DSSSL WWW Enhancements

[Hakon Lie <howcome@xxxxxx>]

James Clark writes:

 > I've started putting together a document
 > (http://www.jclark.com/dsssl/web-dsssl.htm) to describe the enhancements
 > that I believe are needed for use DSSSL on the Web. 

This is a very interesting document. If these enhancements are added
to DSSSL-*, I believe DSSSL will be suited for use on the Web, and
will be much easier convert CSS1 [1] style sheets into DSSSL. CSS1 can
then be viewed -- as some people have all along -- as a declarative
subset of DSSSL and the tensions between the two communities could be
eased.

[1] http://www.w3.org/pub/WWW/TR/REC-CSS1

James has a good understanding of the CSS1 formatting model and he's in
a good position -- to say it the least -- to propose how these
enhancements should be added to DSSSL. 

My initial comments fall into two categories:

 1) comments on the document itself
 2) CSS1 features that can still be tricky to convert


1) comments to the document

- on the issue of identifying the first letter, generated text is
listed as a complicating factor. Generated text is not a part of CSS1,
but there are proposals for adding it. I would not find it natural to
have the 'first-letter' pseudo-element be affected by generated text.

 - the description of drop-caps in CSS1 is accurate, and you're right
is saying it's not an ideal solution. Part of the reason why we're not
extended it is that we haven't had a list of requirements for other
languages. Your description of Thai is therefore very welcome. The
proposed "first-letter-drop-n-lines" seems like a viable solution.

 - the proposed support for old-style numerals in the same manner as
small-caps is a nice addition

 - the proposed background image characteristics are said to be
inherited. This is not the case in CSS1 -- why should they inherit?

 - the document suggests a "side-flow-multiple" to control if floating
areas can be placed next to each other horizontally. Can't you just
use the proposed "side-float-clear" for this?

 - the question "Should there also be a characteristic to control
blink rate?" can safely be answered with a "No". This is a bottomless
pit -- as are all the other areas we're trying to control -- but the
price/performance seems higher than for most other possible
characteristics

 - the document briefly mentions that the functionality of the CSS
positioning draft should be replicated in DSSSL. The ideal solution
would be if one could find a way to reuse formatting properties
directly without having to rephrase specs. The name of the working
group that does CSS within W3C is now "Cascading Style Sheets and
Formatting Properties" to reflect the fact that not only code in CSS
syntax will set those properties -- you can already do it from
VBscript in IE4.



2) CSS1 features that can still be tricky to convert

 - the matching rules for the font properties in CSS1 are very
specific. E.g., the order in which things are matched is specified.
Unless DSSSL is extended in the same direction, converted style sheets
may not end up using the same font. 

 - font-weight takes a different set of values than does the
corresponding characteristic in DSSSL. We need to define a mapping
table of some kind

 - 'ex' units seems to be missing in DSSSL.

 - relative and percentage values. There seems to be no easy
conversion of relative keyword values (e.g. 'bolder' on 'font-weight')
or percentage values (e.g. 'width: 30%' which sets the width of an
element to be 30% of the width of the parent element)

Also, it should be noted that a CSS1->DSSSL conversion can only take
place after cascading.

Regards,

-h&kon

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