Re: [CSS21] WD 5.12.1, 5.12.2: first-line and first-letter generally

Removing the existing text may also facilitate related upcoming work.
CSS regions (appearance influenced by what region it appears in) is
one example recently discussed on www-style.  It may also be relevant
to page-specific appearance (such as an element using a different
containing block size on different pages).  A common type of
region-specific styling that I don't yet see in CSS specs is having
text that's ragged-end in most places but justified where line boxes
are shortened by the presence of floats [or other exclusion regions].

Some of the undecided behavioural questions for :first-letter and
:first-line also apply to these other regions (e.g. inheritance
behaviour for out-of-flow things).  There is some value in the
different types of regions having a common behaviour: not just from
a consistency perspective but also because it simplifies both
specification and implementation if there's only one behaviour for
region-specific appearance.

:first-line, :first-letter and these other region-like things all make
significant demands on how box generation occurs, so it wouldn't be too
surprising if something codified in CSS2.1 on the matter (or something
implemented in a user agent in response to what CSS2.1 currently says
on the matter) were to conflict with, or at least complicate the
specification & implementation of, how we later discover we want one of
those other regions to behave.

pjrm.