Mail: Add option to group messages into flat threads
Current behavior:
In threaded mode ("Group by thread"), the message structure is a tree, per the reply-to header.
UX Problems:
UX Problem 1. When one browses a thread, one wants to quickly spot the last message to reply to it. For long threads (think dozens of messages), it's often hard for me to find this last message, because of the tree structure. The last message is lost somewhere in the middle of the tree, and I look for it.
UX Problem 2. For long threads, lots of blank space waste screen space, because of tree structure indentation.
Solution: new ordering type within a thread: by date only
Within a thread, all messages are sorted by date only. All messages within a thread become a flat list. This solves both UX Problem 1 and UX Problem 2.
UX impact:
This may mean having two kinds of "Group by thread":
- (legacy) "Group by thread (tree)"
- (new proposed here) "Group by thread (flat)"
Edited by Martin Monperrus