ChartLineLabelPlugin/index.html at main · SelectLine/ChartLineLabelPlugin · GitHub

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<!doctype html>
<html lang="en">

<head>
  <meta charset="utf-8">
  <title>PieLabel13</title>
  <base href="/">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" type="image/x-icon" href="favicon.ico">
</head>

<body>
  <div style="width: 97%; margin: auto;">
    <canvas id="myChart"></canvas>
  </div>

  <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
  <script>
    const baseColors = ['#a26d97', '#e3a711', '#55a0d3', '#93b856', '#c56055', '#406685', '#a26d97', '#e3a711', '#55a0d3', '#93b856', '#c56055', '#406685', '#a26d97', '#e3a711', '#55a0d3', '#93b856', '#c56055', '#406685'];

    const data = {
      labels: [
        'January is a very very long label with a lot of text',
        'February is short but the label text is longer',
        'March',
        'April',
        'May',
        'June',
        'July',
        'August',
        'September',
        'October',
        'November',
        'December'
      ],
      datasets: [
        {
          label: "# of Votes",
          data: [20, 10, 26, 9, 16, 21, 10, 12, 10, 5, 3, 10],
          backgroundColor: baseColors
        }
      ]
    };


    const options = {
      layout: {
        padding: {
          top: 0,
          left: 0,
          right: 0,
          bottom: 0
        }
      },
      plugins: {
        chartLineLabelPlugin: {
          labelSpace: 120,
          //labelSpacePercent: 15,
          lineHeightFactor: 1.2,
          anchorCenterPercent: 100,
          font: "12px 'Helvetica Neue', 'Helvetica', 'Arial', sans-serif",
          color: 'gray',
          edgePadding: 25,
          halo: true,
          alignLabels: false,
          showDebugInfos: false
        },
        legend: {
          display: true
        },
      }
    };

    const chartAreaBorder = {
      id: 'chartAreaBorder',
      afterDraw(chart, args, options) {
        const { ctx, chartArea: { left, top, width, height } } = chart;
        ctx.save();
        ctx.strokeStyle = options.borderColor;
        ctx.lineWidth = options.borderWidth;
        ctx.setLineDash(options.borderDash || []);
        ctx.lineDashOffset = options.borderDashOffset;
        //ctx.strokeRect(left, top, width, height);
        ctx.restore();
      }
    };

    const chartLineLabelPlugin = {
      id: 'chartLineLabelPlugin',

      resize(chart) {
        //Get the plugin options or default values
        const options = getPluginOptions(chart);

        // Check if plugin is enabled
        const display = options.display;
        if (display === false) {
          return;
        }

        const labelSpace = getLabelSpace(chart, options);
        //This overwrites the original padding
        chart.options.layout.padding.left = labelSpace;
        chart.options.layout.padding.right = labelSpace;
      },


      afterDraw: (chart) => {
        //Get the plugin options or default values
        const options = getPluginOptions(chart);

        // Check if plugin is enabled
        const display = options.display;
        if (display === false) {
          return;
        }

        if (chart.config.data.labels === undefined || chart.config.data.labels.size === 0) {
          return;
        }

        // Grab the necessarry values from the chart
        const { ctx, chartArea: { top, bottom, left, right, width, height }, scales: { x, y } } = chart;
        ctx.font = options.font;

        const lineHeightInPixel = getLineHeightInPixel(ctx, options.lineHeightFactor);

        const chartCenterPoint = {
          x: (chart.chartArea.right - chart.chartArea.left) / 2 + chart.chartArea.left,
          y: (chart.chartArea.bottom - chart.chartArea.top) / 2 + chart.chartArea.top
        };

        let [allLabels, radius] = calculateCoordinates(chart, chartCenterPoint, options);

        //Y-Value for line zero
        let lineZeroY = chartCenterPoint.y - (radius + lineHeightInPixel);
        if (chartCenterPoint.y - radius < chart.chartArea.top) {
          lineZeroY += lineHeightInPixel;
        }

        allLabels = calculateLineNumbers(
          allLabels,
          lineHeightInPixel,
          lineZeroY,
          'left',
          chartCenterPoint,
          radius,
          chart.chartArea.height);

        allLabels = calculateLineNumbers(
          allLabels,
          lineHeightInPixel,
          lineZeroY,
          'right',
          chartCenterPoint,
          radius,
          chart.chartArea.height);

        drawLabels(allLabels, ctx, chartCenterPoint, options);
      }
    };

    const calculateCoordinates = (chart, chartCenterPoint, pluginOptions) => {
      const allLabels = [];
      let model = {};
      let radius = 0;
      //Iterate all labels and calculate their coordinates
      chart.config.data.labels.forEach((label, i) => {
        // Do not calc and draw the label if it hidden by legend striketrough
        if (chart.legend.legendItems[i].hidden === true) {
          return;
        }
        const meta = chart.getDatasetMeta(0);
        model = meta.data[i];
        if (model === undefined) {
          return;
        }

        const dataset = chart.config.data.datasets[0];

        radius = model.outerRadius + pluginOptions.edgePadding;

