customize xref

[James K. Lowden]

I have an elisp syntax question.

I'd like to customize xref such that, when I jump to a definition, it
puts the line it finds at the top of the window. "customize group" led
me to xref-after-jump-hook, which calls recenter, and recenter takes an
optional argument that, if provided, is the line to "recenter" on.
Indeed, if I use "C-u 0 M-x recenter", it puts the line the cursor is
on at the top of the window.

By passing "xref" to customize-group, I was able to see roughly what to
do. In my .emacs I now see this (other settings elided):

(custom-set-variables
'(xref-after-jump-hook
(quote (recenter xref-pulse-momentarily))))

How to sneak an argument in there? I tried this:

(custom-set-variables
'(xref-after-jump-hook
(quote ((recenter 0) xref-pulse-momentarily))))

but that only produces the error:

run-hooks: Invalid function: (recenter 0)

I know I'm in the vicinity of quoting, but I'm not sure how to see
around the corner. Help?

--jkl

[James K. Lowden]

On Tue, 10 Jan 2017 13:28:08 -0500
"James K. Lowden" <jklo...@speakeasy.net> wrote:

> (custom-set-variables
> '(xref-after-jump-hook
> (quote (recenter xref-pulse-momentarily))))

I see:

(custom-set-variables
'(xref-after-jump-hook
(quote (lambda () (recenter 0) xref-pulse-momentarily))))

Because recenter is a function, it needs to be replaced with a
function, not a function invocation, and not the output of a function.
Unless, that is -- as in the case of lambda -- the function returns a
function.

In this case, xref-after-jump-hook takes as parameters two arguments,
each a function. I can't pass it 3 arguments

(recenter 0 xref-pulse-momentarily)

nor the result of recentering,

((recenter 0) xref-pulse-momentarily)

but I can pass it an unnamed function. The lisp interpreter reduces

(quote (lambda () (recenter 0) xref-pulse-momentarily))

by executing the lambda to

(quote (anonymous-func xref-pulse-momentarily))

where anonymous-func calls (recenter 0).

--jkl

[Ralf Fassel]

* "James K. Lowden" <jklo...@speakeasy.net>

| > (custom-set-variables
| > '(xref-after-jump-hook
| > (quote (recenter xref-pulse-momentarily))))
>
| I see:
>
| (custom-set-variables
| '(xref-after-jump-hook
| (quote (lambda () (recenter 0) xref-pulse-momentarily))))

What is the 'xref-pulse-momentarily' good for?
From my understanding of elisp, you should be good with

| > (custom-set-variables
| > '(xref-after-jump-hook
| > (quote (recenter 0))))

HTH
R'