Re: Question on style-italic vs style=italicface

[Wolfgang Schuster via ntg-context <ntg-context@ntg.nl>]

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Rik Kabel via ntg-context schrieb am 27.09.2021 um 00:20:
> On 9/26/2021 16:29, Wolfgang Schuster via ntg-context wrote:
>> Rik Kabel via ntg-context schrieb am 26.09.2021 um 22:13:
>>>
>>> Hello list mavens,
>>>
>>> What are the circumstances under which style=italicface should be 
>>> used instead of style=italic. I note a difference when I define 
>>> highlighting. I expected to see no difference in the line before and 
>>> line after the hairline the example below, but see that italicface 
>>> adapts to nesting, while italic does not:
>>>
>>> Are there other places where this makes a difference?
>>>
>>>     \setupbodyfontenvironment
>>>             [default]
>>>             [em=italicface] %same with italic for this example
>>>     \definehighlight
>>>             [emIt]
>>>             [style=italic]
>>>     \definehighlight
>>>             [emIf]
>>>             [style=italicface]
>>>     \definehighlight
>>>             [emEm]
>>>             [style=\em]
>>>
>>>     \starttext
>>>
>>>     {\em abc {\em def} ghi}: \type{\em}
>>>
>>>     \emph{abc {\emph def} ghi}: \type{\emph}
>>>
>>>     \emEm{abc {\emEm def} ghi}: \type{\emEm \definehighlight[style=\em]}
>>>
>>>     \emIf{abc {\emIf def} ghi}: \type{\emIf
>>>     \definehighlight[style=italicface]}
>>>
>>>     \hairline
>>>
>>>     \emIt{abc {\emIt def} ghi}: \type{\emIt
>>>     \definehighlight[style=italic]}
>>>
>>>     \stoptext
>>>
>>
>> The \em command has two special values which are allowed when you 
>> change the style with
>>
>>     \setupbodyfontenvironment[default][em=...]
>>
>> with the value "slanted" and "italic". When you choose one of them 
>> the result depends on the current weight (\tf or \bf) but with every 
>> other value you're just using whatever the style command/name provides.
>>
>>
>> When you pass "italicface" you're using a style which uses either \it 
>> or \bi dependant on the current weight. The result from the "italic" 
>> value doesn't depend on the behavior or the normal italic style (\it) 
>> which is the reason why you get different result when you use \em 
>> compared with \it.
>>
>>
>> Example:
>>
>> \starttext
>>
>> \tex{it}: normal {\it italic} {\bf bold {\it italic}}
>>
>> \tex{italicface}: normal {\italicface italic} {\bf bold {\italicface 
>> italic}}
>>
>> \tex{em}: normal {\em italic} {\bf bold {\em italic}}
>>
>> \stoptext
>>
>>
>> Wolfgang 
>
>
> Wolfgang,
>
> I understand that mechanism, but I am asking a different question, I 
> think.
>
> When we specify style=\em or style=italic (and most examples I see use 
> the later) in a setup of some sort, I think most folks expect similar 
> behavior, but clearly it is not because italic does not track changes 
> in emphasis. However, style=italicface does seem to match the behavior 
> of style=\em (mostly, see the bug report below).
>

The basic font commands are \tf, \it, \sl, \bf, \bs and \bi and when you 
want for example bold italic text you always have to use \bi even the 
current text is already bold because \it produces normal italic text.

\em is a special case because it affects also italic text:

\starttext

\startlines
\tf normal {\em emphasized}
\sl slanted {\em emphasized}
\it italic {\em emphasized}
\bf bold {\em emphasized}
\bs bold slanted {\em emphasized}
\bi bold italic {\em emphasized}
\stoplines

\stoptext

> So, I am asking whether, in places where folks often use style=italic, 
> it might be better to consider style=italicface.
>
> Bug report: \meaning\italicface gives:
>
>     protected macro:\relax \ifx \fontalternative \s!tf \it \orelse
>     \ifx \fontalternative
>     \s!bf \bi \else \tf \fi
>
> This leaves out the transition from bi to bf. That transition is done 
> by \emph, but \emph may give slanted while \italicface is always italic.
>

The \italicface command uses either \it or \bi as result but it never 
result in upright text and the "italic" in the name tells you this, 
there are commands (e.g. \boldface) with similar results. To get a 
slanted style you have to use the \slantedface command.

Wolfgang


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