<zk xmlns:w="client">
    <script type="text/javascript"><![CDATA[
    function moveCursor(wgt) {
        var inp = wgt.getInputNode(),
            temp = jq(inp).focus().val();
        jq(inp).val('').val(temp);
    }
    ]]></script>
    <textbox value="test" focus="true" w:onFocus="moveCursor(this)" />
</zk>