pgfkeys pass font command

Question

I am defining options using the pgfkeys command.

\newcommand{\subtitlefont}{}
\pgfkeys{
   /titleblock/.is family, /titleblock,
   default/.style = 
       {titlesize = 48, titlelineskip = 52,
        subtitlesize = 36, subtitlelineskip = 39, subtitlefont=\itshape,
       },
   titlesize/.estore in = \titlesize,
   titlelineskip/.estore in = \titlelineskip,
   subtitlesize/.estore in = \subtitlesize,
   subtitlelineskip/.estore in = \subtitlelineskip,
   subtitlefont/.add code={}{\subtitlefont},
}

Them I want to use this options in a node font option.

\node[align=left, inner sep=0mm, outer sep=0mm,
 font={\fontsize{\subtitlesize}{\subtitlelineskip}\subtitlefont\selectfont},
 text=\titleblockcolor,
 below= 0.1cm of title.south west, anchor=north west] (subtitle) {
   \thesubtitle%
   };

The document compiles but the \itshape is not selected for the subtitle. What is the best way to define an option that consist in macros that can be passed to a node option?

Complete MWE

\documentclass{article}

\usepackage{tikz}
\usepackage{pgfkeys}

\newcommand{\subtitlefont}{}
\pgfkeys{
   /titleblock/.is family, /titleblock,
   default/.style = 
       {
         subtitlesize = 36, subtitlelineskip = 39, subtitlefont=\itshape,
       },
   subtitlesize/.estore in = \subtitlesize,
   subtitlelineskip/.estore in = \subtitlelineskip,
   subtitlefont/.add code={}{\subtitlefont},
}



\newcommand{\titleblock}[1][]{%
\pgfkeys{/titleblock, default, #1}%
\begin{tikzpicture}
  \node[align=left, inner sep=0mm, outer sep=0mm,
  font={\fontsize{\subtitlesize}{\subtitlelineskip}\subtitlefont\selectfont},
  text=black] (subtitle) {A nice title};
\end{tikzpicture}

}

\begin{document}
\titleblock
\end{document}

Answer 1

From pgfmanual page, 889

Hence you should be using store in instead of estore in. Also use subtitlefont/.add code={}{\subtitlefont}, instead of subtitlefont/.store in=\subtitlefont,. Adding to this, since you are using large font sizes, it is better to use lmodern package which provides nice scalable fonts and you wouldn't get warnings.

With these your code becomes

\documentclass{article}

\usepackage{tikz}
\usepackage{pgfkeys}
\usepackage{lmodern}

\newcommand{\subtitlefont}{}
\pgfkeys{
   /titleblock/.is family, /titleblock,
   default/.style =
       {
         subtitlesize = 36, subtitlelineskip = 39, subtitlefont=\itshape,
       },
   subtitlesize/.store in = \subtitlesize,
   subtitlelineskip/.store in = \subtitlelineskip,
   subtitlefont/.store in=\subtitlefont,
}



\newcommand{\titleblock}[1][]{%
\pgfkeys{/titleblock, default, #1}%
\begin{tikzpicture}
  \node[align=left, inner sep=0mm, outer sep=0mm,
  font={\fontsize{\subtitlesize}{\subtitlelineskip}\subtitlefont\selectfont},
  text=black] (subtitle) {A nice title};
\end{tikzpicture}

}

\begin{document}
\titleblock
\end{document}