getRootComponents()[0];
                if (defaultRoot) {
                    // If the default root is based upon the body, then it will already be focused, and will not fire a focus event to
                    // trigger its own onFocus processing, so we have to programatically blur it first.
                    if (defaultRoot.getFocusEl() === me.focusEl) {
                        me.focusEl.blur();
                    }
                    defaultRoot.focus();
                }
            } else {
                // Drill into child ref items of the focused cmp, if applicable.
                // This works for any Component with a getRefItems implementation.
                firstChild = focusedCmp.hasFocus ? Ext.ComponentQuery.query('>:focusable', focusedCmp)[0] : focusedCmp;
                if (firstChild) {
                    firstChild.focus();
                } else {
                    // Let's try to fire a click event, as if it came from the mouse
                    if (Ext.isFunction(focusedCmp.onClick)) {
                        e.button = 0;
                        focusedCmp.onClick(e);
                        if (focusedCmp.isVisible(true)) {
                            focusedCmp.focus();
                        } else {
                            me.navigateOut();
                        }
                    }
                }
            }
        },

        navigateOut: function(e) {
            var me = this,
                parent;

            if (!me.focusedCmp || !(parent = me.focusedCmp.up(':focusable'))) {
                me.focusEl.focus();
            } else {
                parent.focus();
            }

            // In some browsers (Chrome) FocusManager can handle this before other
            // handlers. Ext Windows have their own Esc key handling, so we need to
            // return true here to allow the event to bubble.
            return true;
        },

        navigateSiblings: function(e, source, parent) {
            var me = this,
                src = source || me,
                key = e.getKey(),
                EO = Ext.EventObject,
                goBack = e.shiftKey || key == EO.LEFT || key == EO.UP,
                checkWhitelist = key == EO.LEFT || key == EO.RIGHT || key == EO.UP || key == EO.DOWN,
                nextSelector = goBack ? 'prev' : 'next',
                idx, next, focusedCmp, siblings;

            focusedCmp = (src.focusedCmp && src.focusedCmp.comp) || src.focusedCmp;
            if (!focusedCmp && !parent) {
                return true;
            }

            if (checkWhitelist && me.isWhitelisted(focusedCmp)) {
                return true;
            }

            // If no focused Component, or a root level one was focused, then siblings are root components.
            if (!focusedCmp || focusedCmp.is(':root')) {
                siblings = me.getRootComponents();
            } else {
                // Else if the focused component has a parent, get siblings from there
                parent = parent || focusedCmp.up();
                if (parent) {
                    siblings = parent.getRefItems();
                }
            }

            // Navigate if we have found siblings.
            if (siblings) {
                idx = focusedCmp ? Ext.Array.indexOf(siblings, focusedCmp) : -1;
                next = Ext.ComponentQuery.query(':' + nextSelector + 'Focus(' + idx + ')', siblings)[0];
                if (next && focusedCmp !== next) {
                    next.focus();
                    return next;
                }
            }
        },

        onComponentBlur: function(cmp, e) {
            var me = this;

            if (me.focusedCmp === cmp) {
                me.previousFocusedCmp = cmp;
                delete me.focusedCmp;
            }

            if (me.focusFrame) {
                me.focusFrame.hide();
            }
        },

        onComponentFocus: function(cmp, e) {
            var me = this,
                chain = me.focusChain,
                parent;

            if (!cmp.isFocusable()) {
                me.clearComponent(cmp);

                // Check our focus chain, so we don't run into a never ending recursion
                // If we've attempted (unsuccessfully) to focus this component before,
                // then we're caught in a loop of child->parent->...->child and we
                // need to cut the loop off rather than feed into it.
                if (chain[cmp.id]) {
                    return;
                }

                // Try to focus the parent instead
                parent = cmp.up();
                if (parent) {
                    // Add component to our focus chain to detect infinite focus loop
                    // before we fire off an attempt to focus our parent.
                    // See the comments above.
                    chain[cmp.id] = true;
                    parent.focus();
                }

                return;
            }
            // Clear our focus chain when we have a focusable component
            me.focusChain = {};

            // Capture the focusEl to frame now.
            // Button returns its encapsulating element during the focus phase
            // So that element gets styled and framed.
            me.focusTask.delay(10, null, null, [cmp, cmp.getFocusEl()]);
        },

        handleComponentFocus: function(cmp, focusEl) {
            var me = this,
                cls,
                ff,
                fw,
                box,
                bt,
                bl,
                bw,
                bh,
                ft,
                fb,
                fl,
                fr;

            if (me.fireEvent('beforecomponentfocus', me, cmp, me.previousFocusedCmp) === false) {
                me.clearComponent(cmp);
                return;
            }

            me.focusedCmp = cmp;

