More cursor keys

[devycarol]

This patch implements toolbar keys for the following previously-reserved codes:

• Page up/down (just didn't have buttons)
• Page start/end

It also adds a new pair: word left/right. These replace line start/end for the left/right long-clicks in the toolbar.

• Full left/right is now under the word-movers, and page start/end is under the pagers
• A more comprehensive config could be implemented later on, maybe allowing choice between repeat input or various cursor actions on those toolbar arrows.

To test these keys, you can replace your numpad layout with this D-pad prototype: dpad_toy.json. The "double-arrow" keys are repeatable the main keyboard.

Small issue
The word-move keys are based on emulated Ctrl+Left/Right arrows. Android handles this differently from PCs:

• It skips through space-separated non-word characters like punctuations and emoji.
• It doesn't advance the cursor past the first/final instance of a word character.
  • This is the more eyebrow-raising one, since you expect the cursor to continue moving until it reaches the end of a text box. Like with any other cursor-mover.
  • In this case, it will continue making the clicking sound when held since "it is possible to delete characters."
• Also, the method they use says to avoid using it whenever possible. Something about "race conditions"—not that I know what that means…

Because I'm CooCoo bananas: I've made a rich-input implementation of "selection units" which is utilized for a word-delete slider in the upcoming more-delete-keys. That can be recycled into a non-keycode implementation of word left/right later on for non-primitive input, just as it'll be recycled for "select adjacent word" keys.

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Split from #925
Progress on #357

[Helium314]

Sorry for creating merge conflicts here, though they should be pretty simple to solve (you don't even need to change the codes for word left/right)

[devycarol]

after a fair bit of hot-wiring, this is ready to go 🙃

[Helium314]

Not much time for review on my side though. May take up to 2 days until I can have a look.

[Helium314]

Code looks good, with exception for the changed key codes.
I'll play a liitle on device trying to find unexpected stuff.

[devycarol]

somehow a bunch of other stuff i was working on got merged in, so I had to force-push it out :/

About the repeat interval, I do think at most 10 per second would be best for the more drastic movers.

[Helium314]

No problem, there was only the keycode change to do
(sorry for introducing build error, for some reason - probably cache - the local build still worked)