Re: `M-.' can't skip to the corresponding DEFUN from within the Apropos buffer.

[Hongyi Zhao]

On Tue, Jul 6, 2021 at 5:27 AM Daniel Martín <mardani29@yahoo.es> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> >>
> >> - Create a buffer-local binding for xref-backend-functions in Apropos
> >>   buffers where you prepend elisp--xref-backend to the list.
> >>
> >
> > I've read some relevant document [1], but still can't figure out how
> > to set this feature in my initialization file.
> >
> > [1] 
> > https://www.gnu.org/software/emacs/manual/html_node/elisp/Creating-Buffer_002dLocal.html
> >
>
> You could add something like
>
> (add-hook 'apropos-mode-hook
>           (lambda ()
>             (add-hook 'xref-backend-functions
>                       #'elisp--xref-backend nil t)))
>

The built-in help document says:

```
(add-hook HOOK FUNCTION &optional DEPTH LOCAL)

[...]
The place where the function is added depends on the DEPTH
parameter.  DEPTH defaults to 0.  By convention, it should be
a number between -100 and 100 where 100 means that the function
should be at the very end of the list, whereas -100 means that
the function should always come first.
Since nothing is "always" true, don’t use 100 nor -100.
When two functions have the same depth, the new one gets added after the
old one if depth is strictly positive and before otherwise.

For backward compatibility reasons, a symbol other than nil is
interpreted as a DEPTH of 90.
```

Here, you set DEPTH to nil. I'm not sure if your usage is equivalent
to the following?

  (add-hook 'apropos-mode-hook
           (lambda ()
             (add-hook 'xref-backend-functions
                       #'elisp--xref-backend 0 t)))

> apropos-mode-hook is the hook that is invoked when apropos-mode is
> turned on.  Notice that I pass t as the fourth argument to add-hook;
> that says to modify the buffer-local value of xref-backend-functions,
> not the global value.  As the code is evaluated when apropos-mode is
> turned on, the current buffer will be the Apropos buffer and the change
> will only have an effect on that buffer.
>

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
NO. 552 North Gangtie Road, Xingtai, China