Refactored custom backend view implementations.

This implementation gets rid of the route attribute 'custom_backend_view = true'.
It introduces a new twig function to wrap specific content blocks with the be_main
template of the Contao backend. This way is more intuitive and a less explicit approach.

src/Resources/config/listener.yml

@@ -146,8 +146,3 @@ services:
         tags:
             - { name: kernel.event_listener, event: kernel.request, method: onKernelRequest }
             - { name: kernel.event_listener, event: kernel.response, method: onKernelResponse }
-
-    contao.listener.custom_backend_view:
-        class: Contao\CoreBundle\EventListener\CustomBackendViewListener
-        tags:
-            - { name: kernel.event_listener, event: kernel.response, method: onKernelResponse }

src/Resources/config/services.yml

@@ -117,3 +117,11 @@ services:
             - "_contao_fe_attributes"
         calls:
             - ["setName", ["contao_frontend"]]
+
+    contao.twig.base_template_wrapper:
+        class: Contao\CoreBundle\Twig\Extension\ContaoBaseTemplateExtension
+        arguments:
+            - "@request_stack"
+        public: false
+        tags:
+            - { name: twig.extension }

src/Resources/views/Backend/be_page.html.twig

@@ -1,17 +1,9 @@
-{% set _panel = block('panel') %}
-{% set _errors = block('errors') %}
+{% set _main  = block('main') %}
+{% set _headline = block('headline') %}
+{% set _error = block('error') %}
 
-{% if _panel is not empty %}
-    <div class="tl_panel">
-        {{ _panel | raw }}
-    </div>
-{% endif %}
-
-{% if _errors is not empty %}
-    <p class="tl_gerror">{{ _errors | raw }}</p>
-{% endif %}
-
-<div class="tl_listing_container">
-    {% block content %}
-    {% endblock %}
-</div>
+{{ contao_base_template_wrapper({
+    main: _main,
+    error: _error,
+    headline: _headline
+}) | raw }}

src/Twig/Extension/ContaoBaseTemplateExtension.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Contao\CoreBundle\Twig\Extension;
+
+use Contao\BackendRoute;
+use Symfony\Component\HttpFoundation\RequestStack;
+
+class ContaoBaseTemplateExtension extends \Twig_Extension
+{
+    protected $requestStack;
+
+    public function __construct(RequestStack $requestStack)
+    {
+        $this->requestStack = $requestStack;
+    }
+
+    public function getFunctions()
+    {
+        return [
+            new \Twig_SimpleFunction('contao_base_template_wrapper', [$this, 'wrapWithBaseTemplate'])
+        ];
+    }
+
+    public function wrapWithBaseTemplate(array $blocks = [])
+    {
+        $scope = $this->requestStack->getCurrentRequest()->attributes->get('_scope');
+
+        if ('backend' !== $scope) {
+            return '';
+        }
+
+        $backendRoute = new BackendRoute();
+        $backendTemplate = $backendRoute->getBaseTemplate();
+
+        foreach ($blocks as $key => $content) {
+            $backendTemplate->{$key} = $content;
+        }
+
+        $response = $backendRoute->run();
+
+        return $response->getContent();
+    }
+
+    public function getName()
+    {
+        return 'base_template_wrapper';
+    }
+
+}