Dependencies Re-Redux
I finally did manage to hack the dependency tracking code into a
state where invalidation of a sheet (done because the user performed the
undo-able removal of the sheet) is distinct from the destruction of
the sheet.
That sounds technical but the nice results are: (1) we no longer
have to clear the undo/redo queues when someone deletes a sheet;
(2) we now track and undo changes to other sheets’ cells when a
sheet is removed; (3) we track and undo changes to global names’
definitions when a sheet is removed.
These are not things you notice when they work, but you do when they
do not work. Chalk one up for user experience.