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  • React / Next.js
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1

Import Components from Chart.js

import { Chart as ChartJS, BarElement } from 'chart.js';
import { Bar } from 'react-chartjs-2'
2

Import Comments Components and Hooks from Velt

  • Add VeltComments to the root of your app. This component is required to render comments in your app.
  • Add the VeltCommentTool component wherever you want to show the comment tool button. Clicking on it initiates comment mode & changes your mouse cursor to a comment pin. 
import { useCommentModeState, VeltCommentPin, VeltCommentTool, VeltComments } from '@veltdev/react';
3

Create a ref for the ChartJS component

  • Create a ref and pass it into the ref property of the ChartJS component.
const chartRef = useRef(null);

<Bar data={data} options={options} ref={chartRef} />
4

Add a container div for the ChartJS component

  1. Apply position: relative style to the div. This ensures accurate positioning of Velt Comment Pins.
  2. Set data-velt-manual-comment-container to true. This:
  • informs Velt which div to use for positioning
  • disables Velt’s automatic comment positioning system within this div, allowing for manual positioning of comment pins
  1. Give a unique ID to the chart to scope comments to the specific chart, isolating them from other charts.
const chartId = 'dataAnalyticsChart'; // Unique ID for the chart

return (
  <div style={{ position: 'relative' }}
    onClick={handleChartClick}
    data-velt-manual-comment-container="true">

    <Bar data={data} options={options} ref={chartRef} />
  </div>
);
5

Add a Comment when the user clicks on the chart

  1. Handle chart click to find nearest data point and add a comment. (Check handleChartClick() method on the right)
  2. Create context object which contains the information about the series, x-axis value, y-axis value, chartId and anything else that’s relevant. This will be used when rendering the comment pin. (Check handleChartClick() method on the right)
  3. Add comment with the context data. (Check addManualComment() method on the right)
  • Only add a comment if the Velt commentModeState is true and the Velt client is available.
6

Render the Velt Comment Pins and set its position

  1. Get all comment annotations.
  2. Loop through it and render the comment pin.
  3. Use the context data in CommentAnnotation, to set the position of the comment pin. (Check showCommentPin() method on the right)
const commentAnnotations = useCommentAnnotations(); // Get Velt comment annotations
const [chartCommentAnnotations, setChartCommentAnnotations] = React.useState([]); // Store annotations for this chart

useEffect(() => {
  // Filter and store comments for the current chart, using unique chart ID
  const chartCommentAnnotations = commentAnnotations?.filter((comment) => comment.context?.chartId === chartId); 
  setChartCommentAnnotations(chartCommentAnnotations as any || []);
}, [commentAnnotations]);

return (
    ... {/* Rest of the container code. */}

    {/* Loop through comment annotations and render the comment pin. */}
    {chartCommentAnnotations.map((comment, index) => showCommentPin(comment))}

    ... {/* Rest of the container code. */}
);

import React, { useEffect, useRef, useMemo } from 'react';
import { Chart as ChartJS, CategoryScale, LinearScale, PointElement, BarElement, Title, Tooltip, Legend, Filler,} from 'chart.js';
import { Bar } from 'react-chartjs-2';
import { useVeltClient, useCommentAnnotations, useCommentModeState, VeltCommentPin } from '@veltdev/react';

// Register the necessary Chart.js components
ChartJS.register(CategoryScale, LinearScale, PointElement, BarElement, Title, Tooltip, Legend, Filler);

// Define the data for the chart
const scores = [6, 5, 5, 5, 3, 4, 6, 4, 5];
const labels = [100, 200, 300, 400, 500, 600, 700];

// Set the options for the chart
const options: any = {
// your chart options
};

const BarChart = () => {
  const chartId = 'dataAnalyticsChart'; // Unique ID for the chart
  const chartRef = useRef(null); // Reference to the chart instance
  const { client } = useVeltClient(); // Get Velt client
  const commentModeState = useCommentModeState(); // Get Velt comment mode state
  const commentAnnotations = useCommentAnnotations(); // Get Velt comment annotations
  const [chartCommentAnnotations, setChartCommentAnnotations] = React.useState([]); // State for chart comments

