It's enabled by default in qt6

korgac/korgacmain.cpp

@@ -24,9 +24,9 @@ int main(int argc, char **argv)
 {
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling, true);
+    QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps, true);
 #endif
     QApplication app(argc, argv);
-    app.setAttribute(Qt::AA_UseHighDpiPixmaps, true);
 #if KCOREADDONS_VERSION < QT_VERSION_CHECK(6, 0, 0)
     Kdelibs4ConfigMigrator migrate(QStringLiteral("korgac"));
 

src/main.cpp

@@ -26,8 +26,8 @@ int main(int argc, char **argv)
 {
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling, true);
-#endif
     QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps, true);
+#endif
     KOrganizerApp app(argc, &argv);
     KCrash::initialize();
     KLocalizedString::setApplicationDomain("korganizer");