Merge pull request #8324 from timvandermeij/es6-annotation-presentation-rendering

Convert the annotation layer builder, presentation mode and rendering queue to ES6 syntax

web/annotation_layer_builder.js

@@ -26,15 +26,11 @@ import { SimpleLinkService } from './pdf_link_service';
  * @property {DownloadManager} downloadManager
  */
 
-/**
+class AnnotationLayerBuilder {
- * @class
- */
-var AnnotationLayerBuilder = (function AnnotationLayerBuilderClosure() {
   /**
    * @param {AnnotationLayerBuilderOptions} options
-   * @constructs AnnotationLayerBuilder
    */
-  function AnnotationLayerBuilder(options) {
+  constructor(options) {
     this.pageDiv = options.pageDiv;
     this.pdfPage = options.pdfPage;
     this.renderInteractiveForms = options.renderInteractiveForms;
@@ -44,32 +40,23 @@ var AnnotationLayerBuilder = (function AnnotationLayerBuilderClosure() {
     this.div = null;
   }
 
-  AnnotationLayerBuilder.prototype =
-      /** @lends AnnotationLayerBuilder.prototype */ {
-
   /**
    * @param {PageViewport} viewport
    * @param {string} intent (default value is 'display')
    */
-    render: function AnnotationLayerBuilder_render(viewport, intent) {
+  render(viewport, intent = 'display') {
-      var self = this;
+    this.pdfPage.getAnnotations({ intent }).then((annotations) => {
       var parameters = {
-        intent: (intent === undefined ? 'display' : intent),
+        viewport: viewport.clone({ dontFlip: true }),
+        div: this.div,
+        annotations,
+        page: this.pdfPage,
+        renderInteractiveForms: this.renderInteractiveForms,
+        linkService: this.linkService,
+        downloadManager: this.downloadManager,
       };
 
-      this.pdfPage.getAnnotations(parameters).then(function (annotations) {
+      if (this.div) {
-        viewport = viewport.clone({ dontFlip: true });
-        parameters = {
-          viewport: viewport,
-          div: self.div,
-          annotations: annotations,
-          page: self.pdfPage,
-          renderInteractiveForms: self.renderInteractiveForms,
-          linkService: self.linkService,
-          downloadManager: self.downloadManager,
-        };
-
-        if (self.div) {
         // If an annotationLayer already exists, refresh its children's
         // transformation matrices.
         AnnotationLayer.update(parameters);
@@ -80,52 +67,47 @@ var AnnotationLayerBuilder = (function AnnotationLayerBuilderClosure() {
           return;
         }
 
-          self.div = document.createElement('div');
+        this.div = document.createElement('div');
-          self.div.className = 'annotationLayer';
+        this.div.className = 'annotationLayer';
-          self.pageDiv.appendChild(self.div);
+        this.pageDiv.appendChild(this.div);
-          parameters.div = self.div;
+        parameters.div = this.div;
 
         AnnotationLayer.render(parameters);
         if (typeof mozL10n !== 'undefined') {
-            mozL10n.translate(self.div);
+          mozL10n.translate(this.div);
         }
       }
     });
-    },
+  }
 
-    hide: function AnnotationLayerBuilder_hide() {
+  hide() {
     if (!this.div) {
       return;
     }
     this.div.setAttribute('hidden', 'true');
   }
-  };
+}
-
-  return AnnotationLayerBuilder;
-})();
 
 /**
- * @constructor
  * @implements IPDFAnnotationLayerFactory
  */
-function DefaultAnnotationLayerFactory() {}
+class DefaultAnnotationLayerFactory {
-DefaultAnnotationLayerFactory.prototype = {
   /**
    * @param {HTMLDivElement} pageDiv
    * @param {PDFPage} pdfPage
    * @param {boolean} renderInteractiveForms
    * @returns {AnnotationLayerBuilder}
    */
-  createAnnotationLayerBuilder: function (pageDiv, pdfPage,
+  createAnnotationLayerBuilder(pageDiv, pdfPage,
-                                          renderInteractiveForms) {
+                               renderInteractiveForms = false) {
     return new AnnotationLayerBuilder({
-      pageDiv: pageDiv,
+      pageDiv,
-      pdfPage: pdfPage,
+      pdfPage,
-      renderInteractiveForms: renderInteractiveForms,
+      renderInteractiveForms,
       linkService: new SimpleLinkService(),
     });
   }
-};
+}
 
