spurious spaces in \pgfmathdeclarefunction

[pgf-tikz-bot]

Migrated from SourceForge
Author: u_fischer
Timestamp: 2019-01-26 21:41:33.503000

I'm not quite sure if this count as a bug. In the following example the definition of testA contains a spurious space. This space deplaces the bounding box of the resulting tikzpicture/plot but curiously only with pdflatex and lualatex. With xelatex both bounding boxes are fine.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
\pgfmathdeclarefunction{testA}{1}{%
        \pgfmathparse{2} %spurious space
    }


\pgfmathdeclarefunction{testB}{1}{%
        \pgfmathparse{2}%
    }

xx\begin{tikzpicture}
\begin{axis}
  \addplot {testA(1)};
\end{axis}
\end{tikzpicture}yy



xx\begin{tikzpicture}
\begin{axis}
  \addplot {testB(1)};
\end{axis}
\end{tikzpicture}yy

\end{document}

[pgf-tikz-bot]

Migrated from SourceForge
Author: hmenke
Timestamp: 2019-01-27 10:22:56.331000

• status: open --> closed-fixed
• assigned_to: Henri Menke

[pgf-tikz-bot]

Migrated from SourceForge
Author: hmenke
Timestamp: 2019-01-27 10:22:57.188000

Fixed in https://sourceforge.net/p/pgf/git/ci/00f4e8d4154dcb3133ed4a106b6254b8faf874e2/ but it broke gcd. I hope it won't break too much else.

As a little gimmick you can get a spaces inside the definition using ~ like in expl3.

[cfeuersaenger]

I fear the solution breaks legal statements.

Take, for example

\documentclass{standalone}

\usepackage{tikz}

\begin{document}
%
\makeatletter

\def\test#1#2{%
	\pgfmathdeclarefunction{#1}{0}{#2}%
}%

\pgfmathdeclarefunction{XXX}{0}{\edef\pgfmathresult{\pgfkeysvaluesof{/pgf/bar width}}}

\test{YYY}{\edef\pgfmathresult{\pgfkeysvaluesof{/pgf/bar width}}}

\show\pgfmathXXX@

\show\pgfmathYYY@

\end{document}

The result is

> \pgfmathXXX@=macro:
->\edef \pgfmathresult {\pgfkeysvaluesof {/pgf/barwidth}}.
l.17 \show\pgfmathXXX@
                      
? 
> \pgfmathYYY@=macro:
->\edef \pgfmathresult {\pgfkeysvaluesof {/pgf/bar width}}.
l.19 \show\pgfmathYYY@

-- one results in a compile error whereas the second works correctly.

\catcode hackery is always prone to such issues, and given

1. that the solution actually hinders most attempts to access key-value pairs (which often contain spaces) inside of math functions,
2. the benefit of auto-correct user errors by filtering out spaces appears to be negligible,
   I will revert the change.

That means: users must not write spurious spaces into the definition of math functions. I know that this is hard to understand for all normal users and even non-TeX programmers, but I fear this is how TeX works -- you must care for spurious spaces, sorry.

[hmenke]

I've now provided a workaround that can be enabled by the user which will not affect already defined instances.

[hmenke]

@u-fischer I had a look at this again and it seems that this is exclusively a pgfplots problem. It doesn't happen when I just use \draw plot (\x,{testA(1)}); in a tikzpicture. Looks like pgfplots switches to a text font and doesn't switch back to nullfont for plotting.