qmk_firmware/users/callum/readme.md

A keymap for 34 keys with 4 layers and no mod-tap.

Details

• Hold sym to activate the symbols layer.
• Hold nav to activate the navigation layer.
• Hold sym and nav together to activate the numbers layer.
• The home row modifiers are oneshot so that it's possible to modify the keys on the base layer, where there are no dedicated modifiers.
• swap win sends cmd-tab for changing focus in macOS but holds cmd between consecutive presses.
• swap lang behaves similarly but sends ctrl-space, for changing input language in macOS.

Oneshot modifiers

The home row modifiers can either be held and used as normal, or if no other keys are pressed while a modifier is down, the modifier will be queued and applied to the next non-modifier keypress. For example to type shift-cmd-t, type sym-o-n (or nav-a-t), release, then hit t.

You can and should hit chords as fast as you like because there are no timers involved.

Cancel unused modifiers by tapping nav or sym.

Userspace oneshot implementation

For my usage patterns I was hitting stuck modifiers frequently with OSM (maybe related to #3963?). I'd like to try to help fix this in QMK proper, but implementing oneshot mods in userspace first was:

1. Fun.
2. A good exploration of how I think oneshot mods should work without timers.

So in the meantime, this userspace oneshot implementation is working well for me.

Swapper

swap win sends cmd-tab, but holds cmd between consecutive keypresses. cmd is released when some other key is hit or released. For example

nav down, swap win, swap win, nav up -> cmd down, tab, tab, cmd up
nav down, swap win, enter -> cmd down, tab, cmd up, enter

swap lang sends ctrl-space to swap input languages in macOS and behaves similarly.

Swapper implementation.

Why no mod-tap?

Mod-tap seems to be by far the most popular tool among users of tiny keyboards to answer the question of where to put the modifiers, and in the right hands it can clearly work brilliantly, but I've always found myself error prone and inconsistent with it.

With dedicated modifiers, there are three ways one might type ctrl-c:

ctrl down, ctrl up, c down, c up
ctrl down, c down, ctrl up, c up
ctrl down, c down, c up, ctrl up

Basically, you never have to worry about the keyups, as long as the keydowns occur in the correct order. Similarly, there are three ways one might type ac:

a down, a up, c down, c up
a down, c down, a up, c up
a down, c down, c up, a up

Replace a with ctrl and this is exactly what we had before! So if we want to put a and ctrl on the same key we have a problem, because without considering timing these sequences become ambiguous. So let's consider timing.

The solution to the ambiguity that QMK employs is to configure the TAPPING_TERM and consider a key held rather than tapped if it is held for long enough. My problem with this is that it forces you to slow down to use modifiers. By its very nature the tapping term must be longer than the longest you would ever hold a key while typing on the slowest laziest Sunday afternoon. I'm not typing at 100% speed at all times, but when I am, having to think about timing and consciously slow down for certain actions never fails to trip me up.

So alas, mod-tap is not for me -- but if it works for you, more power to you. :)

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My github