Merge pull request #8636 from Snuffleupagus/es6-PDFViewer-class

Convert `PDFViewer` to an ES6 class

web/app.js

@@ -977,7 +977,7 @@ let PDFViewerApplication = {
             !initialParams.hash) {
           return;
         }
-        if (this.hasEqualPageSizes) {
+        if (pdfViewer.hasEqualPageSizes) {
           return;
         }
         this.initialDestination = initialParams.destination;
@@ -1217,19 +1217,6 @@ let PDFViewerApplication = {
     }
   },
 
-  // Whether all pages of the PDF have the same width and height.
-  get hasEqualPageSizes() {
-    let firstPage = this.pdfViewer.getPageView(0);
-    for (let i = 1, ii = this.pagesCount; i < ii; ++i) {
-      let pageView = this.pdfViewer.getPageView(i);
-      if (pageView.width !== firstPage.width ||
-          pageView.height !== firstPage.height) {
-        return false;
-      }
-    }
-    return true;
-  },
-
   afterPrint: function pdfViewSetupAfterPrint() {
     if (this.printService) {
       this.printService.destroy();

web/pdf_viewer.js

@@ -26,14 +26,14 @@ import { PDFPageView } from './pdf_page_view';
 import { SimpleLinkService } from './pdf_link_service';
 import { TextLayerBuilder } from './text_layer_builder';
 
-var PresentationModeState = {
+const PresentationModeState = {
   UNKNOWN: 0,
   NORMAL: 1,
   CHANGING: 2,
   FULLSCREEN: 3,
 };
 
-var DEFAULT_CACHE_SIZE = 10;
+const DEFAULT_CACHE_SIZE = 10;
 
 /**
  * @typedef {Object} PDFViewerOptions
@@ -58,16 +58,10 @@ var DEFAULT_CACHE_SIZE = 10;
  * @property {IL10n} l10n - Localization service.
  */
 
-/**
- * Simple viewer control to display PDF content/pages.
- * @class
- * @implements {IRenderableView}
- */
-var PDFViewer = (function pdfViewer() {
 function PDFPageViewBuffer(size) {
-    var data = [];
+  let data = [];
   this.push = function cachePush(view) {
-      var i = data.indexOf(view);
+    let i = data.indexOf(view);
     if (i >= 0) {
       data.splice(i, 1);
     }
@@ -101,10 +95,14 @@ var PDFViewer = (function pdfViewer() {
 }
 
 /**
-   * @constructs PDFViewer
+ * Simple viewer control to display PDF content/pages.
+ * @implements {IRenderableView}
+ */
+class PDFViewer {
+  /**
    * @param {PDFViewerOptions} options
    */
-  function PDFViewer(options) {
+  constructor(options) {
     this.container = options.container;
     this.viewer = options.viewer || options.container.firstElementChild;
     this.eventBus = options.eventBus || getGlobalEventBus();
@@ -135,28 +133,27 @@ var PDFViewer = (function pdfViewer() {
     }
   }
 
-  PDFViewer.prototype = /** @lends PDFViewer.prototype */{
   get pagesCount() {
     return this._pages.length;
-    },
+  }
 
   getPageView(index) {
     return this._pages[index];
-    },
+  }
 
   /**
    * @returns {boolean} true if all {PDFPageView} objects are initialized.
    */
   get pageViewsReady() {
     return this._pageViewsReady;
-    },
+  }
 
   /**
    * @returns {number}
    */
   get currentPageNumber() {
     return this._currentPageNumber;
-    },
+  }
 
   /**
    * @param {number} val - The page number.
@@ -170,13 +167,12 @@ var PDFViewer = (function pdfViewer() {
     }
     // The intent can be to just reset a scroll position and/or scale.
     this._setCurrentPageNumber(val, /* resetCurrentPageView = */ true);
-    },
+  }
 
   /**
    * @private
    */
-    _setCurrentPageNumber:
-        function PDFViewer_setCurrentPageNumber(val, resetCurrentPageView) {
+  _setCurrentPageNumber(val, resetCurrentPageView = false) {
     if (this._currentPageNumber === val) {
       if (resetCurrentPageView) {
         this._resetCurrentPageView();
@@ -185,12 +181,12 @@ var PDFViewer = (function pdfViewer() {
     }
 
     if (!(0 < val && val <= this.pagesCount)) {
-        console.error('PDFViewer_setCurrentPageNumber: "' + val +
-                      '" is out of bounds.');
+      console.error(
+        `PDFViewer._setCurrentPageNumber: "${val}" is out of bounds.`);
       return;
     }
 
