it's enabled by default in qt6

src/main.cpp

@@ -21,7 +21,9 @@ int main (int argc, char *argv[])
      * Create application first
      */
     QApplication app(argc, argv);
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     app.setAttribute(Qt::AA_UseHighDpiPixmaps, true);
+#endif
 
     /**
      * construct about data for KTeaTime