#2180 Remove repeat dom value lookups

src/definitions/modules/popup.js

@@ -470,18 +470,24 @@ $.fn.popup = function(parameters) {
           },
           offstagePosition: function(position) {
             var
-              boundary  = {
+              screen = {
                 top    : $(window).scrollTop(),
-                bottom : $(window).scrollTop() + $(window).height(),
+                left   : $(window).scrollLeft(),
+                width  : $(window).width(),
+                height : $(window).height()
+              },
+              boundary = {
+                top    : screen.top,
+                bottom : screen.top + screen.height,
                 left   : 0,
-                right  : $(window).scrollLeft() + $(window).width()
+                right  : screen.left + screen.width
               },
-              popup     = {
+              popup = {
                 width  : $popup.width(),
                 height : $popup.height(),
                 offset : $popup.offset()
               },
-              offstage  = {},
+              offstage = {},
               offstagePositions = []
             ;
             position = position || false;