How to put tabs in the window header (like in a browser)?

Question

User interface

It is necessary to place tabs on the top bar of the Windows window, as in a browser. I use the qt library, and I know that you can set the FramelessWindowHint flag and create this header yourself, while registering dragging, window scaling is not a problem, I already did it. The point is that when dragging a window to the top edge of the monitor, it does not expand to full screen, and in "full screen mode" the application has gray bars on the sides.

Answer 1

What prevents you from checking the coordinates of the window and opening it yourself?