fix: Using canvas as a direct source (#701)

Author: eKoopmans

src/worker.js

@@ -61,7 +61,7 @@ Worker.prototype.from = function from(src, type) {
   function getType(src) {
     switch (objType(src)) {
       case 'string':  return 'string';
-      case 'element': return src.nodeName.toLowerCase === 'canvas' ? 'canvas' : 'element';
+      case 'element': return src.nodeName.toLowerCase && src.nodeName.toLowerCase() === 'canvas' ? 'canvas' : 'element';
       default:        return 'unknown';
     }
   }
@@ -168,7 +168,8 @@ Worker.prototype.toImg = function toImg() {
 Worker.prototype.toPdf = function toPdf() {
   // Set up function prerequisites.
   var prereqs = [
-    function checkCanvas() { return this.prop.canvas || this.toCanvas(); }
+    function checkCanvas() { return this.prop.canvas || this.toCanvas(); },
+    function checkPageSize() { return this.prop.pageSize || this.setPageSize(); }
   ];
 
   // Fulfill prereqs then create the image.

test/reference/snapshot/all-tags.pdf

@@ -31,6 +31,10 @@ describe('snapshot', () => {
       runner: window => defaultCondition(window, { margin: 1, jsPDF: { unit: 'in' } }),
       name: file => `${file}_margin.pdf`,
     },
+    selectCanvas: {
+      runner: window => defaultCondition(window, {}, window.document.getElementById('canvas')),
+      name: file => `${file}_canvas.pdf`,
+    },
     selectMainId: {
       runner: window => defaultCondition(window, {}, window.document.getElementById('main')),
       name: file => `${file}.pdf`,
@@ -56,7 +60,7 @@ describe('snapshot', () => {
   const filesToTest = {
     'blank': [ 'default' ],
     'lorem-ipsum': [ 'default', 'legacy', 'margin' ],
-    'all-tags': [ 'default' ],
+    'all-tags': [ 'default', 'selectCanvas' ],
     'css-selectors': [ 'selectMainId' ],
     'pagebreaks': [ 'pagebreakLegacy', 'pagebreakCss', 'pagebreakAvoidAll', 'pagebreakSpecify' ],
   };