Documentation comments

src/viewport.js

@@ -1522,22 +1522,52 @@ $.Viewport.prototype = {
     },
 
     /**
-     * Toggle flip state and demands a new drawing on navigator and viewer objects.
-    */
+     * Toggles flip state and demands a new drawing on navigator and viewer objects.
+     * @function
+     * @return {OpenSeadragon.Viewport} Chainable.
+     */
     toggleFlip: function() {
       this.setFlip(!this.getFlip());
       if(this.viewer.navigator){
         this.viewer.navigator.setFlip();
       }
       this.viewer.forceRedraw();
+      return this;
     },
 
+
+    /**
+     * Gets flip state stored on viewport.
+     * @function
+     * @return {Boolean} Flip state.
+     */
     getFlip: function() {
       return this.flipped;
     },
 
+
+    /**
+     * Sets flip state according to the state input argument.
+     * @function
+     * @return {OpenSeadragon.Viewport} Chainable.
+     */
     setFlip: function( state ) {
+      if ( this.flipped != state ) {
+        /**
+         * Raised when flip state has been changed.
+         *
+         * @event flip
+         * @memberof OpenSeadragon.Viewer
+         * @type {object}
+         * @property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised the event.
+         * @property {Number} flipped - The flip state after this change.
+         * @property {?Object} userData - Arbitrary subscriber-defined object.
+         */
+        this.viewer.raiseEvent('flip', {"flipped": state});
+      }
+
       this.flipped = state;
+      return this;
     }
 
 };