How to unfold the thread by default when there are unread emails

[Enze Li]

Hi all,

This is my cofiguration,
...
(setq gnus-thread-hide-subtree
      '(not gnus-article-unread-p))
...
However, it doesn't work well.  Here's what I got,

+ root email
 +-> subthread-1
 |    \-> email-1
 +-> subthread-2
      \-> email-2

This is a thread tree, all the emails are unread.  If I read the
"email-1", the thread will not hide when I restart the gnus and enter
the group; If I read the "subthread-1", the thread will hide.

My question is that can Gnus hide the subtree only when *all* emails
have been read?

Thanks,
Enze