added comments to canvas

lib/network/modules/Canvas.js

@@ -13,6 +13,7 @@ let util = require('../../util');
 class Canvas {
   constructor(body) {
     this.body = body;
+    this.pixelRatio = 1;
 
     this.options = {};
     this.defaultOptions = {
@@ -21,6 +22,7 @@ class Canvas {
     }
     util.extend(this.options, this.defaultOptions);
 
+    // bind the events
     this.body.emitter.once("resize", (obj) => {
       if (obj.width !== 0) {
         this.body.view.translation.x = obj.width * 0.5;
@@ -31,9 +33,8 @@ class Canvas {
     });
     this.body.emitter.on("destroy", () => this.hammer.destroy());
 
+    // automatically adapt to a changing size of the browser.
     window.onresize = () => {this.setSize(); this.body.emitter.emit("_redraw");};
-
-    this.pixelRatio = 1;
   }
 
   setOptions(options) {
@@ -42,6 +43,10 @@ class Canvas {
     }
   }
 
+
+  /**
+   * Create the HTML
+   */
   create() {
     // remove all elements from the container element.
     while (this.body.container.hasChildNodes()) {
@@ -52,7 +57,7 @@ class Canvas {
     this.frame.className = 'vis network-frame';
     this.frame.style.position = 'relative';
     this.frame.style.overflow = 'hidden';
-    this.frame.tabIndex = 900;
+    this.frame.tabIndex = 900; // tab index is required for keycharm to bind keystrokes to the div instead of the window
 
     //////////////////////////////////////////////////////////////////