Im using this in order to make my windows frameless and create a custom titlebar for it. everything is fine except I want to make my windows corners round, but if I do that then I will have something like

as you can see original windows frame is still visible... so my question is how can I actually making it round without using the native windows functionality? Im asking because if I use something like

HWND hwnd = (HWND)this->winId();
HRGN hRegion = ::CreateRoundRectRgn(0, 0, w, h, 11, 11);
SetWindowRgn(hwnd, hRegion, true);

it will actually make the corners round, but there is still 2 problem

1. the new rounded corner is soo sharp that hurt my eyes to just look at.
2. this somehow will disable windows shadow, but I do actually want it...

so what can I do for it?