overflow should only be enabled for fixed-layout pan-zoom, not reflow…

… or scroll views. Fixes readium/readium-js-viewer#232

(fixes Chrome extension/cloud reader, as well as native apps (although they do not expose "zoom" UI affordances yet))
(trivial tested fix, no need for feature branch + pull request)

js/views/fixed_view.js

@@ -313,7 +313,9 @@ ReadiumSDK.Views.FixedView = function(options, reader){
 
         var horScale = potentialContentSize.width / _contentMetaSize.width;
         var verScale = potentialContentSize.height / _contentMetaSize.height;
-
+
+        _$viewport.css("overflow", "auto");
+
         var scale;
         if (_zoom.style == 'fit-width'){
             scale = horScale;
@@ -326,6 +328,9 @@ ReadiumSDK.Views.FixedView = function(options, reader){
         }
         else{
             scale = Math.min(horScale, verScale);
+
+            // no need for pan during "viewport fit" zoom
+            _$viewport.css("overflow", "hidden");
         }
 
         _currentScale = scale;

js/views/reader_view.js

@@ -80,8 +80,15 @@ ReadiumSDK.Views.ReaderView = function(options) {
 
     this.createViewForType = function(viewType, options) {
         var createdView;
+
+        // NOTE: _$el == options.$viewport
+        _$el.css("overflow", "hidden");
+
         switch(viewType) {
             case ReadiumSDK.Views.ReaderView.VIEW_TYPE_FIXED:
+
+                _$el.css("overflow", "auto"); // for content pan, see self.setZoom()
+
                 createdView = new ReadiumSDK.Views.FixedView(options, self);
                 break;
             case ReadiumSDK.Views.ReaderView.VIEW_TYPE_SCROLLED_DOC: