if (typeof $Loading == "undefined") var $Loading = {
    /**
     * quantity of actual ajax requests processing
     */
    ajax_request_number: 0,
    addRequest: function() {

        if ($Loading.ajax_request_number == 0) {
            $('#loading_dlg').dialog('open');
        } else {
            $('#loading_dlg').dialog('moveToTop');
        }
        $Loading.ajax_request_number++;
    },

    removeRequest: function() {
        $Loading.ajax_request_number--;
        if ($Loading.ajax_request_number == 0) {
            $('#loading_dlg').dialog('close');
        }
    },

    moveToTop: function() {
        $("#loading_dlg").dialog( 'close' );
        $("#loading_dlg").dialog( 'open' );
        $("#loading_dlg").dialog( 'moveToTop' );
    }


}