Registry::processExtension

protected Registry::processExtension(array &$cache, $name, $type, $theme, $path)

protected function processExtension(array &$cache, $name, $type, $theme, $path) {
  $result = array();

  $hook_defaults = array(
    'variables' => TRUE,
    'render element' => TRUE,
    'pattern' => TRUE,
    'base hook' => TRUE,
  );

  $module_list = array_keys($this->moduleHandler->getModuleList());

  // Invoke the hook_theme() implementation, preprocess what is returned, and
  // merge it into $cache.
  $function = $name . '_theme';
  if (function_exists($function)) {
    $result = $function($cache, $type, $theme, $path);
    foreach ($result as $hook => $info) {
      // When a theme or engine overrides a module's theme function
      // $result[$hook] will only contain key/value pairs for information being
      // overridden.  Pull the rest of the information from what was defined by
      // an earlier hook.

      // Fill in the type and path of the module, theme, or engine that
      // implements this theme function.
      $result[$hook]['type'] = $type;
      $result[$hook]['theme path'] = $path;

      // If a theme hook has a base hook, mark its preprocess functions always
      // incomplete in order to inherit the base hook's preprocess functions.
      if (!empty($result[$hook]['base hook'])) {
        $result[$hook]['incomplete preprocess functions'] = TRUE;
      }

      if (isset($cache[$hook]['includes'])) {
        $result[$hook]['includes'] = $cache[$hook]['includes'];
      }

      // Load the includes, as they may contain preprocess functions.
      if (isset($info['includes'])) {
        foreach ($info['includes'] as $include_file) {
          include_once $this->root . '/' . $include_file;
        }
      }

      // If the theme implementation defines a file, then also use the path
      // that it defined. Otherwise use the default path. This allows
      // system.module to declare theme functions on behalf of core .include
      // files.
      if (isset($info['file'])) {
        $include_file = isset($info['path']) ? $info['path'] : $path;
        $include_file .= '/' . $info['file'];
        include_once $this->root . '/' . $include_file;
        $result[$hook]['includes'][] = $include_file;
      }

      // A template file is the default implementation for a theme hook, but
      // if the theme hook specifies a function callback instead, check to
      // ensure the function actually exists.
      if (isset($info['function'])) {
        if (!function_exists($info['function'])) {
          throw new \BadFunctionCallException(sprintf(
          'Theme hook "%s" refers to a theme function callback that does not exist: "%s"', 
          $hook, 
          $info['function']
          ));
        }
      }
      // Provide a default naming convention for 'template' based on the
      // hook used. If the template does not exist, the theme engine used
      // should throw an exception at runtime when attempting to include
      // the template file.
      elseif (!isset($info['template'])) {
        $info['template'] = strtr($hook, '_', '-');
        $result[$hook]['template'] = $info['template'];
      }

      // Prepend the current theming path when none is set. This is required
      // for the default theme engine to know where the template lives.
      if (isset($result[$hook]['template']) && !isset($info['path'])) {
        $result[$hook]['path'] = $path . '/templates';
      }

      // If the default keys are not set, use the default values registered
      // by the module.
      if (isset($cache[$hook])) {
        $result[$hook] += array_intersect_key($cache[$hook], $hook_defaults);
      }

      // Preprocess variables for all theming hooks, whether the hook is
      // implemented as a template or as a function. Ensure they are arrays.
      if (!isset($info['preprocess functions']) || !is_array($info['preprocess functions'])) {
        $info['preprocess functions'] = array();
        $prefixes = array();
        if ($type == 'module') {
          // Default variable preprocessor prefix.
          $prefixes[] = 'template';
          // Add all modules so they can intervene with their own variable
          // preprocessors. This allows them to provide variable preprocessors
          // even if they are not the owner of the current hook.
          $prefixes = array_merge($prefixes, $module_list);
        }
        elseif ($type == 'theme_engine' || $type == 'base_theme_engine') {
          // Theme engines get an extra set that come before the normally
          // named variable preprocessors.
          $prefixes[] = $name . '_engine';
          // The theme engine registers on behalf of the theme using the
          // theme's name.
          $prefixes[] = $theme;
        }
        else {
          // This applies when the theme manually registers their own variable
          // preprocessors.
          $prefixes[] = $name;
        }
        foreach ($prefixes as $prefix) {
          // Only use non-hook-specific variable preprocessors for theming
          // hooks implemented as templates. See the @defgroup themeable
          // topic.
          if (isset($info['template']) && function_exists($prefix . '_preprocess')) {
            $info['preprocess functions'][] = $prefix . '_preprocess';
          }
          if (function_exists($prefix . '_preprocess_' . $hook)) {
            $info['preprocess functions'][] = $prefix . '_preprocess_' . $hook;
          }
        }
      }
      // Check for the override flag and prevent the cached variable
      // preprocessors from being used. This allows themes or theme engines
      // to remove variable preprocessors set earlier in the registry build.
      if (!empty($info['override preprocess functions'])) {
        // Flag not needed inside the registry.
        unset($result[$hook]['override preprocess functions']);
      }
      elseif (isset($cache[$hook]['preprocess functions']) && is_array($cache[$hook]['preprocess functions'])) {
        $info['preprocess functions'] = array_merge($cache[$hook]['preprocess functions'], $info['preprocess functions']);
      }
      $result[$hook]['preprocess functions'] = $info['preprocess functions'];
    }

    // Merge the newly created theme hooks into the existing cache.
    $cache = $result + $cache;
  }

  // Let themes have variable preprocessors even if they didn't register a
  // template.
  if ($type == 'theme' || $type == 'base_theme') {
    foreach ($cache as $hook => $info) {
      // Check only if not registered by the theme or engine.
      if (empty($result[$hook])) {
        if (!isset($info['preprocess functions'])) {
          $cache[$hook]['preprocess functions'] = array();
        }
        // Only use non-hook-specific variable preprocessors for theme hooks
        // implemented as templates. See the @defgroup themeable topic.
        if (isset($info['template']) && function_exists($name . '_preprocess')) {
          $cache[$hook]['preprocess functions'][] = $name . '_preprocess';
        }
        if (function_exists($name . '_preprocess_' . $hook)) {
          $cache[$hook]['preprocess functions'][] = $name . '_preprocess_' . $hook;
          $cache[$hook]['theme path'] = $path;
        }
      }
    }
  }
}