Re: Bug in CONTEXT/LuaTeX or just buggy font

[Hans Hagen <pragma@wxs.nl>]

On 8/10/2016 5:19 PM, Mohammad Hossein Bateni wrote:
>
>
> On Wed, Aug 10, 2016 at 11:03 AM, Hans Hagen <pragma@wxs.nl
> <mailto:pragma@wxs.nl>> wrote:
>
>     On 8/9/2016 10:41 PM, Mohammad Hossein Bateni wrote:
>
>         Hello,
>
>         I have a bunch of simple fonts for Arabic/Persian.  These fonts lack
>         Latin characters, etc., so I use fallbacks to work with them.
>
>         I just noticed that \high does not work with them, and have not been
>         able to pinpoint the issue.  See the MWE below.
>
>
>         \starttypescript [serif][samim][name]
>           \definefontsynonym[Serif][Samim]
>         \stoptypescript
>
>         \definetypeface [myfont][rm] [serif][samim][default]
>         \setupbodyfont [myfont]
>
>         \starttext
>         %\definedfont[Samim*arabic]
>         ۱۲۳\high{۴}۵۶.
>         \stoptext
>
>
>         I am using Persian digits because the font lacks Latin digits as I
>         mentioned.  If I use the \definedfont approach, I don't see the
>         character ۴ (argument of \high) at all.  With the typescript
>         approach,
>         the same character /is/ typeset but is /not/ raised; it appears
>         on the
>         baseline but with smaller size.
>
>         Any ideas why this is happening?  Could it be that some
>         parameters, for
>         instance, \exheight are not properly set/read for this font?
>         Actually,
>         I looked at the non-math fontdimens in syst-fnt.mkiv, and everything
>         except \slantperpoint (expected) and \exheight (awkward) is
>         non-zero.  I
>         don't know where \exheight comes from—perhaps from the height of
>         glyph
>         for 'x', which the font lacks—however, \emheight is 12pt,
>         although the
>         font also lacks a glyph for 'm'.
>
>         I am also attaching the font in case that helps.
>
>
>     Normally one sets up a proper bodyfont (and environment if needed)
>     while you use just a simple font switch and that one is unrelated to
>     any other font setting.
>
>
> Thanks!  But what does a `proper' bodyfont contain beside defining rm,
> ss, tt and mm for 'myfont' above (with regular, bold, italic, and
> bolditalic)?  The above was a MWE but in my real example I am setting up
> these things that I mentioned in a larger typescript.  How can I modify
> the font or the typescript definitions (or the environment) to get
> \exheight right?

at least rm (or ss), mm and tt

x heights and emwidths come from the font (parameters) and as last 
resort are derived from other properties

>     I'll add two new commands: \sx and \sxx so that you can say:
>
>         \setuplow [style=\sx]
>         \setuphigh[style=\sx]
>
>
>  If I do this, this will not get attached to the font; right?  For
> instance, if I define two bodyfonts 'myfonta' and 'myfontb', and switch
> between them in the document, then I have to stick to these two setups
> if one font, say 'myfonta', is problematic.  Is that correct?

it's dynamicly calculated (for performance reasons once per font instance)

you can play with these:

\setuplow [down=.48\exheight]
\setuphigh[up=.86\exheight]

e.g. use other values, but if your ex and em are bad you can expect many 
other issues (so best use decent fonts)

>     for such cases. However, as these are derived relative scales they
>     are normally not compatible with \tx and txx sizes.
>
>     Hans
>
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>                                               Hans Hagen | PRAGMA ADE
>                   Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>            tel: 038 477 53 69 | www.pragma-ade.nl
>     <http://www.pragma-ade.nl> | www.pragma-pod.nl
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>
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-- 

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________