bug#39902: 28.0.50; Marking in dired with active region

[Drew Adams <drew.adams@oracle.com>]

> > Could you give a recipe/example of your use of
> > keyboard keys for this, or otherwise explain
> > the rationale for it?
> 
> Say the files in the dired buffer are photos/songs or so.  I mark all of
> them, or those of them I'm interested in.  I open the files with a
> viewer or vlc or whatever.  There I have a look at them, in the same
> order as they originally appeared in dired.  Now say I am interrupted,
> and/or I have deleted some of the files, and want to resume with the
> rest of the files, or some other subset.  I.e. I want to mark subsets
> (of subsequent files) in a dired buffer to look at the files in this
> order, and the most natural way for me to do this is to use the region
> for marking.

I still don't understand well.

1. You mark some files in Dired, then open them in
some other app.  Those files are still marked in
Dired, I suppose.  Or do you unmark them?  Or
doesn't it matter?

2. In that app, you do something with the files,
viewing and manipulating them in the same order
they had in Dired.  You may even delete some or
add some new ones.

3. You're interrupted.  How so - is Emacs closed?
is the other app closed?  What's the significance
of the interruption?

4. Later (same Emacs session?) you want to resume
using the external app with some of the marked files
you haven't yet manipulated.

That much I get.  I don't understand the rest.

5. You want to mark, in Dired, some of the files
you haven't yet worked with in the app.  OK.

"to look at the files in this order"  In what order?
What's the importance of the order?

Can you describe what you want to do at this point?
In particular, what do you want to do wrt selecting
and then marking the selected files?

IOW, I still have the same question: What's your
expected use of keyboard keys for this, and why?

For example, why wouldn't you just use `g' (to
refresh the listing, to reflect deleted or added
files), then `C-u 99999 m' starting where you left
off?

To be clear, I'm not trying to say you should do
something different from what you're requesting.
I'm just trying to understand what you want to do
and why.