Merge pull request #2306 from MohitBansal321/addButton

add custom button for this viewer

src/buttongroup.js

@@ -112,6 +112,17 @@ $.ButtonGroup = function( options ) {
 /** @lends OpenSeadragon.ButtonGroup.prototype */
 $.ButtonGroup.prototype = {
 
+    /**
+     * Adds the given button to this button group.
+     *
+     * @functions
+     * @param {OpenSeadragon.Button} button
+     */
+    addButton: function( button ){
+        this.buttons.push(button);
+        this.element.appendChild(button.element);
+    },
+
     /**
      * TODO: Figure out why this is used on the public API and if a more useful
      * api can be created.

src/viewer.js

@@ -978,6 +978,16 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
         this.forceRedraw();
     },
 
+    /**
+     * Adds the given button to this viewer.
+     *
+     * @functions
+     * @param {OpenSeadragon.Button} button
+     */
+    addButton: function( button ){
+        this.buttonGroup.addButton(button);
+    },
+
     /**
      * @function
      * @returns {Boolean}