relation between X class and X_p class

[vorlket]

As per the title, what is the relation between X class and X_p class?

[raven-worx]

@vorlket
please be more specific.
But i assume you are talking about the private part of an API class.
You may want to look up the term "Pimpl pattern" or "Pimpl idiom" on the web

[VRonin]

https://wiki.qt.io/D-Pointer