According to https://en.wikibooks.org/wiki/LaTeX/Basics#Spaces
… opening space is generally ignored.
First of all, I don't know what generally refers to.
I came across this using chktex
a program to warn about possible typographic or logical errors which latex itself does not warn about.
For instance, chktex
raises a warning if in front of \label
or \index
a space/tab is found (Warning 24: Delete this space to maintain correct pagereferences.
).
The reason for this warning is that labels should always be on the same page to that the label relates to (see $ texdoc chktex
, chapt. 7, p. 19, v1.7.4).
However, I usually indent lines within my figure environments:
\begin{figure}
\centering
\includegraphics{}
\caption{}
\label{}
\end{figure}
Therefore, chktex complains about the indentation of \label{}
.
In this particular case being a floating box, everything inside the floating box is, afaik, anyhow on the same page (possibly similarly to \begin{equation}...\n\label{eq:first}\end{equation}
).
The question: I wonder whether an opening space in front of \label
can lead to a wrong pagereference?
Consider indentation in figure environments or for example this situation:
\paragraph{Introduction}%
text of paragraph...%
\label{par:end_intro}%can this be on a new page
Consequently, is it reasonable to extend chktex to distinguish "opening spaces" from spaces after first non-space characters to remove false positives as in my case the indentation within the figure environment?
Or in other words is the warning in my case a false positive?
If someone knows a better situation where this is relevant, I'd be happy if you could insert this to the question.
Update chktex version 1.7.5 (2015-12-07) and higher tracks whether the previous line ended in a comment and does not raise warning 24 in the above given example.
Best Answer
The check program is clearly being over cautious (ie wrong) to say page breaks can always happen at spaces before
\label
.However the form you give is not optimal,. but for a different reason: If you put the
\label
after the caption (whether or not you leave a blank space or newline before it) the vertical space is adversely affected.Consider
The first form has visibly less space between the caption and the centred text as the space from
center
is merged with the space already added by the caption. However in the second version the\write
node from\label
prevents thecenter
environment from detecting the vertical space already added so it adds its full amount of space.(Note the first example posted here was completely wrong as explained in the other answer. The example above has been added after the original posting.)