google form / docs redirect

[Supplement]

I have an idea of what I need to do but I keep falling short of getting it right.

What all do i have to edit to create a redirect to a custom page after the form has been submitted?

   * @return HTML
     */
    function RenderGForm($atts) {
        $params = shortcode_atts(array(
            'form'           => false,                   // Google Form URL
            'confirm'        => false,                   // Custom confirmation page URL to redirect to
            'alert'          => null,                    // Optional Alert Message
            'class'          => 'gform',                 // Container element's custom class value
            'legal'          => 'on',                    // Display Google Legal Stuff
            'br'             => 'off',                   // Insert <br> tags between labels and inputs
            'suffix'         => null,                    // Add suffix character(s) to all labels
            'prefix'         => null,                    // Add suffix character(s) to all labels
            'readonly'       => 'off',                   // Set all form elements to disabled
            'title'          => 'on',                    // Remove the H1 element(s) from the Form
            'maph1h2'        => 'off',                   // Map H1 element(s) on the form to H2 element(s)
            'email'          => 'off',                   // Send an email confirmation to blog admin on submission
            'sendto'         => null,                    // Send an email confirmation to a specific address on submission
            'spreadsheet'    => false,                   // Google Spreadsheet URL
            'unitethemehack' => 'off',                   // Send an email confirmation to blog admin on submission
            'style'          => WPGFORM_CONFIRM_REDIRECT // How to present the custom confirmation after submit
        ), $atts) ;

        return wpGForm::ConstructGForm($params) ;
    } 

Change the confirm to 'true' correct?

[Supplement]

The function below 'WPGFORM_CONFIRM_REDIRECT' looks like it needs to be edited but i'm not really sure ... i've tried a few things and can't get it right. help please

        $js = sprintf('
<script type="text/javascript">
jQuery(document).ready(function($) {
    $("div.%sss-form-container input:checkbox").each(function(index) {
        this.name = this.name + \'[]\';
    });
', $prefix) ;
        //  Before closing the <script> tag, is the form read only?
        if ($readonly) $js .= sprintf('
    $("div.%sss-form-container :input").attr("disabled", true);
        ', $prefix) ;

/*
        //  Serialize the POST variables?
        if ($wpgform_options['serialize_post_vars'] == 1)
        {
            $js .= sprintf('
    $("#%sss-form").submit(function(event) {
        //$("#%sss-form").children().each(function(){
        $.each($("#%sss-form input, #%sss-form textarea"), function() {
        //access to form element via $(this)
            $(this).val($.base64Encode($(this).val()));
            alert($(this).val());
        });
    });
        //var i = 0;
//$.each($("#%sss-form input:text, #%sss-form input:hidden #%sss-form textarea"), function(i,v) {
//$.each($("#%sss-form input, #%sss-form textarea"), function(i,v) {
    //var theTag = v.tagName;
    //var theElement = $(v);
    //var theValue = theElement.val();
    //alert(i + ":  " + theValue) ;
    //$(v).val($.base64Encode($(v).val()));
    //alert($.base64Encode(theValue)) ;
    //i++;
//});
        
        
//alert("waiting ...");
    //});', $prefix, $prefix, $prefix, $prefix, $prefix, $prefix, $prefix, $prefix, $prefix) ;
        }
*/

        //  Before closing the <script> tag, is this the confirmation
        //  AND do we have a custom confirmation page or alert message?

        if (self::$posted && is_null($action) && !is_null($alert))
            $js .= PHP_EOL . 'alert("' . $alert . '") ;' ;

        //  Load the confirmation URL via AJAX?
        if (self::$posted && is_null($action) && !is_null($confirm) && $style === WPGFORM_CONFIRM_AJAX)
            $js .= PHP_EOL . '$("body").load("' . $confirm . '") ;' ;

        //  Load the confirmation URL via Redirect?
        if (self::$posted && is_null($action) && !is_null($confirm) && $style === WPGFORM_CONFIRM_REDIRECT)
            //printf('<h2>%s::%s</h2>', basename(__FILE__), __LINE__) ;
            $js .= PHP_EOL . 'window.location.replace("' . $confirm . '") ;' ;

        $js .= '
});
</script>