-      var arg = {
+    let arg = {
       source: this,
       pageNumber: val,
       pageLabel: this._pageLabels && this._pageLabels[val - 1],
@@ -202,7 +198,7 @@ var PDFViewer = (function pdfViewer() {
     if (resetCurrentPageView) {
       this._resetCurrentPageView();
     }
-    },
+  }
 
   /**
    * @returns {string|null} Returns the current page label,
@@ -210,7 +206,7 @@ var PDFViewer = (function pdfViewer() {
    */
   get currentPageLabel() {
     return this._pageLabels && this._pageLabels[this._currentPageNumber - 1];
-    },
+  }
 
   /**
    * @param {string} val - The page label.
@@ -224,7 +220,7 @@ var PDFViewer = (function pdfViewer() {
       }
     }
     this.currentPageNumber = pageNumber;
-    },
+  }
 
   /**
    * @returns {number}
@@ -232,7 +228,7 @@ var PDFViewer = (function pdfViewer() {
   get currentScale() {
     return this._currentScale !== UNKNOWN_SCALE ? this._currentScale :
                                                   DEFAULT_SCALE;
-    },
+  }
 
   /**
    * @param {number} val - Scale of the pages in percents.
@@ -245,14 +241,14 @@ var PDFViewer = (function pdfViewer() {
       return;
     }
     this._setScale(val, false);
-    },
+  }
 
   /**
    * @returns {string}
    */
   get currentScaleValue() {
     return this._currentScaleValue;
-    },
+  }
 
   /**
    * @param val - The scale of the pages (in percent or predefined value).
@@ -262,14 +258,14 @@ var PDFViewer = (function pdfViewer() {
       return;
     }
     this._setScale(val, false);
-    },
+  }
 
   /**
    * @returns {number}
    */
   get pagesRotation() {
     return this._pagesRotation;
-    },
+  }
 
   /**
    * @param {number} rotation - The rotation of the pages (0, 90, 180, 270).
@@ -293,7 +289,7 @@ var PDFViewer = (function pdfViewer() {
     if (this.defaultRenderingQueue) {
       this.update();
     }
-    },
+  }
 
   /**
    * @param pdfDocument {PDFDocument}
@@ -308,9 +304,9 @@ var PDFViewer = (function pdfViewer() {
     if (!pdfDocument) {
       return;
     }
-      var pagesCount = pdfDocument.numPages;
+    let pagesCount = pdfDocument.numPages;
 
-      var pagesCapability = createPromiseCapability();
+    let pagesCapability = createPromiseCapability();
     this.pagesPromise = pagesCapability.promise;
 
     pagesCapability.promise.then(() => {
@@ -321,11 +317,11 @@ var PDFViewer = (function pdfViewer() {
       });
     });
 
-      var isOnePageRenderedResolved = false;
-      var onePageRenderedCapability = createPromiseCapability();
+    let isOnePageRenderedResolved = false;
+    let onePageRenderedCapability = createPromiseCapability();
     this.onePageRendered = onePageRenderedCapability.promise;
 
-      var bindOnAfterAndBeforeDraw = (pageView) => {
+    let bindOnAfterAndBeforeDraw = (pageView) => {
       pageView.onBeforeDraw = () => {
         // Add the page to the buffer at the start of drawing. That way it can
         // be evicted from the buffer and destroyed even if we pause its
@@ -340,20 +336,20 @@ var PDFViewer = (function pdfViewer() {
       };
     };
 
-      var firstPagePromise = pdfDocument.getPage(1);
+    let firstPagePromise = pdfDocument.getPage(1);
     this.firstPagePromise = firstPagePromise;
 
