# [NTG-context] Difficulties with \startformula

Hans Hagen pragma at wxs.nl
Tue Jan 14 18:36:38 CET 2014

On 1/14/2014 12:13 AM, Elspeth McGullicuddy wrote:
> Hi,
>
> 1- I put here a far too long example to show difficulties that I have
> with formulas in conjunction with framed:
> I haven't find a way to insert a formula (displaystyle, vertical
> mode), at the beginning of a \framed.

Here is a small example:

\nopdfcompression

\startTEXpage[offset=3cm]
\hbox{$x+y$}
\stopTEXpage

If you look in the pdf file you will see the following:

/FontBBox    [-1042 -3060 4082 3560]
/Ascent      3560
/CapHeight   683
/Descent     -3060
/ItalicAngle 0
/StemV       93
/XHeight     431

The less clever viewer can use that information for the selection
dimensions. Acrobat instead uses the glyph properties.

If you run instead

\starttext
\hbox{$$x+y$$}
\stoptext

you will not get math at all because the $$== an empty inline math so there a text font is used: /FontBBox [-422 -280 1394 1127] /Ascent 1127 /CapHeight 683 /Descent -280 /ItalicAngle 0 /StemV 91 /XHeight 431 In context, \hbox{\startformula x+y \stopformula} boils down to \hbox{\par$$ x+y $$\par} plus some more so i decided to turn this into \hbox{\par \Ustartdisplaymath x+y \Ustopdisplaymath \par} Now, believe it it not, when I tested that one luatex crashed as we never thought about the fact that$$ is catched in the main loop and
\Ustartdisplaymath falls through and creates havoc. So, after some
debugging Luigi and I figured out that this was too messy to catch. Math
magician Taco will fix it in luatex's parser part. So, be warned, don't
this this trickery now.

In the meantime, i fixed context to deal with such matters. Of course
that bug doesn't relate to your observations.

Hans

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