Re: Improving input-methods docs

[Chris Feng <chris.w.feng@gmail.com>]

> Stefan Monnier wrote  (on gnu.emacs.help list):
>> Rusi Mody wrote:
>> > I see (info "(elisp)input methods")
>> > that in emacs including 25, docs are still at
>> >
>> > | How to define input methods is not yet documented in this manual,
>> > | but here we describe how to use them.
>> >
>> > Is there something I can do (within my capacity!) to move this forward?
>
>> Start to document what you know?  Or try to document what you think
>> should be there, and if you don't know what to write because you don't
>> know how it works, then ask on emacs-devel.

AFAIK to define a new input method it only requires one to register it
to `input-method-alist' and feed `input-method-function' a customized
function.  But it seems most input methods in Emacs are defined as
Quail packages, so an intro to `quail-define-package' (and perhaps
other parts of Quail) may also be helpful.

> Ok
> First a basic question:
> When I do describe-input-method
> I see a lot of stuff 'described'
> However unlike describe-function|variable etc that links to the relevant stuff
> here there is no such.
>
> Is there any way to get to the input method (source) from an activated
> input-method?

You can find most input methods in 'lisp/leim/leim-list.el' as they're
registered there.  For example, there's a form for the 'TeX' input
method indicating that it's actually a Quail package named
'quail/latin-ltx', so its source is in 'lisp/leim/quail/latin-ltx.el'.

> Strangely even describe-key shows (say) self-insert-command for "\" in
> tex-input-method
> which seems strange if not plain wrong.

IIUC input methods do not create new key bindings but translate
characters, so `describe-key' doesn't make much sense here.