run peep-dired-display-file-other-window when the selected line changes after applying a mark in dired

[DivineDominion]

peep-dired works when you hit the arrow keys or C-n/C-p. When you use n/p in the dired buffer, point will move down a line, but the peeped-at file won't change.

Similarly, when you peep at a file and press d to mark for deletion, dired puts point one line further down. peep-dired will not pick up these changes either. That makes interaction a bit awkward; the best quick fix after hitting d (using peep to review files for deletion) is to hit C-p C-n to move the selection up and down and then show the correct file preview.

There's no hook in dired.el to react to point position changes.

• Maybe it makes sense to add a buffer-local hook to moving point in general, sort of a reactive approach? Downside: this would peep at files when you scroll.
• Or advise around dired-mark? That will fix this issue and keep the scrolling/paging behavior unchanged.

(I know that you're looking for a new maintainer, but I wanted to submit this to track the request. Maybe I can figure out how to implement this myself.)

[DivineDominion]

Ok that was rather simple :)

(defun ct/peep-dired-display-file-after-mark (&rest args)
  "Peep at file at point in dired after changing a mark."
  (peep-dired-display-file-other-window))

(advice-add #'dired-mark :after #'ct/peep-dired-display-file-after-mark)

Will test this some more and then propose a PR.

[DivineDominion]

Noticed I need to add a check if peep-dired is running at all, otherwise this will produce warnings/errors in the minibuffer