code: function() {
              var docElement = document.documentElement || {},
                  body    = document.body || {};
  
              if ( typeof ( window.innerWidth ) == 'number' ) {
                  $.getWindowSize = function(){
                      return new $.Point(
                          window.innerWidth,
                          window.innerHeight
                      );
                  };
              } else if ( docElement.clientWidth || docElement.clientHeight ) {
                  $.getWindowSize = function(){
                      return new $.Point(
                          document.documentElement.clientWidth,
                          document.documentElement.clientHeight
                      );
                  };
              } else if ( body.clientWidth || body.clientHeight ) {
                  $.getWindowSize = function(){
                      return new $.Point(
                          document.body.clientWidth,
                          document.body.clientHeight
                      );
                  };
              } else {
                  throw new Error("Unknown window size, no known technique.");
              }
  
              return $.getWindowSize();
          }
docs: Determines the size of the browsers window.
  @function
  @returns {OpenSeadragon.Point}