SetWindowRgn function user32
The SetWindowRgn function sets the window region of a window. The window region determines the area within the window where the system permits drawing. The system does not display any portion of a window that lies outside of the window region
int SetWindowRgn(
HWND hWnd,
HRGN hRgn,
BOOL bRedraw
);
Implementation
int SetWindowRgn(int hWnd, int hRgn, int bRedraw) =>
_SetWindowRgn(hWnd, hRgn, bRedraw);