GetWindowRgn function Null safety
The GetWindowRgn function obtains a copy of the window region of a window. The window region of a window is set by calling the SetWindowRgn function. 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 GetWindowRgn( HWND hWnd, HRGN hRgn );
int GetWindowRgn(int hWnd, int hRgn) => _GetWindowRgn(hWnd, hRgn);