From bd4921c2856c14049aae57c2d67bd809af51c62d Mon Sep 17 00:00:00 2001
From: Shaun Whitely <albinoshaun@hotmail.com>
Date: Tue, 25 Aug 2015 22:06:53 +1000
Subject: [PATCH] Added option to avoid image from snapping to home bounds on
 resize.

---
 src/openseadragon.js |  6 ++++++
 src/viewer.js        | 24 ++++++++++++++++++------
 test/demo/basic.html | 24 +++++++++++++++++-------
 3 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/src/openseadragon.js b/src/openseadragon.js
index 6eb8d09a..d2235381 100644
--- a/src/openseadragon.js
+++ b/src/openseadragon.js
@@ -255,6 +255,11 @@
   * @property {Boolean} [preserveImageSizeOnResize=false]
   *     Set to true to have the image size preserved when the viewer is resized. This requires autoResize=true (default).
   *
+  * @property {Boolean} [allowZoomToConstraintsOnResize=false]
+  *     Set to true to allow the image to remain zoomed out past the home zoom level during resize.
+  *     If false the image will be zoomed in if necessary such that it touches the edge of the viewer.
+  *     This requires autoResize=true (default).
+  *
   * @property {Number} [pixelsPerWheelLine=40]
   *     For pixel-resolution scrolling devices, the number of pixels equal to one scroll line.
   *
@@ -995,6 +1000,7 @@ window.OpenSeadragon = window.OpenSeadragon || function( options ){
             pixelsPerWheelLine:     40,
             autoResize:             true,
             preserveImageSizeOnResize: false, // requires autoResize=true
+            allowZoomToConstraintsOnResize: false, // requires autoResize=true
 
             //DEFAULT CONTROL SETTINGS
             showSequenceControl:     true,  //SEQUENCE
diff --git a/src/viewer.js b/src/viewer.js
index b0ee7757..0ed8b9ed 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -2947,11 +2947,18 @@ function resizeViewportAndRecenter( viewer, containerSize, oldBounds, oldCenter
 
     viewport.resize( containerSize, true );
 
-    // We try to remove blanks as much as possible
-    var worldBounds = viewer.world.getHomeBounds();
-    var newWidth = oldBounds.width <= worldBounds.width ? oldBounds.width : worldBounds.width;
-    var newHeight = oldBounds.height <= worldBounds.height ?
-        oldBounds.height : worldBounds.height;
+    var newWidth = oldBounds.width;
+    var newHeight = oldBounds.height;
+
+    if (!viewer.allowZoomToConstraintsOnResize) {
+        var worldBounds = viewer.world.getHomeBounds();
+        if (oldBounds.width > worldBounds.width) {
+            newWidth = worldBounds.width;
+        }
+        if (oldBounds.height > worldBounds.height) {
+            newHeight = worldBounds.height;
+        }
+    }
 
     var newBounds = new $.Rect(
         oldCenter.x - ( newWidth / 2.0 ),
@@ -2959,7 +2966,12 @@ function resizeViewportAndRecenter( viewer, containerSize, oldBounds, oldCenter
         newWidth,
         newHeight
         );
-    viewport.fitBounds( newBounds, true );
+
+    if (viewer.allowZoomToConstraintsOnResize) {
+        viewport.fitBoundsWithConstraints( newBounds, true );
+    } else {
+        viewport.fitBounds( newBounds, true );
+    }
 }
 
 function drawWorld( viewer ) {
diff --git a/test/demo/basic.html b/test/demo/basic.html
index 19572b86..9222a237 100644
--- a/test/demo/basic.html
+++ b/test/demo/basic.html
@@ -5,11 +5,20 @@
     <script type="text/javascript" src='../../build/openseadragon/openseadragon.js'></script>
     <script type="text/javascript" src='../lib/jquery-1.9.1.min.js'></script>
     <style type="text/css">
-
-      .openseadragon1 {
-          width: 800px;
-          height: 600px;
-      }
+    
+    html, body {
+        width: 100%;
+        height: 100%;
+        margin: 0;
+        padding: 0;
+    }
+    
+    .openseadragon1 {
+        width: 80%;
+        height: 80%;
+        background-color: white;
+        border: 10px solid black;
+    }
 
     </style>
 </head>
@@ -21,11 +30,12 @@
     <script type="text/javascript">
 
         var viewer = OpenSeadragon({
-            // debugMode: true,
+            debugMode: true,
             id: "contentDiv",
             prefixUrl: "../../build/openseadragon/images/",
             tileSources: "../data/testpattern.dzi",
-            showNavigator:true
+            minZoomImageRatio: 0.8,
+            allowZoomToConstraintsOnResize: true
         });
 
     </script>