Re: Undo - Redo?
Re: Undo - Redo?
- Subject: Re: Undo - Redo?
- From: Bill Cheeseman <email@hidden>
- Date: Sat, 27 Apr 2002 12:34:18 -0400
on 02-04-26 10:28 AM, Marcel Weiher at email@hidden wrote:
>
On Friday, April 26, 2002, at 02:53 Uhr, Manfred Lippert wrote:
>
>
>> In a standard implementation of undo/redo, choosing undo invokes the
>
>> undo
>
>> action you registered, applying the original values that you
>
>> registered it
>
>> with, and then automatically moves the action from the undo stack to
>
>> the
>
>> redo stack. Then, when you choose redo, the action is invoked again ...
>
>
Actually, I don't think the last part is correct. It certainly doesn't
>
make sense to me, because a redo action cannot be derived from the undo
>
action. Take inserting a word. The undo action is to delete a range of
>
text. The 'redo' action must insert the word again, but that word is
>
not found in the undo action.
It was actually I who wrote the offending lines. I was thinking of the
simplest undo case when I wrote that -- the accessor method that registers
itself as its own undo/redo action. My statement is certainly wrong as to
more complex undo/redo situations, but I covered those in the following
paragraph of my original message.
--
Bill Cheeseman - email@hidden
Quechee Software, Quechee, Vermont, USA
http://www.quecheesoftware.com
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http://members.valley.net/croquetvermont
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