bug#33992: 27.0.50; xref-find-definitions wastes too much space

[Juri Linkov <juri@linkov.net>]

>>>>> Does it feel the same way to you?
>>>>
>>>> The difference is that completions pop up in a small unobtrusive window.
>>>
>>> Small window? I usually have a side-by-side fullscreen split, and if
>>> I initiate completion in one of the windows, *Completion* takes up the
>>> whole other window. Temporarily, of course.
>>
>> The key word here is 'Temporarily'.  Unlike *Completions*,
>> the *xref* buffer doesn't go out easily.
>
> I can understand that. So yes, I can see myself preferring some different
> behavior for a particular command.
>
>>>>     (defun display-buffer-condition-from-xref (_buffer-name _action)
>>>>       (string-match-p "\\`\\*\\(xref\\)\\*\\(\\|<[0-9]+>\\)\\'"
>>>>                       (buffer-name (current-buffer))))
>>>
>>> This function seems unused.
>>
>> It's unused because it would be useful only in the *xref* buffer
>> created by the xref-find-definitions command, so xref needs to
>> provide a way to distinguish such case.
>
> Shouldn't it be referenced somewhere else in your patch as well?

A patch is proposed in a separate bug#35737.

>>>>     (setq display-buffer-alist
>>>>        '((display-buffer-condition-xref
>>>>           display-buffer-in-direction
>>>
>>> And this function is undefined in my Emacs.
>>
>> This function is implemented by Martin in bug#33870.
>
> OK, found it, tried it. Seems to work okay-ish for xref-find-definitions,

Created a separate bug#35592.

> except xref-quit-and-goto-xref doesn't seem to be functioning too well
> together with your customization (every other time it seemed to use
> a different window to display the location, not the one I called
> xref-find-definitions from).

Yes, it should change its behavior depending on xref--original-command.

>>>>     (with-eval-after-load 'xref
>>>>       (define-key xref--button-map [(control ?m)] #'xref-quit-and-goto-xref))
>>>>
>>>> How do you like that?
>>>
>>> I might, but since I can't really try your customization myself yet, I'll
>>> repeat a question you might be familiar with already:
>>>
>>>    Will this also affect xref-find-references and project-find-regexp?
>>
>> It should not affect them due to (memq this-command '(xref-find-definitions))
>> above.
>
> It would affect them due to the modification of xref--button-map above,
> though. This part I don't like.
>
>> But also to not affect commands active in the *xref* buffer,
>> xref should provide a way to check if the *xref* buffer was created
>> by xref-find-definitions.
>
> Yes, we should retain some extra information, e.g. to support revert-buffer.

Created a separate bug#35702.