home | career | drupal | java | mac | mysql | perl | php | scala | uml | unix

Drupal example source code file (theme.api.php)

This example Drupal source code file (theme.api.php) is included in the DevDaily.com "Drupal Source Code Warehouse" project. The intent of this project is to help you "Learn Drupal by Example".

PHP - Drupal tags/keywords

array, attributes, context, element, foreach, function, hooks, if, isset, key, php, theme, variable_name, variables

The theme.api.php Drupal example source code

<?php
// $Id: theme.api.php,v 1.5 2011/01/03 18:03:54 webchick Exp $

/**
 * @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.
 *
 * @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.
 *
 * @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.
 *
 * @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.
 *
 * @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();
}

Other Drupal examples (source code examples)

Here is a short list of links related to this Drupal theme.api.php source code file:

new blog posts

"Drupal" is a registered trademark of Dries Buytaert.

my drupal tutorials and examples  

Copyright 1998-2016 Alvin Alexander, alvinalexander.com
All Rights Reserved.

Beginning in 2016, a portion of the proceeds from pages under the '/drupal-code-examples/' URI will be donated to charity.