Re-factor `ViewHistory` to make it properly asynchronous

Rather than having to manually use `initializedPromise`, which really ought to be a private property, to ensure that setting/getting values in the `ViewHistory` works as intended, this re-factoring simply changes all of its methods to be asynchronous.

Furthermore, a `getMultiple` method (mirroring the existing `setMultiple` one) is also added to `ViewHistory`.

Finally, this patch also addresses an existing issue, where certain preferences (e.g. the default zoom level) would be ignored when calling `setInitialView` if reading from the `ViewHistory` fails for some reason.

web/app.js

@@ -882,7 +882,7 @@ var PDFViewerApplication = {
     var pdfThumbnailViewer = this.pdfThumbnailViewer;
     pdfThumbnailViewer.setDocument(pdfDocument);
 
-    firstPagePromise.then(function(pdfPage) {
+    firstPagePromise.then((pdfPage) => {
       downloadedPromise.then(function () {
         self.eventBus.dispatch('documentload', {source: self});
       });
@@ -905,58 +905,65 @@ var PDFViewerApplication = {
       }
 
       var initialParams = {
-        destination: self.initialDestination,
+        destination: this.initialDestination,
-        bookmark: self.initialBookmark,
+        bookmark: this.initialBookmark,
         hash: null,
       };
+      var storedHash = this.viewerPrefs['defaultZoomValue'] ?
+        ('zoom=' + this.viewerPrefs['defaultZoomValue']) : null;
+      var sidebarView = this.viewerPrefs['sidebarViewOnLoad'];
 
-      store.initializedPromise.then(function resolved() {
+      new Promise((resolve, reject) => {
-        var storedHash = null, sidebarView = null;
+        if (!this.viewerPrefs['showPreviousViewOnLoad']) {
-        if (self.viewerPrefs['showPreviousViewOnLoad'] &&
+          resolve();
-            store.get('exists', false)) {
+          return;
-          var pageNum = store.get('page', '1');
-          var zoom = self.viewerPrefs['defaultZoomValue'] ||
-                     store.get('zoom', DEFAULT_SCALE_VALUE);
-          var left = store.get('scrollLeft', '0');
-          var top = store.get('scrollTop', '0');
-
-          storedHash = 'page=' + pageNum + '&zoom=' + zoom + ',' +
-                       left + ',' + top;
-
-          sidebarView = store.get('sidebarView', SidebarView.NONE);
-        } else if (self.viewerPrefs['defaultZoomValue']) {
-          storedHash = 'page=1&zoom=' + self.viewerPrefs['defaultZoomValue'];
         }
-        self.setInitialView(storedHash,
+        store.getMultiple({
-          { scale: scale, sidebarView: sidebarView });
+          exists: false,
-
+          page: '1',
+          zoom: DEFAULT_SCALE_VALUE,
+          scrollLeft: '0',
+          scrollTop: '0',
+          sidebarView: SidebarView.NONE,
+        }).then((values) => {
+          if (!values.exists) {
+            resolve();
+            return;
+          }
+          storedHash = 'page=' + values.page +
+            '&zoom=' + (this.viewerPrefs['defaultZoomValue'] || values.zoom) +
+            ',' + values.scrollLeft + ',' + values.scrollTop;
+          sidebarView = this.viewerPrefs['sidebarViewOnLoad'] ||
+                        (values.sidebarView | 0);
+          resolve();
+        }).catch(function() {
+          resolve();
+        });
+      }).then(() => {
+        this.setInitialView(storedHash, { sidebarView, scale, });
         initialParams.hash = storedHash;
 
         // Make all navigation keys work on document load,
         // unless the viewer is embedded in a web page.
-        if (!self.isViewerEmbedded) {
+        if (!this.isViewerEmbedded) {
-          self.pdfViewer.focus();
+          this.pdfViewer.focus();
         }
-      }, function rejected(reason) {
+        return pagesPromise;
-        console.error(reason);
+      }).then(() => {
-        self.setInitialView(null, { scale: scale });
+        // For documents with different page sizes, once all pages are resolved,
-      });
-
-      // For documents with different page sizes,
         // ensure that the correct location becomes visible on load.
-      pagesPromise.then(function resolved() {
         if (!initialParams.destination && !initialParams.bookmark &&
             !initialParams.hash) {
           return;
         }
-        if (self.hasEqualPageSizes) {
+        if (this.hasEqualPageSizes) {
           return;
         }
-        self.initialDestination = initialParams.destination;
+        this.initialDestination = initialParams.destination;
-        self.initialBookmark = initialParams.bookmark;
+        this.initialBookmark = initialParams.bookmark;
 
