(function ($) {
    if (!document.defaultview || !document.defaultview.getcomputedstyle) {
        var oldcurcss = jquery.curcss;
        jquery.curcss = function (elem, name, force) {
            if (name === 'background-position') {
                name = 'backgroundposition';
            }
            if (name !== 'backgroundposition' || !elem.currentstyle || elem.currentstyle[name]) {
                return oldcurcss.apply(this, arguments);
            }
            var style = elem.style;
            if (!force && style && style[name]) {
                return style[name];
            }
            return oldcurcss(elem, 'backgroundpositionx', force) + ' ' + oldcurcss(elem, 'backgroundpositiony', force);
        };
    }

    var oldanim = $.fn.animate;
    $.fn.animate = function (prop) {
        if ('background-position' in prop) {
            prop.backgroundposition = prop['background-position'];
            delete prop['background-position'];
        }
        if ('backgroundposition' in prop) {
            prop.backgroundposition = '(' + prop.backgroundposition + ')';
        }
        return oldanim.apply(this, arguments);
    };

    function toarray(strg) {
        strg = strg.replace(/left|top/g, '0px');
        strg = strg.replace(/right|bottom/g, '100%');
        strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g, "$1px$2");
        var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
        return [parsefloat(res[1], 10), res[2], parsefloat(res[3], 10), res[4]];
    }

    $.fx.step.backgroundposition = function (fx) {
        if (!fx.bgposready) {
            var start = $.curcss(fx.elem, 'backgroundposition');

            if (!start) {//ff2 no inline-style fallback
                start = '0px 0px';
            }

            start = toarray(start);

            fx.start = [start[0], start[2]];

            var end = toarray(fx.end);
            fx.end = [end[0], end[2]];

            fx.unit = [end[1], end[3]];
            fx.bgposready = true;
        }

        var nowposx = [];
        nowposx[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
        nowposx[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
        fx.elem.style.backgroundposition = nowposx[0] + ' ' + nowposx[1];
    };
})(jquery);