mh-mm-inline-media-tests needs an autoload cookie
This was fixed July 2023 by Bill Wohler, who added "(require 'mh-mime)" to mh-show.el with commit a92ee5ca3c.
mh-mm-inline-media-tests needs an autoload cookie
In fall 2021 (for Emacs 29), Stefan Kangas removed all calls to mh-funcall-if-exists and declared it obsolete. Probably all that remains to be done is to remove the definition itself.
I can reproduce this in 27.0.91. It appears to be a timing issue with external viewers. MH-E points all MIME viewers at the show buffer. This works well for internal viewers: they update the show buffer, they finish, and MH-E sets the buffer as unmodified. This strategy doesn't work as well with external viewers. An external viewer is a background process, and it might write logging or error messages to the show buffer after MH-E has called (set-buffer-modified-p nil).
MH-E discards text properties in emacs > v24
Thanks, Mike, for reviewing my patch. I committed it to the emacs-27 release branch as 7f01dfca56.
Is this still a bug? I used to get "buffer modified", but I no longer do with Emacs 25 or the 27 release branch.