Re: Stepping Back: A Wealth Of Completion systems Re: [ELPA] New package: vertico

[Dmitry Gutov <dgutov@yandex.ru>]

On 10.04.2021 02:48, Stefan Monnier wrote:
>> Mind you, I generally prefer completion UIs that show the options before you
>> start typing, but xref-show-definitions-completing-read makes a really
>> strong case for it. Which is unfortunate, because otherwise it's my #1
>> choice for xref-show-definitions-function's default value, and changing
>> Emacs's completion UI is not in the cards in any near future.
>>
>> So I would only be happy if you disagree with this assessment.
> 
> I think it would be desirable to change the default UI just enough so
> that a code like Xref can make `completing-read` display the
> completions eagerly.

The *Completions* window, you mean? It would still miss the ability to 
quickly accept one of them with RET.

> One thing we can already do is to make Xref use a completion category
> with an entry in `completion-category-defaults` which specifies a value
> of t for `completion-cycle-threshold`.  This way a simple TAB should
> select the first entry.

The result is... interesting. Not my first choice of the UI, but it does 
improve on the issue I mentioned above (while missing the ability to 
look at all options at once, which is particularly useful for the 
function is question).

Does anybody feel like it's an improvement enough to make 
xref-show-definitions-completing-read a viable default?

Here's the patch to try (though we might want to replace t with a number 
like 4):

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 5f594679ca..0ba55916c9 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -957,7 +957,8 @@ completion-category-defaults
      ;; A new style that combines substring and pcm might be better,
      ;; e.g. one that does not anchor to bos.
      (project-file (styles . (substring)))
-    (xref-location (styles . (substring)))
+    (xref-location . ((styles . (substring))
+                      (cycle . t)))
      (info-menu (styles . (basic substring))))
    "Default settings for specific completion categories.
  Each entry has the shape (CATEGORY . ALIST) where ALIST is