Tooltips

Tooltip Configuration

The tooltip configuration is passed into the options.tooltips namespace. The global options for the chart tooltips is defined in Chart.defaults.global.tooltips.

Position Modes

Possible modes are:

• 'average'
• 'nearest'

'average' mode will place the tooltip at the average position of the items displayed in the tooltip. 'nearest' will place the tooltip at the position of the element closest to the event position.

New modes can be defined by adding functions to the Chart.Tooltip.positioners map.

Example:

/**
 * Custom positioner
 * @function Chart.Tooltip.positioners.custom
 * @param elements {Chart.Element[]} the tooltip elements
 * @param eventPosition {Point} the position of the event in canvas coordinates
 * @returns {Point} the tooltip position
 */
Chart.Tooltip.positioners.custom = function(elements, eventPosition) {
    /** @type {Chart.Tooltip} */
    var tooltip = this;

    /* ... */

    return {
        x: 0,
        y: 0
    };
}

Sort Callback

Allows sorting of tooltip items. Must implement at minimum a function that can be passed to Array.prototype.sort. This function can also accept a third parameter that is the data object passed to the chart.

Filter Callback

Allows filtering of tooltip items. Must implement at minimum a function that can be passed to Array.prototype.filter. This function can also accept a second parameter that is the data object passed to the chart.

Tooltip Callbacks

The tooltip label configuration is nested below the tooltip configuration using the callbacks key. The tooltip has the following callbacks for providing text. For all functions, 'this' will be the tooltip object created from the Chart.Tooltip constructor.

All functions are called with the same arguments: a tooltip item and the data object passed to the chart. All functions must return either a string or an array of strings. Arrays of strings are treated as multiple lines of text.

Label Callback

The label callback can change the text that displays for a given data point. A common example to round data values; the following example rounds the data to two decimal places.

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        tooltips: {
            callbacks: {
                label: function(tooltipItem, data) {
                    var label = data.datasets[tooltipItem.datasetIndex].label || '';

                    if (label) {
                        label += ': ';
                    }
                    label += Math.round(tooltipItem.yLabel * 100) / 100;
                    return label;
                }
            }
        }
    }
});

Label Color Callback

For example, to return a red box for each item in the tooltip you could do:

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        tooltips: {
            callbacks: {
                labelColor: function(tooltipItem, chart) {
                    return {
                        borderColor: 'rgb(255, 0, 0)',
                        backgroundColor: 'rgb(255, 0, 0)'
                    }
                },
                labelTextColor:function(tooltipItem, chart){
                    return '#543453';
                }
            }
        }
    }
});

Tooltip Item Interface

The tooltip items passed to the tooltip callbacks implement the following interface.

{
    // X Value of the tooltip as a string
    xLabel: String,

    // Y value of the tooltip as a string
    yLabel: String,

    // Index of the dataset the item comes from
    datasetIndex: Number,

    // Index of this data item in the dataset
    index: Number,

    // X position of matching point
    x: Number,

    // Y position of matching point
    y: Number,
}

External (Custom) Tooltips

Custom tooltips allow you to hook into the tooltip rendering process so that you can render the tooltip in your own custom way. Generally this is used to create an HTML tooltip instead of an oncanvas one. You can enable custom tooltips in the global or chart configuration like so:

var myPieChart = new Chart(ctx, {
    type: 'pie',
    data: data,
    options: {
        tooltips: {
            // Disable the on-canvas tooltip
            enabled: false,

            custom: function(tooltipModel) {
                // Tooltip Element
                var tooltipEl = document.getElementById('chartjs-tooltip');

                // Create element on first render
                if (!tooltipEl) {
                    tooltipEl = document.createElement('div');
                    tooltipEl.id = 'chartjs-tooltip';
                    tooltipEl.innerHTML = "<table></table>";
                    document.body.appendChild(tooltipEl);
                }

                // Hide if no tooltip
                if (tooltipModel.opacity === 0) {
                    tooltipEl.style.opacity = 0;
                    return;
                }