     // Fetch a single page so we can get a viewport that will be the default
     // viewport for all pages
     return firstPagePromise.then((pdfPage) => {
-        var scale = this.currentScale;
-        var viewport = pdfPage.getViewport(scale * CSS_UNITS);
-        for (var pageNum = 1; pageNum <= pagesCount; ++pageNum) {
-          var textLayerFactory = null;
+      let scale = this.currentScale;
+      let viewport = pdfPage.getViewport(scale * CSS_UNITS);
+      for (let pageNum = 1; pageNum <= pagesCount; ++pageNum) {
+        let textLayerFactory = null;
         if (!PDFJS.disableTextLayer) {
           textLayerFactory = this;
         }
-          var pageView = new PDFPageView({
+        let pageView = new PDFPageView({
           container: this.viewer,
           eventBus: this.eventBus,
           id: pageNum,
@@ -380,10 +376,10 @@ var PDFViewer = (function pdfViewer() {
           pagesCapability.resolve();
           return;
         }
-          var getPagesLeft = pagesCount;
+        let getPagesLeft = pagesCount;
         for (let pageNum = 1; pageNum <= pagesCount; ++pageNum) {
           pdfDocument.getPage(pageNum).then((pdfPage) => {
-              var pageView = this._pages[pageNum - 1];
+            let pageView = this._pages[pageNum - 1];
             if (!pageView.pdfPage) {
               pageView.setPdfPage(pdfPage);
             }
@@ -405,12 +401,12 @@ var PDFViewer = (function pdfViewer() {
         this.findController.resolveFirstPage();
       }
     });
-    },
+  }
 
   /**
    * @param {Array|null} labels
    */
-    setPageLabels: function PDFViewer_setPageLabels(labels) {
+  setPageLabels(labels) {
     if (!this.pdfDocument) {
       return;
     }
@@ -419,17 +415,17 @@ var PDFViewer = (function pdfViewer() {
     } else if (!(labels instanceof Array &&
                  this.pdfDocument.numPages === labels.length)) {
       this._pageLabels = null;
-        console.error('PDFViewer_setPageLabels: Invalid page labels.');
+      console.error('PDFViewer.setPageLabels: Invalid page labels.');
     } else {
       this._pageLabels = labels;
     }
     // Update all the `PDFPageView` instances.
-      for (var i = 0, ii = this._pages.length; i < ii; i++) {
-        var pageView = this._pages[i];
-        var label = this._pageLabels && this._pageLabels[i];
+    for (let i = 0, ii = this._pages.length; i < ii; i++) {
+      let pageView = this._pages[i];
+      let label = this._pageLabels && this._pageLabels[i];
       pageView.setPageLabel(label);
     }
-    },
+  }
 
   _resetView() {
     this._pages = [];
@@ -445,28 +441,26 @@ var PDFViewer = (function pdfViewer() {
 
     // Remove the pages from the DOM.
     this.viewer.textContent = '';
-    },
+  }
 
   _scrollUpdate() {
     if (this.pagesCount === 0) {
       return;
     }
     this.update();
-    },
+  }
 
-    _setScaleDispatchEvent: function pdfViewer_setScaleDispatchEvent(
-        newScale, newValue, preset) {
-      var arg = {
+  _setScaleDispatchEvent(newScale, newValue, preset = false) {
+    let arg = {
       source: this,
       scale: newScale,
       presetValue: preset ? newValue : undefined,
     };
     this.eventBus.dispatch('scalechanging', arg);
     this.eventBus.dispatch('scalechange', arg);
-    },
+  }
 
-    _setScaleUpdatePages: function pdfViewer_setScaleUpdatePages(
-        newScale, newValue, noScroll, preset) {
+  _setScaleUpdatePages(newScale, newValue, noScroll = false, preset = false) {
     this._currentScaleValue = newValue.toString();
 
     if (isSameScale(this._currentScale, newScale)) {
@@ -476,13 +470,13 @@ var PDFViewer = (function pdfViewer() {
       return;
     }
 
-      for (var i = 0, ii = this._pages.length; i < ii; i++) {
+    for (let i = 0, ii = this._pages.length; i < ii; i++) {
       this._pages[i].update(newScale);
     }
     this._currentScale = newScale;
 
     if (!noScroll) {
-        var page = this._currentPageNumber, dest;
+      let page = this._currentPageNumber, dest;
       if (this._location && !PDFJS.ignoreCurrentPositionOnZoom &&
           !(this.isInPresentationMode || this.isChangingPresentationMode)) {
         page = this._location.pageNumber;
@@ -501,25 +495,25 @@ var PDFViewer = (function pdfViewer() {
     if (this.defaultRenderingQueue) {
       this.update();
     }
-    },
+  }
 
