[scroll-animations-1] Replace timeline-attachment with timeline-scope #7759

[fantasai]

Alternative to #8902

[andruud]

Are you sure? Wouldn't that be a nice way to prevent an ancestor timeline-scope from attaching to a local timeline that needs to stay local?

.ancestor {
  timeline-scope: --t;
}

.child {
  scroll-timeline: --t;
  timeline-scope: --t; /* Forgetaboutit */
}

[fantasai]

Well, that would require also specifying that if you set timeline-scope on multiple ancestors, the closest one determines the scope. But actually as currently defined, we pull the scope all the way up to the highest scope with that name. I think this is fine? But in any case if we want to change that, we should open an issue to discuss. :)

[flackr]

Well, this was certainly my intention all along that it only goes to the nearest ancestor with the scope for that name so that you could set a timeline-scope name for a subtree and not have to worry about an ancestor with the same name name resulting in an ambiguous timeline selection. Apologies if this wasn't clear in the issue:

From #7759 (comment)

The downside is that without the double handshake you would still be contaminating the ancestor timeline namespace with a timeline that was only intended to be used in its subtree - which a developer could avoid by making the subtree also an explicit timeline root for the name.

[fantasai]

OK, I updated the definition to say that, see new commit.

It does seem like if this is the direction we want to go, we might also want to add:

• a keyword that blocks all timeline names
• a keyword that only blocks timeline names defined locally on this element

So I'll open a new issue...

[fantasai]

Filed #8915

[andruud]

This looks good. :-)

[andruud]

This looks good. :-)

EDIT: I somehow managed to double-submit.