C3/D3 pie legend format / label overlap

Question

I have a piechart using C3. I have changed the default legend names by adding values and percentages and now.

1. I am looking for a way to format this legend nicely

Answer 1

It is possible to create a custom legend. Then you can create & style it as you like in either SVG or HTML.

var columns = ['data11', 'data2', 'data347', 'data40098'];
var data = [150, 250, 300, 50];
var colors = ['#0065A3', '#767670', '#D73648', '#7FB2CE', '#00345B'];
var padding = 5;

var legendData = [];
var sumTotal = 0

//prepare pie data

var columnData = [];
var columnNames = {};
for (i = 0; i < columns.length; i++) {
  columnData.push([columns[i]].concat(data[i]));
  var val = (Array.isArray(data[i])) ? data[i].reduce(function(pv, cv) {
    return pv + cv;
  }, 0) : data[i];
  sumTotal += val;
  legendData.push({
    id: columns[i],
    value: val,
    ratio: 0.0
  });
}
legendData.forEach(function(el, i) {
  el.ratio = el.value / sumTotal
  columnNames[el.id] = el.id + ': ' + d3.format(",.0f")(el.value) + " = " + d3.format(",.1%")(el.ratio);
});

var chart = c3.generate({
  bindto: d3.select('#chart'),
  data: {
    columns: [
      [columns[0]].concat(data[0])
    ],
    names: columnNames,
    type: 'pie',
  },
  legend: {
    position: 'right',
    show: false
  },
  pie: {
    label: {
      threshold: 0.001,
      format: function(value, ratio, id) {
        return [id, d3.format(",.0f")(value), "[" + d3.format(",.1%")(ratio) + "]"].join(';');
      }
    }
  },
  color: {
    pattern: colors
  },
  onrendered: redrawLabelBackgrounds
});



function addLabelBackground(index) {
  //get label text element
  var textLabel = d3.select(".c3-target-" + columns[index] + " > text");
  //add rect to parent
  var labelNode = textLabel.node();
  if (labelNode /*&& labelNode.innerHTML.length > 0*/ ) {
    var p = d3.select(labelNode.parentNode).insert("rect", "text")
      .style("fill", colors[index]);
  }
}

for (var i = 0; i < columns.length; i++) {
  if (i > 0) {

    setTimeout(function(column) {
      chart.load({
        columns: [
          columnData[column],
        ]
      });
      //chart.data.names(columnNames[column])
      addLabelBackground(column);

    }, (i * 5000 / columnData.length), i);
  } else {
    addLabelBackground(i);
  }
}


function redrawLabelBackgrounds() {
  //for all label texts drawn yet
  //for all label texts drawn yet
  d3.select('#chart').selectAll(".c3-chart-arc > text").each(function(v) {
    // get d3 node
    var label = d3.select(this);
    var labelNode = label.node();
    //check if label is drawn
    if (labelNode) {
      if (labelNode.childElementCount === 0 && labelNode.innerHTML.length > 0) {
        //build data
        var data = labelNode.innerHTML.split(';');
        label.text("");
        data.forEach(function(i, n) {
          label.append("tspan")
            .text(i)
            .attr("dy", (n === 0) ? 0 : "1.2em")
            .attr("x", 0)
            .attr("text-anchor", "middle");
        }, label);
      }
      //check if element is visible
      if (d3.select(labelNode.parentNode).style("display") !== 'none') {

        //get pos of the label text
        var pos = label.attr("transform").match(/-?\d+(\.\d+)?/g);
        if (pos) {
          // TODO: mofify the pos of the text
          //            pos[0] = (pos[0]/h*90000);
          //            pos[1] = (pos[1]/h*90000);
          // remove dy and move label
          //d3.select(this).attr("dy", 0);
          //d3.select(this).attr("transform", "translate(" + pos[0] + "," + pos[1] + ")");

          //get surrounding box of the label
          var bbox = labelNode.getBBox();

          //now draw and move the rects
          d3.select(labelNode.parentNode).select("rect")
            .attr("transform", "translate(" + (pos[0] - (bbox.width + padding) / 2) +
              "," + (pos[1] - bbox.height / labelNode.childElementCount) + ")")
            .attr("width", bbox.width + padding)
            .attr("height", bbox.height + padding);
        }
      }
    }
  });
}

//console.log(columnData)


function toggle(id) {
  chart.toggle(id);
}

var table = d3.select('#chart')
  .append('table').attr('class', 'legend')

var row = table.selectAll('row').data(columnData)
var rowEnter = row.enter().append('tr').attr('class', 'legend-row')
rowEnter.append('td').attr('style', (d, i) => `width: 20px;background-color:${colors[i]}`)
rowEnter.append('td').text(d => d[0])
rowEnter.append('td').text(d => d[1])


rowEnter.on('mouseover', function(id) {
  if (!this.classList.contains('legend-row-disabled')) {
    rowEnter.classed('legend-row-inactive', true)
    chart.focus(id);
  }

});

rowEnter.on('mouseout', function(id) {
  rowEnter.classed('legend-row-inactive', false)
  if (!this.classList.contains('legend-row-disabled')) {
    chart.focus()
  }
})

rowEnter.on('click', function(id) {
  chart.toggle(id);
  this.classList.toggle('legend-row-disabled');
  chart.focus()

});

.legend {
  font: 12px sans-serif;
  border-collapse: collapse;
}

.legend .legend-row {
  cursor: pointer;
}

.legend .legend-row td:first-child {
  width: 14px !important;
}

.legend .legend-row.legend-row-inactive {
  opacity: 0.3;
}

.legend .legend-row.legend-row-inactive:hover {
  opacity: 1.0;
}

.legend .legend-row.legend-row-disabled,
.legend .legend-row.legend-row-disabled:hover {
  opacity: 0.2;
}

.legend td {
  padding: 5px;
}