[cone] Automatic Refresh for local Maildir's mail counts?

[Linux-Fan <Ma_...@we...>]

Dear Cone users,

In [1] I asked if it might be possible to add a means of filtering
accross account boundaries to Cone in order to be able to replicate
my mail setup with it. I have understood it does not work that way
because moving across accounts is conceptually different from moving
inside the same account.

Still, I have not given up on trying to configure Cone in a way I could
use it as my mail client: While I did not try to amend Cone's filtering
system to work across server boundaries, I have thought of another
solution to the problem: In order to have filtering across account
boundaries, I could use an external program to process incoming e-mails
and then only read (and write) them in Cone.

The setup is intended to look something like this

  Offlineimap               Filtering tool¹        Cone
  ---------------------     ------------------     ---------------------
  Downloads mails and   --> Moves mails inside --> Is used to read from
  uploads changes to an     a local Maildir        the local Maildir and
  IMAP Server               structure              send via SMTP.

Now in order for this to work as I expect it, Cone needs to
automatically update the e-mail counts from local Maildirs to display
the changes made externally via Offlineimap and the filtering tool.

As far as I understand, there is an option called `/noop=N` [2] to
poll IMAP accounts. I tried to use that (testing with an IMAP account),
but it did not automatically tell me `... unread` after receiving a new
mail until I opened and closed the folder again?

Alternatively, I have tried to implement a refresh via a `SIGUSR1` to
Cone by collapsing and expanding the currently selected subtree. This is
a hack and while it does something similar to what I want (if the
correct entry is selected, it refreshes the mail counters), it does not
do it right: It depends on the current selection and it marks all
folders (as if they were highlighted by the cursor) for reasons unknown
to me :)

Now my question is: Is there a recommended way to achieve automatic
updating of (new-)mail counters for offline accounts / e-mail data
processed by a separate tool? If not, is there a chance of getting the
`/noop=N` thing to work with local Maildirs making it update
e-mail counts without interaction or is there a chance of implementing a
`SIGUSR1` to refresh in a more sensible way than I did?

In order to illustrate what I am thinking about, I have attached my
patch to enhance cone-0.92 with a hacky `SIGUSR1` support. If you think
it might be a good idea to rewrite the patch to apply to the newest
Cone version, I will try to do that. However, I do not think that
my hack is the way to go with respect to the issue I want to solve.

¹) I do not know which filtering tool to use, yet.

TIA and Yours Sincerely
Linux-Fan

[1] https://sourceforge.net/p/courier/mailman/message/35086282/
[2] http://www.courier-mta.org/cone/cone06newaccount.html

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