                // Set caret Position
                tooltipEl.classList.remove('above', 'below', 'no-transform');
                if (tooltipModel.yAlign) {
                    tooltipEl.classList.add(tooltipModel.yAlign);
                } else {
                    tooltipEl.classList.add('no-transform');
                }

                function getBody(bodyItem) {
                    return bodyItem.lines;
                }

                // Set Text
                if (tooltipModel.body) {
                    var titleLines = tooltipModel.title || [];
                    var bodyLines = tooltipModel.body.map(getBody);

                    var innerHtml = '<thead>';

                    titleLines.forEach(function(title) {
                        innerHtml += '<tr><th>' + title + '</th></tr>';
                    });
                    innerHtml += '</thead><tbody>';

                    bodyLines.forEach(function(body, i) {
                        var colors = tooltipModel.labelColors[i];
                        var style = 'background:' + colors.backgroundColor;
                        style += '; border-color:' + colors.borderColor;
                        style += '; border-width: 2px';
                        var span = '<span style="' + style + '"></span>';
                        innerHtml += '<tr><td>' + span + body + '</td></tr>';
                    });
                    innerHtml += '</tbody>';

                    var tableRoot = tooltipEl.querySelector('table');
                    tableRoot.innerHTML = innerHtml;
                }

                // `this` will be the overall tooltip
                var position = this._chart.canvas.getBoundingClientRect();

                // Display, position, and set styles for font
                tooltipEl.style.opacity = 1;
                tooltipEl.style.position = 'absolute';
                tooltipEl.style.left = position.left + tooltipModel.caretX + 'px';
                tooltipEl.style.top = position.top + tooltipModel.caretY + 'px';
                tooltipEl.style.fontFamily = tooltipModel._bodyFontFamily;
                tooltipEl.style.fontSize = tooltipModel.bodyFontSize + 'px';
                tooltipEl.style.fontStyle = tooltipModel._bodyFontStyle;
                tooltipEl.style.padding = tooltipModel.yPadding + 'px ' + tooltipModel.xPadding + 'px';
            }
        }
    }
});

See samples for examples on how to get started with custom tooltips.

Tooltip Model

The tooltip model contains parameters that can be used to render the tooltip.

{
    // The items that we are rendering in the tooltip. See Tooltip Item Interface section
    dataPoints: TooltipItem[],

    // Positioning
    xPadding: Number,
    yPadding: Number,
    xAlign: String,
    yAlign: String,

    // X and Y properties are the top left of the tooltip
    x: Number,
    y: Number,
    width: Number,
    height: Number,
    // Where the tooltip points to
    caretX: Number,
    caretY: Number,

    // Body
    // The body lines that need to be rendered
    // Each object contains 3 parameters
    // before: String[] // lines of text before the line with the color square
    // lines: String[], // lines of text to render as the main item with color square
    // after: String[], // lines of text to render after the main lines
    body: Object[],
    // lines of text that appear after the title but before the body
    beforeBody: String[],
    // line of text that appear after the body and before the footer
    afterBody: String[],
    bodyFontColor: Color,
    _bodyFontFamily: String,
    _bodyFontStyle: String,
    _bodyAlign: String,
    bodyFontSize: Number,
    bodySpacing: Number,

    // Title
    // lines of text that form the title
    title: String[],
    titleFontColor: Color,
    _titleFontFamily: String,
    _titleFontStyle: String,
    titleFontSize: Number,
    _titleAlign: String,
    titleSpacing: Number,
    titleMarginBottom: Number,

    // Footer
    // lines of text that form the footer
    footer: String[],
    footerFontColor: Color,
    _footerFontFamily: String,
    _footerFontStyle: String,
    footerFontSize: Number,
    _footerAlign: String,
    footerSpacing: Number,
    footerMarginTop: Number,

    // Appearance
    caretSize: Number,
    cornerRadius: Number,
    backgroundColor: Color,

    // colors to render for each item in body[]. This is the color of the squares in the tooltip
    labelColors: Color[],

    // 0 opacity is a hidden tooltip
    opacity: Number,
    legendColorBackground: Color,
    displayColors: Boolean,
}