How to remove title but with frame border?

[Spitfire]

Hmm I don't quite understand what you mean by 'put my widget on the title bar with qt'.

Do you want to get rid of the title bar of a widget (top part of a widget with title, max/min/close buttons)?
Or do you want to get rid of entry on the window task bar (on the bottom of the screen when icon of your app appears)?

Whatever you want, I can bet that there's no need to go native, this way you make your code not-portable.
Qt should suffice.

And what 'screen edge problem' you mean?

[Berryblue031]

If you have a frameless window and want to be able to maximize / minimize / close it by the system you need to add some more window flags

FramelessWindow::FramelessWindow()
: QWidget(0, Qt::WindowFlags(Qt::FramelessWindowHint | Qt::WindowMinMaxButtonsHint | Qt::WindowSystemMenuHint))

FramelessWindow::FramelessWindow()
: QWidget(0, Qt::WindowFlags(Qt::FramelessWindowHint | Qt::WindowMinMaxButtonsHint | Qt::WindowSystemMenuHint))

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If you want to be able to grab the edges of your window and resize it you will have to implement this yourself or use a utility like Frameless Window Helper