Function handler

jquery.mousewheel.js:102–227

( event )

    function handler( event ) {
        var orgEvent   = event || window.event,
            args       = slice.call( arguments, 1 ),
            delta      = 0,
            deltaX     = 0,
            deltaY     = 0,
            absDelta   = 0;
        event = $.event.fix( orgEvent );
        event.type = "mousewheel";

        // Old school scrollwheel delta
        if ( "detail" in orgEvent ) {
            deltaY = orgEvent.detail * -1;
        }
        if ( "wheelDelta" in orgEvent ) {
            deltaY = orgEvent.wheelDelta;
        }
        if ( "wheelDeltaY" in orgEvent ) {
            deltaY = orgEvent.wheelDeltaY;
        }
        if ( "wheelDeltaX" in orgEvent ) {
            deltaX = orgEvent.wheelDeltaX * -1;
        }

        // Firefox < 17 horizontal scrolling related to DOMMouseScroll event
        if ( "axis" in orgEvent && orgEvent.axis === orgEvent.HORIZONTAL_AXIS ) {
            deltaX = deltaY * -1;
            deltaY = 0;
        }

        // Set delta to be deltaY or deltaX if deltaY is 0 for backwards compatability
        delta = deltaY === 0 ? deltaX : deltaY;

        // New school wheel delta (wheel event)
        if ( "deltaY" in orgEvent ) {
            deltaY = orgEvent.deltaY * -1;
            delta  = deltaY;
        }
        if ( "deltaX" in orgEvent ) {
            deltaX = orgEvent.deltaX;
            if ( deltaY === 0 ) {
                delta  = deltaX * -1;
            }
        }

        // No change actually happened, no reason to go any further
        if ( deltaY === 0 && deltaX === 0 ) {
            return;
        }

        // Need to convert lines and pages to pixels if we aren't already in pixels
        // There are three delta modes:
        //   * deltaMode 0 is by pixels, nothing to do
        //   * deltaMode 1 is by lines
        //   * deltaMode 2 is by pages
        if ( orgEvent.deltaMode === 1 ) {
            var lineHeight = $.data( this, "mousewheel-line-height" );
            delta  *= lineHeight;