pgfpositionnodelater 的多种用途

Question

当您加载时xparse，最好充分利用的功能expl3以更简单的方式开展该业务。

\makeatletter
\ExplSyntaxOn
% some helper / wrapper commands around \pgfplacenodelater
% #1 = identifier for nodes to be placed later
% #2 = elements to be placed 
\DeclareDocumentCommand \@placenodelater {r() +m}{
  \cs_new_protected:cpn {mtd@#1-save}
   {
    % Save Necessary Registers
    \box_gset_eq:cN {mtd@#1-box} \pgfpositionnodelaterbox
    \cs_gset_eq:cN {mtd@#1-name} \pgfpositionnodelatername
    \cs_gset_eq:cN {mtd@#1-minx} \pgfpositionnodelaterminx
    \cs_gset_eq:cN {mtd@#1-miny} \pgfpositionnodelaterminy
    \cs_gset_eq:cN {mtd@#1-maxx} \pgfpositionnodelatermaxx
    \cs_gset_eq:cN {mtd@#1-maxy} \pgfpositionnodelatermaxy
    % Calculate Length and Width as well
    \pgfmathsetmacro{\mtd@templen}
      {\pgfpositionnodelatermaxx - \pgfpositionnodelaterminx}
    \pgfmathsetmacro{\mtd@tempwid}
      {\pgfpositionnodelatermaxy - \pgfpositionnodelaterminy}
    \cs_gset_eq:cN {mtd@#1-length} \mtd@templen
    \cs_gset_eq:cN {mtd@#1-width} \mtd@tempwid
    % Print Some debug information. 
    \typeout{\pgfpositionnodelaterbox}
    \typeout{\pgfpositionnodelatername}
  }
  {
    \exp_args:Nc \pgfpositionnodelater {mtd@#1-save} #2
  }
}

% #1 = identifier for nodes already saved by \@placenodelater
% #2 = location for the node to be placed at
\DeclareDocumentCommand \@placenodenow {r() +m}{
  \cs_set_eq:Nc \pgfpositionnodelatername {mtd@#1-name}
  \cs_set_eq:Nc \pgfpositionnodelaterminx {mtd@#1-minx}
  \cs_set_eq:Nc \pgfpositionnodelaterminy {mtd@#1-miny}
  \cs_set_eq:Nc \pgfpositionnodelatermaxx {mtd@#1-maxx}
  \cs_set_eq:Nc \pgfpositionnodelatermaxy {mtd@#1-maxy}
  \box_set_eq:Nc \pgfpositionnodelaterbox {mtd@#1-box}
  \pgfpositionnodenow{#2}
}
\ExplSyntaxOff
\makeatother

该构造\cs_gset_eq:cN {foo} \baz相当于

\global\expandafter\let\csname foo\endcsname \baz

而\cs_set_eq:Nc \foo {baz}相当于

\expandafter\let\expandafter\foo\csname baz\endcsname

gset和的区别在于set前者进行全局分配，而后者只进行局部分配。

请注意你的代码

\let\pgfpositionnodelatername\expandafter=\csname mtd@#1-name \endcsname

设置\pgfpositionnode为等同于，\expandafter并且以下标记将像在普通文本中一样进行处理。

\box_gset:cN对于和也类似\box_set:Nc。

最后，笨拙的

\expandafter\pgfpositionnodelater\csname mtd@#1-save \endcsname
#2

可以变得更容易

\exp_args:Nc \pgfpositionnodelater {mtd@#1-save} #2

我修复了示例代码中的明显错误，现在运行时没有错误（但我不能说它完成了它应该做的事情）。

使用前应分配一个盒子
你有一个mts@前缀，应该是mtd@
您不能使用 \mtd@upper-width as a control sequence name; I remedied with\use:c{mtd@#1-width}`
在代码中，名称中带有空格的 PGF 键应使用~（明确的空格）expl3。

这是代码。

\documentclass[crop,tikz]{standalone}% 'crop' is the default for v1.0, before it was 'preview'

\usepackage{xparse}
%\usepackage{expl3} % redundant, already loaded by xparse

\usetikzlibrary{
  graphs,
  shapes,
  calc,
  intersections,
  through,
  fit,
  backgrounds,
  positioning,
  arrows,%
  shapes.misc,% wg. rounded rectangle
  shapes.arrows,%
  chains,%
  matrix,%
  scopes,%
  decorations.pathmorphing,% /pgf/decoration/random steps | erste Graphik
  shadows,%
  fixedpointarithmetic
}

\makeatletter
\ExplSyntaxOn

% QUESTION: How can I convert these commands to treat the macro parameters like
%           an expl3 typed parameter? can I do it while keeping the nice xparse
%           syntax? 

