Freezing the execution

<zk>
	<window id="logWin" border="normal" title="Login (name='ben' and pw='bai')" closable="true"
		visible="false" position="center, top">
		<attribute name="onClose"><![CDATA[
			// redirect to the same page
			Executions.getCurrent().sendRedirect("");
		]]></attribute>
		name: <textbox id="name" forward="onOK=btn.onClick" onCreate="self.focus();" />
		pw: <textbox id="pw" forward="onOK=btn.onClick" />
		<button id="btn" label="Login">
			<attribute name="onClick"><![CDATA[
				if ("ben".equals(name.getValue()) && "bai".equals(pw.getValue())) {
					Sessions.getCurrent().setAttribute("ALREADY_LOGIN", "true");
					// logged in, clear busy mask, hide login window and show content
					Clients.clearBusy(contentWin);
					contentWin.getFellow("content").setVisible(true);
					logWin.setVisible(false);
				} else {
					// redirect to the same page
					Executions.getCurrent().sendRedirect("");
				}
			]]></attribute>
		</button>
	</window>
	<window id="contentWin" height="100%" width="100%">
		<div id="content">
			other content
		</div>
	</window>
	<zscript><![CDATA[
		// hide content, show busy mask and show login window if not logged in
		if (!"true".equals(Sessions.getCurrent().getAttribute("ALREADY_LOGIN"))) {
			contentWin.getFellow("content").setVisible(false);
		 	Clients.showBusy(contentWin, "please login");
		 	logWin.setVisible(true);
		 	logWin.doOverlapped();
		}
	]]></zscript>
</zk>