function ThemeManager::render

Overrides ThemeManagerInterface::render

File

core/lib/Drupal/Core/Theme/ThemeManager.php, line 129

Class

ThemeManager

Provides the default implementation of a theme manager.

Namespace

Code

public function render($hook, array $variables) {
    static $default_attributes;
    $active_theme = $this->getActiveTheme();
    // If called before all modules are loaded, we do not necessarily have a
    // full theme registry to work with, and therefore cannot process the theme
    // request properly. See also \Drupal\Core\Theme\Registry::get().
    if (!$this->moduleHandler
        ->isLoaded() && !defined('MAINTENANCE_MODE')) {
        throw new \Exception('The theme implementations may not be rendered until all modules are loaded.');
    }
    $theme_registry = $this->themeRegistry
        ->getRuntime();
    // If an array of hook candidates were passed, use the first one that has an
    // implementation.
    if (is_array($hook)) {
        foreach ($hook as $candidate) {
            if ($theme_registry->has($candidate)) {
                break;
            }
        }
        $hook = $candidate;
    }
    // Save the original theme hook, so it can be supplied to theme variable
    // preprocess callbacks.
    $original_hook = $hook;
    // If there's no implementation, check for more generic fallbacks.
    // If there's still no implementation, log an error and return an empty
    // string.
    if (!$theme_registry->has($hook)) {
        // Iteratively strip everything after the last '__' delimiter, until an
        // implementation is found.
        while ($pos = strrpos($hook, '__')) {
            $hook = substr($hook, 0, $pos);
            if ($theme_registry->has($hook)) {
                break;
            }
        }
        if (!$theme_registry->has($hook)) {
            // Only log a message when not trying theme suggestions ($hook being an
            // array).
            if (!isset($candidate)) {
                \Drupal::logger('theme')->warning('Theme hook %hook not found.', [
                    '%hook' => $hook,
                ]);
            }
            // There is no theme implementation for the hook passed. Return FALSE so
            // the function calling
            // \Drupal\Core\Theme\ThemeManagerInterface::render() can differentiate
            // between a hook that exists and renders an empty string, and a hook
            // that is not implemented.
            return FALSE;
        }
    }
    $info = $theme_registry->get($hook);
    if (isset($info['deprecated'])) {
        @trigger_error($info['deprecated'], E_USER_DEPRECATED);
    }
    // If a renderable array is passed as $variables, then set $variables to
    // the arguments expected by the theme function.
    if (isset($variables['#theme']) || isset($variables['#theme_wrappers'])) {
        $element = $variables;
        $variables = [];
        if (isset($info['variables'])) {
            foreach (array_keys($info['variables']) as $name) {
                if (\array_key_exists("#{$name}", $element)) {
                    $variables[$name] = $element["#{$name}"];
                }
            }
        }
        else {
            $variables[$info['render element']] = $element;
            // Give a hint to render engines to prevent infinite recursion.
            $variables[$info['render element']]['#render_children'] = TRUE;
        }
    }
    // Merge in argument defaults.
    if (!empty($info['variables'])) {
        $variables += $info['variables'];
    }
    elseif (!empty($info['render element'])) {
        $variables += [
            $info['render element'] => [],
        ];
    }
    // Supply original caller info.
    $variables += [
        'theme_hook_original' => $original_hook,
    ];
    $suggestions = $this->buildThemeHookSuggestions($hook, $info['base hook'] ?? '', $variables);
    // Check if each suggestion exists in the theme registry, and if so,
    // use it instead of the base hook. For example, a function may use
    // '#theme' => 'node', but a module can add 'node__article' as a suggestion
    // via hook_theme_suggestions_HOOK_alter(), enabling a theme to have
    // an alternate template file for article nodes.
    foreach (array_reverse($suggestions) as $suggestion) {
        if ($theme_registry->has($suggestion)) {
            $info = $theme_registry->get($suggestion);
            break;
        }
    }
    // Include a file if the variable preprocessor is held elsewhere.
    if (!empty($info['includes'])) {
        foreach ($info['includes'] as $include_file) {
            include_once $this->root . '/' . $include_file;
        }
    }
    // Invoke the variable preprocessors, if any.
    if (isset($info['base hook'])) {
        $base_hook = $info['base hook'];
        $base_hook_info = $theme_registry->get($base_hook);
        // Include files required by the base hook, since its variable
        // preprocessors might reside there.
