Re: [css-snappoints] Various issues

Following up with more data and a fairly drastic revision to the
scroll-snap-edges proposal.

Now that Miranda's implemented a basic prototype of our proposal, we
immediately realized that it doesn't make sense to simply snap the scroll
position to the top/left/right edge of some element. For example, when
scrolling down, you're not interested in aligning the top edge of some
element with the top of the container. Instead you want the bottom edge of
some element aligned with the bottom edge of the container because you want
to see whole elements at the bottom of the container, even if it means you
have to show partial elements at the top.

So I've revised https://wiki.mozilla.org/Gecko:CSSScrollSnapping to make
scroll-snap-edges take "none", "border-box" and "margin-box" values. When
scrolling down you snap the bottom edge of the specified box to the bottom
edge of the container, and analogously for the other directions. This makes
RTL a non-issue. It does however mean that scroll-snap-type:mandatory can't
be strict apart from scroll gestures, because in a lot of cases (e.g.
DOM/style changes) we don't know what direction to use for snapping.

Rob
-- 
Jtehsauts  tshaei dS,o n" Wohfy  Mdaon  yhoaus  eanuttehrotraiitny  eovni
le atrhtohu gthot sf oirng iyvoeu rs ihnesa.r"t sS?o  Whhei csha iids  teoa
stiheer :p atroa lsyazye,d  'mYaonu,r  "sGients  uapr,e  tfaokreg iyvoeunr,
'm aotr  atnod  sgaoy ,h o'mGee.t"  uTph eann dt hwea lmka'n?  gBoutt  uIp
waanndt  wyeonut  thoo mken.o w