Applying condition around \intertext and \shortintertext leaves excess vertical space

Question

When I try to make either \intertext or \shortintertext conditional I get excess vertical spacing prior to the conditional text as per the MWE below. Note the excess vertical spacing prior to "Albert insisted that" and "but we know".

The minipage on the right represents the correct spacing as it does not have the \ConditionalText{} macro applied.

However, when the conditional is disabled, via the \toggletrue{}, the text is suppressed and the spacing is fine:

Notes:

• It seems that with

  \NewDocumentCommand{\ConditionalText}{O{red} +m}{#2}%
  

  the spacing problem is still there. However, the problem is resolved if I use the \iftoggle directly within the align environment as:

  \newcommand{\TextWithConditional}{%
      \hfill\textbf{Intertext with Conditionals}\hfill%
      Newton said:
      \begin{align*}
          F &= ma \\
          \iftoggle{SupressConditionalText}{}{\intertext{Albert insisted that}}
          E &=mc^2 \\
          \iftoggle{SupressConditionalText}{}{\shortintertext{but we know}}
          E &=\frac{1}{2}mv^2
      \end{align*}
      Text after a conditional display math formula.%
  }%
  

Failed Solution:

• Well, I had what I thought was a brilliant fix, but it seems that all I can do is to quote Edison and say "I have discovered a method that does not work". Not sure why it does not work though.

  \NewDocumentCommand{\ConditionalText}{O{red} +m}{%
      \ignorespaces%
      \iftoggle{SupressConditionalText}{}{%
          \ifmmode%
              \let\OldIntertext\intertext%
              \let\OldShortIntertext\shortintertext%
              \def\intertext{\vspace*{\baselineskip}\OldIntertext}%
              \def\shortintertext{\vspace*{-\baselineskip}\OldShortIntertext}%            
              #2% Don't underline if in math mode
          \else%
              %\UnderlineText[#1]{#2}% This case not used in this MWE.
          \fi%
      }%
      \ignorespacesafterend%
  }%
  

---

Code:

\documentclass{article}
\usepackage{xparse}% Not essential for this problem.
\usepackage{xcolor}
\usepackage{etoolbox}
\usepackage{mathtools}
\usepackage{soul}
\usepackage{parskip}% Eliminate need for \noindent
%\usepackage{showframe}

\newtoggle{SupressConditionalText}%

\togglefalse{SupressConditionalText}% This has too much space BEFORE the conditional \intertext.


\NewDocumentCommand{\UnderlineText}{O{red} +m}{%
    \setulcolor{#1}\ul{#2}%
}%

\NewDocumentCommand{\ConditionalText}{O{red} +m}{%
    \ignorespaces%
    \iftoggle{SupressConditionalText}{}{%
        \ifmmode%
            #2% Don't underline if in math mode
        \else%
            \UnderlineText[#1]{#2}%
        \fi%
    }%
    \ignorespacesafterend%
}%

\newcommand{\TextWithConditional}{%
    \hfill\textbf{Intertext with Conditionals}\hfill%
    Newton \ConditionalText{often} said:
    \begin{align*}
        F &= ma \\
        \intertext{Albert \ConditionalText{awkwardly} insisted that}
        E &=mc^2 \\
        \ConditionalText{\shortintertext{but we know}}
        E &=\frac{1}{2}mv^2 \\
        \ConditionalText{\intertext{But, equating the two we obtain.}}    
        mc^2 &= \frac{1}{2}mv^2
        \shortintertext{from which \ConditionalText{we obtain}}
        v &= \sqrt{2}c
    \end{align*}
    Text after a conditional display math formula.%
}%


