How to create a command that creates commands?

Question

I recently learned how to make key=value commands with the pgfkeys package. I'm currently trying to define a command, let's call it \commander, with key=value options that can define new commands also with key=value functions. (Something like supercommand or metacommand.) The syntax of \commander is roughly the following:

\commander[color=red,pos=up,invert=false]{\thenewcommand}

Our \thenewcommand is expected to have some (but not all) of the same key=value options of \commander; furthermore, their default values have to be the values called by \commander (or the default values of \commander if they aren't explicitly called). For example, if \thenewcommand is defined as above, then calling:

\thenewcommand[color=blue]

is just the same as calling:

\thenewcommand[color=blue,pos=up,invert=false]

I have made some steps towards defining \commander. Here are its pgfkeys.

\newif\ifcommanderinvert
\pgfkeys{
    /commander/.is family, /commander,
    % "commander" options
    color/.estore in = \commanderColor,
    pos/.estore in = \commanderPos,
    invert/.is if=commanderinvert,
    % Ignore this: It is just for showing that I'm using the .unknown feature
    .unknown/.code={\edef\commanderUnk{\commanderUnk,\pgfkeyscurrentname=#1}},%
}

And here is an incomplete definition of \commander:

% (Optional) argument #1 is for the options
% (Non-optional) argument #2 is the name of the new command
%                                    (e.g.: \thenewcommand)
\newcommand{\commander}[2][]{%
% Loading \commander's pgfkeys
\pgfkeys{/commander,%
    color=black,%
    pos=up,%
    invert=false,#1}%
%
% Here goes some code 
Code...
%
% Here I define the pgfkeys for \thenewcommand.
% Every appearance of the string "thenewcommand" has to be replaced
% by the actual name of our new command or an abbreviation.
% Else, we risk making conflicting names each time we call \commander.
\newif\ifthenewcommandinvert
\pgfkeys{
    /thenewcommand/.is family, /thenewcommand,
    % "thenewcommand" options
    % Notice I'm not using the "pos" option
    color/.estore in = \thenewcommandColor,
    invert/.is if=thenewcommandinvert,
}
% Defining \thenewcommand: it only has optional arguments
% Notice that the name of the new command is #2 of \commander
\newcommand{#2}[1][]{%
\pgfkeys{/thenewcommand,%
    color=\commanderColor,%
    %invert=?,
    % How do I pass here the value of /commander invert/?
    #1}%
% Here goes some code
\ifthenewcommandinvert%
    Code...%
\else%
    Code...\fi%
% (By the way, how can I distinctly refer to
% argument #1 of \commander and to argument #1 of \thenewcommand?)
}

With a definition along these lines, if we call \commander as follows:

\commander[color=blue]{\bluecommand}

then calling:

\bluecommand[invert=true]

must be the same as calling:

\bluecommand[color=blue,pos=up,invert=true]

In order to complete this function I have to overcome two challenges:

1. What is the best strategy for recursively creating the pgfkeys for each new command created with \commander?
2. How do I the pass value of the invert key of \commander as the default value of the invert key of the new command.

I hope someone can give me some hand here. Thanks in advance.

PS: For this command I'm using/requiring the packages graphicx, pgfkeys and tikz and, optionally, the class beamer.

Answer 1

This answer provides two code versions, one using expkv-cs, one using pgfkeys-only.

Using expkv-cs

The following could be used for this, but circumvents much of the expansion problems of using pgfkeys for \commander by using expkv-cs. The advantage is that as long as you're using simple macros with only few keys the \ekvcSplit-approach provides you with the values of your keys as they were given by the user as macro parameters.

\documentclass{article}
\usepackage{pgfkeys}
\usepackage{expkv-cs}
\makeatletter
\newcommand*\commander[1][]{\commander@k{#1}}
\newif\ifcommander@invert
\ekvcSplitAndForward\commander@k\commander@d
  {
     color = black
    ,pos = up
    ,invert = false
  }
\pgfqkeys{/commander}%
  {%
    .is family
    ,color/.store in = \commander@color
    ,pos/.store in = \commander@pos
    ,invert/.is if=commander@invert
    ,.unknown/.code=%
      {\edef\commander@unk{\commander@unk,\pgfkeyscurrentname={##1}}}%
  }
\newcommand\commander@d[4]
  {%
    \newcommand#4[1][]
      {%
        \begingroup
          \pgfqkeys{/commander}{color={#1},pos={#2},invert={#3},##1}%
          \ifcommander@invert
            \commander@color\space code being inverted at \commander@pos
          \else
            \commander@color\space code at \commander@pos
          \fi
        \endgroup
      }%
  }
\makeatother
\commander[color=blue]\thenewcommand
\commander[invert=true]\thenewcommandinvert
\begin{document}
\thenewcommand
\thenewcommand[color=green,invert=false]
\thenewcommandinvert
\thenewcommandinvert[color=green,invert=false]
\end{document}

---

Using only pgfkeys

This version uses a temporary definition \commander@tmp that helps expanding the current values of your keys.

\documentclass{article}
\usepackage{pgfkeys}
\makeatletter
\newcommand\commander[2][]
  {%
    \begingroup
    \pgfqkeys{/commander}{#1}%
    \edef\commander@tmp % <- shouldn't be used by a key
      {%
        \endgroup
        \unexpanded{\newcommand#2[1][]}%
          {%
            \begingroup
            \unexpanded{\pgfqkeys{/commander}}%
              {%
                 color={\unexpanded\expandafter{\commander@color}}%
                ,pos={\unexpanded\expandafter{\commander@pos}}%
                ,invert=\ifcommander@invert true\else false\fi
                ,####1%
              }%
            \unexpanded{\commander@code}%
            \endgroup
          }%
      }%
    \commander@tmp
  }
\newcommand\commander@code
  {%
    \ifcommander@invert
      \commander@color\space code being inverted at \commander@pos
    \else
      \commander@color\space code at \commander@pos
    \fi
  }
\newif\ifcommander@invert
\pgfqkeys{/commander}%
  {%
    .is family
    ,color/.store in = \commander@color
    ,color=black
    ,pos/.store in = \commander@pos
    ,pos=up
    ,invert/.is if=commander@invert
    ,invert=false
    ,.unknown/.code=%
      {\edef\commander@unk{\commander@unk,\pgfkeyscurrentname={##1}}}%
  }
\makeatother
\commander[color=blue]\thenewcommand
\commander[invert=true]\thenewcommandinvert
\begin{document}
\thenewcommand
\thenewcommand[color=green,invert=false]
\thenewcommandinvert
\thenewcommandinvert[color=green,invert=false]
\end{document}

---

Output of both