I haven't personally tested this yet, but would it return E_INVALIDARG if pVisible is NULL? (I'm basing this assumption on https://docs.microsoft.com/en-us/previous-versions/ms786966(v=vs.85) )‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐On Monday, September 7, 2020 1:09 AM, dongpengpeng@uniontech.com <dongpengpeng@uniontech.com> wrote: