Delay call to tooltip calc function

[Rivka]

We have a chart with around 500 points and a custom tooltip function that takes 2 msec to run.

As a consequence, there is a penalty of 1000 msec on chart rendering.

Is there a way to be lazy on tooltip calculation and call the function only upon user interaction?

Or maybe there are other way to be more efficient?

[Daniel LaLiberte]

Hi Rivka,

If you use html tooltips, the contents can be computed dynamically if you handle the 'onmouseover' event in your chart.  Since there really is only one actual tooltip element, and the contents will be populated by your custom tooltip text, what you could do is just specify a div with an id like this, using a view where you set the columns:  

    var myDataView = new google.visualization.DataView(myData);

    var columns = [ .. other columns ];

    columns.push({

        type: 'string',

        role: 'tooltip',

        properties: {html: true},

        calc: function(data, row) {

            var s = String(data.getValue(row, 1));

            return '<div id="tooltip_chart_div"' + 

                ' style="width: 175px; height: 150px"></div>';

        }

    });

    myDataView.setColumns(columns);

Then in your 'onmousover' handler, you can do something like this to display a BarChart in the div:

    var container = document.getElementById('tooltip_chart_div');

    if (!container) { return }

    var tooltipChart = new google.visualization.BarChart(container);

    ...

    tooltipChart.draw(barData, barOptions);

Hope that helps.

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Daniel LaLiberte  - 978-394-1058

dlaliberte@Google.com   5CC, Cambridge MA

daniel.laliberte@GMail.com 9 Juniper Ridge Road, Acton MA