Introduce class ipl\Web\Compat\StyleWithNonce

src/Compat/StyleWithNonce.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace ipl\Web\Compat;
+
+use Icinga\Application\Version;
+use Icinga\Util\Csp;
+use ipl\Web\Style;
+
+/**
+ * Use this class to define inline style which is compatible
+ * with Icinga Web &lt; 2.12 and with CSP support in &gt;= 2.12
+ */
+class StyleWithNonce extends Style
+{
+    public function getNonce(): ?string
+    {
+        if ($this->nonce === null) {
+            $this->nonce = version_compare(Version::VERSION, '2.12.0', '>=')
+                ? Csp::getStyleNonce() ?? ''
+                : '';
+        }
+
+        return parent::getNonce();
+    }
+}

src/Style.php

@@ -102,7 +102,7 @@ public function render(): string
 
         return (new HtmlElement(
             'style',
-            (new Attributes())->addAttribute(new Attribute('nonce', $this->nonce)),
+            (new Attributes())->addAttribute(new Attribute('nonce', $this->getNonce())),
             HtmlString::create($ruleset->renderCss())
         ))->render();
     }