-    _setScale: function PDFViewer_setScale(value, noScroll) {
-      var scale = parseFloat(value);
+  _setScale(value, noScroll = false) {
+    let scale = parseFloat(value);
 
     if (scale > 0) {
-        this._setScaleUpdatePages(scale, value, noScroll, false);
+      this._setScaleUpdatePages(scale, value, noScroll, /* preset = */ false);
     } else {
-        var currentPage = this._pages[this._currentPageNumber - 1];
+      let currentPage = this._pages[this._currentPageNumber - 1];
       if (!currentPage) {
         return;
       }
-        var hPadding = (this.isInPresentationMode || this.removePageBorders) ?
+      let hPadding = (this.isInPresentationMode || this.removePageBorders) ?
         0 : SCROLLBAR_PADDING;
-        var vPadding = (this.isInPresentationMode || this.removePageBorders) ?
+      let vPadding = (this.isInPresentationMode || this.removePageBorders) ?
         0 : VERTICAL_PADDING;
-        var pageWidthScale = (this.container.clientWidth - hPadding) /
+      let pageWidthScale = (this.container.clientWidth - hPadding) /
                            currentPage.width * currentPage.scale;
-        var pageHeightScale = (this.container.clientHeight - vPadding) /
+      let pageHeightScale = (this.container.clientHeight - vPadding) /
                             currentPage.height * currentPage.scale;
       switch (value) {
         case 'page-actual':
@@ -535,21 +529,21 @@ var PDFViewer = (function pdfViewer() {
           scale = Math.min(pageWidthScale, pageHeightScale);
           break;
         case 'auto':
-            var isLandscape = (currentPage.width > currentPage.height);
+          let isLandscape = (currentPage.width > currentPage.height);
           // For pages in landscape mode, fit the page height to the viewer
           // *unless* the page would thus become too wide to fit horizontally.
-            var horizontalScale = isLandscape ?
+          let horizontalScale = isLandscape ?
             Math.min(pageHeightScale, pageWidthScale) : pageWidthScale;
           scale = Math.min(MAX_AUTO_SCALE, horizontalScale);
           break;
         default:
-            console.error('PDFViewer_setScale: "' + value +
-                          '" is an unknown zoom value.');
+          console.error(
+            `PDFViewer._setScale: "${value}" is an unknown zoom value.`);
           return;
       }
-        this._setScaleUpdatePages(scale, value, noScroll, true);
+      this._setScaleUpdatePages(scale, value, noScroll, /* preset = */ true);
+    }
   }
-    },
 
   /**
    * Refreshes page view: scrolls to the current page and updates the scale.
@@ -561,9 +555,9 @@ var PDFViewer = (function pdfViewer() {
       this._setScale(this._currentScaleValue, true);
     }
 
-      var pageView = this._pages[this._currentPageNumber - 1];
+    let pageView = this._pages[this._currentPageNumber - 1];
     scrollIntoView(pageView.div);
-    },
+  }
 
   /**
    * @typedef ScrollPageIntoViewParameters
@@ -578,14 +572,14 @@ var PDFViewer = (function pdfViewer() {
    * Scrolls page into view.
    * @param {ScrollPageIntoViewParameters} params
    */
-    scrollPageIntoView: function PDFViewer_scrollPageIntoView(params) {
+  scrollPageIntoView(params) {
     if (!this.pdfDocument) {
       return;
     }
     if ((typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) &&
         (arguments.length > 1 || typeof params === 'number')) {
       console.warn('Call of scrollPageIntoView() with obsolete signature.');
-        var paramObj = {};
+      let paramObj = {};
       if (typeof params === 'number') {
         paramObj.pageNumber = params; // pageNumber argument was found.
       }
@@ -594,29 +588,29 @@ var PDFViewer = (function pdfViewer() {
       }
       params = paramObj;
     }
-      var pageNumber = params.pageNumber || 0;
-      var dest = params.destArray || null;
-      var allowNegativeOffset = params.allowNegativeOffset || false;
+    let pageNumber = params.pageNumber || 0;
+    let dest = params.destArray || null;
+    let allowNegativeOffset = params.allowNegativeOffset || false;
 
     if (this.isInPresentationMode || !dest) {
-        this._setCurrentPageNumber(pageNumber, /* resetCurrentPageView */ true);
+      this._setCurrentPageNumber(pageNumber, /* resetCurrentPageView = */ true);
       return;
     }
 
