Try making the hover state of nested blocks more visible

[kjellr]

Following up from #14961.

Currently, when you hover over the new dashed borders for nested blocks, nothing happens:

In the original PR, we briefly discussed improving upon this by adopting a hover state. This PR implements a similar hover state to the one proposed there, but it uses a border-style change instead, which I think is a little more visible than jus the color change. Still could use some iteration though:

Todo:

• Make this work for an individual column block when its child is selected. Something's blocking that right now.
• Build in styles for dark mode.

[kjellr]

I've adjusted the colors a little bit to make this a little smoother:

Now, the all-around hover border color more closely matches the thick left border (and breadcrumb), which feels much more subtle and considered.

In order to make this feel natural, I had to lighten the dashed border colors by a couple steps. This makes them a little less easier to see, but I think it still feels pretty solid overall.

[karmatosed]

I like this a lot, it's subtle enough to give me feedback but also feels not overwhelming. I do think testing this with some deep level nesting is important but getting it in seems sensible to me as a starting point.

[kjellr]

Thanks, @karmatosed! I've pushed a couple small fixes:

• Dark mode styles, to match those already in place for the standard block borders.
• A fix that allows these hover states to show up in situations where nesting runs 3+ levels deep (like the columns block).

Mind giving this one more look?

[mapk]

After just testing this, I believe it looks good! There's some subtle hover and click targeting that seems off a bit though. I imagine these issues are more about nesting than this specific PR, so I don't want to hold this one back b/c of them. But this is what I was experiencing.

[kjellr]

I imagine these issues are more about nesting than this specific PR, so I don't want to hold this one back b/c of them. But this is what I was experiencing.

Yeah, I've seen that too. I think the block boundaries need to be fine-tuned a little bit, but that's probably a much more complicated problem. 😄

[karmatosed]

Works well for me with changes. I stand by we should iterate based on feedback of deeper nesting and I do also agree there is something weird going on about boundaries to fix in another issue.