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<?php
// $Id$
/**
* @defgroup themeable Default theme implementations
* @{
* Functions and templates for the user interface to 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 (Bartik) to
* implement the 'table' hook, the phptemplate.engine would find
* bartik_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.'),
);
}
/**
* Preprocess theme variables.
*
* This hook allows modules to preprocess theme variables for theme templates.
* It is called for all invocations of theme(), to allow modules to add to
* or override variables for all theme hooks.
*
* For more detailed information, see theme().
*
* @param $variables
* The variables array (modify in place).
* @param $hook
* The name of the theme hook.
*/
function hook_preprocess(&$variables, $hook) {
static $hooks;
// Add contextual links to the variables, if the user has permission.
if (!user_access('access contextual links')) {
return;
}
if (!isset($hooks)) {
$hooks = theme_get_registry();
}
// Determine the primary theme function argument.
if (isset($hooks[$hook]['variables'])) {
$keys = array_keys($hooks[$hook]['variables']);
$key = $keys[0];
}
else {
$key = $hooks[$hook]['render element'];
}
if (isset($variables[$key])) {
$element = $variables[$key];
}
if (isset($element) && is_array($element) && !empty($element['#contextual_links'])) {
$variables['title_suffix']['contextual_links'] = contextual_links_view($element);
if (!empty($variables['title_suffix']['contextual_links'])) {
$variables['classes_array'][] = 'contextual-links-region';
}
}
}
/**
* Preprocess theme variables for a specific theme hook.
*
* This hook allows modules to preprocess theme variables for a specific theme
* hook. It should only be used if a module needs to override or add to the
* theme preprocessing for a theme hook it didn't define.
*
* For more detailed information, see theme().
*
* @param $variables
* The variables array (modify in place).
*/
function hook_preprocess_HOOK(&$variables) {
// This example is from rdf_preprocess_image(). It adds an RDF attribute
// to the image hook's variables.
$variables['attributes']['typeof'] = array('foaf:Image');
}
/**
* Process theme variables.
*
* This hook allows modules to process theme variables for theme templates.
* It is called for all invocations of theme(), to allow modules to add to
* or override variables for all theme hooks.
*
* For more detailed information, see theme().
*
* @param $variables
* The variables array (modify in place).
* @param $hook
* The name of the theme hook.
*/
function hook_process(&$variables, $hook) {
// Wraps variables in RDF wrappers.
if (!empty($variables['rdf_template_variable_attributes_array'])) {
foreach ($variables['rdf_template_variable_attributes_array'] as $variable_name => $attributes) {
$context = array(
'hook' => $hook,
'variable_name' => $variable_name,
'variables' => $variables,
);
$variables[$variable_name] = theme('rdf_template_variable_wrapper', array('content' => $variables[$variable_name], 'attributes' => $attributes, 'context' => $context));
}
}
}
/**
* Process theme variables for a specific theme hook.
*
* This hook allows modules to process theme variables for a specific theme
* hook. It should only be used if a module needs to override or add to the
* theme processing for a theme hook it didn't define.
*
* For more detailed information, see theme().
*
* @param $variables
* The variables array (modify in place).
*/
function hook_process_HOOK(&$variables) {
$variables['classes'] .= ' my_added_class';
}
/**
* Respond to themes being enabled.
*
* @param array $theme_list
* Array containing the names of the themes being enabled.
*
* @see theme_enable()
*/
function hook_themes_enabled($theme_list) {
foreach ($theme_list as $theme) {
block_theme_initialize($theme);
}
}
/**
* Respond to themes being disabled.
*
* @param array $theme_list
* Array containing the names of the themes being disabled.
*
* @see theme_disable()
*/
function hook_themes_disabled($theme_list) {
// Clear all update module caches.
_update_cache_clear();
}
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