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The Atomium theme is a Drupal 7 base theme.

The goal of this base theme is to rewrite most of the core theme functions of Drupal and use proper render arrays and templates instead. This will allow users to customize at will most of the elements in a custom sub-theme using preprocess functions or by providing a custom template.

Table of contents:

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Installation & requirements

Since the branch 7-x-3.x, Atomium requires the module Registry on steroids and its submodule to be installed and enabled.

As it is technically not possible for a theme to depends on a module, please make sure that these modules are enabled.

Download the theme manually or using Drush.

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To enable the theme, go to admin/appearance and select an Atomium based theme.

Atomium comes with 1 sub-theme "Atomium Bartik" provided as an example, it can be used as a starter-kit as well. It is a fork on the Bartik core theme but based on Atomium.

The sub-theme provide examples of preprocess functions and templates so you can craft your own theme quickly.

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Atomium is not intended to be a full featured theme as you might find on, full of configurable settings and with a nice user interface. The sole purpose of this theme is to provide clean markup that you can easily extend.

However, Atomium provides the following settings:

  • Allow CSS double underscore.
  • Move inline javascript to a file.

As of Drupal 7.51, a new allow_css_double_underscores variable has been added to allow for double underscores in CSS identifiers. In order to allow CSS identifiers to contain double underscores (.example__selector) for Drupal's BEM-style naming standards, this variable can be set to TRUE.

Atomium allows you to move inline Javascript (like the Drupal settings) into a file that is automatically loaded as a regular Javascript file.

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Atomium is licenced under the EUPL Licence. All contributions to Atomium and its sub-themes are made on Github, the main Atomium repository.

To ensure its code quality, Atomium depends on GrumPHP.

In order to use it and pass the automated tests, run:

$ composer install

This will:

  1. Build a target test site in ./build
  2. Run $ ./vendor/bin/run drupal:site-setup which will setup site and tests configuration files, such as phpunit.xml

After that:

  1. Copy runner.yml.dist into runner.yml and customize it according to your local environment
  2. Install the site by running $ ./vendor/bin/run drupal:site-install

For a list of available commands run:


For more information about how to customise the building process check the OpenEuropa Task Runner project page.

The best way to submit code is by providing a pull request on Github.

This also helps us to have the automated tests triggered automatically and save times on checking code styles.

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Atomium provides a way of extending just by creating some files without modifying the core Atomium files. Each theme definition, core or custom, is treated as a component. You can find all the theme definitions in the templates directory of each sub-theme.

To create a new theme definition:

  • Create a directory in templates and name it as you will. A good practice is to give it the name of the definition.
  • Create the function [NAME-OF-THE-THEME]_atomium_theme_[NAME-OF-THE-THEME-DEFINITION](),
  • Create a file [NAME-OF-THE-THEME_DEFINITION].css and/or [NAME-OF-THE-THEME_DEFINITION].js to get these files automatically loaded.

Atomium provides a custom page available on the path: atomium-overview. This particular page is only available to users with administer themes permission.

This page acts as a showcase page of components. To add a component in there, your component needs to define two hooks:

  • hook_atomium_definition_hook().

    This hook allows you to define simply a component.

  • hook_atomium_definition_form_hook().

    This hook allows you to define one or multiple components in a Drupal form.

For a better understanding and examples, see the atomium.api.php file.

Do not forget to clear the cache every time a new theme definition or process/preprocess is added or removed.

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Developer's note

During the development of this project, a lot of time has been put into analyzing how Drupal's core functions were implemented and how to improve them for better customization.

A good example of this is the breadcrumb generation.

Let's analyse how it's currently done in Drupal and how we've implemented it.

$variables['breadcrumb'] = theme('breadcrumb', array('breadcrumb' => drupal_get_breadcrumb()));

By default, Drupal uses the function drupal_get_breadcrumb() in its template_process_page() hook.

The function drupal_get_breadcrumb() returns raw HTML. Thus, it's impossible to alter the breadcrumbs links properly.

In order to get a render array, we have to go deeper and rewrite functions accordingly.

drupal_get_breadcrumb() calls menu_get_active_breadcrumb(). This is actually the function that returns the HTML.

There is no way to alter the result of that function as it returns an array of raw HTML links.

Unfortunately, in order to change this behaviour, we have to create two extra functions in Atomium and change the way the breadcrumb is generated.

  $variables['breadcrumb'] = array(
    '#theme' => array('breadcrumb'),
    '#breadcrumb' => atomium_drupal_get_breadcrumb(),

atomium_drupal_get_breadcrumb() is an atomium internal function written only for the breadcrumb handling. Instead of calling menu_get_active_breadcrumb(), it calls atomium_menu_get_active_breadcrumb() which is also a custom Atomium function that, instead of returning an array of raw HTML links, returns an array of render arrays.

This is why, in page.tpl.php, instead of writing:

<?php print $breadcrumb; ?>

You have to use:

<?php print render($breadcrumb); ?>

The rendering process is at the very end of the Drupal's chain of preprocess, process and render functions.

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Known issues

  • Vertical tabs: Unable to apply the theme function call inheritance. It has a link with the process function.

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In the press

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