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Re: small revision to CSS1

From: Bert Bos <Bert.Bos@sophia.inria.fr>
Date: Fri, 31 May 1996 21:10:26 +0200
Message-Id: <199605311910.VAA26065@mygale.inria.fr>
To: dseibert@sqwest.bc.ca (David Seibert)
Cc: www-style@w3.org, howcome@w3.org, dsr@w3.org
David Seibert writes:
 > I am currently working on translating CSS1 to DSSSL-o, and

That's excellent! We are writing a document that describes the
mapping, intended to be published as a WD "soon". Some people may have
seen an early draft of it. (If you're interested, ask me; the draft is
still there, it's just not currently linked from anywhere.)

 > have run into a problem that could be very easily fixed by
 > a small change in the CSS1 specification.  Translating the
 > values for the attribute 'font-style' is difficult to do
 > cleanly because 'small-caps' involves a transformation of
 > the characters of the text, while the other values ('none',
 > 'italic', and 'oblique') can be translated as a style
 > description.  My problem would be remedied if the value 
 > 'small-caps' were instead given to the attribute
 > 'text-transform'.  

Text-transform replaces characters by other characters, `rot13' is a
text-transform (it replaces `a' by `n') and so is `uppercase' (it
replaces `a' by `A'). A small-caps font just happens to have an `a'
that looks like a reduced and then stretched `A', but it is really
still the same `a' character.

In DSSSL, small-caps is supposed to be handled with a glyph
substitution table, the same one you would use to substitute a swash
letter for a normal one, or a ligature for a sequence of letters. In
fact, the italic shapes of most fonts are so different that you might
want to consider that a glyph substitution as well. But glyph
substitution is a concept that CSS1 doesn't have, and that is anyway
too technical for most people. Typographically, small-caps is just a
different font within the same font family.

Modern electronic typesetting is able to produce oblique small-caps as
well, and so we allowed that combination in the font-style
property. (We also allowed italic small-caps, although that doesn't
make as much sense, because italic and oblique are almost synonyms for
many people.)

 > This move makes sense in the context of CSS, as 'small-caps'
 > is orthogonal to any of the other possible values of
 > 'font-style' (i.e., it can be specified independently of
 > those values), but not to the values of 'text-transform'
 > ('none', 'lowercase', 'uppercase', and 'capitalize'). This 
 > quickly becomes apparent if you try to imagine producing
 > 'small-caps uppercase' text.  The move also makes sense 

Small-caps combined with uppercase happens to leave you with the same
shapes as normal uppercase (at least in most fonts), except that they
will usually be drawn from a different font file.

Small-caps + capitalize or small-caps + lowercase make perfect
sense. In fact small-caps + capitalize is Netscape's `house style'.

 > for the DSSSL-o translation of 'text-transform', as all of
 > these values (except 'none', of course) obviously involves
 > transformations of the text as well, making the grouping
 > more natural.

Only Glyph substitutions (which use a glyph-subst-table in DSSSL), but
not character transformations (which use a char-map).

 > I realize that CSS has officially become stable, but I
 > doubt that this small change would represent a problem to
 > anyone trying to implement it at present.  It should at
 > most involve moving a small amount of code between
 > subroutines, as there will be no change in the behavior
 > required to implement the value.  As it would be 
 > advantageous for DSSSL and DSSSL-o translation, and would
 > help keep users from specifying style prescriptions that
 > are impossible to render, I suggest that this change be
 > made as soon as possible.

I expect that in most implementations, the routines for font-style and
text-transform are very different. Trying to add the functionality of
small-caps to text-transform would mean that the latter routine would
suddenly have to interface to the font subsystem, where it used to be
a self-contained bit-shift function.


Bert

PS. What are your plans with the CSS1 to DSSSL-o translation, will it
be a program or just a document? And will it be available to
everybody?
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/pub/WWW/People/Bos/                      INRIA/W3C
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 93 65 77 71                 06902 Sophia Antipolis Cedex, France
Received on Friday, 31 May 1996 15:10:35 GMT

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