  // Update chart comments when annotations change
  useEffect(() => {
    // Filter comments for the current chart, using unique chart ID
    const chartCommentAnnotations = commentAnnotations?.filter((comment) => comment.context?.chartId === chartId); 
    setChartCommentAnnotations(chartCommentAnnotations as any || []);
  }, [commentAnnotations]);

  // Handle chart clicks to find nearest data point and add a comment
  const handleChartClick = (event: any) => {
    const chart: any = chartRef.current;
    if (chart) {
      // Get the nearest element to the click event
      const elements = chart.getElementsAtEventForMode(event.nativeEvent, 'nearest', { intersect: true }, false);
      if (elements.length > 0) {
        const element = elements[0];
        const datasetIndex = element.datasetIndex;
        const index = element.index;
        const dataset = chart.data.datasets[datasetIndex];
        const xValue = chart.data.labels[index];
        const yValue = dataset.data[index];
        const context = { seriesId: dataset.label, xValue, yValue, chartId };
        addManualComment(context); // Add a comment at the nearest data point with the context data
      }
    }
  };

  // Add a manual comment to the chart
  const addManualComment = (context: any) => {
    try {
      if (client && commentModeState) {
        const commentElement = client.getCommentElement();
        commentElement.addManualComment({ context }); // Add a Velt comment
      }
    } catch (error) {
      console.error('Error adding manual comment', error);
    }
  };

  // Find the exact point on the chart to place a comment pin
  const findPoint = (seriesId: any, xValue: any, yValue: any) => {
    const chart: any = chartRef.current;
    if (chart) {
      const dataset = chart.data.datasets.find((dataset: any) => dataset.label === seriesId);
      const index = chart.data.labels.indexOf(xValue);
      if (dataset && index !== -1) {
        const yValueInDataset = dataset.data[index];
        if (yValueInDataset === yValue) {
          return { x: chart.scales.x.getPixelForValue(index), y: chart.scales.y.getPixelForValue(yValue) }; // Set the x, y position for the comment pin
        }
      }
    }
    return null;
  };

  // Show the comment pin on the chart at the specified point
  const showCommentPin = (commentAnnotation: any) => {
    const context = commentAnnotation.context || {};
    const point = findPoint(context.seriesId, context.xValue, context.yValue);
    if (point) {
      const { x, y } = point;
      return (
        <div
          key={commentAnnotation.annotationId}
          style={{
            left: `${x}px`,
            top: `${y}px`,
            position: 'absolute',
            transform: 'translate(0%, -100%)',
            zIndex: 1000,
          }}
        >
          <VeltCommentPin annotationId={commentAnnotation.annotationId} /> {/* Velt comment pin component */}
        </div>
      );
    }
    return null;
  };

  // Memoize the chart data
  const data = useMemo(() => {
    return {
      datasets: [
        {
          label: 'Mis datos',
          tension: 0.3,
          data: scores,
          borderColor: 'rgb(75, 192, 192)',
          backgroundColor: 'rgba(75, 192, 192, 0.3)',
        },
      ],
      labels,
    };
  }, []);

  return (
    <div className="dashlet-card">
      <div className="dashlet-card-header">Bar Chart With Comments</div>
      {/* Keep the parent div as relative, as comment pin will be placed with absolute position */}
      {/* Set "data-velt-manual-comment-container" to true, so that comment pin will know which div to consider while positioning */}
      <div style={{ position: 'relative' }} onClick={handleChartClick} data-velt-manual-comment-container="true"> 
        <Bar data={data} options={options} ref={chartRef} /> {/* Render the Bar chart */}
        {chartCommentAnnotations.map((comment, index) => showCommentPin(comment))} {/* Show all comment pins */}
      </div>
    </div>
  );
};

export default BarChart;