Change application start procedure, add a login step.

src/main.cpp

@@ -1,11 +1,22 @@
 #include "mainwindow.h"
 #include <QApplication>
+#include "loginwindow.h"
 
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
+    needLogin:
+    LoginWindow l;
+    l.showFullScreen();
     MainWindow w;
-    w.show();
+    int rec =  l.exec();
+    if (rec !=QDialog::Accepted )
+    {
+        goto needLogin;
+    }
+//    l.deleteLater();
+
+    w.showFullScreen();
 
     return a.exec();
 }