"C++: Windows Toast Notification" by Shao Voon Wong
https://www.codeproject.com/Articles/5286393/Cplusplus-Windows-Toast-Notification
"Windows Toast is a small window appearing at the bottom-right of the
screen, is a common method whereby an application notifies its user an
event of interest has occurred, for instance, a video encoding session
has completed. Compared to MesssageBox() which shows a child modal
window of your application is like a shove in your user's face
especially when your application is currently not in the foreground. In
this regard, Windows Toast is less intrusive. But to understand and use
its complex API correctly is not an easy task."
Lynn