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<?php
// $Id$
/**
* @defgroup themeable Default theme implementations
* @{
* Functions and templates that present output to the user, and can be
* implemented by themes.
*
* Drupal's presentation layer is a pluggable system known as the theme
* layer. Each theme can take control over most of Drupal's output, and
* has complete control over the CSS.
*
* Inside Drupal, the theme layer is utilized by the use of the theme()
* function, which is passed the name of a component (the theme hook)
* and an array of variables. For example,
* theme('table', array('header' => $header, 'rows' => $rows));
* Additionally, the theme() function can take an array of theme
* hooks, which can be used to provide 'fallback' implementations to
* allow for more specific control of output. For example, the function:
* theme(array('table__foo', 'table'), $variables) would look to see if
* 'table__foo' is registered anywhere; if it is not, it would 'fall back'
* to the generic 'table' implementation. This can be used to attach specific
* theme functions to named objects, allowing the themer more control over
* specific types of output.
*
* As of Drupal 6, every theme hook is required to be registered by the
* module that owns it, so that Drupal can tell what to do with it and
* to make it simple for themes to identify and override the behavior
* for these calls.
*
* The theme hooks are registered via hook_theme(), which returns an
* array of arrays with information about the hook. It describes the
* arguments the function or template will need, and provides
* defaults for the template in case they are not filled in. If the default
* implementation is a function, by convention it is named theme_HOOK().
*
* Each module should provide a default implementation for theme_hooks that
* it registers. This implementation may be either a function or a template;
* if it is a function it must be specified via hook_theme(). By convention,
* default implementations of theme hooks are named theme_HOOK. Default
* template implementations are stored in the module directory.
*
* Drupal's default template renderer is a simple PHP parsing engine that
* includes the template and stores the output. Drupal's theme engines
* can provide alternate template engines, such as XTemplate, Smarty and
* PHPTal. The most common template engine is PHPTemplate (included with
* Drupal and implemented in phptemplate.engine, which uses Drupal's default
* template renderer.
*
* In order to create theme-specific implementations of these hooks, themes can
* implement their own version of theme hooks, either as functions or templates.
* These implementations will be used instead of the default implementation. If
* using a pure .theme without an engine, the .theme is required to implement
* its own version of hook_theme() to tell Drupal what it is implementing;
* themes utilizing an engine will have their well-named theming functions
* automatically registered for them. While this can vary based upon the theme
* engine, the standard set by phptemplate is that theme functions should be
* named THEMENAME_HOOK. For example, for Drupal's default theme (Garland) to
* implement the 'table' hook, the phptemplate.engine would find
* garland_table().
*
* The theme system is described and defined in theme.inc.
*
* @see theme()
* @see hook_theme()
*
* @} End of "defgroup themeable".
*/
/**
* Allow themes to alter the theme-specific settings form.
*
* With this hook, themes can alter the theme-specific settings form in any way
* allowable by Drupal's Forms API, such as adding form elements, changing
* default values and removing form elements. See the Forms API documentation on
* api.drupal.org for detailed information.
*
* Note that the base theme's form alterations will be run before any sub-theme
* alterations.
*
* @param $form
* Nested array of form elements that comprise the form.
* @param $form_state
* A keyed array containing the current state of the form.
*/
function hook_form_system_theme_settings_alter(&$form, &$form_state) {
// Add a checkbox to toggle the breadcrumb trail.
$form['toggle_breadcrumb'] = array(
'#type' => 'checkbox',
'#title' => t('Display the breadcrumb'),
'#default_value' => theme_get_setting('toggle_breadcrumb'),
'#description' => t('Show a trail of links from the homepage to the current page.'),
);
}
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