elementHighlight

Overview

The elementHighlight interaction targets chart elements. When the mouse hovers over an element, that element will be highlighted.

• Trigger: Mouse hover over element.

• End: Mouse leaves element.

• Affected states:

Hovered elements change to active state.

Other elements change to inactive state.

Built-in interaction states:

({
  // Active state elements have 1px black border
  state: { active: { lineWidth: '1', stroke: '#000' } },
});

import { Chart } from '@antv/g2';

const chart = new Chart({ container: 'container' });

chart.options({
  type: 'interval',
  data: {
    type: 'fetch',
    value:
      'https://gw.alipayobjects.com/os/bmw-prod/fb9db6b7-23a5-4c23-bbef-c54a55fee580.csv',
  },
  encode: { x: 'letter', y: 'frequency' },
  state: { active: { fill: 'orange' }, inactive: { opacity: 0.5 } },
  axis: { y: { labelFormatter: '.0%' } },
  interaction: { elementHighlight: true },
});

chart.render();

Usage

There are two ways to configure the elementHighlight interaction:

First, pass a boolean to set whether to enable the interaction.

({
  type: 'interval',
  interaction: { elementHighlight: true }, // Use default configuration
});

Second, pass configuration options to configure the interaction.

({
  type: 'line',
  interaction: {
    elementHighlight: {
      background: true,
    },
  },
});

Configuration Level

Interaction can be configured at the Mark level:

({
  type: 'interval',
  interaction: { elementHighlight: true },
});

It can also be configured at the View level. Interactions declared on the view will be passed to marks declared in children. If the mark has declared the corresponding interaction, they will be merged; otherwise, it won’t be affected.

({
  type: 'view',
  interaction: { elementHighlight: true },
});

Configuration Options

Element highlight interaction configuration has two parts:

1. Interaction configuration
2. Element highlight style

Interaction Configuration

Element Highlight Style

Element highlight style, see example Custom Highlight

When configuring background in active elements, it’s not configured as an object, but using the background prefix with property names.

({
  state: {
    active: {
      backgroundRadius: 50,
      backgroundFill: '#000',
      backgroundFillOpacity: 0.9,
      backgroundStroke: '#DAF5EC',
      backgroundStrokeOpacity: 0.9,
      backgroundLineWidth: 2,
      backgroundLineDash: [4, 8],
      backgroundOpacity: 1,
      backgroundShadowColor: '#d3d3d3',
      backgroundShadowBlur: 10,
      backgroundShadowOffsetX: 10,
      backgroundShadowOffsetY: 10,
      backgroundCursor: 'pointer',
    },
  },
});

Events

Listening to Events

The following events are supported:

• element:highlight - Triggered when element is highlighted
• element:unhighlight - Triggered when element highlight is removed

chart.on('element:highlight', (e) => {
  console.log(e.data.data);
  console.log(e.data.group);
  console.log(e.nativeEvent);
});

chart.on('element:unhighlight', (e) => {
  console.log(e.nativeEvent);
});

Triggering Interaction

The following events are supported:

• element:highlight - Highlight data
• element:unhighlight - Remove highlight

chart.emit('element:highlight', {
  data: { data: { population: 5038433 } },
});

chart.emit('element:unhighlight', {});

Examples

Basic Highlight

import { Chart } from '@antv/g2';

const chart = new Chart({
  container: 'container',
});
chart.options({
  type: 'interval',
  autoFit: true,
  data: {
    type: 'fetch',
    value:
      'https://gw.alipayobjects.com/os/bmw-prod/fb9db6b7-23a5-4c23-bbef-c54a55fee580.csv',
  },
  encode: { x: 'letter', y: 'frequency' },
  transform: [{ type: 'sortX', by: 'y', reverse: true, slice: 5 }],
  axis: { y: { labelFormatter: '.0%' } },
  interaction: { elementHighlight: { background: true, region: true } },
});

chart.render();

