This appears to be X11-specific, and X11 essentially does not have native platform controls. Also if you're in X11 you've quite likely already given up any real hope of all your windows looking the same. You also seem to be casually assuming this would be cross-platform, but this would be the equivalent of implementing something in raw Win32 API calls. There's zero cross-platform concerns here, on the grounds it'll never be cross-platform. In fact, given that it's pretty likely the move to Wayland would be completed by the Linux community before this project could reach a point where it would be something you might consider using seriously for a non-trivial project, it's debatable whether it's even good for one platform.
This appears to be X11-specific, and X11 essentially does not have native platform controls. Also if you're in X11 you've quite likely already given up any real hope of all your windows looking the same. You also seem to be casually assuming this would be cross-platform, but this would be the equivalent of implementing something in raw Win32 API calls. There's zero cross-platform concerns here, on the grounds it'll never be cross-platform. In fact, given that it's pretty likely the move to Wayland would be completed by the Linux community before this project could reach a point where it would be something you might consider using seriously for a non-trivial project, it's debatable whether it's even good for one platform.