Show speaker in the spotlight in large grids

[robintown]

Based on https://github.com/element-hq/element-call/pull/2382

[robintown]

I think I do have an argument against basing the decision on whether there is a scroll bar:

• Speakers are always promoted to the start of the grid, so it should be exceedingly rare that a speaker stays outside the visible area.
• So then, the purpose of this PR is not so much to bring obscured speakers into view, but rather to reduce the cognitive load of finding the speaker in a large grid of people.
• I think it's reasonable to assume that cognitive load is correlated to the number of participants in a call, but not necessarily to whether there is a scroll bar. (For example, if I have a large window showing 30 participants without a scroll bar, and then I make the window smaller so that it has a scroll bar and only shows the most important 15 participants, has the cognitive load really increased? I think it's gone down, if anything.)
• So, I think using a heuristic based on number of participants is appropriate.

However I totally get the desire to not use an arbitrary number. Basing the decision on whether there is a scroll bar would be pretty non-trivial, and this part of the designs is still subject to change (we want to workshop it further), so: I suggest that the scroll bar method is not worth the time investment at this stage, regardless of whether my argument above makes sense.

[toger5]

I suggest that the scroll bar method is not worth the time investment at this stage, regardless of whether my argument above makes sense.

I get behind this! I was mostly thinking that the reason for this is to always have the speaker visible. With more ppl (or a scroll container) there is the chance (independent of the user being at the bottom or the top) to not see a user so it makes sense to at least make sure the speaker is visible.

But I like going with this first and making a decision that requires a lot of dev effort based on more usage experience!