when calling view->show(); before setting setFixedSize... then the app Window is not created correctly (top bar missing)

[dsyleixa]

hi,
when calling
view->show();
before setting
...->setFixedSize...
then the app Window is not created correctly as the top window bar is missing or respectively out ouf screen (feat. maximize, minimize, close).
OTOH, when calling view->show(); as the last, all is fine.

(Platform: Raspberry Pi 3B, OS Stretch, Qt5 creator, Full-HD HDMI display)

// show the view
    //view->show();  // faulty
    view->setFixedSize(800,600);
    scene->setSceneRect(0,0,800,600);
    view->show();  // correct