Introduce IndexCell

[emilk]

Related

• Part of Add a timeline type for relative time #8635

What

Introduces a new type, IndexCell:

pub struct IndexCell {
    pub typ: TimeType,
    pub value: NonMinI64,
}

And changes TimePoint to use it:

pub struct TimePoint(BTreeMap<TimelineName, IndexCell>);

Naming

The thought behind the name IndexCell is two-fold:

A) It is symmetrical with DataCell
B) It will allow us to at some point broaden to more types of indices (e.g. UUID)

I’d like to rename TimeType to IndexType at some point. I haven’t planned this in detail though; I mostly want to avoid having to rename the new things I add.

TODO

• Full check

Future work

There are A LOT of tests using Timeline and TimeInt that would be better seved by using TimelineName and IndexCell, but this is too much to clean up in this PR.

There is also A LOT of (old) parameters of the type impl TryInt<TimeInt> which in effect means "An i64 or TimeInt that will be converted to a non-static TimeInt via saturating cast". It took me a long time to figure out that this is what it meant. We should come up with a nicer pattern for this.

Maybe deprecate TimePoint::with and TimePoint::insert?

[github-actions]

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Result	Commit	Link	Manifest
✅	482834a	https://rerun.io/viewer/pr/9226	+nightly +main

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[emilk]

@rerun-bot full-check

[github-actions]

Started a full build: https://github.com/rerun-io/rerun/actions/runs/13718027176

[teh-cmc]

"nonstatic" sounds a bit weird, but I guess we gotta stay away from "temporal" if we want to move towards generic indexes... 🤷

[emilk]

Good point 🤔
I'll add a TODO about that naming to the parent issue