\newcommand{\TextWithoutConditional}{%
    \hfill\textbf{Intertext without Conditionals}\hfill%
    Newton said:
    \begin{align*}
        F &= ma \\
        \intertext{Albert awkwardly insisted that}
        E &=mc^2 \\
        \shortintertext{but we know}
        E &=\frac{1}{2}mv^2
    \end{align*}
    Text after a conditional display math formula.%
}%
\newcommand{\TextWithoutConditionalWithoutInterText}{%
    \hfill\textbf{No Intertext, No Conditionals}\hfill%
    Newton said:
    \begin{align*}
        F &= ma \\
        E &=mc^2 \\
        E &=\frac{1}{2}mv^2
    \end{align*}
    Text after a conditional display math formula.%
}%

\begin{document}
\begin{minipage}[t]{0.45\linewidth}
    \TextWithConditional
\end{minipage}
\hfill\vrule\hfill% 
\begin{minipage}[t]{0.45\linewidth}
    \TextWithoutConditional
\end{minipage}

\bigskip\hrule
\toggletrue{SupressConditionalText}%  Disable conditional text
%
With conditional text supressed, things work fine:

\begin{minipage}[t]{0.45\linewidth}
    \TextWithConditional
\end{minipage}%
\hfill\vrule\hfill% 
\begin{minipage}[t]{0.45\linewidth}
    \TextWithoutConditionalWithoutInterText
\end{minipage}%
\end{document}

Answer 1

This does what I think you want and keeps the tests expandable, it takes the math branch if you are in align* or ifmmode is true. It would need extending for other environmants.

\documentclass{article}
\usepackage{xparse}% Not essential for this problem.
%\usepackage{xcolor}
\usepackage{etoolbox}
\usepackage{mathtools}
%\usepackage{soul}
\usepackage{parskip}% Eliminate need for \noindent
%\usepackage{showframe}
\makeatletter
\newtoggle{SupressConditionalText}%
\togglefalse{SupressConditionalText}% This has too much space BEFORE the conditional \intertext.
% Not used in this paritcular example
\NewDocumentCommand{\UnderlineText}{O{red} +m}{%
    \setulcolor{#1}\ul{#2}%
}%
\def\xaligns{align*}
\def\ConditionalText#1{%
    \iftoggle{SupressConditionalText}{}{%
        \ifx@currenvir\xaligns
          #1%
        \else\ifmmode
           #1% Don't underline if in math mode
        \else%
           \UnderlineText[red]{#1}% This case not used in this MWE.
        \fi
       \fi
    }%
    \ignorespacesafterend%
}%
\newcommand{\TextWithConditional}{%
    \hfill\textbf{Intertext with Conditionals}\hfill%
    Newton said:
    \begin{align}
        F &= ma \
        \ConditionalText{\intertext{Albert insisted that}}
        E &=mc^2 \
        \ConditionalText{\shortintertext{but we know}}
        E &=\frac{1}{2}mv^2
    \end{align}
    Text after a conditional display math formula.%
}%
\newcommand{\TextWithoutConditional}{%
    \hfill\textbf{Intertext without Conditionals}\hfill%
    Newton said:
    \begin{align}
        F &= ma \
        \intertext{Albert insisted that}
        E &=mc^2 \
        \shortintertext{but we know}
        E &=\frac{1}{2}mv^2
    \end{align}
    Text after a conditional display math formula.%
}%
\newcommand{\TextWithoutConditionalWithoutInterText}{%
    \hfill\textbf{No Intertext, No Conditionals}\hfill%
    Newton said:
    \begin{align}
        F &= ma \
        E &=mc^2 \
        E &=\frac{1}{2}mv^2
    \end{align}
    Text after a conditional display math formula.%
}%
\begin{document}
\begin{minipage}[t]{0.45\linewidth}
    \TextWithConditional
\end{minipage}
\hfill\vrule\hfill% 
\begin{minipage}[t]{0.45\linewidth}
    \TextWithoutConditional
\end{minipage}
\bigskip\hrule
\toggletrue{SupressConditionalText}%  Disable conditional text
%
With conditional text supressed, things work fine:
\begin{minipage}[t]{0.45\linewidth}
    \TextWithConditional
\end{minipage}%
\hfill\vrule\hfill% 
\begin{minipage}[t]{0.45\linewidth}
    \TextWithoutConditionalWithoutInterText
\end{minipage}%
\end{document}