-      var pageView = this._pages[pageNumber - 1];
+    let pageView = this._pages[pageNumber - 1];
     if (!pageView) {
-        console.error('PDFViewer_scrollPageIntoView: ' +
-                      'Invalid "pageNumber" parameter.');
+      console.error(
+        'PDFViewer.scrollPageIntoView: Invalid "pageNumber" parameter.');
       return;
     }
-      var x = 0, y = 0;
-      var width = 0, height = 0, widthScale, heightScale;
-      var changeOrientation = (pageView.rotation % 180 === 0 ? false : true);
-      var pageWidth = (changeOrientation ? pageView.height : pageView.width) /
+    let x = 0, y = 0;
+    let width = 0, height = 0, widthScale, heightScale;
+    let changeOrientation = (pageView.rotation % 180 === 0 ? false : true);
+    let pageWidth = (changeOrientation ? pageView.height : pageView.width) /
       pageView.scale / CSS_UNITS;
-      var pageHeight = (changeOrientation ? pageView.width : pageView.height) /
+    let pageHeight = (changeOrientation ? pageView.width : pageView.height) /
       pageView.scale / CSS_UNITS;
-      var scale = 0;
+    let scale = 0;
     switch (dest[1].name) {
       case 'XYZ':
         x = dest[2];
@@ -656,8 +650,8 @@ var PDFViewer = (function pdfViewer() {
         y = dest[3];
         width = dest[4] - x;
         height = dest[5] - y;
-          var hPadding = this.removePageBorders ? 0 : SCROLLBAR_PADDING;
-          var vPadding = this.removePageBorders ? 0 : VERTICAL_PADDING;
+        let hPadding = this.removePageBorders ? 0 : SCROLLBAR_PADDING;
+        let vPadding = this.removePageBorders ? 0 : VERTICAL_PADDING;
 
         widthScale = (this.container.clientWidth - hPadding) /
           width / CSS_UNITS;
@@ -666,8 +660,8 @@ var PDFViewer = (function pdfViewer() {
         scale = Math.min(Math.abs(widthScale), Math.abs(heightScale));
         break;
       default:
-          console.error('PDFViewer_scrollPageIntoView: \'' + dest[1].name +
-                        '\' is not a valid destination type.');
+        console.error(`PDFViewer.scrollPageIntoView: "${dest[1].name}" ` +
+                      'is not a valid destination type.');
         return;
     }
 
@@ -682,12 +676,12 @@ var PDFViewer = (function pdfViewer() {
       return;
     }
 
-      var boundingRect = [
+    let boundingRect = [
       pageView.viewport.convertToViewportPoint(x, y),
       pageView.viewport.convertToViewportPoint(x + width, y + height)
     ];
-      var left = Math.min(boundingRect[0][0], boundingRect[1][0]);
-      var top = Math.min(boundingRect[0][1], boundingRect[1][1]);
+    let left = Math.min(boundingRect[0][0], boundingRect[1][0]);
+    let top = Math.min(boundingRect[0][1], boundingRect[1][1]);
 
     if (!allowNegativeOffset) {
       // Some bad PDF generators will create destinations with e.g. top values
@@ -697,25 +691,25 @@ var PDFViewer = (function pdfViewer() {
       top = Math.max(top, 0);
     }
     scrollIntoView(pageView.div, { left, top, });
-    },
+  }
 
   _updateLocation(firstPage) {
-      var currentScale = this._currentScale;
-      var currentScaleValue = this._currentScaleValue;
-      var normalizedScaleValue =
+    let currentScale = this._currentScale;
+    let currentScaleValue = this._currentScaleValue;
+    let normalizedScaleValue =
       parseFloat(currentScaleValue) === currentScale ?
       Math.round(currentScale * 10000) / 100 : currentScaleValue;
 
