From 2b9a51036fb2235db1311b3c603381c5b3b6fd7c Mon Sep 17 00:00:00 2001
From: Ian Gilman <ian@iangilman.com>
Date: Tue, 20 Jan 2015 16:09:54 -0800
Subject: [PATCH] Fixed change detection for viewport (after recent spring
 change)

---
 src/viewport.js | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/viewport.js b/src/viewport.js
index d6fc2984..d6fd8606 100644
--- a/src/viewport.js
+++ b/src/viewport.js
@@ -132,6 +132,10 @@ $.Viewport = function( options ) {
         animationTime:   this.animationTime
     });
 
+    this._oldCenterX = this.centerSpringX.current.value;
+    this._oldCenterY = this.centerSpringY.current.value;
+    this._oldZoom    = this.zoomSpring.current.value;
+
     if (this.contentSize) {
         this.resetContentSize( this.contentSize );
     } else {
@@ -856,10 +860,7 @@ $.Viewport.prototype = /** @lends OpenSeadragon.Viewport.prototype */{
      * @function
      */
     update: function() {
-        var oldCenterX = this.centerSpringX.current.value,
-            oldCenterY = this.centerSpringY.current.value,
-            oldZoom    = this.zoomSpring.current.value,
-            oldZoomPixel,
+        var oldZoomPixel,
             newZoomPixel,
             deltaZoomPixels,
             deltaZoomPoints;
@@ -870,7 +871,7 @@ $.Viewport.prototype = /** @lends OpenSeadragon.Viewport.prototype */{
 
         this.zoomSpring.update();
 
-        if (this.zoomPoint && this.zoomSpring.current.value != oldZoom) {
+        if (this.zoomPoint && this.zoomSpring.current.value != this._oldZoom) {
             newZoomPixel    = this.pixelFromPoint( this.zoomPoint, true );
             deltaZoomPixels = newZoomPixel.minus( oldZoomPixel );
             deltaZoomPoints = this.deltaPointsFromPixels( deltaZoomPixels, true );
@@ -884,9 +885,15 @@ $.Viewport.prototype = /** @lends OpenSeadragon.Viewport.prototype */{
         this.centerSpringX.update();
         this.centerSpringY.update();
 
-        return this.centerSpringX.current.value != oldCenterX ||
-            this.centerSpringY.current.value != oldCenterY ||
-            this.zoomSpring.current.value != oldZoom;
+        var changed = this.centerSpringX.current.value != this._oldCenterX ||
+            this.centerSpringY.current.value != this._oldCenterY ||
+            this.zoomSpring.current.value != this._oldZoom;
+
+        this._oldCenterX = this.centerSpringX.current.value;
+        this._oldCenterY = this.centerSpringY.current.value;
+        this._oldZoom    = this.zoomSpring.current.value;
+
+        return changed;
     },