[ticket/15187] Add paths of newly enabled extensions to template

When enabling an extension its paths aren't added immediately to
the template which results in ACP events not being registered in
the compiled template files.

PHPBB3-15187

phpBB/phpbb/extension/manager.php

@@ -227,6 +227,8 @@ class manager
 		if ($active)
 		{
 			$this->config->increment('assets_version', 1);
+
+			$this->update_template_paths($name, $this->container->get('template'));
 		}
 
 		return !$active;
@@ -589,4 +591,38 @@ class manager
 		}
 		return $finder;
 	}
+
+	/**
+	* Make the template aware of ACP template events of a newly enabled extension
+	*
+	* @param string						$name		The extension's name
+	* @param \phpbb\template\base|null	$template	The template service
+	* @return null
+	*/
+	protected function update_template_paths($name, \phpbb\template\base $template = null)
+	{
+		if ($template instanceof \phpbb\template\base)
+		{
+			$possible_paths = array(
+				$this->phpbb_root_path . 'ext/' . $name . '/adm/style',
+				$this->phpbb_root_path . 'ext/' . $name . '/styles',
+			);
+
+			$paths = array_filter($possible_paths, 'is_dir');
+
+			if ($paths)
+			{
+				$names = array(
+					array(
+						'name' 		=> 'adm',
+						'ext_path' 	=> 'adm/style/',
+					),
+				);
+
+				$paths[] = $this->phpbb_root_path . 'adm/style';
+
+				$template->set_custom_style($names, $paths);
+			}
+		}
+	}
 }