Tooltips

Tooltips are popups that help the user to read a chart as the pointer moves.

Behaviour

On Windows or MacOS you can move the pointer over the chart to display the tooltip, tooltips will be closed when the pointer leaves the chart area.

On Android or iOS slide your finger over the chart to display the tooltip, the tooltip will be closed when the finger goes up.

TooltipPosition property

You can place a tooltip at Top, Bottom, Left, Right, Center or Hidden positions, for now tooltips for the PieChart class only support the Center position, default value is Top.

Notice the Hidden position will disable tooltips in a chart.

<lvc:CartesianChart
    Series="{Binding Series}"
    TooltipPosition="Top"><!-- mark -->
</lvc:CartesianChart>
<lvc:CartesianChart
    Series="{Binding Series}"
    TooltipPosition="Bottom"><!-- mark -->
</lvc:CartesianChart>
<lvc:CartesianChart
    Series="{Binding Series}"
    TooltipPosition="Left"><!-- mark -->
</lvc:CartesianChart>
<lvc:CartesianChart
    Series="{Binding Series}"
    TooltipPosition="Right"><!-- mark -->
</lvc:CartesianChart>
<lvc:CartesianChart
    Series="{Binding Series}"
    TooltipPosition="Center"><!-- mark -->
</lvc:CartesianChart>
<lvc:CartesianChart
    Series="{Binding Series}"
    TooltipPosition="Hidden"><!-- mark -->
</lvc:CartesianChart>

FindingStrategy property

Every point drawn by the library defines a HoverArea, it defines an area in the chart that "triggers" the point, it is specially important to fire tooltips, a point will be included in a tooltip when the hover area was triggered by the pointer position.

The FindingStrategy property determines the hover area planes (X or Y) that a chart will use to trigger the HoverArea instances. In a chart, the following options are available:

CompareAll: Selects all the points whose hover area contain the pointer position.

CompareOnlyX: Selects all the points whose hover area contain the pointer position, but it ignores the Y plane.

CompareOnlyY: Selects all the points whose hover area contain the pointer position, but it ignores the X plane.

ExactMatch: Selects all the points whose drawn shape contain the pointer position.

CompareAllTakeClosest: Selects the points whose hover area contain the pointer position, if overlapped then takes the closest to the pointer in each series.

CompareOnlyXTakeClosest: Selects the points whose hover area contain the pointer position, but it ignores the Y plane, if overlapped then takes the closest to the pointer in each series.

CompareOnlyYTakeClosest: Selects the points whose hover area contain the pointer position, but it ignores the X plane, if overlapped then takes the closest to the pointer in each series.

ExactMatchTakeClosest: Selects all the points whose drawn shape contain the pointer position, if overlapped then takes the closest to the pointer in each series.

Automatic (default): Based on the series in the chart, LiveCharts will determine a finding strategy (one of the previous mentioned), all the series have a preferred finding strategy, normally vertical series prefer the CompareOnlyXTakeClosest strategy, horizontal series prefer CompareOnlyYTakeClosest, and scatter series prefers CompareAllTakeClosest, if all the series prefer the same strategy, then that strategy will be selected for the chart, if any series differs then the CompareAllTakeClosest strategy will be used.

<lvc:CartesianChart
    Series="{Binding Series}"
    FindingStrategy="CompareOnlyX"><!-- mark -->
</lvc:CartesianChart>

Customize FindingStrategy

Depending on the series type and FindingStrategy, LiveCharts decides the logic to show points on tooltips and also the points passed to any pointer event in the library (like Hover, HoverLeft or PointerDown), lets take as an example the default behavior of the ColumnSeries<T>, it selects all the points that share the same X coordinate:

But for this example, we want to override this behavior, instead we only need the tooltip to display the exact column where the pointer is in:

When the FindingStrategy, is not enough, we can override the logic to determine whether a given point is inside a drawn ChartPoint. This method will be used by the library to resolve the points to show in a tooltip, or the points passed in any pointer event:

using System.Collections.Generic;
using System.Linq;
using LiveChartsCore;
using LiveChartsCore.Drawing;
using LiveChartsCore.Kernel;
using LiveChartsCore.Kernel.Drawing;
using LiveChartsCore.Measure;
using LiveChartsCore.SkiaSharpView;

namespace ViewModelsSamples.Events.OverrideFind;

public class ViewModel
{
    public ISeries[] Series { get; set; } = [
        new CustomColumnSeries<int> { Values = [9, 5, 7, 3, 7, 3] },
        new CustomColumnSeries<int> { Values = [8, 2, 3, 2, 5, 2] }
    ];

    public class CustomColumnSeries<T> : ColumnSeries<T>
    {
        protected override IEnumerable<ChartPoint> FindPointsInPosition(
            Chart chart, LvcPoint pointerPosition, FindingStrategy strategy, FindPointFor findPointFor)
        {
            return Fetch(chart).Where(point =>
            {
                var ha = (RectangleHoverArea?)point.Context.HoverArea;
                if (ha is null) return false;

                var isInsideX = ha.X <= pointerPosition.X && pointerPosition.X <= ha.X + ha.Width;
                var isInsideY = ha.Y <= pointerPosition.Y && pointerPosition.Y <= ha.Y + ha.Height;

                return findPointFor == FindPointFor.HoverEvent
                    ? isInsideX
                    : isInsideY;
            });
        }
    }
}

