    /**
     * Simple class that can provide a shadow effect for any element.  Note that the element
     * MUST be absolutely positioned, and the shadow does not provide any shimming.  This
     * should be used only in simple cases - for more advanced functionality that can also
     * provide the same shadow effect, see the {@link Ext.Layer} class.
     */
    Ext.define('Ext.Shadow', {
        requires: ['Ext.ShadowPool'],

        /**
         * Creates new Shadow.
         * @param {Object} config (optional) Config object.
         */
        constructor: function(config) {
            var me = this,
                adjusts,
                offset,
                rad;

            Ext.apply(me, config);
            if (!Ext.isString(me.mode)) {
                me.mode = me.defaultMode;
            }
            offset = me.offset;
            rad = Math.floor(offset / 2);
            me.opacity = 50;
            switch (me.mode.toLowerCase()) {
                // all this hideous nonsense calculates the various offsets for shadows
                case "drop":
                    if (Ext.supports.CSS3BoxShadow) {
                        adjusts = {
                            t: offset,
                            l: offset,
                            h: -offset,
                            w: -offset
                        };
                    }
                    else {
                        adjusts = {
                            t: -rad,
                            l: -rad,
                            h: -rad,
                            w: -rad
                        };
                    }
                    break;
                case "sides":
                    if (Ext.supports.CSS3BoxShadow) {
                        adjusts = {
                            t: offset,
                            l: 0,
                            h: -offset,
                            w: 0
                        };
                    }
                    else {
                        adjusts = {
                            t: - (1 + rad),
                            l: 1 + rad - 2 * offset,
                            h: -1,
                            w: rad - 1
                        };
                    }
                    break;
                case "frame":
                    if (Ext.supports.CSS3BoxShadow) {
                        adjusts = {
                            t: 0,
                            l: 0,
                            h: 0,
                            w: 0
                        };
                    }
                    else {
                        adjusts = {
                            t: 1 + rad - 2 * offset,
                            l: 1 + rad - 2 * offset,
                            h: offset - rad - 1,
                            w: offset - rad - 1
                        };
                    }
                    break;
            }
            me.adjusts = adjusts;
        },

        /**
         * @cfg {String} mode
         * The shadow display mode.  Supports the following options:
         *
         * - sides : Shadow displays on both sides and bottom only</li>
         * - frame : Shadow displays equally on all four sides</li>
         * - drop : Traditional bottom-right drop shadow</li>
         */

        /**
         * @cfg {Number} offset
         * The number of pixels to offset the shadow from the element
         */
        offset: 4,

        // private
        defaultMode: "drop",

        // private - CSS property to use to set the box shadow
        boxShadowProperty: (function() {
            var property = 'boxShadow',
                style = document.documentElement.style;

            if (!('boxShadow' in style)) {
                if ('WebkitBoxShadow' in style) {
                    // Safari prior to version 5.1 and Chrome prior to version 10
                    property = 'WebkitBoxShadow';
                }
                else if ('MozBoxShadow' in style) {
                    // FF 3.5 & 3.6
                    property = 'MozBoxShadow';
                }
            }

            return property;
        }()),

        /**
         * Displays the shadow under the target element
         * @param {String/HTMLElement/Ext.Element} targetEl The id or element under which the shadow should display
         */
        show: function(target) {
            var me = this,
                index;

            target = Ext.get(target);
            if (!me.el) {
                me.el = Ext.ShadowPool.pull();
                if (me.el.dom.nextSibling != target.dom) {
                    me.el.insertBefore(target);
                }
            }
            index = (parseInt(target.getStyle("z-index"), 10) - 1) || 0;
            me.el.setStyle("z-index", me.zIndex || index);
            if (Ext.isIE && !Ext.supports.CSS3BoxShadow) {
                me.el.dom.style.filter = "progid:DXImageTransform.Microsoft.alpha(opacity=" + me.opacity + ") progid:DXImageTransform.Microsoft.Blur(pixelradius=" + (me.offset) + ")";
            }
            me.realign(
                target.getLeft(true),
                target.getTop(true),
                target.dom.offsetWidth,
                target.dom.offsetHeight
            );
            me.el.dom.style.display = "block";
        },

        /**
         * Returns true if the shadow is visible, else false
         */
        isVisible: function() {
            return this.el ? true: false;
        },

        /**
         * Direct alignment when values are already available. Show must be called at least once before
         * calling this method to ensure it is initialized.
         * @param {Number} left The target element left position
         * @param {Number} top The target element top position
         * @param {Number} width The target element width
         * @param {Number} height The target element height
         */
        realign: function(l, t, targetWidth, targetHeight) {
            if (!this.el) {
                return;
            }
            var adjusts = this.adjusts,
                d = this.el.dom,
                targetStyle = d.style,
                shadowWidth,
                shadowHeight,
                sws,
                shs;

            targetStyle.left = (l + adjusts.l) + "px";
            targetStyle.top = (t + adjusts.t) + "px";
            shadowWidth = Math.max(targetWidth + adjusts.w, 0);
            shadowHeight = Math.max(targetHeight + adjusts.h, 0);
            sws = shadowWidth + "px";
            shs = shadowHeight + "px";
            if (targetStyle.width != sws || targetStyle.height != shs) {
                targetStyle.width = sws;
                targetStyle.height = shs;

                if (Ext.supports.CSS3BoxShadow) {
                    targetStyle[this.boxShadowProperty] = '0 0 ' + this.offset + 'px #888';
                }
            }
        },

        /**
         * Hides this shadow
         */
        hide: function() {
            var me = this;

            if (me.el) {
                me.el.dom.style.display = "none";
                Ext.ShadowPool.push(me.el);
                delete me.el;
            }
        },

        /**
         * Adjust the z-index of this shadow
         * @param {Number} zindex The new z-index
         */
        setZIndex: function(z) {
            this.zIndex = z;
            if (this.el) {
                this.el.setStyle("z-index", z);
            }
        },

        /**
         * Sets the opacity of the shadow
         * @param {Number} opacity The opacity
         */
        setOpacity: function(opacity){
            if (this.el) {
                if (Ext.isIE && !Ext.supports.CSS3BoxShadow) {
                    opacity = Math.floor(opacity * 100 / 2) / 100;
                }
                this.opacity = opacity;
                this.el.setOpacity(opacity);
            }
        }
    });