Windows QPA: Take hasBorderInFullScreen into account when checking for fullscreen

Add a margin to the window geometry.

Task-number: QTBUG-61595
Change-Id: I12c557d7cfb1fe954a9845848c0777817c4cbf27
Reviewed-by: Thomas Sondergaard <thomas@sondergaard.cc>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -1758,6 +1758,8 @@ bool QWindowsWindow::isFullScreen_sys() const
     if (!w->isTopLevel())
         return false;
     QRect geometry = geometry_sys();
+    if (testFlag(HasBorderInFullScreen))
+        geometry += QMargins(1, 1, 1, 1);
     QPlatformScreen *screen = screenForGeometry(geometry);
     return screen && geometry == QHighDpi::toNativePixels(screen->geometry(), screen);
 }