 export {
   AnnotationLayerBuilder,

web/interfaces.js

@@ -108,14 +108,13 @@ IPDFTextLayerFactory.prototype = {
 /**
  * @interface
  */
-function IPDFAnnotationLayerFactory() {}
+class IPDFAnnotationLayerFactory { // eslint-disable-line no-unused-vars
-IPDFAnnotationLayerFactory.prototype = {
   /**
    * @param {HTMLDivElement} pageDiv
    * @param {PDFPage} pdfPage
    * @param {boolean} renderInteractiveForms
    * @returns {AnnotationLayerBuilder}
    */
-  createAnnotationLayerBuilder: function (pageDiv, pdfPage,
+  createAnnotationLayerBuilder(pageDiv, pdfPage,
-                                          renderInteractiveForms) {}
+                               renderInteractiveForms = false) {}
-};
+}

web/pdf_presentation_mode.js

@@ -15,10 +15,19 @@
 
 import { normalizeWheelEventDelta } from './ui_utils';
 
-var DELAY_BEFORE_RESETTING_SWITCH_IN_PROGRESS = 1500; // in ms
+const DELAY_BEFORE_RESETTING_SWITCH_IN_PROGRESS = 1500; // in ms
-var DELAY_BEFORE_HIDING_CONTROLS = 3000; // in ms
+const DELAY_BEFORE_HIDING_CONTROLS = 3000; // in ms
-var ACTIVE_SELECTOR = 'pdfPresentationMode';
+const ACTIVE_SELECTOR = 'pdfPresentationMode';
-var CONTROLS_SELECTOR = 'pdfPresentationModeControls';
+const CONTROLS_SELECTOR = 'pdfPresentationModeControls';
+const MOUSE_SCROLL_COOLDOWN_TIME = 50; // in ms
+const PAGE_SWITCH_THRESHOLD = 0.1;
+
+// Number of CSS pixels for a movement to count as a swipe.
+const SWIPE_MIN_DISTANCE_THRESHOLD = 50;
+
+// Swipe angle deviation from the x or y axis before it is not
+// considered a swipe in that direction any more.
+const SWIPE_ANGLE_THRESHOLD = Math.PI / 6;
 
 /**
  * @typedef {Object} PDFPresentationModeOptions
@@ -30,15 +39,11 @@ var CONTROLS_SELECTOR = 'pdfPresentationModeControls';
  *   to the context menu in Presentation Mode.
  */
 
-/**
+class PDFPresentationMode {
- * @class
- */
-var PDFPresentationMode = (function PDFPresentationModeClosure() {
   /**
-   * @constructs PDFPresentationMode
    * @param {PDFPresentationModeOptions} options
    */
-  function PDFPresentationMode(options) {
+  constructor(options) {
     this.container = options.container;
     this.viewer = options.viewer || options.container.firstElementChild;
     this.pdfViewer = options.pdfViewer;
@@ -53,37 +58,31 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     this.touchSwipeState = null;
 
     if (contextMenuItems) {
-      contextMenuItems.contextFirstPage.addEventListener('click',
+      contextMenuItems.contextFirstPage.addEventListener('click', () => {
-          function PDFPresentationMode_contextFirstPageClick(e) {
         this.contextMenuOpen = false;
         this.eventBus.dispatch('firstpage');
-      }.bind(this));
+      });
-      contextMenuItems.contextLastPage.addEventListener('click',
+      contextMenuItems.contextLastPage.addEventListener('click', () => {
-          function PDFPresentationMode_contextLastPageClick(e) {
         this.contextMenuOpen = false;
         this.eventBus.dispatch('lastpage');
-      }.bind(this));
+      });
-      contextMenuItems.contextPageRotateCw.addEventListener('click',
+      contextMenuItems.contextPageRotateCw.addEventListener('click', () => {
-          function PDFPresentationMode_contextPageRotateCwClick(e) {
         this.contextMenuOpen = false;
         this.eventBus.dispatch('rotatecw');
-      }.bind(this));
+      });
-      contextMenuItems.contextPageRotateCcw.addEventListener('click',
+      contextMenuItems.contextPageRotateCcw.addEventListener('click', () => {
-          function PDFPresentationMode_contextPageRotateCcwClick(e) {
         this.contextMenuOpen = false;
         this.eventBus.dispatch('rotateccw');
-      }.bind(this));
+      });
     }
   }
 