        // Prepare data to draw
        // important point 1
        const centerPoint = model.getCenterPoint();
        const color = pluginOptions.color;
        const labelColor = pluginOptions.color;

        const angle = Math.atan2(
          centerPoint.y - chartCenterPoint.y,
          centerPoint.x - chartCenterPoint.x
        );

        const point2X = chartCenterPoint.x + Math.cos(angle) * (radius);
        const point2Y = chartCenterPoint.y + Math.sin(angle) * (radius);

        //Modify centerPoint with pluginOptions.anchorCenterPercent
        centerPoint.x = chartCenterPoint.x + Math.cos(angle) * (model.outerRadius * pluginOptions.anchorCenterPercent / 100);
        centerPoint.y = chartCenterPoint.y + Math.sin(angle) * (model.outerRadius * pluginOptions.anchorCenterPercent / 100);

        let direction;
        if (point2X < chartCenterPoint.x) {
          direction = 'left';
        } else {
          direction = 'right';
        }

        let value = dataset.data[i];
        if (dataset.polyline && dataset.polyline.formatter) {
          value = dataset.polyline.formatter(value);
        }

        const labelSpace = getLabelSpace(chart, pluginOptions);
        const somethingLikeDistanceToCenter = model.outerRadius + labelSpace;

        const edgePointX =
          point2X < chartCenterPoint.x
            ? chartCenterPoint.x - somethingLikeDistanceToCenter
            : chartCenterPoint.x + somethingLikeDistanceToCenter;

        if (pluginOptions.formatter !== undefined) {
          label = pluginOptions.formatter(value, chart.config.data.labels, i, chart.config.data.datasets);
        }

        allLabels.push({
          centerPoint,
          edgePointX,
          point2X,
          point2Y,
          labelColor,
          color,
          label,
          direction,
          lineNumber: 0
        });
      });

      return [allLabels, radius];
    };

    const calculateLineNumbers = (labels, lineHeightInPixel, lineZeroY, direction, chartCenter, radius, maxHeight) => {
      // Caculate the line numbers by pointY2 - pointY2 is a point without crossing lines - thus, the labels must not change in order.
      // Sort lines by y-Coordinate
      labels.sort((a, b) => (a.point2Y > b.point2Y) ? 1 : ((b.point2Y > a.point2Y) ? -1 : 0));
      let initialLineNumber = 0;
      const maxLine = Math.floor(maxHeight / lineHeightInPixel);
      labels.forEach((item) => {
        if (item.direction === direction) {
          let proposedLineNumber = Math.ceil((item.point2Y - lineZeroY) / lineHeightInPixel);
          if (proposedLineNumber > maxLine) {
            proposedLineNumber = maxLine;
          }
          while (proposedLineNumber <= initialLineNumber) {
            proposedLineNumber++;
          }
          item.lineNumber = proposedLineNumber;
          initialLineNumber = proposedLineNumber;
        }
      });

      labels.forEach((item) => {
        if (item.direction === direction) {
          item.point2Y = lineZeroY + item.lineNumber * lineHeightInPixel;

          // Now that Y is new - we need to recalc x,
          const diffY = chartCenter.y - item.point2Y;
          const diffX = Math.sqrt(Math.abs((radius * radius) - (diffY * diffY)));
          if (direction === 'left') {
            item.point2X = chartCenter.x - diffX;
          }
          else {
            item.point2X = chartCenter.x + diffX;
          }
        }
      });

      return labels;
    };

    const drawLabels = (labels, ctx, chartCenterPoint, options) => {
      labels.forEach((item) => {

        // Add line number for debug
        if (options.showDebugInfos) {
          item.label += '/' + item.lineNumber;
        }

        const labelText = shortenLabelText(ctx, item.label, Math.abs(item.point2X - item.edgePointX));

        // Correct the edgePointX, if labels are not aligned
        if (!options.alignLabels) {
          const labelWidth = ctx.measureText(labelText).width;
          if (item.direction === 'left') {
            item.edgePointX = item.point2X - labelWidth;
          }
          else {
            item.edgePointX = item.point2X + labelWidth;
          }
        }

        // first line: connect between arc's center point and outside point
        if (options.halo) {
          drawLine(ctx, item.centerPoint.x, item.centerPoint.y, item.point2X, item.point2Y, 'white', 3);
        }
        drawLine(ctx, item.centerPoint.x, item.centerPoint.y, item.point2X, item.point2Y, item.color, 1);

