[texhax] \rlap at the beginning of a \parbox

[jfbu]

le 26/02/2014 15:37 selon jfbu:
> le 26/02/2014 11:59 selon Michael Rutter:
>> I am confused as to the behaviour of \rlap (or a \makebox of zero width} 
>> at the beginning of a parbox. It seems to force a new line, whereas it 
>> behaves differently if preceded by an \hspace*{0pt}. Could someone explain 
>> to me the output of the following LaTeX which illustrates this issue? (It 
>> was an attempt to produce a dollar sign with the same width as a pounds 
>> sign, for neater tables of mixed currencies.)
>>
>> \documentclass{article}
>>
>> \newcommand{\dollars}{\rlap{\$}\hphantom{\pounds}}
>> \parindent 0pt
>> \begin{document}
>>
>> \parbox{3in}{\pounds{}6}
>>
>> \parbox{3in}{\hspace*{0pt}\dollars{}6}
>>
>> \parbox{3in}{\dollars{}6}
>>
>> \end{document}
>>
>> Regards,
>>
>> Michael Rutter
>>
> 
> \rlap uses \hbox not the LaTeX \makebox or \mbox, 
> hence when in vertical mode at the beginning of the
> \parbox, its use will result in a full (empty) line.

sorry I didn't mean to say "empty" line. The \$ stands 
on a line (no extra vertical space above it) then
for some reason presumably from the \parbox code
I didn't look at there is an empty line and then
the line containing the 6. The whole thing is vertically centered
as is the default with a \parbox
as you can see by adding some characters before and after the \parbox


> 
> \leavevmode\rlap fixes the problem.
> 

by the way you said "or a \makebox of zero width" but there is no issue
then
\parbox{3in}{\makebox[0pt][l]{\$}\hphantom{\pounds}{}6}

Best

> Best,
> 
> Jean-Francois
> 
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