Re: question about linespace adjustment

[Lars Huttar <lars_huttar@sil.org>]

Luigi,
Thanks for your reply.

On 9/24/2013 2:18 PM, luigi scarso wrote:
>
> On Tue, Sep 24, 2013 at 7:45 PM, Lars Huttar <lars_huttar@sil.org
> <mailto:lars_huttar@sil.org>> wrote:
>
>
>     Is it that \switchdobodyfont changes the *body* font, which
>     engages the
>     associated bodyfont environment...
>     whereas \tfc changes the *font*, not the *body* font?
>
>     Lars
>
> You can look into
>  font-pre.mkiv

OK. I'm looking at it,
http://repo.or.cz/w/context.git/blob/HEAD:/tex/context/base/font-pre.mkiv
Is there anything in particular you had in mind that I can learn from it?
I found some aliases, e.g. \smaller, which are handy to know. But I
don't know how much I can rely on the undocumented ones to continue to
do what they do now.

> \tfc augment the fontsize of a factor of 1.728
> It's relative to the default fount size not to the current fontsize:
> {\tfc foo {\tfc foo}} both foo have the same size

Thank you, this is an important nugget that I didn't understand when
reading the documentation. \setsmallbodyfont and \setbigbodyfont, in
contrast, change the font size relative to the current size.

>
> But interlinespace is not modified, so we need to reset
> \starttext
> OK: \input knuth\blank{\tfx WRONG: \input knuth\blank \tfc WRONG:
> \input knuth\relax} \page
> OK: \input knuth\blank{\tfx\setupinterlinespace OK: \input knuth\blank
> \tfc WRONG: \input knuth\blank} \page
> OK: \input knuth\blank{\tfx\setupinterlinespace OK: \input knuth\blank
> \tfc\setupinterlinespace OK: \input knuth\blank}
> \stoptext

Ok. This confirms what Aditya said, and what the manual says: that you
have to use \setupinterlinespace after \tfx or \tfc if you want the
interlinespace to be adjusted.

But I would really like to understand the categories involved here.
So we have one category of font size selector commands, which includes
\setsmallbodyfont and \setbigbodyfont, that cause interlinespace to be
adjusted automatically.
Then we have another category, including \tfc, \tfx, \ita, and others,
that do not cause interlinespace to be adjusted.

What is the rhyme or reason behind these categories? And that would help
me know, which other commands belong to which category? E.g. would
\serif cause interlinespace to be adjusted? An experiment would reveal
the answer, at least in the circumstances that I think of testing, but
I'd like to understand the conceptual model.
Maybe the concept is that the first category affects the "body font"
(and therefore interacts with the properties of the body font
environment), and the second category only affects the "font" (and I'm
still not clear on how the "body font" differs from the current font).

Thanks for your help,
Lars

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