Show Text in the Center of a Donut Chart

Environment

Product Version	2018.2.620
Product	Progress® Kendo UI® Chart for jQuery

Description

How can I place and center multiple lines of text inside the center of a Kendo UI Donut Chart?

Solution

Make a custom drawing on top of the Donut Chart and show the multi-line text and other content in its center.

1. Use the series.visual function to store the position and size of the Donut Chart center.

   js

   // global variables
   var center,
   radius;
   
   ........
   
   series: [{
       type: "donut",
       field: "share",
       categoryField: "kind",
       visual: function(e){
           // Obtain parameters for the segments
           center = e.center;
           radius = e.innerRadius;
   
           // Create default visual
           return e.createVisual();
       }
   }]
   

2. In the render event of the Chart, draw your custom content on top of the Chart by using the Kendo UI Drawing library.

   js

           render: function(e){
             var circleGeometry = new kendo.geometry.Circle(center, radius);
             var bbox = circleGeometry.bbox();
   
             // Render the text
             //
             // https://docs.telerik.com/kendo-ui/api/javascript/drawing/text
             var heading = new kendo.drawing.Text('45.2%', [0, 0], {
               font: '22px Verdana,Arial,sans-serif'
             });
   
             var line1 = new kendo.drawing.Text('of which', [0, 0], {
               font: '12px Verdana,Arial,sans-serif'
             });
   
             var line2 = new kendo.drawing.Text('renewables', [0, 0], {
               font: '14px Verdana,Arial,sans-serif',
               fill: {
                 color: 'green'
               }
             });
   
             // Reflow the text in the bounding box
             //
             // https://docs.telerik.com/kendo-ui/api/javascript/drawing/layout
             var layout = new kendo.drawing.Layout(bbox, {
               alignContent: 'center',
               alignItems: 'center',
               justifyContent: 'center',
               spacing: 5
             });
   
             layout.append(heading, line1, line2);
             layout.reflow();
   
             // Draw it on the Chart drawing surface
             //
             // https://docs.telerik.com/kendo-ui/api/javascript/dataviz/ui/chart/fields/surface
             e.sender.surface.draw(layout);
           }

The following example demonstrates how to render three differently styled lines of text in the center of the Donut Chart.

    <div id="chart"></div>
    <script>
      function createChart() {
        var center,
            radius;

        $("#chart").kendoChart({
          title: {
            text: "What is you favourite sport?"
          },
          legend: {
            position: "top"
          },
          dataSource: {
            data: [{
              kind: 'Hydroelectric', share: 0.175
            }, {
              kind: 'Nuclear', share: 0.238
            }, {
              kind: 'Coal', share: 0.118
            }, {
              kind: 'Solar', share: 0.052
            }, {
              kind: 'Wind', share: 0.225
            }, {
              kind: 'Other', share: 0.192
            }]
          },
          seriesDefaults: {
            labels: {
              template: "#= category # - #= kendo.format('{0:P}', percentage)#",
              position: "outsideEnd",
              visible: true,
              background: "transparent"
            }
          },
          series: [{
            type: "donut",
            field: "share",
            categoryField: "kind",
            visual: function(e){
              // Obtain parameters for the segments
              center = e.center;
              radius = e.innerRadius;

              // Create default visual
              return e.createVisual();
            }
          }],
          tooltip: {
            visible: true,
            template: "#= category # - #= kendo.format('{0:P}', percentage) #"
          },
          render: function(e){
            var circleGeometry = new kendo.geometry.Circle(center, radius);
            var bbox = circleGeometry.bbox();

            // Render the text
            //
            // https://docs.telerik.com/kendo-ui/api/javascript/drawing/text
            var heading = new kendo.drawing.Text('45.2%', [0, 0], {
              font: '22px Verdana,Arial,sans-serif'
            });

            var line1 = new kendo.drawing.Text('of which', [0, 0], {
              font: '12px Verdana,Arial,sans-serif'
            });

            var line2 = new kendo.drawing.Text('renewables', [0, 0], {
              font: '14px Verdana,Arial,sans-serif',
              fill: {
                color: 'green'
              }
            });

            // Reflow the text in the bounding box
            //
            // https://docs.telerik.com/kendo-ui/api/javascript/drawing/layout
            var layout = new kendo.drawing.Layout(bbox, {
              alignContent: 'center',
              alignItems: 'center',
              justifyContent: 'center',
              spacing: 5
            });

            layout.append(heading, line1, line2);
            layout.reflow();

            // Draw it on the Chart drawing surface
            //
            // https://docs.telerik.com/kendo-ui/api/javascript/dataviz/ui/chart/fields/surface
            e.sender.surface.draw(layout);
          }
        });
      }

      $(document).ready(function() {
        createChart();
      });
    </script>

See Also

• Kendo UI Drawing API Reference