How to tell drupal an added region is to be taken into account in $body_class

Ok... with your help, I am beggining to understand it (bear it in mind that I am not at all an experienced programmer).

1) $body_classes seems to be an array, that takes values based on the following preprocess function, found in the Zen Theme's template.php file:

/**
* Override or insert variables into the page templates.
*
* @param $vars
* An array of variables to pass to the theme template.
* @param $hook
* The name of the template being rendered ("page" in this case.)
*/
function zen_preprocess_page(&$vars, $hook) {
// Add an optional title to the end of the breadcrumb.
if (theme_get_setting('zen_breadcrumb_title') && $vars['breadcrumb']) {
$vars['breadcrumb'] = substr($vars['breadcrumb'], 0, -6) . $vars['title'] . '';
}

// Add conditional stylesheets.
if (!module_exists('conditional_styles')) {
$vars['styles'] .= $vars['conditional_styles'] = variable_get('conditional_styles_' . $GLOBALS['theme'], '');
}

// Classes for body element. Allows advanced theming based on context
// (home page, node of certain type, etc.)
$body_classes = array($vars['body_classes']);
if (!$vars['is_front']) {
// Add unique classes for each page and website section
$path = drupal_get_path_alias($_GET['q']);
list($section, ) = explode('/', $path, 2);
$body_classes[] = zen_id_safe('page-' . $path);
$body_classes[] = zen_id_safe('section-' . $section);
if (arg(0) == 'node') {
if (arg(1) == 'add') {
if ($section == 'node') {
array_pop($body_classes); // Remove 'section-node'
}
$body_classes[] = 'section-node-add'; // Add 'section-node-add'
}
elseif (is_numeric(arg(1)) && (arg(2) == 'edit' || arg(2) == 'delete')) {
if ($section == 'node') {
array_pop($body_classes); // Remove 'section-node'
}
$body_classes[] = 'section-node-' . arg(2); // Add 'section-node-edit' or 'section-node-delete'
}
}
}
if (theme_get_setting('zen_wireframes')) {
$body_classes[] = 'with-wireframes'; // Optionally add the wireframes style.
}
$vars['body_classes'] = implode(' ', $body_classes); // Concatenate with spaces
}

2) I have to copy and paste this function, into my subtheme folder's template.php file, and change its name to:

function subthemename_preprocess_page(&$vars, $hook) {

3) Now... looking at this code, I really don't see any reference, to the origination of the two-sidebars class, or other classes related to the number of sidebars in the page.

This, makes me think of the other thing you mention in your message: looking at the Core preprocess API.

4) The two aspects mentioned in includes/theme.inc, that you refered to, are:

and

5) With these elements of the recipe, what kind of information should I include in the overriding function :

function subthemename_preprocess_page(&$vars, $hook) {
etc...

??

6) How can I, for example, force $body_classes array, to have a value? What should the function look like?

Thank you.

Ok... after a lot of trial and error, this overriding function I added to template.php in my subtheme folder....

... the following body classes:

However, as it can be seen in the body classes, I haven't been able to get rid of the class "one-sidebar". Altought my css two-sidebars is overriding it when it comes to content styling, I still wonder how could I tell drupal not to include it in my body classes?

On thing I did notice is that the underlying (core and zen theme) preprocess functions don't scale as I would expect; so I had to add a big ammount of code.

Thank you for your help.

L

Ok, here's where I stand at this point. I will say in detail what I have done.

Note 1) "plc_theme" is the name of my Zen's subtheme
Note 2) Some of my own insights are included in the code, with // comments

1) in plc_theme_template.php

2) in page.tpl.php

Result so far:

The body class that I am getting at this point (example):

Notice that it still prints one-sidebar and sidebar-left. BUT it also prints my so desired .two-right-sidebars class.
So, I noticed that when working out the .css of this body class output, I can put the code of .two-right-sidebars #content below the code .one-sidebar #content in my layout.css file. So this means that in a .ccs file, the code that appears below, seems to override the code above. So...

3) in layout.css added, below the code .two-sidebars #content

4) in layout.css changed

To

And added, below /** sidebar-right **/

This is getting me the desired result: An region called right_2 to be displayed nicely along with the default region right

*****

Indeed. I was mistaken when I said that other template_preprocess stages were not being called... because I could in the end verify that they were being called.

Now, how I verified it was just by assumption: seeing what was printed in <body class="... etc">, and comparing with all the preprocess functions, both of Drupal API, and the Zen theme.

A) What I would like to know is *how* I could "check the content of $vars[] in my own preprocess hook as passed from the theme system". What could I exactly do to know this?
An idea that comes to my mind is by temporarily printing the array at the header or footer in my page.tpl.php.

B) You are right when you notice that "$vars['body_classes'] includes 'one-sidebar' already". This is exactly why I had to write, in my "self-tutorial", all that stuff about css overriding code from "above" with code form "below".

It would be much more convenient to "strip that [one-sidebar class] out". How could I do this?

Thank you again for following up on my issue.

After some days of having written this support request, I found another interesting approach: the one found in the Newswire theme:

In template.php

and in page.tpl.php

Simple... and just fine!

Regards.