[#235] Backport styles.php caching for moodle 4.1

Author: jnlar

lib.php

@@ -1060,8 +1060,39 @@ public function show_editor(?array $capabilities = ['moodle/course:manageactivit
  * Moodle native lib/navigationlib.php calls this hook allowing us to override UI.
  */
 function format_onetopic_before_http_headers() {
-    global $PAGE;
-    $PAGE->requires->css('/course/format/onetopic/styles.php');
+    global $PAGE, $COURSE;
+
+    // Don't require styles script if the course format isn't 'onetopic'.
+    if ($PAGE->course && isset($COURSE->id) && $COURSE->format == 'onetopic') {
+
+        // Check if site-wide tab styles are configured, if not, do nothing.
+        if (!get_config('format_onetopic', 'tabstyles')) {
+            return;
+        }
+
+        $revision = format_onetopic_get_tabstyles_revision();
+        $PAGE->requires->css(new \moodle_url('/course/format/onetopic/styles.php', [
+            'revision' => $revision,
+        ]));
+    }
+}
+
+/**
+ * Generates an 8-character hash from the tab styles configuration.
+ * When styles change, the hash changes, creating a new URL that
+ * busts the cache.
+ *
+ * @return string
+ */
+function format_onetopic_get_tabstyles_revision(): string {
+    $tabstyles = get_config('format_onetopic', 'tabstyles');
+
+    if (empty($tabstyles)) {
+        return '0';
+    }
+
+    // Use first 8 chars of md5 hash as revision.
+    return substr(md5($tabstyles), 0, 8);
 }
 
 /**

styles.php

@@ -28,8 +28,7 @@
 // phpcs:disable moodle.Files.RequireLogin.Missing
 require_once('../../../config.php');
 
-@header('Content-Disposition: inline; filename="styles.php"');
-@header('Content-Type: text/css; charset=utf-8');
+$revision = optional_param('revision', 0, PARAM_ALPHANUM);
 
 $withunits = ['font-size', 'line-height', 'margin', 'padding', 'border-width', 'border-radius'];
 $csscontent = '';
@@ -133,4 +132,37 @@
     }
 }
 
+$csstabstyles = trim($csstabstyles);
+$etag = md5($csstabstyles . $revision);
+
+// ETag validation: Return 304 if client has the current version. This will
+// preserve the existing cache for $cache_lifetime.
+if (isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
+    $clientetag = trim($_SERVER['HTTP_IF_NONE_MATCH'], '"');
+    if ($clientetag === $etag) {
+        header('HTTP/1.1 304 Not Modified');
+        header('ETag: "' . $etag . '"');
+        exit;
+    }
+}
+
+// Return empty response for edge cases (no styles configured & direct URL access).
+if (empty($csstabstyles)) {
+    header('HTTP/1.1 304 Not Modified');
+    header('Content-Length: 0');
+    exit;
+}
+
+// Cache for 1 year, this is safe due to cache busting via revision param.
+$cache_lifetime = 31536000;
+header('Cache-Control: public, max-age=' . $cache_lifetime . ', immutable');
+header('Expires: ' . gmdate('D, d M Y H:i:s', time() + $cache_lifetime) . ' GMT');
+header('ETag: "' . $etag . '"');
+
+// Content headers.
+header('Content-Length: ' . strlen($csstabstyles));
+header('Content-Disposition: inline; filename="styles.php"');
+header('Content-Type: text/css; charset=utf-8');
+header('X-Content-Type-Options: nosniff');
+
 echo $csstabstyles;