API: slider SliderThumb.js (YUI Library)

# Yahoo! UI Library

### Slider Widget 2.8.1

Yahoo! UI Library > slider > SliderThumb.js (source view)
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    /**
     * A drag and drop implementation to be used as the thumb of a slider.
     * @class SliderThumb
     * @extends YAHOO.util.DD
     * @constructor
     * @param {String} id the id of the slider html element
     * @param {String} sGroup the group of related DragDrop items
     * @param {int} iLeft the number of pixels the element can move left
     * @param {int} iRight the number of pixels the element can move right
     * @param {int} iUp the number of pixels the element can move up
     * @param {int} iDown the number of pixels the element can move down
     * @param {int} iTickSize optional parameter for specifying that the element
     * should move a certain number pixels at a time.
     */
    YAHOO.widget.SliderThumb = function(id, sGroup, iLeft, iRight, iUp, iDown, iTickSize) {

        if (id) {
            YAHOO.widget.SliderThumb.superclass.constructor.call(this, id, sGroup);

            /**
             * The id of the thumbs parent HTML element (the slider background
             * element).
             * @property parentElId
             * @type string
             */
            this.parentElId = sGroup;
        }

        this.logger = new YAHOO.widget.LogWriter(this.toString());

        /**
         * Overrides the isTarget property in YAHOO.util.DragDrop
         * @property isTarget
         * @private
         */
        this.isTarget = false;

        /**
         * The tick size for this slider
         * @property tickSize
         * @type int
         * @private
         */
        this.tickSize = iTickSize;

        /**
         * Informs the drag and drop util that the offsets should remain when
         * resetting the constraints.  This preserves the slider value when
         * the constraints are reset
         * @property maintainOffset
         * @type boolean
         * @private
         */
        this.maintainOffset = true;

        this.initSlider(iLeft, iRight, iUp, iDown, iTickSize);

        /**
         * Turns off the autoscroll feature in drag and drop
         * @property scroll
         * @private
         */
        this.scroll = false;

    };

    YAHOO.extend(YAHOO.widget.SliderThumb, YAHOO.util.DD, {

        /**
         * The (X and Y) difference between the thumb location and its parent
         * (the slider background) when the control is instantiated.
         * @property startOffset
         * @type [int, int]
         */
        startOffset: null,

        /**
         * Override the default setting of dragOnly to true.
         * @property dragOnly
         * @type boolean
         * @default true
         */
        dragOnly : true,

        /**
         * Flag used to figure out if this is a horizontal or vertical slider
         * @property _isHoriz
         * @type boolean
         * @private
         */
        _isHoriz: false,

        /**
         * Cache the last value so we can check for change
         * @property _prevVal
         * @type int
         * @private
         */
        _prevVal: 0,

        /**
         * The slider is _graduated if there is a tick interval defined
         * @property _graduated
         * @type boolean
         * @private
         */
        _graduated: false,

        /**
         * Returns the difference between the location of the thumb and its parent.
         * @method getOffsetFromParent
         * @param {[int, int]} parentPos Optionally accepts the position of the parent
         * @type [int, int]
         */
        getOffsetFromParent0: function(parentPos) {
            var myPos = YAHOO.util.Dom.getXY(this.getEl()),
                ppos  = parentPos || YAHOO.util.Dom.getXY(this.parentElId);

            return [ (myPos[0] - ppos[0]), (myPos[1] - ppos[1]) ];
        },

        getOffsetFromParent: function(parentPos) {

            var el = this.getEl(), newOffset,
                myPos,ppos,l,t,deltaX,deltaY,newLeft,newTop;

            if (!this.deltaOffset) {

                myPos = YAHOO.util.Dom.getXY(el);
                ppos  = parentPos || YAHOO.util.Dom.getXY(this.parentElId);

                newOffset = [ (myPos[0] - ppos[0]), (myPos[1] - ppos[1]) ];

                l = parseInt( YAHOO.util.Dom.getStyle(el, "left"), 10 );
                t = parseInt( YAHOO.util.Dom.getStyle(el, "top" ), 10 );

                deltaX = l - newOffset[0];
                deltaY = t - newOffset[1];

                if (isNaN(deltaX) || isNaN(deltaY)) {
                    this.logger.log("element does not have a position style def yet");
                } else {
                    this.deltaOffset = [deltaX, deltaY];
                }

