memoir: Adding text below part title?

Question

I would like to be able to add a bit of text below the title on a part page. Based on this answer to this question, I came up with

\documentclass{memoir}

\usepackage{lipsum}
\usepackage{ragged2e}

\makeatletter
\def\@parttext{}
\newcommand{\parttext}[1]{\gdef\@parttext{\normalsize\normalfont\justify #1}}
\renewcommand{\printparttitle}[1]{\parttitlefont #1\vfil\@parttext\vfil\gdef\@parttext{}}
\makeatother

\begin{document}

\parttext{\lipsum[1-2]}
\part{This is part one}

\end{document}

which gives:

but I must admit that I do not fully understand what is going on, so I would be glad for feedback on how to improve the new and renewed commands.

EDIT: One aspect of the renewed command that bothers me is that even if I do not add any text, the part number and title are moved up. How can I avoid this?

Answer 1

There is another way to do this by redefining the \partpageend macro but I'm not going to go into that.

In the solution you presented the \parttext macro creates the \@parttext macro holding the formatted text to be printed after the part title.

The \printparttitle macro, which prints the part number and title, is extended to call \@parttext to print the after-title text. The \vfil macros vertically center the text between the title and the bottom of the textblock, and then finally emptying \@parttext.

I'm not sure that it can be improved; it works.