Re: Undo mode

[Gregory Heytings]

It is deeply saddening to see that the "Undelete Frame" feature has become 
the subject of a quarrel.

The original design added a single "Undelete Frame" item in the File menu, 
under the "Delete Frame" item.  The conclusion of the discussion in 
bug#51883 was that this feature shouldn't be enabled by default, which 
means that this "Undelete Frame" menu item would have remained inactive, 
unlike other items in the menus whose state change from inactive to active 
when their actions become feasible.

Users could have reasonably expected to see this menu item become active 
after they used the "Delete Frame" menu item, just like the "Remove Other 
Windows" item becomes active after using one of the "New Window" items.

Therefore, to help users discover that this menu item required an explicit 
activation in their init files to become usable, I added a "Enable Frame 
Undeletion" item in the File menu, with a tooltip which said "Enable frame 
undeletion for this session", and which replaced the "Undelete Frame" item 
when undelete-frame-mode was not active.  IOW, this feature always used 
one and only one item in the File menu: either "Enable Frame Undeletion", 
or "Undelete Frame".

The hard-coded limit of 16 deleted frames was also a conscious design 
choice, to avoid adding yet another defcustom that nobody had asked (yet). 
A user might want to undelete a few frames, so recording a single deleted 
frame is not enough, and 16 seemed like a reasonable upper limit that 
should cover all needs.

I respectfully suggest to go back to that original design.