-      var pageNumber = firstPage.id;
-      var pdfOpenParams = '#page=' + pageNumber;
+    let pageNumber = firstPage.id;
+    let pdfOpenParams = '#page=' + pageNumber;
     pdfOpenParams += '&zoom=' + normalizedScaleValue;
-      var currentPageView = this._pages[pageNumber - 1];
-      var container = this.container;
-      var topLeft = currentPageView.getPagePoint(
+    let currentPageView = this._pages[pageNumber - 1];
+    let container = this.container;
+    let topLeft = currentPageView.getPagePoint(
       (container.scrollLeft - firstPage.x),
       (container.scrollTop - firstPage.y));
-      var intLeft = Math.round(topLeft[0]);
-      var intTop = Math.round(topLeft[1]);
+    let intLeft = Math.round(topLeft[0]);
+    let intTop = Math.round(topLeft[1]);
     pdfOpenParams += ',' + intLeft + ',' + intTop;
 
     this._location = {
@@ -725,27 +719,27 @@ var PDFViewer = (function pdfViewer() {
       left: intLeft,
       pdfOpenParams,
     };
-    },
+  }
 
-    update: function PDFViewer_update() {
-      var visible = this._getVisiblePages();
-      var visiblePages = visible.views;
+  update() {
+    let visible = this._getVisiblePages();
+    let visiblePages = visible.views;
     if (visiblePages.length === 0) {
       return;
     }
 
-      var suggestedCacheSize = Math.max(DEFAULT_CACHE_SIZE,
+    let suggestedCacheSize = Math.max(DEFAULT_CACHE_SIZE,
                                       2 * visiblePages.length + 1);
     this._buffer.resize(suggestedCacheSize);
 
     this.renderingQueue.renderHighestPriority(visible);
 
-      var currentId = this._currentPageNumber;
-      var firstPage = visible.first;
+    let currentId = this._currentPageNumber;
+    let firstPage = visible.first;
+    let stillFullyVisible = false;
 
-      for (var i = 0, ii = visiblePages.length, stillFullyVisible = false;
-           i < ii; ++i) {
-        var page = visiblePages[i];
+    for (let i = 0, ii = visiblePages.length; i < ii; ++i) {
+      let page = visiblePages[i];
 
       if (page.percent < 100) {
         break;
@@ -770,28 +764,28 @@ var PDFViewer = (function pdfViewer() {
       source: this,
       location: this._location,
     });
-    },
+  }
 
   containsElement(element) {
     return this.container.contains(element);
-    },
+  }
 
   focus() {
     this.container.focus();
-    },
+  }
 
   get isInPresentationMode() {
     return this.presentationModeState === PresentationModeState.FULLSCREEN;
-    },
+  }
 
   get isChangingPresentationMode() {
     return this.presentationModeState === PresentationModeState.CHANGING;
-    },
+  }
 
   get isHorizontalScrollbarEnabled() {
     return (this.isInPresentationMode ?
       false : (this.container.scrollWidth > this.container.clientWidth));
-    },
+  }
 
   _getVisiblePages() {
     if (!this.isInPresentationMode) {
@@ -799,46 +793,46 @@ var PDFViewer = (function pdfViewer() {
     }
     // The algorithm in getVisibleElements doesn't work in all browsers and
     // configurations when presentation mode is active.
-      var visible = [];
-      var currentPage = this._pages[this._currentPageNumber - 1];
+    let visible = [];
+    let currentPage = this._pages[this._currentPageNumber - 1];
     visible.push({ id: currentPage.id, view: currentPage, });
     return { first: currentPage, last: currentPage, views: visible, };
-    },
+  }
 
   cleanup() {
-      for (var i = 0, ii = this._pages.length; i < ii; i++) {
+    for (let i = 0, ii = this._pages.length; i < ii; i++) {
       if (this._pages[i] &&
           this._pages[i].renderingState !== RenderingStates.FINISHED) {
         this._pages[i].reset();
       }
     }
-    },
+  }
 
   /**
    * @private
    */
-    _cancelRendering: function PDFViewer_cancelRendering() {
-      for (var i = 0, ii = this._pages.length; i < ii; i++) {
+  _cancelRendering() {
+    for (let i = 0, ii = this._pages.length; i < ii; i++) {
       if (this._pages[i]) {
         this._pages[i].cancelRendering();
       }
     }
-    },
+  }
 
