On Fri, Feb 1, 2019, 07:30 Eli Zaretskii <
eliz@gnu.org> wrote:
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Fri, 1 Feb 2019 04:39:09 +0300
> Cc: 33870@debbugs.gnu.org
>
> On 01.02.2019 03:17, João Távora wrote:
> > emacs -Q
> > C-x 2
> > C-x o
> > C-x 4 . xref-backend-definitions RET
> > n
> >
> > <...> in
> > your version, it works quite correctly.
>
> When I try this with the new patch, it results in a third window being
> created (the original window is being split, and the definition is shown
> there).
> Is this the behavior we want?
No, I don't think so.
It might not be the behavior you want, but it was the behavior I designed it to have.
You start with two windows, A and B. You ask to find definitions in another window from A, because you want to preserve its contents. The symbol you searched for happened to have multiple definitions so you decide to browse them from *xref* using bare 'n' and 'p' before settling on the definition you want. Those "prospects" can't be shown in A because that would break the original "other-window" contract/intention, and they can't be shown in B because that's where you're browsing from. They need a new window C which is not available. When the frame is relatively small (as it is with emacs -Q), C is created by splitting horizontally, which is kind of akward, but the decision where to create C changes with larger frames.
For some reason, 26.1 sometimes decides to make another frame for C, but only if you start from B, i.e you add onde 'C-x o' to the beginning of the recipe, after splitting. This is a bug in the current xref.el or, more likely, in window.el's window-splitting heuristics. The bug goes away when you have larger frames, which explains why I didn't catch it earlier.
Fortunately, the whole point of this bug report opened by Juri is to make this configurable. Later, we can decide on a better default, something Juri is also very much in favor of. If you add your voice to his and decide to change the default, and then give me a way to recover 26.1's behavior (minus the bug), I won't object (much).