code: function(theDialog) {
              var body = $('body');
              var blockout = $('<div class="modalBlockout"></div>')
                  .css({ 'z-index': dialog.getNextZIndex(), 'opacity': this.blockoutOpacity })
                  .appendTo(body);
  
              var host = $('<div class="modalHost"></div>')
                  .css({ 'z-index': dialog.getNextZIndex() })
                  .appendTo(body);
  
              theDialog.host = host.get(0);
              theDialog.blockout = blockout.get(0);
  
              if (!dialog.isOpen()) {
                  theDialog.oldBodyMarginRight = body.css("margin-right");
                  theDialog.oldInlineMarginRight = body.get(0).style.marginRight;
  
                  var html = $("html");
                  var oldBodyOuterWidth = body.outerWidth(true);
                  var oldScrollTop = html.scrollTop();
                  $("html").css("overflow-y", "hidden");
                  var newBodyOuterWidth = $("body").outerWidth(true);
                  body.css("margin-right", (newBodyOuterWidth - oldBodyOuterWidth + parseInt(theDialog.oldBodyMarginRight, 10)) + "px");
                  html.scrollTop(oldScrollTop); // necessary for Firefox
              }
          }
docs: In this function, you are expected to add a DOM element to the tree which will serve as the "host" for the modal's composed view. You must add a property called host to the modalWindow object which references the dom element. It is this host which is passed to the composition module.
  @method addHost
  @param {Dialog} theDialog The dialog model.