add css class to "main menu" (drupal, integration with columnal grid system)

Question

I have a question for you.

I'm trying to make a website with drupal 7, it's almost done except for some little problems, I need that the first level of the main menu had some custom css classes in order to integrate it to columnal, this is the way I print the main menu:

<?php
    print theme(
        'links__system_main_menu',
        array(
            'links' => $main_menu,
            'attributes' => array(
                            'id' => 'main-menu',
                            'class' => array('menu')
            )
        )
    );
?>

and this is what I get:

<ul id="main-menu" class="menu">
    <li class="menu-NNN first active">
        <a href="url" title="" class="active">Home</a>
    </li>
    <li class="menu-NNN">
        <a href="url">click me</a>
    </li>
    <li class="menu-NNN">
        <a href="url">click me</a>
    </li>
    <li class="menu-NNN">
        <a href="url">click me</a>
    </li>
    <li class="menu-NNN last">
        <a href="url">click me</a>
    </li>
</ul>

I need that the first level of the main menu has the class "col_1":

<ul id="main-menu" class="menu">
    <li class="menu-NNN first .col_1 active">
        <a href="url" title="" class="active">Home</a>
    </li>
    <li class="menu-NNN .col_1">
        <a href="url">click me</a>
    </li>
    <li class="menu-NNN .col_1">
        <a href="url">click me</a>
    </li>
    <li class="menu-NNN .col_1">
        <a href="url">click me</a>
    </li>
    <li class="menu-NNN .col_1 last">
        <a href="url">click me</a>
    </li>
</ul>

the layout would look something like this:

/****************************************************************************************
*   *    .row                                                                       *   *
*   *********************************************************************************   *
*   *    #logo.col_5         *   * .pre_1|              .col_5              |.suf_1 *   *
*   *                        *   *       |                                  |       *   *
*   *                        *   *       |                                  |       *   *
*   *                        *   *       |__________________________________|       *   *
*   *                        *mar*       |.col_1|.col_1|.col_1|.col_1|.col_1|       *   *
*   *                        *gin*padding| menu1| menu2| menu3| menu4| menu5|padding*   *
*mar*********************************************************************************mar*
*gin*                                                                               *gin*
****************************************************************************************/
//I'm expecting to have just 5 links in the main menu

maybe I can set the width and the margin manually with css but I think this isn't the right approach, so, "using CSS to set properties to every sub element" won't work, I also try using "MYTHEME_menu_link" but that adds the properties to all the menus but the main menu, so that won't work too.

so the question is:

is there another way to add css classes to the first level of the main menu in drupal?

Answer 1

After some investigation. I found a way to achieve my goal without using a workaround or any external module based on this article (HOWTO create dropdown menus for Bartik in Drupal 7), I used 'variable_get', 'menu_tree' and 'drupal_render' to override the variable 'main_menu' with a string containing the menu with the format I needed, to override the variable 'main_menu' I used 'THEME_process_page';

function MYTHEME_process_page(&$variables) {
    global $language;

if($variables['main_menu']){

    $tree = menu_tree(variable_get('menu_main_links_source', 'main-menu'));
    foreach($tree as $key => $val){

        if(isset($tree[$key]['#href'])){ //just to make sure this is a link

            if($language->language!=$tree[$key]["#localized_options"]["langcode"])
                unset($tree[$key]);
            else
                $tree[$key]['#attributes']['class'][] = 'col_1';

        }

    }

    $variables['main_menu'] = drupal_render($tree);

}

}

Before this modification the 'main_menu' was an array, but now it is a string containing the menu, so, now, I have to replace the function 'theme' in the tamplate.

<?php
    print theme(
        'links__system_main_menu',
        array(
            'links' => $main_menu,
            'attributes' => array(
                            'id' => 'main-menu',
                            'class' => array('menu')
            )
        )
    );
?>

With something like this;

<?php print $main_menu; ?>