Danny Danny - 7 months ago 1648
Javascript Question

Chart.js v2: How to make tooltips always appear on pie chart?

I have found similar questions in Stack Overflow, but all of them were addressed one and two years ago. Now Chart.js has come up in version 2, and lots of the documentation changes. Can someone please help me showing an example of pie chart with labels - or pie chart with all of its segment's tooltips are visible?

UPDATE

Thanks to @potatopeelings, his answer works perfectly for Chart.js v2.1.

Although I initially asked how to permanently show tooltips on pie chart here, I found a better solution: showing values as labels in percentages! It is now enabled for pie chart in Chart.js v2.1. In the chart options:

animation: {
duration: 0,
onComplete: function () {
var self = this,
chartInstance = this.chart,
ctx = chartInstance.ctx;

ctx.font = '18px Arial';
ctx.textAlign = "center";
ctx.fillStyle = "#ffffff";

Chart.helpers.each(self.data.datasets.forEach(function (dataset, datasetIndex) {
var meta = self.getDatasetMeta(datasetIndex),
total = 0, //total values to compute fraction
labelxy = [],
offset = Math.PI / 2, //start sector from top
radius,
centerx,
centery,
lastend = 0; //prev arc's end line: starting with 0

for (var val of dataset.data) { total += val; }

Chart.helpers.each(meta.data.forEach( function (element, index) {
radius = 0.9 * element._model.outerRadius - element._model.innerRadius;
centerx = element._model.x;
centery = element._model.y;
var thispart = dataset.data[index],
arcsector = Math.PI * (2 * thispart / total);
if (element.hasValue() && dataset.data[index] > 0) {
labelxy.push(lastend + arcsector / 2 + Math.PI + offset);
}
else {
labelxy.push(-1);
}
lastend += arcsector;
}), self)

var lradius = radius * 3 / 4;
for (var idx in labelxy) {
if (labelxy[idx] === -1) continue;
var langle = labelxy[idx],
dx = centerx + lradius * Math.cos(langle),
dy = centery + lradius * Math.sin(langle),
val = Math.round(dataset.data[idx] / total * 100);
ctx.fillText(val + '%', dx, dy);
}

}), self);
}
},

Answer

With the new Chart.js 2.1 you can write a plugin to do this and control it via an options property


Preview

enter image description here


Script

Note that you need to register the plugin before you initialize the chart

Chart.pluginService.register({
    beforeRender: function (chart) {
        if (chart.config.options.showAllTooltips) {
            // create an array of tooltips
            // we can't use the chart tooltip because there is only one tooltip per chart
            chart.pluginTooltips = [];
            chart.config.data.datasets.forEach(function (dataset, i) {
                chart.getDatasetMeta(i).data.forEach(function (sector, j) {
                    chart.pluginTooltips.push(new Chart.Tooltip({
                        _chart: chart.chart,
                        _chartInstance: chart,
                        _data: chart.data,
                        _options: chart.options,
                        _active: [sector]
                    }, chart));
                });
            });

            // turn off normal tooltips
            chart.options.tooltips.enabled = false;
        }
    },
    afterDraw: function (chart, easing) {
        if (chart.config.options.showAllTooltips) {
            // we don't want the permanent tooltips to animate, so don't do anything till the animation runs atleast once
            if (!chart.allTooltipsOnce) {
                if (easing !== 1)
                    return;
                chart.allTooltipsOnce = true;
            }

            // turn on tooltips
            chart.options.tooltips.enabled = true;
            Chart.helpers.each(chart.pluginTooltips, function (tooltip) {
                tooltip.initialize();
                tooltip.update();
                // we don't actually need this since we are not animating tooltips
                tooltip.pivot();
                tooltip.transition(easing).draw();
            });
            chart.options.tooltips.enabled = false;
        }
    }
});

and then

new Chart(ctx, {
    type: 'pie',
    data: data,
    options: {
        showAllTooltips: true
        ...

With the older 2.x version, you should able to move the same (or similar, I'm not sure about the earlier data structure ) to the options.animation.onComplete


Fiddle - http://jsfiddle.net/q15ta78q/