From 9f68e3f1bc38cc18191976f309becb94f70f7239 Mon Sep 17 00:00:00 2001
From: Yury Delendik <ydelendik@mozilla.com>
Date: Wed, 4 May 2016 11:06:07 -0500
Subject: [PATCH] Disable pagechange event if page is not changing.

---
 web/dom_events.js |  1 -
 web/pdf_viewer.js | 56 +++++++++++++++++++++++------------------------
 2 files changed, 27 insertions(+), 30 deletions(-)

diff --git a/web/dom_events.js b/web/dom_events.js
index 64c190005..ff048c87f 100644
--- a/web/dom_events.js
+++ b/web/dom_events.js
@@ -52,7 +52,6 @@
     eventBus.on('pagechange', function (e) {
       var event = document.createEvent('UIEvents');
       event.initUIEvent('pagechange', true, true, window, 0);
-      event.updateInProgress = e.updateInProgress;
       event.pageNumber = e.pageNumber;
       event.previousPageNumber = e.previousPageNumber;
       e.source.container.dispatchEvent(event);
diff --git a/web/pdf_viewer.js b/web/pdf_viewer.js
index 3f6d7786a..1a79b3745 100644
--- a/web/pdf_viewer.js
+++ b/web/pdf_viewer.js
@@ -138,7 +138,6 @@ var PDFViewer = (function pdfViewer() {
     }
 
     this.scroll = watchScroll(this.container, this._scrollUpdate.bind(this));
-    this.updateInProgress = false;
     this.presentationModeState = PresentationModeState.UNKNOWN;
     this._resetView();
 
@@ -165,12 +164,19 @@ var PDFViewer = (function pdfViewer() {
         this._currentPageNumber = val;
         return;
       }
+      this._setCurrentPageNumber(val);
+      // The intent can be to just reset a scroll position and/or scale.
+      this._resetCurrentPageView();
+    },
 
+    _setCurrentPageNumber: function pdfViewer_setCurrentPageNumber(val) {
+      if (this._currentPageNumber === val) {
+        return;
+      }
       var arg;
       if (!(0 < val && val <= this.pagesCount)) {
         arg = {
           source: this,
-          updateInProgress: this.updateInProgress,
           pageNumber: this._currentPageNumber,
           previousPageNumber: val
         };
@@ -181,19 +187,12 @@ var PDFViewer = (function pdfViewer() {
 
       arg = {
         source: this,
-        updateInProgress: this.updateInProgress,
         pageNumber: val,
         previousPageNumber: this._currentPageNumber
       };
-      this.eventBus.dispatch('pagechanging', arg);
       this._currentPageNumber = val;
+      this.eventBus.dispatch('pagechanging', arg);
       this.eventBus.dispatch('pagechange', arg);
-
-      // Check if the caller is `PDFViewer_update`, to avoid breaking scrolling.
-      if (this.updateInProgress) {
-        return;
-      }
-      this.scrollPageIntoView(val);
     },
 
     /**
@@ -499,6 +498,19 @@ var PDFViewer = (function pdfViewer() {
       }
     },
 
+    /**
+     * Refreshes page view: scrolls to the current page and updates the scale.
+     */
+    _resetCurrentPageView: function () {
+      if (this.isInPresentationMode) {
+        // Fixes the case when PDF has different page sizes.
+        this._setScale(this._currentScaleValue, true);
+      }
+
+      var pageView = this._pages[this._currentPageNumber - 1];
+      scrollIntoView(pageView.div);
+    },
+
     /**
      * Scrolls page into view.
      * @param {number} pageNumber
@@ -511,23 +523,13 @@ var PDFViewer = (function pdfViewer() {
         return;
       }
 
-      var pageView = this._pages[pageNumber - 1];
-
-      if (this.isInPresentationMode) {
-        if (this._currentPageNumber !== pageView.id) {
-          // Avoid breaking getVisiblePages in presentation mode.
-          this.currentPageNumber = pageView.id;
-          return;
-        }
-        dest = null;
-        // Fixes the case when PDF has different page sizes.
-        this._setScale(this._currentScaleValue, true);
-      }
-      if (!dest) {
-        scrollIntoView(pageView.div);
+      if (this.isInPresentationMode || !dest) {
+        this._setCurrentPageNumber(pageNumber);
+        this._resetCurrentPageView();
         return;
       }
 
+      var pageView = this._pages[pageNumber - 1];
       var x = 0, y = 0;
       var width = 0, height = 0, widthScale, heightScale;
       var changeOrientation = (pageView.rotation % 180 === 0 ? false : true);
@@ -644,8 +646,6 @@ var PDFViewer = (function pdfViewer() {
         return;
       }
 
-      this.updateInProgress = true;
-
       var suggestedCacheSize = Math.max(DEFAULT_CACHE_SIZE,
           2 * visiblePages.length + 1);
       this._buffer.resize(suggestedCacheSize);
@@ -673,13 +673,11 @@ var PDFViewer = (function pdfViewer() {
       }
 
       if (!this.isInPresentationMode) {
-        this.currentPageNumber = currentId;
+        this._setCurrentPageNumber(currentId);
       }
 
       this._updateLocation(firstPage);
 
-      this.updateInProgress = false;
-
       this.eventBus.dispatch('updateviewarea', {
         source: this,
         location: this._location