-  PDFPresentationMode.prototype = {
   /**
    * Request the browser to enter fullscreen mode.
    * @returns {boolean} Indicating if the request was successful.
    */
-    request: function PDFPresentationMode_request() {
+  request() {
-      if (this.switchInProgress || this.active ||
+    if (this.switchInProgress || this.active || !this.viewer.hasChildNodes()) {
-          !this.viewer.hasChildNodes()) {
       return false;
     }
     this._addFullscreenChangeListeners();
@@ -108,12 +107,12 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     };
 
     return true;
-    },
+  }
 
   /**
    * @private
    */
-    _mouseWheel: function PDFPresentationMode_mouseWheel(evt) {
+  _mouseWheel(evt) {
     if (!this.active) {
       return;
     }
@@ -121,10 +120,6 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     evt.preventDefault();
 
     var delta = normalizeWheelEventDelta(evt);
-
-      var MOUSE_SCROLL_COOLDOWN_TIME = 50;
-      var PAGE_SWITCH_THRESHOLD = 0.1;
-
     var currentTime = (new Date()).getTime();
     var storedTime = this.mouseScrollTimeStamp;
 
@@ -149,19 +144,17 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
         this.mouseScrollTimeStamp = currentTime;
       }
     }
-    },
+  }
 
   get isFullscreen() {
-      return !!(document.fullscreenElement ||
+    return !!(document.fullscreenElement || document.mozFullScreen ||
-                document.mozFullScreen ||
+              document.webkitIsFullScreen || document.msFullscreenElement);
-                document.webkitIsFullScreen ||
+  }
-                document.msFullscreenElement);
-    },
 
   /**
    * @private
    */
-    _goToPreviousPage: function PDFPresentationMode_goToPreviousPage() {
+  _goToPreviousPage() {
     var page = this.pdfViewer.currentPageNumber;
     // If we're at the first page, we don't need to do anything.
     if (page <= 1) {
@@ -169,12 +162,12 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     }
     this.pdfViewer.currentPageNumber = (page - 1);
     return true;
-    },
+  }
 
   /**
    * @private
    */
-    _goToNextPage: function PDFPresentationMode_goToNextPage() {
+  _goToNextPage() {
     var page = this.pdfViewer.currentPageNumber;
     // If we're at the last page, we don't need to do anything.
     if (page >= this.pdfViewer.pagesCount) {
@@ -182,18 +175,18 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     }
     this.pdfViewer.currentPageNumber = (page + 1);
     return true;
-    },
+  }
 
   /**
    * @private
    */
-    _notifyStateChange: function PDFPresentationMode_notifyStateChange() {
+  _notifyStateChange() {
     this.eventBus.dispatch('presentationmodechanged', {
       source: this,
       active: this.active,
-        switchInProgress: !!this.switchInProgress
+      switchInProgress: !!this.switchInProgress,
     });
-    },
+  }
 
   /**
    * Used to initialize a timeout when requesting Presentation Mode,
@@ -201,34 +194,34 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
    * This timeout is used to prevent the current page from being scrolled
    * partially, or completely, out of view when entering Presentation Mode.
    * NOTE: This issue seems limited to certain zoom levels (e.g. page-width).
+   *
    * @private
    */
-    _setSwitchInProgress: function PDFPresentationMode_setSwitchInProgress() {
+  _setSwitchInProgress() {
     if (this.switchInProgress) {
       clearTimeout(this.switchInProgress);
     }
-      this.switchInProgress = setTimeout(function switchInProgressTimeout() {
+    this.switchInProgress = setTimeout(() => {
       this._removeFullscreenChangeListeners();
       delete this.switchInProgress;
       this._notifyStateChange();
-      }.bind(this), DELAY_BEFORE_RESETTING_SWITCH_IN_PROGRESS);
+    }, DELAY_BEFORE_RESETTING_SWITCH_IN_PROGRESS);
-    },
+  }
 
