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Re: Comments on Section 1 of the CSS Inline Spec

From: L. David Baron <dbaron@dbaron.org>
Date: Wed, 26 Aug 2015 12:57:31 +0200
To: Stephen Zilles <szilles@adobe.com>
Cc: "www-style@w3.org list (www-style@w3.org)" <www-style@w3.org>
Message-ID: <20150826105731.GA11091@pescadero.dbaron.org>
On Wednesday 2015-08-26 10:32 +0000, Stephen Zilles wrote:
> 2.      This spec seems to be missing the "inherit" value of the 2.1 "vertical-align" property

In general, we've avoided explicitly listing inherit, initial, etc.,
in post-level-2 modules.

> 3.      This new syntax allows the specification of both a baseline alignment and the specification of a shift. I presume, but the spec is not clear about this, that the baseline alignment is done first and the shift is done subsequent to that alignment. The spec should make this clear.
> 
> 
> 
> 4.      Why are "percentage" values of "baseline-shift" relative to the line height? It would seem that font-size would be more relevant. Font size is what is used to scale the baseline pos

baseline-shift is one of the longhands resulting from splitting
vertical-align into a shorthand.  Percentage values of
vertical-align have been relative to line-height since:
http://www.w3.org/TR/REC-CSS1-961217#vertical-align
so it's probably a little late to change it. :-)

> 5.      With respect to Issue 3. It is clear that these alignments are not baseline alignments, but they were historically part of "vertical-align". It would seem to make sense for these three values (and an additional "auto" value) to be the values of a third shorthand, "subtree-alignment". The "auto" value would be the default and would mean use the "alignment-baseline" value. In this case the syntax would become
> "[[<length><https://drafts.csswg.org/css-values-3/#length-value> |<https://drafts.csswg.org/css-values-3/#comb-one> <percentage><https://drafts.csswg.org/css-values-3/#percentage-value> |<https://drafts.csswg.org/css-values-3/#comb-one> sub |<https://drafts.csswg.org/css-values-3/#comb-one> super] || [baseline |<https://drafts.csswg.org/css-values-3/#comb-one> text-bottom |<https://drafts.csswg.org/css-values-3/#comb-one> alphabetic |<https://drafts.csswg.org/css-values-3/#comb-one> middle |<https://drafts.csswg.org/css-values-3/#comb-one> central |<https://drafts.csswg.org/css-values-3/#comb-one> mathematical |<https://drafts.csswg.org/css-values-3/#comb-one> text-top]] && [<https://drafts.csswg.org/css-values-3/#comb-one>bottom |<https://drafts.csswg.org/css-values-3/#comb-one> center |<https://drafts.csswg.org/css-values-3/#comb-one> top]"
> 
> This, however, would remove applying a "baseline-shift" to a "center"ed sub-tree. Is that something that is needed? Currently, shifts cannot be applied to sub-trees that are top or bottom positioned.

There's some issue of compatibility with SVG here, though.

(See also the history in
https://bugzilla.mozilla.org/show_bug.cgi?id=308338 ; Gecko hasn't
implemented the split yet.)

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)

Received on Wednesday, 26 August 2015 10:58:05 UTC

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