Update jquery.contextMenu.js

Adding "activated" method in options so user can bind his function to run after contextMenu showed on page.
Adding handler to fix contextMenu position on over boundary screen. (making contextMenu scrollable)

Author: AliShahrivarian

src/jquery.contextMenu.js

@@ -236,7 +236,8 @@
             // events
             events: {
                 show: $.noop,
-                hide: $.noop
+                hide: $.noop,
+                activated: $.noop
             },
             // default callback
             callback: null,
@@ -997,6 +998,9 @@
                 // position and show context menu
                 opt.$menu.css(css)[opt.animation.show](opt.animation.duration, function () {
                     $trigger.trigger('contextmenu:visible');
+                    
+                    opt.activated();
+                    opt.events.activated();
                 });
                 // make options available and set state
                 $trigger
@@ -1527,6 +1531,29 @@
                 // Wait for promise completion. .then(success, error, notify) (we don't track notify). Bind the opt
                 // and root to avoid scope problems
                 promise.then(completedPromise.bind(this, opt, root), errorPromise.bind(this, opt, root));
+            },
+            // operation that will run after contextMenu showed on screen
+            activated: function(opt){
+                var $menu = opt.$menu;
+                var $menuOffset = $menu.offset();
+                var winHeight = $(window).height();
+                var winScrollTop = $(window).scrollTop();
+                var menuHeight = $menu.height();
+                if(menuHeight > winHeight){
+                    $menu.css({
+                        'height' : winHeight + 'px',
+                        'overflow-x': 'hidden',
+                        'overflow-y': 'auto',
+                        'top': winScrollTop + 'px'
+                    });
+                } else if(
+                            ($menuOffset.top < winScrollTop) || 
+                           ($menuOffset.top + menuHeight > winScrollTop + winHeight)
+                          ){
+                    $menu.css({
+                        'top': '0px'
+                    });
+                } 
             }
         };