Improved on the QT implementation of the new approach, per suggestion by Manaatti.

src/qt/qt_mainwindow.hpp

@@ -167,6 +167,10 @@ private:
     bool resizableonce       = false;
     bool vnc_enabled         = false;
 
+    /* Full screen ON and OFF signals */
+    static bool fs_on_signal = false;
+    static bool fs_off_signal = false;
+
     friend class SpecifyDimensions;
     friend class ProgSettings;
     friend class RendererCommon;