            } else {
                newLeft = parseInt( YAHOO.util.Dom.getStyle(el, "left"), 10 );
                newTop  = parseInt( YAHOO.util.Dom.getStyle(el, "top" ), 10 );

                newOffset  = [newLeft + this.deltaOffset[0], newTop + this.deltaOffset[1]];
            }

            return newOffset;
        },

        /**
         * Set up the slider, must be called in the constructor of all subclasses
         * @method initSlider
         * @param {int} iLeft the number of pixels the element can move left
         * @param {int} iRight the number of pixels the element can move right
         * @param {int} iUp the number of pixels the element can move up
         * @param {int} iDown the number of pixels the element can move down
         * @param {int} iTickSize the width of the tick interval.
         */
        initSlider: function (iLeft, iRight, iUp, iDown, iTickSize) {
            this.initLeft = iLeft;
            this.initRight = iRight;
            this.initUp = iUp;
            this.initDown = iDown;

            this.setXConstraint(iLeft, iRight, iTickSize);
            this.setYConstraint(iUp, iDown, iTickSize);

            if (iTickSize && iTickSize > 1) {
                this._graduated = true;
            }

            this._isHoriz  = (iLeft || iRight);
            this._isVert   = (iUp   || iDown);
            this._isRegion = (this._isHoriz && this._isVert);

        },

        /**
         * Clear's the slider's ticks
         * @method clearTicks
         */
        clearTicks: function () {
            YAHOO.widget.SliderThumb.superclass.clearTicks.call(this);
            this.tickSize = 0;
            this._graduated = false;
        },

        /**
         * Gets the current offset from the element's start position in
         * pixels.
         * @method getValue
         * @return {int} the number of pixels (positive or negative) the
         * slider has moved from the start position.
         */
        getValue: function () {
            return (this._isHoriz) ? this.getXValue() : this.getYValue();
        },

        /**
         * Gets the current X offset from the element's start position in
         * pixels.
         * @method getXValue
         * @return {int} the number of pixels (positive or negative) the
         * slider has moved horizontally from the start position.
         */
        getXValue: function () {
            if (!this.available) {
                return 0;
            }
            var newOffset = this.getOffsetFromParent();
            if (YAHOO.lang.isNumber(newOffset[0])) {
                this.lastOffset = newOffset;
                return (newOffset[0] - this.startOffset[0]);
            } else {
                this.logger.log("can't get offset, using old value: " +
                    this.lastOffset[0]);
                return (this.lastOffset[0] - this.startOffset[0]);
            }
        },

        /**
         * Gets the current Y offset from the element's start position in
         * pixels.
         * @method getYValue
         * @return {int} the number of pixels (positive or negative) the
         * slider has moved vertically from the start position.
         */
        getYValue: function () {
            if (!this.available) {
                return 0;
            }
            var newOffset = this.getOffsetFromParent();
            if (YAHOO.lang.isNumber(newOffset[1])) {
                this.lastOffset = newOffset;
                return (newOffset[1] - this.startOffset[1]);
            } else {
                this.logger.log("can't get offset, using old value: " +
                    this.lastOffset[1]);
                return (this.lastOffset[1] - this.startOffset[1]);
            }
        },

        /**
         * Thumb toString
         * @method toString
         * @return {string} string representation of the instance
         */
        toString: function () {
            return "SliderThumb " + this.id;
        },

        /**
         * The onchange event for the handle/thumb is delegated to the YAHOO.widget.Slider
         * instance it belongs to.
         * @method onChange
         * @private
         */
        onChange: function (x, y) {
        }

    });

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