AnnotationChart scaleColums doesn't display 3rd scale in the middle

[robertoschwald]

API doc says: "If you specify three values, a scale for the third series will be added to the middle of the chart." See https://developers.google.com/chart/interactive/docs/gallery/annotationchart

But that seems not to work. 3rd scale is displayed on the right y axis instead, which overlaps the 2nd one. Example code:

google.charts.load('current', {'packages':['annotationchart']});
google.charts.setOnLoadCallback(drawChart);
function drawChart() {
        var data = new google.visualization.DataTable();
        data.addColumn('date', 'Date');
        data.addColumn('number', 'Level');
        data.addColumn('number', 'Flow');
        data.addColumn('number', 'Temperature');
        data.addRows([
            [new Date(2020, 9, 15, 11, 0, 0, 0), 20, 10645, 10.5],
            [new Date(2020, 9, 15, 12, 0, 0, 0), 21, 12374, 11.5],
            [new Date(2020, 9, 15, 13, 0, 0, 0), 22, 15766, 12.5],
            [new Date(2020, 9, 15, 14, 0, 0, 0), 25, 34334, 13.5],
            [new Date(2020, 9, 15, 15, 0, 0, 0), 17, 66467, 11.5],
            [new Date(2020, 9, 15, 16, 0, 0, 0), 18, 79463, 10.5]
        ]);

        var chart = new google.visualization.AnnotationChart(document.getElementById('chart_div'));

        var options = {
          displayAnnotations: true,
          colors: ["green", "red", "blue"],
          scaleColumns: [0,1,2],
        };

        chart.draw(data, options);
}

[dlaliberte]

This is one feature that the old AnnotatedTimeline used to support which we have not yet implemented in the AnnotationChart. I'm not sure if or when we will get around to it, so the documentation should be updated at least.