The otherwise excellent note-taking app Bear has an interesting bug that’s worth talking about while it’s still here.

When you’re around to-do items, you can press ⌘. (period) to toggle any task complete or incomplete. It’s actually a really fun shortcut in practice:

But when you have a larger selection with a mixed state (some checkmarks are on, others off), this is what happens:

This feels like an obvious thing to implement, and this is also where the code itself wants to go when left alone.

But this is not great. The rule is: When you have a mixed state, changing it should collapse (or: normalize) the entire selection to one state or the other, rather than perform individual inversion. Try ⌘B in your text editor on partially bolded text, and you can see that collapse in action:

It feels strange to recommend that, particularly as it seems like it loses data. So, what gives?

The first argument is “do not make the user jump through hoops” or maybe “respect a large selection.” If, as a user, I want to actually make sure all my tasks are done, the shortcut not being idempotent means that I now have to go through tasks one by one, and that’s a lot of work – especially since we’re talking about text selection, which is famously unpleasant.

The second reason is that even the UI layer has an opinion here. In the above bolding example, Pages collapsing the selection to bold when you press the B toggle, makes the toggle UI behave exactly as it normally would with a simple selection:

Elsewhere, in Figma, typing a number on top of a “mixed” state changes all the properties of relevant objects to that number:

Imagine how awful it would feel mechanically in both the above examples if your action would still leave the text in the “mixed” state. It would simply appear like the UI broke, since the change didn’t fully “stick” – kind of like those tiny hated moments when you close the door, but it doesn’t latch on and reopens on its own, or when you engage the turn signal stalk, but it refuses to stay put and snaps right back.

There is also one last reason. It’s the simplest one that I sometimes have to remind myself to put in my head before I jump too deep into the mechanics, or details, or technical nuances. Let’s say the toggles invert individually on a large selection. Who would ever benefit from it behaving this way?