Multiline footer in tcolorbox

Question

I have been struggling to get text in the tcolorbox border. See the MWE:

\documentclass[table]{standalone}
\usepackage{polyglossia, lipsum}
\usepackage[most]{tcolorbox}
\newtcolorbox{mybox}[2][]{%
  enhanced,
  before upper=\setlength{\parskip}{\bigskipamount},
  boxrule=2mm,
  bottomrule=9mm,
  overlay={%
    \node[white, font=\small, anchor=south] at (frame.south) {Footer \ With Two Lines};},
  title=#2,#1}
\newcommand{\xxbody}{
\lipsum[1]
}
\newcommand{\xxheading}{
  Header \ With Two Lines
}
\begin{document}
\begin{mybox}{\LARGE \xxheading{}}
\xxbody{}
\end{mybox}
\end{document}

I would like to have a multi-line footer like the multi-line heading. And if possible, set the height of bottom border automatically to accommodate the footer. Is there any way it can be done?

This is kind of sequel to this Earlier Question.

Answer 1

Another approach that uses bicolor skin and sets the style for lower part so it plays the role of footnote.

Pros: No need to set node options.

Cons: You have to manually insert \tcblower, otherwise there will be no lower part.

% !TeX TS-program = xelatex
\documentclass[table]{standalone}
\usepackage{polyglossia, lipsum}
\usepackage[most]{tcolorbox}
\newtcolorbox{mybox}[2][]{%
  skin=bicolor,
  % geometry
  boxrule=2mm,
  % color and font
  collower=white,
  colbacklower=tcbcolframe,
  fonttitle=\LARGE,
  % segmentation
  segmentation empty,
  % box content
  title=#2,
  before upper=\setlength{\parskip}{\bigskipamount},
  before lower={Footer \ With Two Lines},
  halign lower=center,
  % more
  #1
}
\newcommand{\xxbody}{
  \lipsum[1]
}
\newcommand{\xxheading}{
  Header \ With Two Lines
}
\begin{document}
\begin{mybox}{\xxheading}
  \xxbody{}
  \tcblower % this must be manually inserted
\end{mybox}
\end{document}

Answer 2

A bit more reading around and I have found a solution --- use minipage in node.

But the code can be simplified even further by incorporating suggestion by @Ignasi. Here is the MWE with his suggestion.

\documentclass[table]{standalone}
\usepackage{polyglossia, lipsum}
\usepackage[most]{tcolorbox}
\newtcolorbox{mybox}[2][]{%
  enhanced,
  before upper=\setlength{\parskip}{\bigskipamount},
  boxrule=2mm,
  bottomrule=9mm,
  overlay={%
    \node[white, font=\small, anchor=south, text width=\textwidth] at (frame.south) {%
    Footer \ With Two Lines};},
  title=#2,#1}
\newcommand{\xxbody}{
\lipsum[1]
}
\newcommand{\xxheading}{
  Header \ With Two Lines
}
\begin{document}
\begin{mybox}{\LARGE \xxheading{}}
\xxbody{}
\end{mybox}
\end{document}