shit.js

// Chart.redraw
redraw: function (animation) {
    var chart = this,
        //...
        series = chart.series,
        //...
        ;

    // ...<snip>...

    // redraw affected series
    each(series, function (serie) {
        if (serie.isDirty && serie.visible &&
                (!serie.isCartesian || serie.xAxis)) { // issue #153
            serie.redraw();  // <==============================
        }
    });
},

///////////// CALLS ///////////////////

// Series.redraw
redraw: function () {
    var series = this,
        chart = series.chart,
        wasDirtyData = series.isDirtyData, // cache it here as it is set to false in render, but used after
        group = series.group,
        xAxis = series.xAxis,
        yAxis = series.yAxis;

    // reposition on resize
    if (group) {
        if (chart.inverted) {
            group.attr({
                width: chart.plotWidth,
                height: chart.plotHeight
            });
        }

        group.animate({
            translateX: pick(xAxis && xAxis.left, chart.plotLeft),
            translateY: pick(yAxis && yAxis.top, chart.plotTop)
        });
    }

    series.translate();
    series.setTooltipPoints(true);

    series.render();
    if (wasDirtyData) {
        fireEvent(series, 'updatedData'); //  <=================================
    }
},

////////////// WHICH FIRES ///////////////////

// Scroller.updatedDataHandler
updatedDataHandler: function () {
    var scroller = this.chart.scroller,
        baseSeries = scroller.baseSeries,
        baseXAxis = baseSeries.xAxis,
        baseExtremes = baseXAxis.getExtremes(),
        baseMin = baseExtremes.min,
        baseMax = baseExtremes.max,
        baseDataMin = baseExtremes.dataMin,
        baseDataMax = baseExtremes.dataMax,
        range = baseMax - baseMin,
        stickToMin,
        stickToMax,
        newMax,
        newMin,
        doRedraw,
        navigatorSeries = scroller.series,
        navXData = navigatorSeries.xData,
        hasSetExtremes = !!baseXAxis.setExtremes;

    // detect whether to move the range
    stickToMax = baseMax >= navXData[navXData.length - 1] - (this.closestPointRange || 0); // #570
    stickToMin = baseMin <= baseDataMin;

    // set the navigator series data to the new data of the base series
    if (!scroller.hasNavigatorData) {
        navigatorSeries.options.pointStart = baseSeries.xData[0];
        navigatorSeries.setData(baseSeries.options.data, false);
        doRedraw = true;
    }

    // if the zoomed range is already at the min, move it to the right as new data
    // comes in
    if (stickToMin) {
        newMin = baseDataMin;
        newMax = newMin + range;
    }

    // if the zoomed range is already at the max, move it to the right as new data
    // comes in
    if (stickToMax) {
        newMax = baseDataMax;
        if (!stickToMin) { // if stickToMin is true, the new min value is set above
            newMin = mathMax(newMax - range, navigatorSeries.xData[0]);
        }
    }

    // update the extremes
    if (hasSetExtremes && (stickToMin || stickToMax)) {
        if (!isNaN(newMin)) {
            baseXAxis.setExtremes(newMin, newMax, true, false, { trigger: 'updatedData' });
        }

    // if it is not at any edge, just move the scroller window to reflect the new series data
    } else {
        if (doRedraw) {
            this.chart.redraw(false); //  <================================== LOOPS
        }

        scroller.render(
            mathMax(baseMin, baseDataMin),
            mathMin(baseMax, baseDataMax)
        );
    }
},