Tooltip text

You can define the text the tooltip will display for a given point, using the YToolTipLabelFormatter, XToolTipLabelFormatter or ToolTipLabelFormatter properties, these properties are of type Func<ChartPoint, string> it means that both are a function, that takes a point as parameter and return a string, the point will be injected by LiveCharts in this function to get a string out of it when it requires to build the text for a point in a tooltip, the injected point will be different as the user moves the pointer over the user interface.

By default the library already defines a default formatter for every series, all the series have a different formatters, but generally the default value uses the Series.Name and the ChartPoint.Coordinate.PrimaryValue properties, the following code snippet illustrates how to build a custom tooltip formatter.

Lets take the example of the next series:"

public ISeries[] Series { get; set; } = [
    new LineSeries<double>
    {
        Values = [2, 1, 3, 5, 3, 4, 6],
        Fill = null,
        GeometrySize = 20,
    },
    new LineSeries<int, StarGeometry>
    {
        Values = [4, 2, 5, 2, 4, 5, 3],
        Fill = null,
        GeometrySize = 20
    }
];

By default the tooltip will be:

We can add format to the tooltip:

public ISeries[] Series { get; set; } = [
    new LineSeries<double>
    {
        Values = [2, 1, 3, 5, 3, 4, 6],
        Fill = null,
        GeometrySize = 20,
        YToolTipLabelFormatter = point => point.Model.ToString("N2") // mark
    },
    new LineSeries<int, StarGeometry>
    {
        Values = [4, 2, 5, 2, 4, 5, 3],
        Fill = null,
        GeometrySize = 20,
        YToolTipLabelFormatter = point => point.Model.ToString("N2") // mark
    }
];

We used the Model property of the point, the Model property is just the item in the Values collection, for example in the next case, the Model property is of type City.

public ISeries[] Series { get; set; } = [
    new LineSeries<City>
    {
        Values = [new() { Population = 4 }, new() { Population = 2}],
        YToolTipLabelFormatter = point => point.Model.Population.ToString("N2") // mark
    }
];

// ...

public class City
{
    public double Population { get; set; }
}

We can also show a label for the X coordinate, the default tooltip uses the X label as the header in the tooltip.

new LineSeries<double>
{
    Values = [2, 1, 3, 5, 3, 4, 6],
    Fill = null,
    GeometrySize = 20,
    XToolTipLabelFormatter = point => point.Index.ToString(), // mark
    YToolTipLabelFormatter = point => point.Model.ToString("C2")
};

When the series is "Stacked" (PieSeries, StackedColumn or StackedRow) we can find information about the stacked data in the StackedValue property, for example:

public ISeries[] Series { get; set; } = [
    new StackedColumnSeries<double>
    {
        Values = [2, 1, 3, 5, 3, 4, 6],
        YToolTipLabelFormatter =
            point => $"{point.Model} / {point.StackedValue!.Total} ({point.StackedValue.Share:P2})"
    },
    new StackedColumnSeries<int>
    {
        Values = [4, 2, 5, 2, 4, 5, 3],
        YToolTipLabelFormatter =
            point => $"{point.Model} / {point.StackedValue!.Total} ({point.StackedValue.Share:P2})"
    }
];

Will result in:

Customize default tooltips

You can quickly change the position, the font, the text size or the background color:

View

<UserControl
    x:Class="WinUISample.Axes.NamedLabels.View"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:lvc="using:LiveChartsCore.SkiaSharpView.WinUI"
    xmlns:vms="using:ViewModelsSamples.Axes.NamedLabels"
    mc:Ignorable="d">

    <UserControl.DataContext>
        <vms:ViewModel/>
    </UserControl.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <lvc:CartesianChart
            Series="{Binding Series}"
            XAxes="{Binding XAxes}"
            YAxes="{Binding YAxes}"
            TooltipPosition="Left"
            TooltipTextPaint="{Binding TooltipTextPaint}"
            TooltipBackgroundPaint="{Binding TooltipBackgroundPaint}"
            TooltipTextSize="16">
        </lvc:CartesianChart>
    </Grid>

