This is an approach of creating a modern (MS Office, Visual Studio like) frameless window in Qt5.
(default)
(little bit tweaking)
git clone https://github.com/naj59/ModernFramlessWindow.git
cd ModernFramlessWindow/
qmake
make / mingw32-make
or just open up the ModernFramlessWindow.pro inside QtCreator.
Do whatever you want, it's just an approach which is hopefully helping anybody who wants to create a nice frameless window.