Default to Fusion based Dark/Bright themes on Windows (#3452)

launcher/Application.cpp

@@ -154,6 +154,7 @@
 
 #if defined Q_OS_WIN32
 #include <windows.h>
+#include <QStyleHints>
 #include "WindowsConsole.h"
 #endif
 
@@ -1109,8 +1110,16 @@ bool Application::createSetupWizard()
         // set default theme after going into theme wizard
         if (!validIcons)
             settings()->set("IconTheme", QString("pe_colored"));
-        if (!validWidgets)
-            settings()->set("ApplicationTheme", QString("system"));
+        if (!validWidgets) {
+#if defined(Q_OS_WIN32) && QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+            const QString style =
+                QGuiApplication::styleHints()->colorScheme() == Qt::ColorScheme::Dark ? QStringLiteral("dark") : QStringLiteral("bright");
+#else
+            const QString style = QStringLiteral("system");
+#endif
+
+            settings()->set("ApplicationTheme", style);
+        }
 
         m_themeManager->applyCurrentlySelectedTheme(true);