feat: add function key modifier

[decodism]

It's a bit hacky as Carbon doesn't support it.

[lwouis]

Hi @decodism,

Thank you for sharing this work.

Adding the function key was discussed in the past. In end, I concluded that opening that door would create support situation that would not be worth. Have you seen this thread perhaps?

It's pretty cool that you managed to implement that! I need to test it to see how it behaves.

As I mentioned above, I'm not sure it's worth to add this feature. It would probably be of niche use, and open the door to all sorts of exotic bugs and behaviors.

What do you think?

Thank you 🙇

[lwouis]

I played around with the PR. Here's some feedback, in addition to my reserves above about opening that door:

• I think the symbol F may be a bit confusing. Perhaps some fn in small letters would be clearer. It's a consistent wording on the physical keyboards
• The app crashed when I tried to use a shortcut with F1. I held fn then the f-keys appeared, and I pressed F1. I see in the debugger that in ControlsTabs.swift, line 194,Shortcut(keyEquivalent: newValue) was nil. newValue was equal to "⌥FF1". It raises the question: how should the fn key interact with f-keys like F1. Should pressing fn then F1 count as F1 only, or as modifier fn + F1 key?

Thank you

[decodism]

Hello,

I'm not sure what issues this addition might bring. I've made some changes following your feedback:

• Replace F with fn, which has the side effect of fixing the crash with F* keys.
• No longer display the function modifier with F* keys

[lwouis]

Hi @decodism,

Thank you for the updates!

Regarding my concerns:

As you've said, it's not supported by Carbon. This means it's exotic and other apps supporting it will be few. Users probably are not used to it or expecting it to work, or the nuances which go with it. For instance, the cases with fn+F1 I've shared previously, or the fact that Apple own UI in System Settings is broken currently when assigning shortcuts with fn

The fn key is used together with the globe key. I think this also adds lots of confusion to supporting this feature. For instance, my setup is an external Logitech K380 keyboard, and a 2022 macbook pro. Here's how they physically look like:

Logitech K380	2022 macbook pro

Notice how the System Settings mention the fn key for the external keyboard, and the globe key for the internal keyboard. Even though both keys features the fn marking on it:

Logitech K380	2022 macbook pro

I can set fn using the internal keyboard, with your PR, but I can't set fn with the external keyboard. There must be an implementation difference. Maybe you catch the globe key code instead of fn.

Do you see what I mean by adding complexity and exotic use-case if we merge this?

What do you think?

Thank you