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

[Eli Zaretskii <eliz@gnu.org>]

> 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.

> 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?

> 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.

> 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.