Why do the Hebrew Alphabetic Presentation Forms Exist

[Richard Wordingham]

On Thu, 4 Jun 2020 17:01:34 -0400
"Mark E. Shoulson via Unicode" <unicode at unicode.org> wrote:

> On 6/4/20 12:15 PM, Richard Wordingham via Unicode wrote:
> > On Thu, 4 Jun 2020 08:28:08 -0400
> > "Mark E. Shoulson via Unicode" <unicode at unicode.org> wrote:

> >> On 6/3/20 11:44 PM, Sławomir Osipiuk via Unicode wrote:  
> >> This isn't a matter for a variation selector.  This is purely a
> >> *scribal* or *presentation* alternation.  It has as much relevance
> >> to the content of the text as choice of font.  This is a matter
> >> for a stylistic alternate in the font tables.  This is *exactly*
> >> what those are for!  
> > That wasn't obvious to whoever first implemented them in MS Word.
> > The feature settings for a font applied throughout the document!  
> 
> Ah.  I'd been seeing it in LibreOffice and other places, where you
> can twiddle the settings on individual spans, and didn't realize that 
> originally these things were expected to be document-wide.  Thank you 
> for correcting me.  Would you say, though, that while it may not be
> what they were originally meant for, that this use fits very well
> into how they can be and are used today?

Features were around long before MS Word implemented user control of
them. The description of some of the features implies interaction
between the author and the rendering machine.  Cascading Style Sheets
(CSS) brought optional features to the masses, and they're not designed
for interactive layout. The CSS approach effectively provides a set of
font customisation, so switching from one set to another seems to be
like switching fonts, which you suggested as one approach.  If it is
implemented that way, then one loses font control across changes of
options.  A lot of Indic script engines appear not to have allowed
interaction between clusters, so there would have been no loss of
control by applying different fonts to different clusters. 

Now, I've seen Windows interfaces that allow the application of
features to be limited to parts of a string.  I don't know how that
works.  I can imagine it becoming more sophisticated over time.

Reviewers of features were horrified that Word required the settings to
apply across the document.  That was widely seen as a design fault, and
I trust it has now been fixed.  My point was simply that what you saw
as an obvious use of features was not obvious to everyone.

> Yes, what I had been envisioning would indeed involve setting the use
> of font-features on small (one-character) spans in the middle of
> words, and I didn't consider how well word-processors can handle such
> a thing, and I don't really know.  What about things like 'swsh'
> tables for swash effects?  Are those applied to a whole word
> (paragraph?) at a time, but the table itself only affects the final
> letters of words?  Or do you have to apply it to each individual
> letter that you would see swashed? If the latter, it's a lot like
> what I'm thinking about in this case.

I haven't used sophisticated layout systems, so I don't know how they
work. I could well imagine that they didn't work with automatic kerning.

Rchard.