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

Question

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);
  }
},

Solution 1

Solution for ChartJs Version > 2.1.5:

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.tooltips,
                    _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;
    }
  }
});

Solution 2

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

---

Preview

---

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/

Solution 3

I was looking for similar solution and came across this chartjs plugin Chart.PieceLabel.js. It has configs to display modes like label, value and percentage.

Solution 4

According to the closed issue on the github page for chart.js, displaying tool tips permanently is not recommended.

This comment closing this issue gives more detail:

https://github.com/chartjs/Chart.js/issues/1861#issuecomment-442852768

and this is the recommended plugin for permanent data labels:

https://github.com/chartjs/chartjs-plugin-datalabels

View more solutions