add method setLineDash (#2158)

* Update jspdf.js

* Update jspdf.unit.spec.js

* Update jspdf.unit.spec.js

* Update jspdf.js

* Update jspdf.unit.spec.js

* Update jspdf.js

* Update jspdf.js

* Update jspdf.unit.spec.js

* Update jspdf.unit.spec.js

* Update jspdf.js

Author: Uzlopak

src/jspdf.js

@@ -2764,6 +2764,39 @@ var jsPDF = (function (global) {
       return this;
     };
 
+    /**
+     * Sets the dash pattern for upcoming lines.
+     * 
+     * To reset the settings simply call the method without any parameters.
+     * @param {array} dashArray The pattern of the line, expects numbers. 
+     * @param {number} dashPhase The phase at which the dash pattern starts.
+     * @function
+     * @instance
+     * @returns {jsPDF}
+     * @memberOf jsPDF
+     * @name setLineDash
+     */
+    var setLineDash = API.__private__.setLineDash = jsPDF.API.setLineDash = function (dashArray, dashPhase) {
+      dashArray = dashArray || [];
+      dashPhase = dashPhase || 0;
+
+      if (isNaN(dashPhase) || !Array.isArray(dashArray)) {
+        throw new Error('Invalid arguments passed to jsPDF.setLineDash');
+      }
+
+      dashArray = dashArray.map(function (x) {return (x * k).toFixed(3)}).join(' ');
+      dashPhase = parseFloat((dashPhase * k).toFixed(3));
+
+      out('[' + dashArray + '] ' + dashPhase + ' d');
+      return this;
+    };
+
+    var lineHeightFactor;
+
+    var getLineHeight = API.__private__.getLineHeight = API.getLineHeight = function () {
+      return activeFontSize * lineHeightFactor;
+    };
+
     var lineHeightFactor;
 
     var getLineHeight = API.__private__.getLineHeight = API.getLineHeight = function () {

tests/init/jspdf.unit.spec.js

@@ -429,7 +429,35 @@ describe('jsPDF unit tests', () => {
 
     expect(writeArray).toEqual(['1687.41 w']);
   });
-  
+   
+    it('jsPDF private function setLineDash', () => {
+    const doc = jsPDF()
+    var writeArray = [];
+    doc.__private__.setCustomOutputDestination(writeArray);
+    
+    expect(function () {doc.__private__.setLineDash('');} ).not.toThrow(new Error('Invalid arguments passed to jsPDF.setLineDash'));
+
+    var writeArray = [];
+    doc.__private__.setCustomOutputDestination(writeArray);
+    expect(function () {doc.__private__.setLineDash();} ).not.toThrow(new Error('Invalid arguments passed to jsPDF.setLineDash'));
+
+    expect(writeArray).toEqual(['[] 0 d']);
+
+    var writeArray = [];
+    doc.__private__.setCustomOutputDestination(writeArray);
+    expect(function () {doc.__private__.setLineDash('1 1', '1');} ).toThrow(new Error('Invalid arguments passed to jsPDF.setLineDash'));
+
+    var writeArray = [];
+    doc.__private__.setCustomOutputDestination(writeArray);
+    expect(function () {doc.__private__.setLineDash('1 1', 1);} ).toThrow(new Error('Invalid arguments passed to jsPDF.setLineDash'));
+
+    var writeArray = [];
+    doc.__private__.setCustomOutputDestination(writeArray);
+    expect(function () {doc.__private__.setLineDash([1,1], 1)} ).not.toThrow(new Error('Invalid arguments passed to jsPDF.setLineDash'));
+
+    expect(writeArray).toEqual(['[2.835 2.835] 2.835 d']);
+  });
+
   it('jsPDF private function getLineHeight', () => {
     const doc = jsPDF()