        if (!empty($base_hook_info['includes'])) {
            foreach ($base_hook_info['includes'] as $include_file) {
                include_once $this->root . '/' . $include_file;
            }
        }
        if (isset($base_hook_info['preprocess functions'])) {
            // Set a variable for the 'theme_hook_suggestion'. This is used to
            // maintain backwards compatibility with template engines.
            $theme_hook_suggestion = $hook;
        }
    }
    if (isset($info['preprocess functions'])) {
        foreach ($info['preprocess functions'] as $preprocessor_function) {
            if (is_callable($preprocessor_function)) {
                call_user_func_array($preprocessor_function, [
                    &$variables,
                    $hook,
                    $info,
                ]);
            }
        }
        // Allow theme preprocess functions to set $variables['#attached'] and
        // $variables['#cache'] and use them like the corresponding element
        // properties on render arrays. In Drupal 8, this is the (only) officially
        // supported method of attaching bubbleable metadata from preprocess
        // functions. Assets attached here should be associated with the template
        // that we are preprocessing variables for.
        $preprocess_bubbleable = [];
        foreach ([
            '#attached',
            '#cache',
        ] as $key) {
            if (isset($variables[$key])) {
                $preprocess_bubbleable[$key] = $variables[$key];
            }
        }
        // We do not allow preprocess functions to define cacheable elements.
        unset($preprocess_bubbleable['#cache']['keys']);
        if ($preprocess_bubbleable) {
            // @todo Inject the Renderer in https://www.drupal.org/node/2529438.
            \Drupal::service('renderer')->render($preprocess_bubbleable);
        }
    }
    // Generate the output using a template.
    $render_function = 'twig_render_template';
    $extension = '.html.twig';
    // The theme engine may use a different extension and a different
    // renderer.
    $theme_engine = $active_theme->getEngine();
    if (isset($theme_engine)) {
        if ($info['type'] != 'module') {
            if (function_exists($theme_engine . '_render_template')) {
                $render_function = $theme_engine . '_render_template';
            }
            $extension_function = $theme_engine . '_extension';
            if (function_exists($extension_function)) {
                $extension = $extension_function();
            }
        }
    }
    // In some cases, a template implementation may not have had
    // template_preprocess() run (for example, if the default implementation
    // is a function, but a template overrides that default implementation).
    // In these cases, a template should still be able to expect to have
    // access to the variables provided by template_preprocess(), so we add
    // them here if they don't already exist. We don't want the overhead of
    // running template_preprocess() twice, so we use the 'directory' variable
    // to determine if it has already run, which while not completely
    // intuitive, is reasonably safe, and allows us to save on the overhead of
    // adding some new variable to track that.
    if (!isset($variables['directory'])) {
        $default_template_variables = [];
        template_preprocess($default_template_variables, $hook, $info);
        $variables += $default_template_variables;
    }
    if (!isset($default_attributes)) {
        $default_attributes = new Attribute();
    }
    foreach ([
        'attributes',
        'title_attributes',
        'content_attributes',
    ] as $key) {
        if (isset($variables[$key]) && !$variables[$key] instanceof Attribute) {
            if ($variables[$key]) {
                $variables[$key] = new Attribute($variables[$key]);
            }
            else {
                // Create empty attributes.
                $variables[$key] = clone $default_attributes;
            }
        }
    }
    // Render the output using the template file.
    $template_file = $info['template'] . $extension;
    if (isset($info['path'])) {
        $template_file = $info['path'] . '/' . $template_file;
    }
    // Add the theme suggestions to the variables array just before rendering
    // the template for backwards compatibility with template engines.
    $variables['theme_hook_suggestions'] = $suggestions;
    // For backwards compatibility, pass 'theme_hook_suggestion' on to the
    // template engine. This is only set when calling a direct suggestion like
    // '#theme' => 'menu__shortcut_default' when the template exists in the
    // current theme.
    if (isset($theme_hook_suggestion)) {
        $variables['theme_hook_suggestion'] = $theme_hook_suggestion;
    }
    $output = $render_function($template_file, $variables);
    return $output instanceof MarkupInterface ? $output : (string) $output;
}