[css-align][css-grid] which position to use for aligning a baseline-aligned subtree of grid items?

I'm implementing baseline alignment for grid layout in Gecko.
I have a couple of spec questions:

https://drafts.csswg.org/css-align-3/#align-by-baseline
"Position this aligned subtree
within the alignment container according to the rules of the box
alignment properties in effect."

It's rather vague what "alignment properties in effect" you're
referring to here.  When aligning grid items the alignment
container is a track, which doesn't have any properties per se.

Should I use the grid container's [align|justify]-content for
aligning the subtree?
If so, since the spec text above calls for a _position_ to align
the subtree to, what should I use when the value is 'stretch',
<baseline-position> or <content-distribution> ?

The spec also needs to have a description of how aligning
a subtree works exactly, especially when overflow is involved.
(I suggest that you define the alignment edges of the subtree
as the union of alignment edges for the individual boxes and
that this union should be aligned as an alignment subject
using the position defined above.)

In general, all the spec sections on baseline alignment would
benefit from illustrations to make your intent clearer.

Thanks,
Mats

Received on Saturday, 14 May 2016 15:16:33 UTC