            // If we have a focus frame, show it around the focused component
            if (me.shouldShowFocusFrame(cmp)) {
                cls = '.' + me.focusFrameCls + '-';
                ff = me.focusFrame;
                box = focusEl.getPageBox();

                // Size the focus frame's t/b/l/r according to the box
                // This leaves a hole in the middle of the frame so user
                // interaction w/ the mouse can continue
                bt = box.top;
                bl = box.left;
                bw = box.width;
                bh = box.height;
                ft = ff.child(cls + 'top');
                fb = ff.child(cls + 'bottom');
                fl = ff.child(cls + 'left');
                fr = ff.child(cls + 'right');

                ft.setWidth(bw).setLeftTop(bl, bt);
                fb.setWidth(bw).setLeftTop(bl, bt + bh - 2);
                fl.setHeight(bh - 2).setLeftTop(bl, bt + 2);
                fr.setHeight(bh - 2).setLeftTop(bl + bw - 2, bt + 2);

                ff.show();
            }

            me.fireEvent('componentfocus', me, cmp, me.previousFocusedCmp);
        },

        onComponentHide: function(cmp) {
            var me = this,
                cmpHadFocus = false,
                focusedCmp = me.focusedCmp,
                parent;

            if (focusedCmp) {
                // See if the Component being hidden was the focused Component, or owns the focused Component
                // In these cases, focus needs to be removed from the focused Component to the nearest focusable ancestor
                cmpHadFocus = cmp.hasFocus || (cmp.isContainer && cmp.isAncestor(me.focusedCmp));
            }

            me.clearComponent(cmp);

            // Move focus onto the nearest focusable ancestor, or this is there is none
            if (cmpHadFocus && (parent = cmp.up(':focusable'))) {
                parent.focus();
            } else {
                me.focusEl.focus();
            }
        },

        onComponentDestroy: function() {

        },

        removeDOM: function() {
            var me = this;

            // If we are still enabled globally, or there are still subscribers
            // then we will halt here, since our DOM stuff is still being used
            if (me.enabled || me.subscribers.length) {
                return;
            }

            Ext.destroy(
                me.focusFrame
            );
            delete me.focusEl;
            delete me.focusFrame;
        },

        /**
         * Removes the specified xtype from the {@link #whitelist}.
         * @param {String/String[]} xtype Removes the xtype(s) from the {@link #whitelist}.
         */
        removeXTypeFromWhitelist: function(xtype) {
            var me = this;

            if (Ext.isArray(xtype)) {
                Ext.Array.forEach(xtype, me.removeXTypeFromWhitelist, me);
                return;
            }

            Ext.Array.remove(me.whitelist, xtype);
        },

        setupSubscriberKeys: function(container, keys) {
            var me = this,
                el = container.getFocusEl(),
                scope = keys.scope,
                handlers = {
                    backspace: me.focusLast,
                    enter: me.navigateIn,
                    esc: me.navigateOut,
                    scope: me
                },

                navSiblings = function(e) {
                    if (me.focusedCmp === container) {
                        // Root the sibling navigation to this container, so that we
                        // can automatically dive into the container, rather than forcing
                        // the user to hit the enter key to dive in.
                        return me.navigateSiblings(e, me, container);
                    } else {
                        return me.navigateSiblings(e);
                    }
                };

            Ext.iterate(keys, function(key, cb) {
                handlers[key] = function(e) {
                    var ret = navSiblings(e);

                    if (Ext.isFunction(cb) && cb.call(scope || container, e, ret) === true) {
                        return true;
                    }

                    return ret;
                };
            }, me);

            return new Ext.util.KeyNav(el, handlers);
        },

        shouldShowFocusFrame: function(cmp) {
            var me = this,
                opts = me.options || {},
                cmpFocusEl = cmp.getFocusEl(),
                cmpFocusElTag = Ext.getDom(cmpFocusEl).tagName;

            // Do not show a focus frame if
            // 1. We are configured not to.
            // 2. No Component was passed
            if (!me.focusFrame || !cmp) {
                return false;
            }

            // Global trumps
            if (opts.focusFrame) {
                return true;
            }

            if (me.focusData[cmp.id].focusFrame) {
                return true;
            }

            return false;
        }
    });