Custom Highlight

import { Chart } from '@antv/g2';

const chart = new Chart({
  container: 'container',
});
chart.options({
  type: 'interval',
  autoFit: true,
  data: {
    type: 'fetch',
    value:
      'https://gw.alipayobjects.com/os/bmw-prod/fb9db6b7-23a5-4c23-bbef-c54a55fee580.csv',
  },
  encode: { x: 'letter', y: 'frequency' },
  transform: [{ type: 'sortX', by: 'y', reverse: true, slice: 5 }],
  axis: { y: { labelFormatter: '.0%' } },
  scale: {
    y: {
      nice: true,
    },
  },
  state: {
    active: {
      offset: 1,
      backgroundRadius: 8,
      backgroundFill: (d) => (d.frequency > 0.1 ? '#EF4444' : '#3B82F6'),
      backgroundFillOpacity: 0.15,
      backgroundStroke: (d) => (d.frequency > 0.1 ? '#EF4444' : '#3B82F6'),
      backgroundStrokeOpacity: 0.8,
      backgroundLineWidth: 2,
      backgroundShadowColor: (d) => (d.frequency > 0.1 ? '#EF4444' : '#3B82F6'),
      backgroundShadowBlur: 8,
      backgroundShadowOffsetX: 0,
      backgroundShadowOffsetY: 2,
      backgroundCursor: 'pointer',
      fill: '#FFFFFF',
      stroke: (d) => (d.frequency > 0.1 ? '#EF4444' : '#3B82F6'),
      strokeWidth: 2,
    },
  },
  interaction: {
    elementHighlight: {
      background: true,
    },
  },
});

chart.render();

Line Chart Background Highlight Configuration

Line Mark Characteristics:

• Each line corresponds to one graphic element (Path), containing multiple data points
• The line’s __data__ includes aggregated data from all points, where x/y values are typically the coordinates of the first data point
• When rendering background highlight, the renderBackground function calculates background rectangles based on the first data point’s position
• If the x-axis uses an ordinal scale (band scale), the background rectangle only covers the bandwidth range corresponding to the first data point

import { Chart } from '@antv/g2';

const chart = new Chart({
  container: 'container',
  autoFit: true,
});

chart.options({
  type: 'line',
  state: {
    active: {
      backgroundFill: 'red',
    },
  },
  interaction: {
    elementHighlight: {
      background: true,
    },
  },
  data: [
    { year: '1991', value: 3 },
    { year: '1992', value: 4 },
    { year: '1993', value: 3.5 },
    { year: '1994', value: 5 },
    { year: '1995', value: 4.9 },
    { year: '1996', value: 6 },
    { year: '1997', value: 7 },
    { year: '1998', value: 9 },
    { year: '1999', value: 13 },
  ],
  encode: { x: 'year', y: 'value' },
  scale: { x: { range: [0, 1] }, y: { domainMin: 0, nice: true } },
});

chart.render();

From the example above, we can see that the background highlight only appears at the starting point of the line, making the effect look incomplete. For Line Mark, it’s recommended to use style properties like stroke and strokeWidth for highlighting. However, if you want to achieve background highlighting, it’s possible by combining other marks in G2, such as the point mark.

Point Mark Characteristics:

• Each data point corresponds to an independent graphic element (such as Circle)
• Each point has its own independent __data__, containing the complete coordinate information for that point
• Background highlighting calculates and renders background rectangles individually for each point
• Each point’s background rectangle completely covers its corresponding bandwidth range

import { Chart } from '@antv/g2';

const chart = new Chart({
  container: 'container',
  autoFit: true,
});

chart.options({
  type: 'view',
  data: [
    { year: '1991', value: 3 },
    { year: '1992', value: 4 },
    { year: '1993', value: 3.5 },
    { year: '1994', value: 5 },
    { year: '1995', value: 4.9 },
    { year: '1996', value: 6 },
    { year: '1997', value: 7 },
    { year: '1998', value: 9 },
    { year: '1999', value: 13 },
  ],
  encode: { x: 'year', y: 'value' },
  scale: { x: { range: [0, 1] }, y: { domainMin: 0, nice: true } },
  children: [
    {
      type: 'line',
      interaction: {
        elementHighlight: false, // Disable highlight interaction
      },
    },
    {
      type: 'point',
      style: { fill: 'white', stroke: '#1890ff', strokeWidth: 2 },
      // Point uses background highlight effect for better results
      state: {
        active: {
          backgroundFill: 'red',
          backgroundFillOpacity: 0.3,
          fill: 'red',
          r: 6,
        },
      },
      interaction: {
        elementHighlight: { background: true, region: true },
      },
      tooltip: false, // Disable point tooltip to avoid duplicate display
    },
  ],
});

chart.render();