Enhanced locale determination logic to evaluate the Accept-Language header from the browser, allowing for improved locale selection based on user preferences. Updated fallback mechanism for locale handling.

src/app.cpp

@@ -140,14 +140,27 @@ Wt::WLocale App::determineLocaleFromBrowser() const {
         }
     }
 
-    // 2. Sonst Locale verwenden, die Wt bereits aus dem Browser/Request ermittelt hat
+    // 2. Accept-Language Header des Browsers auswerten
+    std::string accept = env_.headerValue("Accept-Language");
+    if (!accept.empty()) {
+        std::stringstream ss(accept);
+        std::string part;
+        while (std::getline(ss, part, ',')) {
+            auto localeName = mapLanguageTag(part);
+            if (!localeName.empty()) {
+                return makeLocale(localeName);
+            }
+        }
+    }
+
+    // 3. Sonst Locale verwenden, die Wt bereits aus dem Request ermittelt hat
     auto envLocaleName = env_.locale().name(); // z.B. "de_DE", "en_GB"
     auto mapped = mapLanguageTag(envLocaleName);
     if (!mapped.empty()) {
         return makeLocale(mapped);
     }
 
-    // Fallback: britisches Englisch
+    // 4. Fallback: britisches Englisch
     return makeLocale("en_GB");
 }