Change Chart.js tooltip caret position

Question

I created a doughnut chart using Chart.js 2.5. The issue I’m having is with the tooltip. When I hover over the chart, a tooltip is displayed with a caret that always stays in the left or right side, like this:

I want to change the caret position so that it always show in the bottom. Is that possible?

Here is my chart code

var myChart = new Chart(ctx, {
    type: 'doughnut',
    data: {
        labels: ['Jan', 'Feb', 'Mar'],
        datasets: [{
            label: 'dataset',
            data: [30, 50, 20],
            backgroundColor: [
            'rgb(153, 102, 255)',
            'rgb(255, 205, 86)',
            'rgb(54, 162, 235)'
            ],
        }],
    }
})

Answer 1

Lot of ways to customize the tooltip. Here's a good example via CodePen.

https://codepen.io/mab213/pen/PZOXdE

customTooltips: function(tooltip) {
  // Tooltip Element
  var tooltipEl = $('#chartjs-tooltip');
  // Hide if no tooltip
  if (!tooltip) {
    tooltipEl.css({
      opacity: 1
    });
    return;
  }
  // Set caret Position
  tooltipEl.removeClass('above below');
  tooltipEl.addClass(tooltip.yAlign);
  tooltipEl.addClass(tooltip.xAlign);
  // Set Text
  tooltipEl.html(tooltip.text);
  // Find Y Location on page
  var top;
  if (tooltip.yAlign == 'above') {
    top = tooltip.y - tooltip.caretHeight - tooltip.caretPadding;
  } else {
    top = tooltip.y + tooltip.caretHeight + tooltip.caretPadding;
  }
  // Display, position, and set styles for font
  tooltipEl.css({
    opacity: 1,
    left: tooltip.chart.canvas.offsetLeft + tooltip.x + 'px',
    top: tooltip.chart.canvas.offsetTop + top + 'px',
    fontFamily: tooltip.fontFamily,
    fontSize: tooltip.fontSize,
    fontStyle: tooltip.fontStyle,
    xOffset: tooltip.xOffset,
  });
}

Answer 2

You could set yAlign property to bottom for tooltips in your chart options to display tooltip's caret always at the bottom position ...

options: {
    tooltips: {
        yAlign: 'bottom'
    }
}

ᴅᴇᴍᴏ

var ctx = document.getElementById("chart").getContext("2d");
var myChart = new Chart(ctx, {
    type: 'doughnut',
    data: {
        labels: ['Jan', 'Feb', 'Mar'],
        datasets: [{
            label: 'dataset',
            data: [30, 50, 20],
            backgroundColor: ['rgb(153, 102, 255)', 'rgb(255, 205, 86)', 'rgb(54, 162, 235)']
        }]
    },
    options: {
        responsive: false,
        tooltips: {
            yAlign: 'bottom'
        }
    }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js"></script>
<canvas id="chart" height="180"></canvas>

Answer 3

You can do this by setting the yAlign tooltips configuration option to "bottom":

options: {
    tooltips: {
      yAlign: "bottom"
    }
}

JSFiddle Demo: https://jsfiddle.net/tksr7bn9/