Sent when a button should be painted.
Note This notification message is provided only for compatibility with 16-bit versions of Microsoft Windows earlier than version 3.0. Applications should use the BS_OWNERDRAW button style and the DRAWITEMSTRUCT structure for this task.
The parent window of the button receives the BN_PAINT notification code through the WM_COMMAND message.
    BN_PAINT
        WPARAM wParam
        LPARAM lParam;
No return value.