        // second line: connect between outside point and chart's edge
        if (options.halo) {
          drawLine(ctx, item.point2X, item.point2Y, item.edgePointX, item.point2Y, 'white', 3);
        }
        drawLine(ctx, item.point2X, item.point2Y, item.edgePointX, item.point2Y, item.color, 1);

        //fill custom label
        const labelAlignStyle = item.edgePointX < chartCenterPoint.x ? 'left' : 'right';
        const labelX = item.edgePointX;
        const labelY = item.point2Y;
        ctx.textAlign = labelAlignStyle;
        ctx.textBaseline = 'bottom';

        ctx.fillStyle = item.labelColor;
        ctx.fillText(labelText, labelX, labelY - 2); // 2 = Distance from line to text
      });
      ctx.restore();
    };

    const drawLine = (ctx, x1, y1, x2, y2, color, width) => {
      ctx.strokeStyle = color;
      ctx.lineWidth = width;
      ctx.beginPath();
      ctx.moveTo(x1, y1);
      ctx.lineTo(x2, y2);
      ctx.stroke();
    };

    const getLabelSpace = (chart, pluginOptions) => {
      let labelSpace = pluginOptions.labelSpace;
      if (labelSpace === undefined) {
        const labelSpacePercent = pluginOptions.labelSpacePercent;
        if (labelSpacePercent === undefined) {
          labelSpace = 250; // Default value if nothing is set
        }
        else {
          labelSpace = chart.width * labelSpacePercent / 100;
        }
      }
      return labelSpace;
    };

    const shortenLabelText = (ctx, labelText, maxWidth) => {
      let length = ctx.measureText(labelText).width;
      if (length > maxWidth) {
        while (length > maxWidth && labelText.length > 3) {
          labelText = labelText.substring(0, labelText.length - 1);
          length = ctx.measureText(labelText + '...').width;
        }
        labelText = labelText + '...';
      }
      return labelText;
    };

    const getLineHeightInPixel = (ctx, lineHeightFactor) => {
      // You can get a very close approximation of the vertical height by checking the length of a capital M.
      const height = ctx.measureText('M').width;
      return height * lineHeightFactor * 2;
    };

    const getPluginOptions = (chart) => {
      //Default values
      let display = false;
      let labelSpace = undefined;
      let labelSpacePercent = undefined;
      let lineHeightFactor = 1.2;
      let formatter = undefined;
      let anchorCenterPercent = 50;
      let font = '13px \'Helvetica Neue\', \'Helvetica\', \'Arial\', sans-serif';
      let color = 'gray';
      let edgePadding = 15;
      let halo = false;
      let alignLabels = true;
      let showDebugInfos = false;

      const pluginOptions = chart.config.options.plugins.chartLineLabelPlugin;
      if (pluginOptions !== undefined) {
        if (pluginOptions.display !== undefined) {
          display = pluginOptions.display;
        }
        else {
          display = true;
        }
        if (pluginOptions.labelSpace !== undefined) {
          labelSpace = pluginOptions.labelSpace;
        }
        if (pluginOptions.labelSpacePercent !== undefined) {
          labelSpacePercent = pluginOptions.labelSpacePercent;
        }
        if (pluginOptions.lineHeightFactor !== undefined) {
          lineHeightFactor = pluginOptions.lineHeightFactor;
        }
        if (pluginOptions.formatter !== undefined) {
          formatter = pluginOptions.formatter;
        }
        if (pluginOptions.anchorCenterPercent !== undefined) {
          anchorCenterPercent = pluginOptions.anchorCenterPercent;
        }
        if (pluginOptions.font !== undefined) {
          font = pluginOptions.font;
        }
        if (pluginOptions.color !== undefined) {
          color = pluginOptions.color;
        }
        if (pluginOptions.edgePadding !== undefined) {
          edgePadding = pluginOptions.edgePadding;
        }
        if (pluginOptions.halo !== undefined) {
          halo = pluginOptions.halo;
        }
        if (pluginOptions.alignLabels !== undefined) {
          alignLabels = pluginOptions.alignLabels;
        }
        if (pluginOptions.showDebugInfos !== undefined) {
          showDebugInfos = pluginOptions.showDebugInfos;
        }
      }

      return {
        display,
        labelSpace,
        labelSpacePercent,
        lineHeightFactor,
        formatter,
        anchorCenterPercent,
        font,
        color,
        edgePadding,
        halo,
        alignLabels,
        showDebugInfos
      }
    };


    const config = {
      type: 'pie',
      data: data,
      options: options,
      plugins: [chartLineLabelPlugin, chartAreaBorder]
    };


    const myChart = new Chart(document.getElementById('myChart'), config);

  </script>

</body>

</html>