Karabiner-Elements: BlockUntilKeyUp functionality

I’d like to implement a “SpaceFN” layer (ie. while space is held down, activate another layer).

Here’s a small example showing how to map Space+J to “left”:

{
    "description": "Space + J = LEFT",
    "from": {
        "key_code": "j",
        "modifiers": {
            "mandatory": [
                "fn"
            ]
        }
    },
    "to": [
        {
            "key_code": "left_arrow"
        }
    ],
    "type": "basic"
},
{
    "description": "Space as fn",
    "from": {
        "key_code": "spacebar"
    },
    "to": [
        {
            "key_code": "fn"
        }
    ],
    "to_if_alone": [
        {
            "key_code": "spacebar"
        }
    ],
    "type": "basic"
},

The problem is, space is pressed very often during normal typing, so it is all too easy for this kind of set-up to produce unwanted “fn” presses instead of spacebar presses when typing fast.

With the old Karabiner, __BlockUntilKeyUp__ took care of this quite nicely, or at least, I think it did if I understand its purpose. It basically meant, I think, that it wouldn’t fire one of the layer events unless Space were pressed before another key, and released after the other key:

# This triggers a layer event (ie. LEFT)
Space down ---> J down ---> J up ---> Space up

# This normal roll-over does not trigger a layer event, just SPACE then J:
Space down ---> J down ---> Space up ---> J up

Here’s the full version of the old Karabiner config: https://github.com/wincent/wincent/blob/c250a81d235bef574d3a7cf2f2bb7a585bcd9686/roles/keyboard/files/spacefn.xml

About this issue

Original URL
State: closed
Created 7 years ago
Reactions: 6
Comments: 23 (2 by maintainers)

Commits related to this issue

Karabiner: back out SpaceFN layer for now Pending resolution of: https://github.com/tekezo/Karabiner-Elements/issues/877 Too easy to get unwanted "fn" presses with this config. — committed to wincent/wincent by wincent 7 years ago
karabiner: Add back SpaceFN, again This one is sooo close to actually working like the old one used to, and is possible thanks to the recently added `to_if_held_down`. - Press and hold Space for at ... — committed to wincent/wincent by wincent 7 years ago
Use SpaceFn Using Right CMD for arrow keys is awkward and limits what other keys can be modified. Space is much more natural, but more difficult to implement without messing with normal typing. The h... — committed to matt-tingen/configs by matt-tingen 5 years ago

Most upvoted comments

@michelkoga: That’s much better. Thanks.

However, I still think I need an equivalent for __BlockUntilKeyUp__. Without this, configurations like the above don’t handle rollover well. I am going to keep playing around and see if I can come up with something in terms of variables and to_if_alone_timeout_milliseconds perhaps, but ultimately I think I need something else.

wincent on Jul 29, 2017

The new to_if_held_down property allows us to get pretty close to what we would need here, but it is not quite there; given this config:

                        "description": "SpaceFN layer",
                        "manipulators": [
                            {
                                "from": {
                                    "key_code": "spacebar",
                                    "modifiers": {
                                        "optional": [
                                            "any"
                                        ]
                                    }
                                },
                                "to_if_held_down": [
                                    {
                                        "set_variable": {
                                            "name": "SpaceFN",
                                            "value": 1
                                        }
                                    }
                                ],
                                "to_after_key_up": [
                                    {
                                        "set_variable": {
                                            "name": "SpaceFN",
                                            "value": 0
                                        }
                                    }
                                ],
                                "to": [
                                  {
                                    "key_code": "spacebar",
                                    "repeat":  false
                                  }
                                ],
                                "type": "basic"
                            },

We can prevent the SpaceFN layer from kicking in until the key is pressed for a while, and we can still enjoy normal rollover while typing fast. The only gotcha is that initial press of the space bar causes an immediate key-down/key-up to be sent, even if you end up just pressing and holding (ie. your intention is to enter SpaceFN mode). This is very close to being usable now, but I think we still need something like __BlockUntilKeyUp__.

wincent on Dec 28, 2017

Seems like it is now though. 😄

For example:

https://github.com/wincent/wincent/commit/8fe03134e1c5201264ed2f1e5373c8720e2019f8

wincent on Feb 28, 2018

Should this issue be reopened? Seems like it is only resolved for @wincent, but everyone else is still waiting for a fix before spacefn is usable 😃

yzhuang on Feb 22, 2019

Let me throw in here the set if heuristics that I’m using in my Linux implementation (in the Xorg input driver): http://www.ljosa.com/~ljosa/software/spacefn-xorg/

I found that simple timeouts were not enough, and that I needed to buffer other keypresses (not just space) until their intention became clear.

ljosa on Jan 4, 2018

I’d second sven’s request. It would have saved me a fair few hours of banging my head against the wall!

nimms on Jan 5, 2019

The SpaceFN configuration listed here should be updated with the fix by @wincent.

svenjacobs on Dec 5, 2018

Karabiner-Elements: __BlockUntilKeyUp__ functionality

About this issue

Commits related to this issue

Most upvoted comments

Karabiner-Elements: BlockUntilKeyUp functionality