   /**
    * @private
    */
-    _resetSwitchInProgress:
+  _resetSwitchInProgress() {
-        function PDFPresentationMode_resetSwitchInProgress() {
     if (this.switchInProgress) {
       clearTimeout(this.switchInProgress);
       delete this.switchInProgress;
     }
-    },
+  }
 
   /**
    * @private
    */
-    _enter: function PDFPresentationMode_enter() {
+  _enter() {
     this.active = true;
     this._resetSwitchInProgress();
     this._notifyStateChange();
@@ -236,10 +229,10 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
 
     // Ensure that the correct page is scrolled into view when entering
     // Presentation Mode, by waiting until fullscreen mode in enabled.
-      setTimeout(function enterPresentationModeTimeout() {
+    setTimeout(() => {
       this.pdfViewer.currentPageNumber = this.args.page;
       this.pdfViewer.currentScaleValue = 'page-fit';
-      }.bind(this), 0);
+    }, 0);
 
     this._addWindowListeners();
     this._showControls();
@@ -250,18 +243,18 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     // for the user to deselect text that is selected (e.g. with "Select all")
     // when entering Presentation Mode, hence we remove any active selection.
     window.getSelection().removeAllRanges();
-    },
+  }
 
   /**
    * @private
    */
-    _exit: function PDFPresentationMode_exit() {
+  _exit() {
     var page = this.pdfViewer.currentPageNumber;
     this.container.classList.remove(ACTIVE_SELECTOR);
 
     // Ensure that the correct page is scrolled into view when exiting
     // Presentation Mode, by waiting until fullscreen mode is disabled.
-      setTimeout(function exitPresentationModeTimeout() {
+    setTimeout(() => {
       this.active = false;
       this._removeFullscreenChangeListeners();
       this._notifyStateChange();
@@ -269,27 +262,27 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
       this.pdfViewer.currentScaleValue = this.args.previousScale;
       this.pdfViewer.currentPageNumber = page;
       this.args = null;
-      }.bind(this), 0);
+    }, 0);
 
     this._removeWindowListeners();
     this._hideControls();
     this._resetMouseScrollState();
     this.container.removeAttribute('contextmenu');
     this.contextMenuOpen = false;
-    },
+  }
 
   /**
    * @private
    */
-    _mouseDown: function PDFPresentationMode_mouseDown(evt) {
+  _mouseDown(evt) {
     if (this.contextMenuOpen) {
       this.contextMenuOpen = false;
       evt.preventDefault();
       return;
     }
     if (evt.button === 0) {
-        // Enable clicking of links in presentation mode. Please note:
+      // Enable clicking of links in presentation mode. Note: only links
-        // Only links pointing to destinations in the current PDF document work.
+      // pointing to destinations in the current PDF document work.
       var isInternalLink = (evt.target.href &&
                             evt.target.classList.contains('internalLink'));
       if (!isInternalLink) {
@@ -298,78 +291,72 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
         this.pdfViewer.currentPageNumber += (evt.shiftKey ? -1 : 1);
       }
     }
-    },
+  }
 
   /**
    * @private
    */
-    _contextMenu: function PDFPresentationMode_contextMenu() {
+  _contextMenu() {
     this.contextMenuOpen = true;
-    },
+  }
 
   /**
    * @private
    */
-    _showControls: function PDFPresentationMode_showControls() {
+  _showControls() {
     if (this.controlsTimeout) {
       clearTimeout(this.controlsTimeout);
     } else {
       this.container.classList.add(CONTROLS_SELECTOR);
     }
-      this.controlsTimeout = setTimeout(function showControlsTimeout() {
+    this.controlsTimeout = setTimeout(() => {
       this.container.classList.remove(CONTROLS_SELECTOR);
       delete this.controlsTimeout;
-      }.bind(this), DELAY_BEFORE_HIDING_CONTROLS);
+    }, DELAY_BEFORE_HIDING_CONTROLS);
-    },
+  }
 
