GUI.Slider = function(numberController, min, max, step, initValue) {

    var clicked = false;
    var _this = this;

    var x, px;

    this.domElement = document.createElement('div');
    this.domElement.setAttribute('class', 'guidat-slider-bg');

    this.fg = document.createElement('div');
    this.fg.setAttribute('class', 'guidat-slider-fg');

    this.domElement.appendChild(this.fg);

    var findPos = function(obj) {
        var curleft = 0, curtop = 0;
        if (obj.offsetParent) {
            do {
                curleft += obj.offsetLeft;
                curtop += obj.offsetTop;
            } while ((obj = obj.offsetParent));
            return [curleft,curtop];
        }
    };

    this.__defineSetter__('value', function(e) {
        var pct = GUI.map(e, min, max, 0, 100);
        this.fg.style.width = pct+"%";
    });

    var onDrag = function(e) {
        if (!clicked) return;
        var pos = findPos(_this.domElement);
        var val = GUI.map(e.pageX, pos[0], pos[0] + _this.domElement.offsetWidth, min, max);
        val = Math.round(val/step)*step;
        numberController.setValue(val);
    };

    this.domElement.addEventListener('mousedown', function(e) {
        clicked = true;
        x = px = e.pageX;
        _this.domElement.setAttribute('class', 'guidat-slider-bg active');
        _this.fg.setAttribute('class', 'guidat-slider-fg active');
        onDrag(e);
        document.addEventListener('mouseup', mouseup, false);
    }, false);


    var mouseup = function(e) {
        _this.domElement.setAttribute('class', 'guidat-slider-bg');
        _this.fg.setAttribute('class', 'guidat-slider-fg');
        clicked = false;
        if (numberController.finishChangeFunction != null) {
            numberController.finishChangeFunction.call(this, numberController.getValue());
        }
        document.removeEventListener('mouseup', mouseup, false);
    };


    document.addEventListener('mousemove', onDrag, false);

    this.value = initValue;

};