undo?

[Russell Nelson]

One more wacky idea: Maybe, instead of saving the session as an XML
file, it should be saved as a sequence of commands?  Thuban would have
a command interpreter which would implement changes made to the layers
and the map.  There would be a command for menu items and any extra
data submitted with them, e.g. filenames or projection selections.  So
when you load something, that's a command, or when you set the
projection, that's a command.  As you do things, the commands are
saved.  And .... there's an undo/redo facility which issues the
reverse of the commands.  So if you botched something accidentally,
you could undo that action.  Anyway, I'm not proposing a patch for
this, just pointing out that it's one way to implement an "undo"
facility.  Users like undo because it lets them experiment safely.

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