Editorial: topmost popover ancestor should not use a map

[annevk]

While this is a reasonable implementation strategy to get O(1), it makes the algorithm a lot harder to read. We should get the index of the item in the list instead when it comes time to compare. That will require defining index in Infra, but that seems like a good thing to be doing regardless.

cc @mfreed7 @josepharhar @domenic

[mfreed7]

While this is a reasonable implementation strategy to get O(1), it makes the algorithm a lot harder to read. We should get the index of the item in the list instead when it comes time to compare. That will require defining index in Infra, but that seems like a good thing to be doing regardless.

Yeah, I see your point. As long as the net effect is the same (and using a map is ok for implementations), I'm ok changing the spec to make it easier to read.

[josepharhar]

@mfreed7 could you outline what the algorithm would look like without a map, or what changes are needed?

That will require defining index in Infra, but that seems like a good thing to be doing regardless.

Do you mean that we should make it so you can do list[index] to get an item in a list like we can do with maps? https://infra.spec.whatwg.org/#map-get

[mfreed7]

@mfreed7 could you outline what the algorithm would look like without a map, or what changes are needed?

That will require defining index in Infra, but that seems like a good thing to be doing regardless.

Do you mean that we should make it so you can do list[index] to get an item in a list like we can do with maps? https://infra.spec.whatwg.org/#map-get

I think @annevk means something like:

To get the index of an item in a list, given item and list:

1. define a variable index and set it equal to 0.
2. Loop through each items in list, in order, and for each entry entry:
   a. Compare entry to item. If they are equal, return index.
   b. Increment index.
3. Return -1.

And then instead of using a map for popover ancestor, you just find the index using the above algorithm, and index into the list.

[annevk]

Indeed, though I might instead assert that item is in the list, at least until we have sufficient motivation to change that.