From c5f73edcd273f1cd33694243740e248bef0472c9 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 5 May 2017 18:12:26 +0200
Subject: [PATCH] Convert the `DOMCanvasFactory` to an ES6 class

For consistency, also updates the `pdf2png.js` example to use the slightly less verbose `canvasAndContext` parameter name.
---
 examples/node/pdf2png/pdf2png.js | 26 ++++++++++++------------
 src/display/dom_utils.js         | 35 ++++++++++++++++----------------
 2 files changed, 30 insertions(+), 31 deletions(-)

diff --git a/examples/node/pdf2png/pdf2png.js b/examples/node/pdf2png/pdf2png.js
index 468d1bab8..b595861d0 100644
--- a/examples/node/pdf2png/pdf2png.js
+++ b/examples/node/pdf2png/pdf2png.js
@@ -29,22 +29,22 @@ NodeCanvasFactory.prototype = {
     };
   },
 
-  reset: function NodeCanvasFactory_reset(canvasAndContextPair, width, height) {
-    assert(canvasAndContextPair.canvas, 'Canvas is not specified');
+  reset: function NodeCanvasFactory_reset(canvasAndContext, width, height) {
+    assert(canvasAndContext.canvas, 'Canvas is not specified');
     assert(width > 0 && height > 0, 'Invalid canvas size');
-    canvasAndContextPair.canvas.width = width;
-    canvasAndContextPair.canvas.height = height;
+    canvasAndContext.canvas.width = width;
+    canvasAndContext.canvas.height = height;
   },
 
-  destroy: function NodeCanvasFactory_destroy(canvasAndContextPair) {
-    assert(canvasAndContextPair.canvas, 'Canvas is not specified');
+  destroy: function NodeCanvasFactory_destroy(canvasAndContext) {
+    assert(canvasAndContext.canvas, 'Canvas is not specified');
 
     // Zeroing the width and height cause Firefox to release graphics
     // resources immediately, which can greatly reduce memory consumption.
-    canvasAndContextPair.canvas.width = 0;
-    canvasAndContextPair.canvas.height = 0;
-    canvasAndContextPair.canvas = null;
-    canvasAndContextPair.context = null;
+    canvasAndContext.canvas.width = 0;
+    canvasAndContext.canvas.height = 0;
+    canvasAndContext.canvas = null;
+    canvasAndContext.context = null;
   },
 };
 
@@ -65,16 +65,16 @@ pdfjsLib.getDocument(rawData).then(function (pdfDocument) {
     // Render the page on a Node canvas with 100% scale.
     var viewport = page.getViewport(1.0);
     var canvasFactory = new NodeCanvasFactory();
-    var canvasAndContextPair = canvasFactory.create(viewport.width, viewport.height);
+    var canvasAndContext = canvasFactory.create(viewport.width, viewport.height);
     var renderContext = {
-      canvasContext: canvasAndContextPair.context,
+      canvasContext: canvasAndContext.context,
       viewport: viewport,
       canvasFactory: canvasFactory
     };
 
     page.render(renderContext).then(function () {
       // Convert the canvas to an image buffer.
-      image = canvasAndContextPair.canvas.toBuffer();
+      var image = canvasAndContext.canvas.toBuffer();
       fs.writeFile('output.png', image, function (error) {
         if (error) {
           console.error('Error: ' + error);
diff --git a/src/display/dom_utils.js b/src/display/dom_utils.js
index cd359ee9a..06dfafd76 100644
--- a/src/display/dom_utils.js
+++ b/src/display/dom_utils.js
@@ -20,37 +20,36 @@ import {
 
 var DEFAULT_LINK_REL = 'noopener noreferrer nofollow';
 
-function DOMCanvasFactory() {}
-DOMCanvasFactory.prototype = {
-  create: function DOMCanvasFactory_create(width, height) {
+class DOMCanvasFactory {
+  create(width, height) {
     assert(width > 0 && height > 0, 'invalid canvas size');
-    var canvas = document.createElement('canvas');
-    var context = canvas.getContext('2d');
+    let canvas = document.createElement('canvas');
+    let context = canvas.getContext('2d');
     canvas.width = width;
     canvas.height = height;
     return {
       canvas,
       context,
     };
-  },
+  }
 
-  reset: function DOMCanvasFactory_reset(canvasAndContextPair, width, height) {
-    assert(canvasAndContextPair.canvas, 'canvas is not specified');
+  reset(canvasAndContext, width, height) {
+    assert(canvasAndContext.canvas, 'canvas is not specified');
     assert(width > 0 && height > 0, 'invalid canvas size');
-    canvasAndContextPair.canvas.width = width;
-    canvasAndContextPair.canvas.height = height;
-  },
+    canvasAndContext.canvas.width = width;
+    canvasAndContext.canvas.height = height;
+  }
 
-  destroy: function DOMCanvasFactory_destroy(canvasAndContextPair) {
-    assert(canvasAndContextPair.canvas, 'canvas is not specified');
+  destroy(canvasAndContext) {
+    assert(canvasAndContext.canvas, 'canvas is not specified');
     // Zeroing the width and height cause Firefox to release graphics
     // resources immediately, which can greatly reduce memory consumption.
-    canvasAndContextPair.canvas.width = 0;
-    canvasAndContextPair.canvas.height = 0;
-    canvasAndContextPair.canvas = null;
-    canvasAndContextPair.context = null;
+    canvasAndContext.canvas.width = 0;
+    canvasAndContext.canvas.height = 0;
+    canvasAndContext.canvas = null;
+    canvasAndContext.context = null;
   }
-};
+}
 
 class DOMCMapReaderFactory {
   constructor({ baseUrl = null, isCompressed = false, }) {