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How to move labels' position on Chart.js pie

I'm using Chart.js and I'm trying to move the labels on my Pie chart outside of the pie area (see red X's):

enter image description here

This my code right now:

<div class="container" id="pieContainer">
    <h4 class="title">Title</h4>
    <center><canvas id="pie"></canvas></center>
</div>

<script>                                  
    var pieData = [
    {
        value: 39,
        color:"#335478",
        label: "Blue"
    },
    {
        value : 4,
        color : "#7f7f7f",
        label: "Grey"
    },
    {
        value : 57,
        color : "#99cb55",
        label: "Green"
    }
    ];

    var optionsPie = {
        responsive : true,
        tooltipEvents: [],
        showTooltips: true,
        onAnimationComplete: function() {
             this.showTooltip(this.segments, true);
        },
        tooltipTemplate: "<%= label %> - <%= value %>%"
    };
    new Chart(document.getElementById("pie").getContext("2d")).Pie(pieData, optionsPie);
</script>

I don't want to use legends and I couldn't find a built-in method to move labels. Is there a way to do that without changing chart.js? What's the best way to achieve my goal?

Solution

  • Just extend the chart to do this. If your labels are static, it might be simpler to just change the tooltipPosition method instead.

    Preview

    enter image description here

    Script

    Chart.types.Pie.extend({
    name: "PieAlt",
    initialize: function(data){
        Chart.types.Pie.prototype.initialize.apply(this, arguments);

        var requiredSpace = 0;
        for (var i = 0; i < data.length; i++)
            requiredSpace = Math.max(ctx.measureText(Chart.helpers.template(this.options.tooltipTemplate, data[i])).width, requiredSpace);
        this.outerRadius -= (requiredSpace + 20);
    },
    draw: function(data){
        Chart.types.Pie.prototype.draw.apply(this, arguments);

        var self = this;
        ctx.save();
        ctx.font = Chart.helpers.fontString(self.options.scaleFontSize, self.options.scaleFontStyle, self.options.scaleFontFamily);
                ctx.textBaseline = "middle";
        self.segments.forEach(function (segment) {
            var outerEdge = Chart.Arc.prototype.tooltipPosition.apply({
                x: this.chart.width / 2,
                y: this.chart.height / 2,
                startAngle: segment.startAngle,
                endAngle: segment.endAngle,
                outerRadius: segment.outerRadius * 2 + 20,
                innerRadius: 0
            })

            var normalizedAngle = (segment.startAngle + segment.endAngle) / 2;
            while (normalizedAngle > 2 * Math.PI) {
                normalizedAngle -= (2 * Math.PI)
            }

            if (normalizedAngle < (Math.PI * 0.4) || (normalizedAngle > Math.PI * 1.5))
                ctx.textAlign = "start";
            else if (normalizedAngle > (Math.PI * 0.4) && (normalizedAngle < Math.PI * 0.6)) {
                outerEdge.y += 5;
                ctx.textAlign = "center";
            }
            else if (normalizedAngle > (Math.PI * 1.4) && (normalizedAngle < Math.PI * 1.6)) {
                outerEdge.y - 5;
                ctx.textAlign = "center";
            }
            else
                ctx.textAlign = "end";

            ctx.fillText(Chart.helpers.template(self.options.tooltipTemplate, segment), outerEdge.x, outerEdge.y);
        });

        ctx.restore();
    }
});

    and then

    new Chart(ctx).PieAlt(data, {
    showTooltips: false
});

    Fiddle - http://jsfiddle.net/h8rggkhp/