general undo methods?

[Richard Gaskin]

Lynch, Jonathan wrote:

 >> I need to add more extensive undo to an app I'm working on.
 >> Seems like a lot of work once you step outside of the subset
 >> of things the engine takes care of for you.
 >>
 >> Any of you have pointers to general methods for implemening
 >> undo across an app?
 >
 > You could set it up so that every time you make a change,
 > you create a copy of the stack in memory. Actually, have
 > like 5 copies of the stack in memory, and for each change,
 > you replace one of those stacks, and keep a list in a
 > global variable of where you are in the rotation through
 > those five copies in memory....

I can see how that approach would be useful for some apps, but this one 
has a large stack and the changes made a very small (moving objects, 
deleting objects, etc.).

Anyone have a link to a good paper on how folks handle undo in "real" apps?

-- 
  Richard Gaskin
  Fourth World Media Corporation
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