Mark thread as read is disabled except for a single selected message in a thread - should always be enabled as in 102 when selection contains one message in a thread, for multiple selected threads etc. To rephrase, here's the expected behaviour in Wayne's words, from 17-year-old bug 327828 comment 1:
"Mark thread as read" marks every thread read in which you have at least one message selected, as one would expect.
This will have a significant impact on ux-efficiency for users with large amounts of mail in threads (think bugmail...)
- View > Layout > Classic View (tabular message list)
- For starters, ensure mail.operate_on_msgs_in_collapsed_threads = true (default). Wayne says it should be the same regardless of the pref - sounds right, but I haven't tried. Furthermore, for the scenario below it doesn't matter if your message list is threaded or not.
- Play with different type of selections, or all at once (see screenshot):
a) single msg which belongs to thread
b) all messages of an open thread (or closed thread)
c) combine a) and b)
d) add to the selection a message which does not belong to a thread.
- Right-click on selection, check enabled status of
Mark > Thread as read
Mark Thread as read is only enabled for case a), single msg which is part of thread
Mark Thread as read is disabled for every other type of selection (this bug)
- (Of course shortcut
R will also fail as the command is disabled)
- This means that even everyday scenarios like marking multiple adjacent collapsed threads as read will fail.
Mark Thread as read should be enabled whenever the selection contains at least one message which is part of a thread.
Mark Thread as read should then do the job as per its label, mark all threads associated with the selection as read (even when they are only partly selected).
- For added convenience, as in 102, case d) of the odd non-thread message in a selection which has at least one thread message shouldn't disable the command, but just mark that message read, too.
Kudos to Wayne for pointing out that the command is no longer working as expected.