   /**
    * @private
    */
-    _hideControls: function PDFPresentationMode_hideControls() {
+  _hideControls() {
     if (!this.controlsTimeout) {
       return;
     }
     clearTimeout(this.controlsTimeout);
     this.container.classList.remove(CONTROLS_SELECTOR);
     delete this.controlsTimeout;
-    },
+  }
 
   /**
    * Resets the properties used for tracking mouse scrolling events.
+   *
    * @private
    */
-    _resetMouseScrollState:
+  _resetMouseScrollState() {
-        function PDFPresentationMode_resetMouseScrollState() {
     this.mouseScrollTimeStamp = 0;
     this.mouseScrollDelta = 0;
-    },
+  }
 
   /**
    * @private
    */
-    _touchSwipe: function PDFPresentationMode_touchSwipe(evt) {
+  _touchSwipe(evt) {
     if (!this.active) {
       return;
     }
-
-      // Must move at least these many CSS pixels for it to count as a swipe
-      var SWIPE_MIN_DISTANCE_THRESHOLD = 50;
-      // The swipe angle is allowed to deviate from the x or y axis by this much
-      // before it is not considered a swipe in that direction any more.
-      var SWIPE_ANGLE_THRESHOLD = Math.PI / 6;
-
     if (evt.touches.length > 1) {
-        // Multiple touch points detected, cancel the swipe.
+      // Multiple touch points detected; cancel the swipe.
       this.touchSwipeState = null;
       return;
     }
+
     switch (evt.type) {
       case 'touchstart':
         this.touchSwipeState = {
           startX: evt.touches[0].pageX,
           startY: evt.touches[0].pageY,
           endX: evt.touches[0].pageX,
-            endY: evt.touches[0].pageY
+          endY: evt.touches[0].pageY,
         };
         break;
       case 'touchmove':
@@ -378,9 +365,8 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
         }
         this.touchSwipeState.endX = evt.touches[0].pageX;
         this.touchSwipeState.endY = evt.touches[0].pageY;
-          // Do a preventDefault to avoid the swipe from triggering browser
+        // Avoid the swipe from triggering browser gestures (Chrome in
-          // gestures (Chrome in particular has some sort of swipe gesture in
+        // particular has some sort of swipe gesture in fullscreen mode).
-          // fullscreen mode).
         evt.preventDefault();
         break;
       case 'touchend':
@@ -394,11 +380,11 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
         if (Math.abs(dx) > SWIPE_MIN_DISTANCE_THRESHOLD &&
             (absAngle <= SWIPE_ANGLE_THRESHOLD ||
              absAngle >= (Math.PI - SWIPE_ANGLE_THRESHOLD))) {
-            // horizontal swipe
+          // Horizontal swipe.
           delta = dx;
         } else if (Math.abs(dy) > SWIPE_MIN_DISTANCE_THRESHOLD &&
             Math.abs(absAngle - (Math.PI / 2)) <= SWIPE_ANGLE_THRESHOLD) {
-            // vertical swipe
+          // Vertical swipe.
           delta = dy;
         }
         if (delta > 0) {
@@ -408,12 +394,12 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
         }
         break;
     }
-    },
+  }
 
   /**
    * @private
    */
-    _addWindowListeners: function PDFPresentationMode_addWindowListeners() {
+  _addWindowListeners() {
     this.showControlsBind = this._showControls.bind(this);
     this.mouseDownBind = this._mouseDown.bind(this);
     this.mouseWheelBind = this._mouseWheel.bind(this);
@@ -429,13 +415,12 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     window.addEventListener('touchstart', this.touchSwipeBind);
     window.addEventListener('touchmove', this.touchSwipeBind);
     window.addEventListener('touchend', this.touchSwipeBind);
-    },
+  }
 