\DeclareDocumentCommand \@placenodelater {r() +m}{
  \cs_new_protected:cpn {mtd@#1-save}
   {
    % Print Some debug information. 
    \typeout{\pgfpositionnodelatername}
    \typeout{\pgfpositionnodelaterminx}
    \typeout{\pgfpositionnodelaterminy}
    \typeout{\pgfpositionnodelatermaxx}
    \typeout{\pgfpositionnodelatermaxy}
    % Save Necessary Registers
    \cs_gset_eq:cN {mtd@#1-name} \pgfpositionnodelatername
    \cs_gset_eq:cN {mtd@#1-minx} \pgfpositionnodelaterminx
    \cs_gset_eq:cN {mtd@#1-miny} \pgfpositionnodelaterminy
    \cs_gset_eq:cN {mtd@#1-maxx} \pgfpositionnodelatermaxx
    \cs_gset_eq:cN {mtd@#1-maxy} \pgfpositionnodelatermaxy
    \box_if_exist:cF{mtd@#1-box} {\box_new:c {mtd@#1-box}}
    \box_gset_eq:cN {mtd@#1-box} \pgfpositionnodelaterbox
    % Calculate Length and Width as well
    \pgfmathsetmacro{\mtd@templen}
      {\pgfpositionnodelatermaxx - \pgfpositionnodelaterminx}
    \pgfmathsetmacro{\mtd@tempwid}
      {\pgfpositionnodelatermaxy - \pgfpositionnodelaterminy}
    \cs_gset_eq:cN {mtd@#1-length} \mtd@templen
    \cs_gset_eq:cN {mtd@#1-width} \mtd@tempwid
  }
  {
    \exp_args:Nc \pgfpositionnodelater {mtd@#1-save} #2
  }
}

% #1 = identifier for nodes already saved by \@placenodelater
% #2 = location for the node to be placed at
\DeclareDocumentCommand \@placenodenow {r() +m}{
  \cs_set_eq:Nc \pgfpositionnodelatername {mtd@#1-name}
  \cs_set_eq:Nc \pgfpositionnodelaterminx {mtd@#1-minx}
  \cs_set_eq:Nc \pgfpositionnodelaterminy {mtd@#1-miny}
  \cs_set_eq:Nc \pgfpositionnodelatermaxx {mtd@#1-maxx}
  \cs_set_eq:Nc \pgfpositionnodelatermaxy {mtd@#1-maxy}
  \box_set_eq:Nc \pgfpositionnodelaterbox {mtd@#1-box}
  % Print Some debug information. 
  \typeout{\pgfpositionnodelatername}
  \typeout{\pgfpositionnodelaterminx}
  \typeout{\pgfpositionnodelaterminy}
  \typeout{\pgfpositionnodelatermaxx}
  \typeout{\pgfpositionnodelatermaxy}
  \pgfpositionnodenow{#2}
}

% #1 = Contents of upper box
% #2 = contents of middle box
% #3 = contents of lower box 
\DeclareDocumentCommand \placetriple {+m +m +m}{

  \@placenodelater(upper){
    \node[anchor = south](topnode){#1};
  }
  \@placenodelater(lower){
    \node[anchor = north](bottomnode){#3};
  }
  \pgfmathsetmacro{\mts@wa}{\use:c{mtd@upper-width} + 1cm}
  \pgfmathsetmacro{\mts@wb}{\use:c{mtd@lower-width} + 1cm}
  \pgfmathsetmacro{\mts@wc}{max(\mts@wa,\mts@wb)}
  \node[minimum~width=\mts@wc](centernode){#2};
  \@placenodenow(upper){\pgfpointanchor{centernode}{north}}
  \@placenodenow(lower){\pgfpointanchor{centernode}{south}}
}

\ExplSyntaxOff
\makeatother
\begin{document}
\begin{tikzpicture}
  \placetriple
    {The center box should}
    {always be wider}
    {than the top and bottom, regardless of content.};
\end{tikzpicture}
\end{document}

Answer 1