bug#74361: [PATCH] New option xref-navigation-display-window-action

[Juri Linkov]

> This adds a capability to customize the destination window selection logic
> for navigation (xref-find-definitions, xref-go-back, xref-go-forward) by
> allowing a user-supplied display window function.
>
> Inspired by the Merlin package and its user option
> merlin-locate-in-new-window
> (https://github.com/ocaml/merlin/blob/a36f42a5b181d0c9cc84174e8eb241b11eeabc0f/emacs/merlin.el#L177C12-L177C39)
> - where the value 'diff' uses a different window if the destination is in
> an file different from the current one.
>
> With the attached patch the customization looks a bit noisier though:
>
>   (setq xref-navigation-display-window-action
>         '(display-buffer-reuse-window))
>
> ^ This makes it try to reuse an existing window and fall back to
> pop-to-window, but the effect is similar to what's described above.
>
> Comments welcome.

This option looks similar to 'display-comint-buffer-action'
whose addition was deemed to be a mistake, so we needed to declare it
obsolete and replace it with '(category . comint)'.

So instead of adding 'xref-navigation-display-window-action',
could you just add a category 'xref' to xref display function calls?
Then users will be able to customize it with e.g.:

  (setq display-buffer-alist '(((category . xref)
                                (display-buffer-reuse-window))))

Or maybe I misunderstand other requirements for this feature.

Ok, meanwhile I'll play more with your patch to see if 'category'
could really help here.