Map more UTF-8 key events

[leostera]

At the moment we are only handling the space " " and keys in a nice way, but it'd be nice to be able to match on KeyDown Enter or KeyDown "<enter>".

Using a variant for all the keys may be a stretch, since we're parsing UTF-8 grapheme clusters, so at least some common ones we want to handle in a way that lets you match over KeyDown easily.

This is currently happening in the minttea/io_loop.ml in the translate function:

https://github.com/leostera/minttea/blob/main/minttea/io_loop.ml#L18

---

Currently implemented keys:

• Enter
• Space
• Backspace
• Left / Down / Up / Right
• Escape
• Key (includes a string with the contents of the matched UTF-8 character)

Missing keys:

• Shift-modifier
• Ctrl-modifier
• Alt-modifier
• ???

[leostera]

As an update, we now have a key variant that we're mapping around the same place in the code, so when you match on a KeyDown event you can discover quickly what the available keys are, and also have some guarantees that your app won't break.

[wllfaria]

Hey! I would love to contribute by adding support for modifier keys.

so far, the Key variation is only a string

type key =
  | Up
  | Down
  | Left
  | Right
  | Space
  | Escape
  | Backspace
  | Enter
  | Key of string

which means its not straight forward to just add a modifier to the key pressed without breaking the interface unless I add a new variation. But I think its a bad API to have both Key and other event for Key with modifier.

I thought about making it be Key of key_event in which key_event would be something like:

type key_modifier = 
  | Ctrl
  | Alt
  | Shift

type key_event = {
  key : string;
  modifier : key_modifier;
}

This would allow for telling which modifier was pressed with a key. But again, this would be a breaking change to the interface, which also requires to change all the examples.

What do you think?

[leostera]

As discussed in #45 we chose to use a pair of key * modifier and make the modifier a variant that includes a No_modifier constructor, so matching on a key event looks like:

| KeyDown (Key "j" | Left, No_mofidier | Shift) -> ...