bug#59381: Should xref--marker-ring be per-window?

[Dmitry Gutov]

On 21/11/22 15:14, Eli Zaretskii wrote:
> > Date: Mon, 21 Nov 2022 01:17:02 +0200
> > Cc: 59381@debbugs.gnu.org, ackerleytng@gmail.com, juri@linkov.net
> > From: Dmitry Gutov <dgutov@yandex.ru>
> >
> > On 20.11.2022 09:59, Eli Zaretskii wrote:
> >
> > > > But maybe it will be helpful for you to elaborate: what the workflow
> > > > would look like. Would it be a parallel set of commands, or simply a
> > > > command to... do what?
> > >
> > > I just did that, above: add a command that starts a new "stack".  All the
> > > rest is unchanged.
> >
> > What would happen with the current stack, though?
>
> It's discarded, as no longer needed.

That sounds odd. The idea regarding windows is about keeping multiple 
stacks at the same time, not about discarding information.

> > Or does it apply to the current window? What about the windows split
> > from it? What about older windows we decide to pop-to-buffer to from one
> > of the new windows?
>
> In my mental picture, the stack is not specific to a window, like it is
> today.
>
> > > > In my workflow, a new stack is more or less created implicitly by
> > > > splitting a window, and discarded by deleting one.
> > >
> > > So you always ever have a given buffer displayed in a single window?
> >
> > Not necessarily, no. If it's a big file, I can have two parallel
> > "investigations" going on in two different window on it. Using two
> > different navigation stacks. That's a feature.
>
> It's a feature if you indeed want a separate stack in each window.  What if
> you want the same stack in all of those windows?

Maybe you never do? Or if you really do, that would require some 
additional manual management (through new commands, I suppose).

> > Whether M-. pop a new window, or you use project-find-regexp, we usually
> > make sure that after you navigate to a location, it's displayed in the
> > same window the search was made in. Unless the user called something
> > like xref-find-definitions-other-window, naturally.
> >
> > So it's generally possible to stay within the same window most of the time.
>
> Not if I split that one window because I want to look at something else as
> well.

In my book that's starting a new line of thought, where it's okay to 
create a new stack. The old one is still around.

> > And you make good points: Emacs often makes you go from a window to a
> > window, reusing older windows as well. So I'm not sure how to solve that
> > better: searching the window hierarchy won't help.
> >
> > So it could be some propagation mechanism working when windows are split
> > or buffers get displayed, which would nevertheless leave a window when
> > the user pressed 'q', for instance. Reverting the window to its previous
> > stack, let's say. And as for separate command, using it explicitly by
> > itself is easy to forget, but it perhaps could be added to some other
> > commands by the user (via before-advice or etc), to mark the beginning
> > of each stack.
> >
> > This is a very rough idea. There's nobody to work on it in the near
> > future, I'm afraid, so adding an optional change in behavior to use
> > window-local storage is probably the best way forward. To get feedback,
> > as Ackerley said.
>
> When this becomes practical, we could try it and see if enough people like
> it.

I don't know if it's practical or not, but it requires some additional 
design for sure. Maybe someday.