Fullscreen application will disappear when I open a dialog such as file dialog or I click on my the second screen.

[Crawl.W]

Re: Qml - ApplicationWindow fullscreen issues
I am facing the same problem and I do not think get a good solution and cause of issue even though I think @GoranShekerov 's method will work.My enviroment is Win10, Qt5.12, msvc2017.Simple testing code is as follows:

Window {
    visible: true
    width: 1920
    height: 1080
    flags: flags | Qt.FramelessWindowHint //just Qt.FramelessWindowHint also the same
}

My the first screen resolution is 1920x1080, that mean a fullscreen application.Surely, I will use @GoranShekerov 's method temporarily.