   /**
    * @private
    */
-    _removeWindowListeners:
+  _removeWindowListeners() {
-        function PDFPresentationMode_removeWindowListeners() {
     window.removeEventListener('mousemove', this.showControlsBind);
     window.removeEventListener('mousedown', this.mouseDownBind);
     window.removeEventListener('wheel', this.mouseWheelBind);
@@ -451,24 +436,23 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
     delete this.resetMouseScrollStateBind;
     delete this.contextMenuBind;
     delete this.touchSwipeBind;
-    },
+  }
 
   /**
    * @private
    */
-    _fullscreenChange: function PDFPresentationMode_fullscreenChange() {
+  _fullscreenChange() {
     if (this.isFullscreen) {
       this._enter();
     } else {
       this._exit();
     }
-    },
+  }
 
   /**
    * @private
    */
-    _addFullscreenChangeListeners:
+  _addFullscreenChangeListeners() {
-        function PDFPresentationMode_addFullscreenChangeListeners() {
     this.fullscreenChangeBind = this._fullscreenChange.bind(this);
 
     window.addEventListener('fullscreenchange', this.fullscreenChangeBind);
@@ -480,13 +464,12 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
       window.addEventListener('MSFullscreenChange',
                               this.fullscreenChangeBind);
     }
-    },
+  }
 
   /**
    * @private
    */
-    _removeFullscreenChangeListeners:
+  _removeFullscreenChangeListeners() {
-        function PDFPresentationMode_removeFullscreenChangeListeners() {
     window.removeEventListener('fullscreenchange', this.fullscreenChangeBind);
     window.removeEventListener('mozfullscreenchange',
                                this.fullscreenChangeBind);
@@ -500,10 +483,7 @@ var PDFPresentationMode = (function PDFPresentationModeClosure() {
 
     delete this.fullscreenChangeBind;
   }
-  };
+}
-
-  return PDFPresentationMode;
-})();
 
 export {
   PDFPresentationMode,

web/pdf_rendering_queue.js

@@ -13,60 +13,55 @@
  * limitations under the License.
  */
 
-var CLEANUP_TIMEOUT = 30000;
+const CLEANUP_TIMEOUT = 30000;
 
-var RenderingStates = {
+const RenderingStates = {
   INITIAL: 0,
   RUNNING: 1,
   PAUSED: 2,
-  FINISHED: 3
+  FINISHED: 3,
 };
 
 /**
  * Controls rendering of the views for pages and thumbnails.
- * @class
  */
-var PDFRenderingQueue = (function PDFRenderingQueueClosure() {
+class PDFRenderingQueue {
-  /**
+  constructor() {
-   * @constructs
-   */
-  function PDFRenderingQueue() {
     this.pdfViewer = null;
     this.pdfThumbnailViewer = null;
     this.onIdle = null;
-
     this.highestPriorityPage = null;
     this.idleTimeout = null;
     this.printing = false;
     this.isThumbnailViewEnabled = false;
   }
 
-  PDFRenderingQueue.prototype = /** @lends PDFRenderingQueue.prototype */ {
   /**
    * @param {PDFViewer} pdfViewer
    */
-    setViewer: function PDFRenderingQueue_setViewer(pdfViewer) {
+  setViewer(pdfViewer) {
     this.pdfViewer = pdfViewer;
-    },
+  }
 
   /**
    * @param {PDFThumbnailViewer} pdfThumbnailViewer
    */
-    setThumbnailViewer:
+  setThumbnailViewer(pdfThumbnailViewer) {
-        function PDFRenderingQueue_setThumbnailViewer(pdfThumbnailViewer) {
     this.pdfThumbnailViewer = pdfThumbnailViewer;
-    },
+  }
 
   /**
    * @param {IRenderableView} view
    * @returns {boolean}
    */
-    isHighestPriority: function PDFRenderingQueue_isHighestPriority(view) {
+  isHighestPriority(view) {
     return this.highestPriorityPage === view.renderingId;
-    },
+  }
 
