QWindow rendered with OpenGL has wrong alignment

When creating a QWindow with surface type "OpenGLSurface" and placing it to window container, the window area is shifted left and down. I've attached the simple source code i used to reproduce the issue.

"MainWindow" class creates a QWindow and a container for it, and then with show event adds this container to its layout.

"NativeWindow" inherits from QWindow, and uses OpenGL to only draw a diagonal line from top left to bottom right corner.

Compiling and running the code with Qt 5.12.2 the diagonal is shifted

,

while using Qt 5.6.0 makes it placed correctly:

I've checked it on Windows, but there was a bug report from my colleagues that the same happens on Linux.