Re: not quite understanding input methods

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 30 Aug 2021 15:13:25 -0400
> Cc: emacs-devel@gnu.org
> From: "Perry E. Metzger" <perry@piermont.com>
> 
> > Before a key sequence bound to a command causes that command to be
> > invoked, it (the key sequence) must be read, and that's the job of
> > read_char.  Only after F19 is read, Emacs calls the command to which
> > you bound it, and that command inserts a character into the buffer.
> >
> Yes, but the point at which the character that's inserted into the 
> buffer is present is after the Quail input method was invoked by 
> read_char.

Yes.  And the fact that the character is inserted means AFAIU that the
input method machinery didn't realize it was part of a sequence that
needs to be translated.

> Again, I'm finding the stack of things involved in the input 
> method getting invoked rather difficult to follow, but it feels like 
> Quail doesn't actually look backwards in the buffer and thus could care 
> less that I inserted a particular character there.

Correct.  Input method works on read_char level, it processes
characters before they get assembled into key sequences, thus before
the key sequences are recognized as being bound to commands.