</UserControl>

View model

[ObservableObject]
public partial class ViewModel
{
    public ISeries[] Series { get; set; } = { ... };
    public Axis[] XAxes { get; set; } = { ... };
    public Axis[] YAxes { get; set; } = { ... };

    public SolidColorPaint TooltipTextPaint { get; set; } = // mark
        new SolidColorPaint // mark
        { // mark
            Color = new SKColor(242, 244, 195), // mark
            SKTypeface = SKTypeface.FromFamilyName("Courier New") // mark
        }; // mark

    public SolidColorPaint TooltipBackgroundPaint { get; set; } = // mark
        new SolidColorPaint(new SKColor(72, 0, 50)); // mark
}

Custom tooltip control

You can also create your own tooltip, the recommended way is to use the LiveCharts API (example bellow) but you can use anything as tooltip as soon as it implements the IChartTooltip<T> interface. In the following example we build a custom control to render tooltips in out charts using the LiveCharts API.

CustomTooltip.cs

using System;
using System.Collections.Generic;
using LiveChartsCore;
using LiveChartsCore.Drawing;
using LiveChartsCore.Kernel;
using LiveChartsCore.Kernel.Sketches;
using LiveChartsCore.SkiaSharpView.Drawing;
using LiveChartsCore.SkiaSharpView.Drawing.Geometries;
using LiveChartsCore.SkiaSharpView.Drawing.Layouts;
using LiveChartsCore.SkiaSharpView.Painting;
using SkiaSharp;

namespace ViewModelsSamples.General.TemplatedTooltips;

public class CustomTooltip : IChartTooltip
{
    private Container<RoundedRectangleGeometry>? _container;
    private StackLayout? _layout;

    public void Show(IEnumerable<ChartPoint> foundPoints, Chart chart)
    {
        if (_container is null || _layout is null)
        {
            _container = new Container<RoundedRectangleGeometry>
            {
                Content = _layout = new StackLayout
                {
                    Padding = new(10),
                    Orientation = ContainerOrientation.Vertical,
                    HorizontalAlignment = Align.Middle,
                    VerticalAlignment = Align.Middle
                }
            };

            _container.Geometry.Fill = new SolidColorPaint(new SKColor(28, 49, 58));
            _container.Animate(new Animation(EasingFunctions.BounceOut, TimeSpan.FromMilliseconds(500)));

            var drawTask = chart.Canvas.AddGeometry(_container);
            drawTask.ZIndex = 10100;
        }

        _container.Opacity = 1;
        _container.ScaleTransform = new LvcPoint(1, 1);

        foreach (var child in _layout.Children.ToArray())
            _ = _layout.Children.Remove(child);

        foreach (var point in foundPoints)
        {
            var series = point.Context.Series;
            var miniature = (IDrawnElement<SkiaSharpDrawingContext>)series.GetMiniatureGeometry(point);

            var label = new LabelGeometry
            {
                Text = point.Coordinate.PrimaryValue.ToString("C2"),
                Paint = new SolidColorPaint(new SKColor(230, 230, 230)),
                TextSize = 15,
                Padding = new Padding(8, 0, 0, 0),
                VerticalAlign = Align.Start,
                HorizontalAlign = Align.Start
            };

            var sp = new StackLayout
            {
                Padding = new Padding(0, 4),
                VerticalAlignment = Align.Middle,
                HorizontalAlignment = Align.Middle,
                Children =
                {
                    miniature,
                    label
                }
            };

            _layout.Children.Add(sp);
        }

        var size = _container.Measure();
        var location = foundPoints.GetTooltipLocation(size, chart);

        _container.X = location.X;
        _container.Y = location.Y;

        chart.Canvas.Invalidate();
    }

    public void Hide(Chart chart)
    {
        if (chart is null || _container is null) return;

        _container.Opacity = 0f;
        _container.ScaleTransform = new LvcPoint(0f, 0f);

        chart.Canvas.Invalidate();
    }
}

View

<UserControl
    x:Class="WinUISample.General.TemplatedTooltips.View"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:lvc="using:LiveChartsCore.SkiaSharpView.WinUI"
    xmlns:vms="using:ViewModelsSamples.General.TemplatedTooltips"
    mc:Ignorable="d">

    <UserControl.DataContext>
        <vms:ViewModel/>
    </UserControl.DataContext>
    <Grid>
        <lvc:CartesianChart Series="{Binding Series}" TooltipPosition="Top" >
            <!-- mark -untilCloses CartesianChart.Tooltip -->
            <lvc:CartesianChart.Tooltip>
                <vms:CustomTooltip></vms:CustomTooltip>
            </lvc:CartesianChart.Tooltip>
        </lvc:CartesianChart>
    </Grid>

</UserControl>