Problem of Dual-Purpose Keys (home row mods)

By Xah Lee. Date: . Last updated: .

What is Dual-Purpose Key

Some keyboard software have a feature to assign a modifier key and a non-modifier key both to the same physical key. For example, set Control and Space both to the Space key. When you press and release Space, it inserts a space, but when you press and hold Space, then press for example c, it does Ctrl+c (copy).

Software that Support Dual-Purpose Key

What is Home Row Mods

Home Row Mods is setting your home row keys to become modifiers. For example

A
S
D
F
 
 
 
 
J
K
L
:

Problem of Home Row Mods

One problem of Home Row Mods is random accidental invocation of key shortcuts, if you are a fast typer.

Problem of Dual-Purpose Keys

When you have a dual-purpose key, you cannot hold the key to repeat.

I know because i used Dual-Purpose Keys on my Gergo Keyboard (QMK firmware), also with on my Ultimate Hacking Keyboard (UHK Agent firmware) .

Try this. Whip your keyboard out. Program the Backspace ⌫ key to be also Ctrl when held down. Now, see if you can hold Backspace ⌫ to delete letters continuously. You can't.

Keys You Need to Hold to Repeat

Space, Backspace ⌫, Delete ⌦, Enter, -

This means, it does not work well if you put dual-purpose keys to a key you need to hold to repeat.

QMK Solution of Dual-Purpose Key Hold to Repeat

2021-04-23 Hans Peter wrote to say that in QMK, the dual-purpose key problem of hold to repeat can be avoided, by press and release the key, then hold it, then the non-modifier function of the key would repeat.

Hold to Repeat is Also a Hack

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