DefMDIChildProc function Null safety user32

int DefMDIChildProc(
  1. int hWnd,
  2. int uMsg,
  3. int wParam,
  4. int lParam

Provides default processing for any window message that the window procedure of a multiple-document interface (MDI) child window does not process. A window message not processed by the window procedure must be passed to the DefMDIChildProc function, not to the DefWindowProc function.

  HWND   hWnd,
  UINT   uMsg,
  WPARAM wParam,
  LPARAM lParam


int DefMDIChildProc(int hWnd, int uMsg, int wParam, int lParam) =>
    _DefMDIChildProc(hWnd, uMsg, wParam, lParam);