   /**
    * @param {PDFPageView} pageView
-     * @returns {PDFPage}
+   * @returns {Promise} Returns a promise containing a {PDFPageProxy} object.
    * @private
    */
   _ensurePdfPageLoaded(pageView) {
     if (pageView.pdfPage) {
       return Promise.resolve(pageView.pdfPage);
     }
-      var pageNumber = pageView.id;
+    let pageNumber = pageView.id;
     if (this._pagesRequests[pageNumber]) {
       return this._pagesRequests[pageNumber];
     }
-      var promise = this.pdfDocument.getPage(pageNumber).then((pdfPage) => {
+    let promise = this.pdfDocument.getPage(pageNumber).then((pdfPage) => {
       if (!pageView.pdfPage) {
         pageView.setPdfPage(pdfPage);
       }
@@ -847,11 +841,11 @@ var PDFViewer = (function pdfViewer() {
     });
     this._pagesRequests[pageNumber] = promise;
     return promise;
-    },
+  }
 
   forceRendering(currentlyVisiblePages) {
-      var visiblePages = currentlyVisiblePages || this._getVisiblePages();
-      var pageView = this.renderingQueue.getHighestPriority(visiblePages,
+    let visiblePages = currentlyVisiblePages || this._getVisiblePages();
+    let pageView = this.renderingQueue.getHighestPriority(visiblePages,
                                                           this._pages,
                                                           this.scroll.down);
     if (pageView) {
@@ -861,7 +855,7 @@ var PDFViewer = (function pdfViewer() {
       return true;
     }
     return false;
-    },
+  }
 
   getPageTextContent(pageIndex) {
     return this.pdfDocument.getPage(pageIndex + 1).then(function(page) {
@@ -869,7 +863,7 @@ var PDFViewer = (function pdfViewer() {
         normalizeWhitespace: true,
       });
     });
-    },
+  }
 
   /**
    * @param {HTMLDivElement} textLayerDiv
@@ -888,7 +882,7 @@ var PDFViewer = (function pdfViewer() {
       enhanceTextSelection: this.isInPresentationMode ? false :
                                                         enhanceTextSelection,
     });
-    },
+  }
 
   /**
    * @param {HTMLDivElement} pageDiv
@@ -897,8 +891,7 @@ var PDFViewer = (function pdfViewer() {
    * @param {IL10n} l10n
    * @returns {AnnotationLayerBuilder}
    */
-    createAnnotationLayerBuilder(pageDiv, pdfPage,
-                                 renderInteractiveForms = false,
+  createAnnotationLayerBuilder(pageDiv, pdfPage, renderInteractiveForms = false,
                                l10n = NullL10n) {
     return new AnnotationLayerBuilder({
       pageDiv,
@@ -908,19 +901,35 @@ var PDFViewer = (function pdfViewer() {
       downloadManager: this.downloadManager,
       l10n,
     });
-    },
+  }
 
   setFindController(findController) {
     this.findController = findController;
-    },
+  }
+
+  /**
+   * @returns {boolean} Whether all pages of the PDF document have identical
+   *                    widths and heights.
+   */
+  get hasEqualPageSizes() {
+    let firstPageView = this._pages[0];
+    for (let i = 1, ii = this._pages.length; i < ii; ++i) {
+      let pageView = this._pages[i];
+      if (pageView.width !== firstPageView.width ||
+          pageView.height !== firstPageView.height) {
+        return false;
+      }
+    }
+    return true;
+  }
 
   /**
    * Returns sizes of the pages.
    * @returns {Array} Array of objects with width/height/rotation fields.
    */
   getPagesOverview() {
-      var pagesOverview = this._pages.map(function (pageView) {
-        var viewport = pageView.pdfPage.getViewport(1);
+    let pagesOverview = this._pages.map(function(pageView) {
+      let viewport = pageView.pdfPage.getViewport(1);
       return {
         width: viewport.width,
         height: viewport.height,
@@ -930,7 +939,7 @@ var PDFViewer = (function pdfViewer() {
     if (!this.enablePrintAutoRotate) {
       return pagesOverview;
     }
-      var isFirstPagePortrait = isPortraitOrientation(pagesOverview[0]);
+    let isFirstPagePortrait = isPortraitOrientation(pagesOverview[0]);
     return pagesOverview.map(function (size) {
       if (isFirstPagePortrait === isPortraitOrientation(size)) {
         return size;
@@ -941,11 +950,8 @@ var PDFViewer = (function pdfViewer() {
         rotation: (size.rotation + 90) % 360,
       };
     });
-    },
-  };
-
-  return PDFViewer;
-})();
+  }
+}
 
 export {
   PresentationModeState,