-    renderHighestPriority: function
+  /**
-        PDFRenderingQueue_renderHighestPriority(currentlyVisiblePages) {
+   * @param {Object} currentlyVisiblePages
+   */
+  renderHighestPriority(currentlyVisiblePages) {
     if (this.idleTimeout) {
       clearTimeout(this.idleTimeout);
       this.idleTimeout = null;
@@ -76,7 +71,7 @@ var PDFRenderingQueue = (function PDFRenderingQueueClosure() {
     if (this.pdfViewer.forceRendering(currentlyVisiblePages)) {
       return;
     }
-      // No pages needed rendering so check thumbnails.
+    // No pages needed rendering, so check thumbnails.
     if (this.pdfThumbnailViewer && this.isThumbnailViewEnabled) {
       if (this.pdfThumbnailViewer.forceRendering()) {
         return;
@@ -91,16 +86,23 @@ var PDFRenderingQueue = (function PDFRenderingQueueClosure() {
     if (this.onIdle) {
       this.idleTimeout = setTimeout(this.onIdle.bind(this), CLEANUP_TIMEOUT);
     }
-    },
+  }
 
-    getHighestPriority: function
+  /**
-        PDFRenderingQueue_getHighestPriority(visible, views, scrolledDown) {
+   * @param {Object} visible
-      // The state has changed figure out which page has the highest priority to
+   * @param {Array} views
-      // render next (if any).
+   * @param {boolean} scrolledDown
-      // Priority:
+   */
-      // 1 visible pages
+  getHighestPriority(visible, views, scrolledDown) {
-      // 2 if last scrolled down page after the visible pages
+    /**
-      // 2 if last scrolled up page before the visible pages
+     * The state has changed. Figure out which page has the highest priority to
+     * render next (if any).
+     *
+     * Priority:
+     * 1. visible pages
+     * 2. if last scrolled down, the page after the visible pages, or
+     *    if last scrolled up, the page before the visible pages
+     */
     var visibleViews = visible.views;
 
     var numVisible = visibleViews.length;
@@ -114,12 +116,11 @@ var PDFRenderingQueue = (function PDFRenderingQueueClosure() {
       }
     }
 
-      // All the visible views have rendered, try to render next/previous pages.
+    // All the visible views have rendered; try to render next/previous pages.
     if (scrolledDown) {
       var nextPageIndex = visible.last.id;
-        // ID's start at 1 so no need to add 1.
+      // IDs start at 1, so no need to add 1.
-        if (views[nextPageIndex] &&
+      if (views[nextPageIndex] && !this.isViewFinished(views[nextPageIndex])) {
-            !this.isViewFinished(views[nextPageIndex])) {
         return views[nextPageIndex];
       }
     } else {
@@ -131,25 +132,25 @@ var PDFRenderingQueue = (function PDFRenderingQueueClosure() {
     }
     // Everything that needs to be rendered has been.
     return null;
-    },
+  }
 
   /**
    * @param {IRenderableView} view
    * @returns {boolean}
    */
-    isViewFinished: function PDFRenderingQueue_isViewFinished(view) {
+  isViewFinished(view) {
     return view.renderingState === RenderingStates.FINISHED;
-    },
+  }
 
   /**
    * Render a page or thumbnail view. This calls the appropriate function
    * based on the views state. If the view is already rendered it will return
-     * false.
+   * `false`.
+   *
    * @param {IRenderableView} view
    */
-    renderView: function PDFRenderingQueue_renderView(view) {
+  renderView(view) {
-      var state = view.renderingState;
+    switch (view.renderingState) {
-      switch (state) {
       case RenderingStates.FINISHED:
         return false;
       case RenderingStates.PAUSED:
@@ -161,18 +162,15 @@ var PDFRenderingQueue = (function PDFRenderingQueueClosure() {
         break;
       case RenderingStates.INITIAL:
         this.highestPriorityPage = view.renderingId;
-          var continueRendering = function () {
+        var continueRendering = () => {
           this.renderHighestPriority();
-          }.bind(this);
+        };
         view.draw().then(continueRendering, continueRendering);
         break;
     }
     return true;
-    },
+  }
-  };
+}
-
-  return PDFRenderingQueue;
-})();
 
 export {
   RenderingStates,