undo (was Re: Why does Dynamic Typing really matter?!?)
eppstein at ics.uci.edu
Sun Feb 9 20:38:09 CET 2003
In article <rGt1a.1528$6a2.545590 at kent.svc.tds.net>,
"Edward K. Ream" <edream at tds.net> wrote:
> Doesn't Photoshop have some kind of flexible undo? If so, I would study
> their model carefully.
As far as I can tell as a user of Photoshop, it has the usual linear
undo history, with two exceptions:
(1) Normally, as with most linear undo history systems, a new operation
clears out the redo part of the history. But if you immediately undo an
operation, it vanishes from the undo history and the previous redo
history is restored.
(2) You can assign names to states in the history, and return to those
named states. But these states do not carry any history with them, so
when you return to them, the undo/redo history is cleared out.
David Eppstein UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/
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