[NTG-context] Re: Why overbar is so big

[Hans Hagen via ntg-context <ntg-context@ntg.nl>]

On 8/13/2023 9:08 AM, Xavier B. wrote:
> So,
> 
> Finally is it a bug in MKIV? It seems you fix some kind of bug in your messages. Is it true?

Not really. It's a a bug in the fonts (that will stay if only for 
compaibility reasons). There is a catch in mkiv that compensates for it 
but only when characters are not there. So, for these two I now force 
the catch.

In lmtx we have a bit different approach: we just assuem they are wrong 
in all fonts and fix them or replace them. We also have a more advanced 
math engine so we can control placement better.

There are also 'font parameters' involved that can be bad (i guess that 
designers can't really test math font parameters). In lmtx we have more 
of them, beyond what opentype math provides.

All of this is handled in goodie files. That mechanism is present in 
mkiv but no one ever bothered to spent time on it. That said: the last 
two years Mikeal and I spent a *lot* of time on math and we don't really 
look back at mkiv / mkii also because there is way more neat things now 
(most probably go unnoticed) ... you can read about it in some documents 
that come with context, articles in tugboat, and there are talks by 
Mikael at tug meetings on YT.

>>      The output with Luametatex is correct but Luatex creates a raised bar
>>      (and different linebreaking).
>>
>> \showglyphs
>>
>> \startTEXpage[offset=1ex]
>>       \ruledhbox{$\overline    {OA} = \overbar      {OA} = 4.2$}
>>       \par
>>       \ruledhbox{$\underline   {OA} = \underbar     {OA} = 4.2$}
>>       \par
>>       \ruledhbox{$\widetilde   {OA} = \widebar      {OA} = 4.2$}
>>       \par
>>       \ruledhbox{$\overbracket {OA} = \underbracket {OA} = 4.2$}
>> \stopTEXpage
>>
>> I'll add a 'force fix in spite of extensible being present' in mkiv. In
>> lmtx we always fix also because we drop in nicer shapes (watch the round
>> tips in lm and fancy tips in antykwa) and concluded that fonts will
>> remain as they are.
>>
>> Hans
> 
> As you suggested, I will give a try to LMTX but be aware most user still use MKIV until most distros upgrade the texlive version of context to LMTX.
It's not that hard to install lmtx alongside. If distributions take from 
texlive then likely you also end up with files that are not needed (base 
package) and lack some fonts (esp math) by default. You'd also benefit 
from the last couple of years advancements. Keep in mind that for a long 
term tex (document) project a snapshot approach is healthy because you 
never know what a distribution adds / replaces (esp fonts can be a mess 
and you want to know what you use).

Hans

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                                           Hans Hagen | PRAGMA ADE
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