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Re: New key binding syntax

From: Yuri Khan
Subject: Re: New key binding syntax
Date: Fri, 5 Nov 2021 19:02:02 +0700

On Fri, 5 Nov 2021 at 18:04, Alexandre Garreau <galex-713@galex-713.eu> wrote:

> > > so it’s like a down, b down, …, f down… and then until I release any
> > > key between a and f, if I press down “g”, the keyboard won’t say
> > > anything to the application/OS?
> >
> > As I said, it depends.
> No I really didn’t understand.  You said the rollover key number changed,
> not that once it was overtook, the behavior varied.  And you said that
> number was most of time 6.  What I want to understand is what goes wrong
> then… presses unreported? releases falsely reported in some order?

Do I need to spell it? Different keyboards behave differently in that regard.

I just fired up xev(1) and held down a-s-d-f with my left hand and j-k
with my right, and tried adding ‘l’. It did not register and the
autorepeat for ‘k’ kept going on. I then released the six keys one by
one, and observed release events for each. This means my keyboard
tracks the first six non-modifier keys I press, and ignores subsequent

> For the autorepeat I could imagine, but for release I had no idea… but
> doesn’t the keyboard generates hardware events? to interrupt OS when
> there’s a change? it’s not scanned at each tick, right?

No, it doesn’t generate events. On USB, only the host can initiate
transfers[*], so it literally scans each device every once in a while.
This is why you see discussions of mouse and keyboard polling rates on
web forums.

[*]: With the exception that a USB device in low power mode is allowed
to send a wake up signal.

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