Text.js

// SVG.Text with added functionality of measing the pixel width server side using NODE.
//
// Depends mainly on 'svg.js' and 'string-pixel-width'.
// 'Check string-pixel-width' on npmjs.org for supported fonts.
//
// COMPLETE EXAMPLE
// 
// const window = require('svgdom');
// const SVG = require('svg.js')(window);
// const document = window.document;
// const draw = SVG(document.documentElement);
// var pixelWidth = require('string-pixel-width');
// 
// SVG.extend(SVG.Text, {
//   pixelWidth: function() {
//       var arr = this.text().split('\n');
//       var family = this.font().family;
//       var size = this.font().size;
//       if(family === undefined) {
//           throw('Font-family is not set.');
//       }
//       if(size === undefined) {
//           throw('Font-size is not set.');
//       }
//       var length = null;
//       var lengthMax = -1;
//       for (var i = 0; i < arr.length; i++) {
//           length = pixelWidth(arr[i], {
//               font: family,
//               size: size
//           });
//           if (length > lengthMax) {
//               lengthMax = length;
//           }
//       }
//       return lengthMax;
//   }
// });
// 
// var text = draw.text(function(add) {
//   add.tspan('Lorem ipsum dolor sit amet ').newLine();
//   add.tspan('consectetur').fill('#f06');
//   add.tspan('.');
//   add.tspan('Cras sodales imperdiet auctor.').newLine();
//   add.tspan('Nunc ultrices lectus at erat').newLine();
//   add.tspan('dictum pharetra elementum ante').newLine();
// }).font({
//     family: 'courier new',
//     size: 18
// });
// 
// // Finds the longest text line and calcualtes its pixel width.
// console.log( text.pixelWidth() ); // Result: 421.2


SVG.extend(SVG.Text, {
  pixelWidth: function() {
      var arr = this.text().split('\n');
      var family = this.font().family;
      var size = this.font().size;
      if(family === undefined) {
          throw('Font-family is not set.');
      }
      if(size === undefined) {
          throw('Font-size is not set.');
      }
      var length = null;
      var lengthMax = -1;
      for (var i = 0; i < arr.length; i++) {
          length = pixelWidth(arr[i], {
              font: family,
              size: size
          });
          if (length > lengthMax) {
              lengthMax = length;
          }
      }
      return lengthMax;
  }
});