[XeTeX] A bug in (Xe)LaTeX?

[Bruno Voisin]

Le 18 août 05 à 23:46, Peter Dyballa a écrit :

> Am 18.08.2005 um 22:46 schrieb Bruno Voisin:
>
>> That probably won't help, but who knows?
>
> No! The \null in the right place makes things work! (I should  
> remember this \null a few times before I die!!)

I have tried many things this morning, even ending up replacing as  
many LaTeX commands as possible with their plain TeX equivalent, to  
no avail. I don't think the \null thing is actually the solution: the  
problem lies in the font themselves.

If you comment out the code

> \voffset=-1truein \hoffset=-1truein
>      \ifpdf
>        \pdfpageheight=\latexitheight
>        \pdfpagewidth=\latexitwidth
>      \else
>        \special{papersize=\latexitheight,\latexitwidth}%
>      \fi

then set in the preamble

     \setlength{\fboxsep}{0pt}

and put the formula in an \fbox by replacing

>      \shipout\vbox{\scalebox{\latexitscalefactor}{\usebox 
> {\latexitbox}}}

with

      \shipout\vbox{\fbox{\scalebox{\latexitscalefactor}{\usebox 
{\latexitbox}}}}

then you'll realize that, for LaTeX, the formula box is actually  
slightly smaller than its content:

-------------- next part --------------
A non-text attachment was scrubbed...
Name: Image 1.png
Type: image/png
Size: 22053 bytes
Desc: not available
Url : http://tug.org/pipermail/xetex/attachments/20050819/4bb519e1/Image1-0001.png
-------------- next part --------------

(see how the frame is superposed on the glyphs themselves).

To understand this, you have to think about how (La)TeX measures  
boxes: by adding up dimensions specified in the metrics files for the  
fonts. I think the problem we see is just a manifestation of the way  
the metrics of the Computer Modern fonts are set. For, if these fonts  
are replaced by the Lucida Bright/New Math fonts, then it seems the  
problem disappears:

-------------- next part --------------
A non-text attachment was scrubbed...
Name: Image 2.png
Type: image/png
Size: 22015 bytes
Desc: not available
Url : http://tug.org/pipermail/xetex/attachments/20050819/4bb519e1/Image2-0001.png
-------------- next part --------------

(see how the frame lies exactly outside the glyphs).

Thus it seems there's no easy cure for the CM fonts, other than a  
rule of thumb consisting in adding some empirically determined length  
to the box dimensions determined by (La)TeX. Has anybody had a look  
at the source code for OOoLaTeXEquation, to see if the same problem  
has been tackled, and how?

A couple more remarks on your code:

- To set the following right:

>       \immediate\write\foo{\the\latexitheight (Height)}
>       \immediate\write\foo{\the\latexitheight (TotalHeight)}

I think you should define a new length \latexittotalheight:

     \newlength{\latexittotalheight}

then replace

>     \addtolength{\latexitheight}{\latexitdepth}

with

     \setlength{\latexittotalheight}{\latexitheight}
     \addtolength{\latexittotalheight}{\latexitdepth}

and replace

>       \immediate\write\foo{\the\latexitheight (TotalHeight)}

with

     \immediate\write\foo{\the\latexittotalheight (TotalHeight)}

- In order to avoid an overfull hbox message, I think you should replace

>      \shipout\vbox{\scalebox{\latexitscalefactor}{\usebox 
> {\latexitbox}}}

with

     \shipout\vbox{\makebox[0pt][l]{\scalebox{\latexitscalefactor} 
{\usebox{\latexitbox}}}}

- The proposed code for dvips doesn't work:

>        \special{papersize=\latexitheight,\latexitwidth}%

in that (i) you must interchange width and height, (ii) you must  
preface them with \the and (iii) it must occur inside the shipped out  
\vbox to be taken into account. All in all, I think you should  
replace the code between \begin{document} and \end{document}:

>     \begin{document}
>     {\voffset=-1truein \hoffset=-1truein
>      \ifpdf
>        \pdfpageheight=\latexitheight
>        \pdfpagewidth=\latexitwidth
>      \else
>        \special{papersize=\latexitheight,\latexitwidth}%
>      \fi
>      \shipout\vbox{\scalebox{\latexitscalefactor}{\usebox 
> {\latexitbox}}}%
>     }%
>     \end{document}

with

     \begin{document}
     \hoffset=-1in
     \voffset=-1in
     \ifpdf
       \pdfpageheight=\latexittotalheight
       \pdfpagewidth=\latexitwidth
       \shipout\vbox{%
         \makebox[0pt][l]{\scalebox{\latexitscalefactor}{\usebox 
{\latexitbox}}}}
     \else
       \shipout\vbox{\special{papersize=\the\latexitwidth,\the 
\latexittotalheight}%
         \makebox[0pt][l]{\scalebox{\latexitscalefactor}{\usebox 
{\latexitbox}}}}
     \fi
     \end{document}


Hope this helps,

Bruno