Convert RenderTask, in src/display/api.js, to an ES6 class

Also deprecates the `then` method, in favour of the `promise` getter.

examples/node/pdf2png/pdf2png.js

@@ -73,7 +73,8 @@ loadingTask.promise.then(function(pdfDocument) {
       canvasFactory: canvasFactory
     };
 
-    page.render(renderContext).then(function () {
+    var renderTask = page.render(renderContext);
+    renderTask.promise.then(function() {
       // Convert the canvas to an image buffer.
       var image = canvasAndContext.canvas.toBuffer();
       fs.writeFile('output.png', image, function (error) {

src/display/api.js

@@ -2280,11 +2280,10 @@ class PDFObjects {
 
 /**
  * Allows controlling of the rendering tasks.
- * @class
  * @alias RenderTask
  */
-var RenderTask = (function RenderTaskClosure() {
-  function RenderTask(internalRenderTask) {
+class RenderTask {
+  constructor(internalRenderTask) {
     this._internalRenderTask = internalRenderTask;
 
     /**
@@ -2296,39 +2295,36 @@ var RenderTask = (function RenderTaskClosure() {
     this.onContinue = null;
   }
 
-  RenderTask.prototype = /** @lends RenderTask.prototype */ {
-    /**
-     * Promise for rendering task completion.
-     * @return {Promise}
-     */
-    get promise() {
-      return this._internalRenderTask.capability.promise;
-    },
+  /**
+   * Promise for rendering task completion.
+   * @return {Promise}
+   */
+  get promise() {
+    return this._internalRenderTask.capability.promise;
+  }
 
-    /**
-     * Cancels the rendering task. If the task is currently rendering it will
-     * not be cancelled until graphics pauses with a timeout. The promise that
-     * this object extends will be rejected when cancelled.
-     */
-    cancel: function RenderTask_cancel() {
-      this._internalRenderTask.cancel();
-    },
+  /**
+   * Cancels the rendering task. If the task is currently rendering it will
+   * not be cancelled until graphics pauses with a timeout. The promise that
+   * this object extends will be rejected when cancelled.
+   */
+  cancel() {
+    this._internalRenderTask.cancel();
+  }
 
-    /**
-     * Registers callbacks to indicate the rendering task completion.
-     *
-     * @param {function} onFulfilled The callback for the rendering completion.
-     * @param {function} onRejected The callback for the rendering failure.
-     * @return {Promise} A promise that is resolved after the onFulfilled or
-     *                   onRejected callback.
-     */
-    then: function RenderTask_then(onFulfilled, onRejected) {
-      return this.promise.then.apply(this.promise, arguments);
-    },
-  };
-
-  return RenderTask;
-})();
+  /**
+   * Registers callbacks to indicate the rendering task completion.
+   *
+   * @param {function} onFulfilled The callback for the rendering completion.
+   * @param {function} onRejected The callback for the rendering failure.
+   * @return {Promise} A promise that is resolved after the onFulfilled or
+   *                   onRejected callback.
+   */
+  then(onFulfilled, onRejected) {
+    deprecated('RenderTask.then method, use the `promise` getter instead.');
+    return this.promise.then.apply(this.promise, arguments);
+  }
+}
 
 /**
  * For internal use only.

test/unit/api_spec.js

@@ -1332,26 +1332,23 @@ describe('api', function() {
 
     // Render the first page of the given PDF file.
     // Fulfills the promise with the base64-encoded version of the PDF.
-    function renderPDF(filename) {
-      var loadingTask = getDocument(filename);
+    async function renderPDF(filename) {
+      const loadingTask = getDocument(filename);
       loadingTasks.push(loadingTask);
-      return loadingTask.promise
-        .then(function(pdf) {
-          pdfDocuments.push(pdf);
-          return pdf.getPage(1);
-        }).then(function(page) {
-          var viewport = page.getViewport(1.2);
-          var canvasAndCtx = CanvasFactory.create(viewport.width,
-                                                  viewport.height);
-          return page.render({
-            canvasContext: canvasAndCtx.context,
-            viewport,
-          }).then(function() {
-            var data = canvasAndCtx.canvas.toDataURL();
-            CanvasFactory.destroy(canvasAndCtx);
-            return data;
-          });
-        });
+      const pdf = await loadingTask.promise;
+      pdfDocuments.push(pdf);
+      const page = await pdf.getPage(1);
+      const viewport = page.getViewport(1.2);
+      const canvasAndCtx = CanvasFactory.create(viewport.width,
+                                                viewport.height);
+      const renderTask = page.render({
+        canvasContext: canvasAndCtx.context,
+        viewport,
+      });
+      await renderTask.promise;
+      const data = canvasAndCtx.canvas.toDataURL();
+      CanvasFactory.destroy(canvasAndCtx);
+      return data;
     }
 
     afterEach(function(done) {

test/unit/custom_spec.js

@@ -48,9 +48,7 @@ describe('custom canvas rendering', function() {
     }).then(function(data) {
       page = data;
       done();
-    }).catch(function (reason) {
-      done.fail(reason);
-    });
+    }).catch(done.fail);
   });
 
   afterAll(function(done) {
@@ -66,20 +64,16 @@ describe('custom canvas rendering', function() {
     var viewport = page.getViewport(1);
     var canvasAndCtx = CanvasFactory.create(viewport.width, viewport.height);
 
-    page.render({
+    const renderTask = page.render({
       canvasContext: canvasAndCtx.context,
       viewport,
-    }).then(function() {
-      var { r, g, b, a, } = getTopLeftPixel(canvasAndCtx.context);
-      CanvasFactory.destroy(canvasAndCtx);
-      expect(r).toEqual(255);
-      expect(g).toEqual(255);
-      expect(b).toEqual(255);
-      expect(a).toEqual(255);
-      done();
-    }).catch(function (reason) {
-      done(reason);
     });
+    renderTask.promise.then(function() {
+      expect(getTopLeftPixel(canvasAndCtx.context)).toEqual(
+        { r: 255, g: 255, b: 255, a: 255, });
+      CanvasFactory.destroy(canvasAndCtx);
+      done();
+    }).catch(done.fail);
   });
 
   it('renders to canvas with a custom background', function(done) {
@@ -89,20 +83,16 @@ describe('custom canvas rendering', function() {
     var viewport = page.getViewport(1);
     var canvasAndCtx = CanvasFactory.create(viewport.width, viewport.height);
 
-    page.render({
+    const renderTask = page.render({
       canvasContext: canvasAndCtx.context,
       viewport,
       background: 'rgba(255,0,0,1.0)',
-    }).then(function() {
-      var { r, g, b, a, } = getTopLeftPixel(canvasAndCtx.context);
-      CanvasFactory.destroy(canvasAndCtx);
-      expect(r).toEqual(255);
-      expect(g).toEqual(0);
-      expect(b).toEqual(0);
-      expect(a).toEqual(255);
-      done();
-    }).catch(function (reason) {
-      done(reason);
     });
+    renderTask.promise.then(function() {
+      expect(getTopLeftPixel(canvasAndCtx.context)).toEqual(
+        { r: 255, g: 0, b: 0, a: 255, });
+      CanvasFactory.destroy(canvasAndCtx);
+      done();
+    }).catch(done.fail);
   });
 });