Add option for the panic sequence to only consider physical key layout

[ficcdaf]

Note: when I refer to physical keys, I'm talking about the LHS of a mapping; the key that keyd detects before remapping it.

Motivation

It's mentioned in #315 that the panic sequence can be disabled by modifying the source code, but being able to disable the feature completely defeats the purpose of it. While I agree, I've found the behavior of triggering the panic sequence a bit inconsistent.

For example, the BS + ESC + ENTER sequence terminates keyd both when those physical keys (regardless of their remappings) are pressed -- this is the behaviour I'd expect. However, it also triggers when the "mapped output" resolves to that sequence as well. So, depending on the layout, there are a lot of different physical key sequences that can possibly resolve to the same "virtual sequence" and trigger the kill switch.

I argue that this behavior is inconsistent, and personally I've managed to trigger it accidentally on a few occasions.

Proposed Solution

I propose introducing a config option with a (tentative) name like kill_switch_physical_only=y/n. When the option is enabled, then keyd should only be terminated if the physical keys corresponding to the escape sequence are typed; if different keys that are mapped to keys corresponding to the escape sequence are pressed, it should be ignored.

I believe this feature would improve the usability and consistency of keyd without defeating the purpose of the panic sequence.

I propose the option should be disabled by default; s.t. keyd will behave exactly as it did before unless the user optionally enables this flag in the config.

Implementation

To the best of my knowledge, only the panic_check function in src/eventloop.c, as well as the functions that parse and process the config file would need to be changed -- so the implementation should not be very difficult.

If the maintainers think this would be a good feature to add but don't think it's high on the priority list, I can attempt to contribute the feature myself.

[rvaiya]

Thanks for alerting me of this.

However, it also triggers when the "mapped output" resolves to that sequence as well. So, depending on the layout, there are a lot of different physical key sequences that can possibly resolve to the same "virtual sequence" and trigger the kill switch.

This should be considered a bug. It has been fixed on master.

I propose introducing a config option with a (tentative) name like kill_switch_physical_only=y/n. When the option is enabled, then keyd should only be terminated if the physical keys corresponding to the escape sequence are typed;

It has always been the intention for the physical sequence to exclusively terminate keyd. Remapped sequences should not count towards the panic sequence.

[ficcdaf]

Thank you very much! I didn't realize it was a bug; I'm glad my report was helpful. Thanks for all your work on keyd!