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* This file is part of the Symfony package.
* (c) Fabien Potencier <>
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
namespace Symfony\Bridge\Twig\Form;
use Symfony\Component\Form\AbstractRendererEngine;
use Symfony\Component\Form\FormView;
use Twig\Environment;
use Twig\Template;
* @author Bernhard Schussek <>
class TwigRendererEngine extends AbstractRendererEngine
* @var Environment
private $environment;
* @var Template
private $template;
public function __construct(array $defaultThemes, Environment $environment)
$this->environment = $environment;
* {@inheritdoc}
public function renderBlock(FormView $view, $resource, $blockName, array $variables = [])
$cacheKey = $view->vars[self::CACHE_KEY_VAR];
$context = $this->environment->mergeGlobals($variables);
// By contract,This method can only be called after getting the resource
// (which is passed to the method). Getting a resource for the first time
// (with an empty cache) is guaranteed to invoke loadResourcesFromTheme(),
// where the property $template is initialized.
// We do not call renderBlock here to avoid too many nested level calls
// (XDebug limits the level to 100 by default)
$this->template->displayBlock($blockName, $context, $this->resources[$cacheKey]);
return ob_get_clean();
* Loads the cache with the resource for a given block name.
* This implementation eagerly loads all blocks of the themes assigned to the given view
* and all of its ancestors views. This is necessary, because Twig receives the
* list of blocks later. At that point, all blocks must already be loaded, for the
* case that the function "block()" is used in the Twig template.
* @see getResourceForBlock()
* @param string $cacheKey The cache key of the form view
* @param FormView $view The form view for finding the applying themes
* @param string $blockName The name of the block to load
* @return bool True if the resource could be loaded, false otherwise
protected function loadResourceForBlockName($cacheKey, FormView $view, $blockName)
// The caller guarantees that $this->resources[$cacheKey][$block] is
// not set, but it doesn't have to check whether $this->resources[$cacheKey]
// is set. If $this->resources[$cacheKey] is set, all themes for this
// $cacheKey are already loaded (due to the eager population, see doc comment).
if (isset($this->resources[$cacheKey])) {
// As said in the previous, the caller guarantees that
// $this->resources[$cacheKey][$block] is not set. Since the themes are
// already loaded, it can only be a non-existing block.
$this->resources[$cacheKey][$blockName] = false;
return false;
// Recursively try to find the block in the themes assigned to $view,
// then of its parent view, then of the parent view of the parent and so on.
// When the root view is reached in this recursion, also the default
// themes are taken into account.
// Check each theme whether it contains the searched block
if (isset($this->themes[$cacheKey])) {
for ($i = \count($this->themes[$cacheKey]) - 1; $i >= 0; --$i) {
$this->loadResourcesFromTheme($cacheKey, $this->themes[$cacheKey][$i]);
// CONTINUE LOADING (see doc comment)
// Check the default themes once we reach the root view without success
if (!$view->parent) {
if (!isset($this->useDefaultThemes[$cacheKey]) || $this->useDefaultThemes[$cacheKey]) {
for ($i = \count($this->defaultThemes) - 1; $i >= 0; --$i) {
$this->loadResourcesFromTheme($cacheKey, $this->defaultThemes[$i]);
// CONTINUE LOADING (see doc comment)
// Proceed with the themes of the parent view
if ($view->parent) {
$parentCacheKey = $view->parent->vars[self::CACHE_KEY_VAR];
if (!isset($this->resources[$parentCacheKey])) {
$this->loadResourceForBlockName($parentCacheKey, $view->parent, $blockName);
// EAGER CACHE POPULATION (see doc comment)
foreach ($this->resources[$parentCacheKey] as $nestedBlockName => $resource) {
if (!isset($this->resources[$cacheKey][$nestedBlockName])) {
$this->resources[$cacheKey][$nestedBlockName] = $resource;
// Even though we loaded the themes, it can happen that none of them
// contains the searched block
if (!isset($this->resources[$cacheKey][$blockName])) {
// Cache that we didn't find anything to speed up further accesses
$this->resources[$cacheKey][$blockName] = false;
return false !== $this->resources[$cacheKey][$blockName];
* Loads the resources for all blocks in a theme.
* @param string $cacheKey The cache key for storing the resource
* @param mixed $theme The theme to load the block from. This parameter
* is passed by reference, because it might be necessary
* to initialize the theme first. Any changes made to
* this variable will be kept and be available upon
* further calls to this method using the same theme.
protected function loadResourcesFromTheme($cacheKey, &$theme)
if (!$theme instanceof Template) {
/* @var Template $theme */
$theme = $this->environment->load($theme)->unwrap();
if (null === $this->template) {
// Store the first Template instance that we find so that
// we can call displayBlock() later on. It doesn't matter *which*
// template we use for that, since we pass the used blocks manually
// anyway.
$this->template = $theme;
// Use a separate variable for the inheritance traversal, because
// theme is a reference and we don't want to change it.
$currentTheme = $theme;
$context = $this->environment->mergeGlobals([]);
// The do loop takes care of template inheritance.
// Add blocks from all templates in the inheritance tree, but avoid
// overriding blocks already set.
do {
foreach ($currentTheme->getBlocks() as $block => $blockData) {
if (!isset($this->resources[$cacheKey][$block])) {
// The resource given back is the key to the bucket that
// contains this block.
$this->resources[$cacheKey][$block] = $blockData;
} while (false !== $currentTheme = $currentTheme->getParent($context));