InvalidateRgn function user32

int InvalidateRgn(
  1. int hWnd,
  2. int hRgn,
  3. int bErase

The InvalidateRgn function invalidates the client area within the specified region by adding it to the current update region of a window. The invalidated region, along with all other areas in the update region, is marked for painting when the next WM_PAINT message occurs.

BOOL InvalidateRgn(
  HWND hWnd,
  HRGN hRgn,
  BOOL bErase


int InvalidateRgn(int hWnd, int hRgn, int bErase) =>
    _InvalidateRgn(hWnd, hRgn, bErase);