-        self.pdfViewer.currentScaleValue = self.pdfViewer.currentScaleValue;
+        this.pdfViewer.currentScaleValue = this.pdfViewer.currentScaleValue;
-        self.setInitialView(initialParams.hash);
+        this.setInitialView(initialParams.hash);
       });
     });
 
@@ -1085,14 +1092,11 @@ var PDFViewerApplication = {
     });
   },
 
-  setInitialView: function pdfViewSetInitialView(storedHash, options) {
+  setInitialView(storedHash, options = {}) {
-    var scale = options && options.scale;
+    var { scale = 0, sidebarView = SidebarView.NONE, } = options;
-    var sidebarView = options && options.sidebarView;
 
     this.isInitialViewSet = true;
-
+    this.pdfSidebar.setInitialView(sidebarView);
-    this.pdfSidebar.setInitialView(this.viewerPrefs['sidebarViewOnLoad'] ||
-                                   (sidebarView | 0));
 
     if (this.initialDestination) {
       this.pdfLinkService.navigateTo(this.initialDestination);
@@ -1645,25 +1649,21 @@ function webViewerPresentationModeChanged(e) {
     active ? PresentationModeState.FULLSCREEN : PresentationModeState.NORMAL;
 }
 
-function webViewerSidebarViewChanged(e) {
+function webViewerSidebarViewChanged(evt) {
   PDFViewerApplication.pdfRenderingQueue.isThumbnailViewEnabled =
     PDFViewerApplication.pdfSidebar.isThumbnailViewVisible;
 
   var store = PDFViewerApplication.store;
-  if (!store || !PDFViewerApplication.isInitialViewSet) {
+  if (store && PDFViewerApplication.isInitialViewSet) {
     // Only update the storage when the document has been loaded *and* rendered.
-    return;
+    store.set('sidebarView', evt.view).catch(function() { });
   }
-  store.initializedPromise.then(function() {
-    store.set('sidebarView', e.view).catch(function() {});
-  });
 }
 
-function webViewerUpdateViewarea(e) {
+function webViewerUpdateViewarea(evt) {
-  var location = e.location, store = PDFViewerApplication.store;
+  var location = evt.location, store = PDFViewerApplication.store;
 
-  if (store) {
+  if (store && PDFViewerApplication.isInitialViewSet) {
-    store.initializedPromise.then(function() {
     store.setMultiple({
       'exists': true,
       'page': location.pageNumber,
@@ -1671,7 +1671,6 @@ function webViewerUpdateViewarea(e) {
       'scrollLeft': location.left,
       'scrollTop': location.top,
     }).catch(function() { /* unable to write to storage */ });
-    });
   }
   var href =
     PDFViewerApplication.pdfLinkService.getAnchorUrl(location.pdfOpenParams);

web/view_history.js

@@ -28,10 +28,8 @@ class ViewHistory {
   constructor(fingerprint, cacheSize = DEFAULT_VIEW_HISTORY_CACHE_SIZE) {
     this.fingerprint = fingerprint;
     this.cacheSize = cacheSize;
-    this.isInitializedPromiseResolved = false;
-    this.initializedPromise = this._readFromStorage().then((databaseStr) => {
-      this.isInitializedPromiseResolved = true;
 
+    this._initializedPromise = this._readFromStorage().then((databaseStr) => {
       var database = JSON.parse(databaseStr || '{}');
       if (!('files' in database)) {
         database.files = [];
@@ -99,28 +97,38 @@ class ViewHistory {
   }
 
   set(name, val) {
-    if (!this.isInitializedPromiseResolved) {
+    return this._initializedPromise.then(() => {
-      return;
-    }
       this.file[name] = val;
       return this._writeToStorage();
+    });
   }
 
   setMultiple(properties) {
-    if (!this.isInitializedPromiseResolved) {
+    return this._initializedPromise.then(() => {
-      return;
-    }
       for (var name in properties) {
         this.file[name] = properties[name];
       }
       return this._writeToStorage();
+    });
   }
 
   get(name, defaultValue) {
-    if (!this.isInitializedPromiseResolved) {
+    return this._initializedPromise.then(() => {
-      return defaultValue;
+      var val = this.file[name];
+      return val !== undefined ? val : defaultValue;
+    });
   }
-    return this.file[name] || defaultValue;
+
+  getMultiple(properties) {
+    return this._initializedPromise.then(() => {
+      var values = Object.create(null);
+
+      for (var name in properties) {
+        var val = this.file[name];
+        values[name] = val !== undefined ? val : properties[name];
+      }
+      return values;
+    });
   }
 }