UndoEngine isn't usable on Windows. Will not open.
UndoToolkit uses Mac declares.
After doing a little more research, it looks like most people, like
yourself, are coding this themselves.
Thanks for your input!
-----Original Message-----
From: gettingstarted-bounces at lists dot realsoftware dot com
[mailto:gettingstarted-bounces at lists dot realsoftware dot com] On Behalf Of
Artly There
Sent: Monday, February 28, 2005 5:37 PM
To: Getting Started
Subject: Re: Undo engine
On Sunday, February 27, 2005, at 11:57 AM, RBNUBE wrote:
> Thanks, Robert.
>
> Unfortunately, it's not cross-platform. I also looked at UndoToolkit
> which is also not cross-platform. This is such a common feature of
> most software, so I wonder why it's not easy to find plugins or
> classes.
>
> Are most of you coding your own or not providing this feature?
What prevents it from working as cross-platform? Can it be altered?
What is it that you are (usually) wishing to undo?
To answer your question...
Assuming I can get the rest of my very large app from another environs
R&D'ed on over as to the workings, I'll be making an application
specific one.
For a text editor I wrote in the other environs, I just shoved a copy
of the current file off to disk (temp items folder) before each major
edit and tracked the files in an array (via FSSpecs). That allowed for
potentially unlimited undos, though I set it for 16 initially. I
deleted any older ones when writing a new one, and loaded up the
correct one as needed on an Undo/ReDo. The first undo/redo was always
from RAM though. This kept the usual needs fast (though disk is not
bad). You need to track free disk space with this setup, and check for
locked volumes.
For my graphics app, I'll be storing things like selections or
color/interface changes in an array, and offloading major bitmap edits
into the Temporary Items or some other folder and reloading as needed
like so...
For each Doc, I kept an array of Undo file FSSpec's (MacOS) . For each
doc I kept an UndoPtr (pointer to the current array location) and each
Undo/Redo would increment or decrement that UndoPtr.
As the last file was deleted, I'd just shuffle the items up a notch,
and put in the new entry at the bottom (location (0) )
If multiple undo's were chosen, leaving one with a pointer at say item
5 out of a possible 10 items (10 was the oldest), and a new edit was
begun, then the list was reset to start at the item 5, and the more
recent bottom 0-4 thrown out...and then the array shuffled again. (or
was it items 6-10) :) I forget. :)
The logic can get kind of convoluted, but as to implementing all this,
it's fairly simple actually. Best to diagram it out perhaps. If your
needs are not that huge, (undoing small edit fields all day ) then
doing this in RAM would be the approach to use.
Robert
> <snip>
> On Saturday, February 26, 2005, at 06:27 PM, RBNUBE wrote:
>
>> Does anyone know of a good, cross-platform undo engine?
>
> I don't know if it's cross platform (should be) but try this one:
> <http://www.belle-nuit.com/realbasic/>
>
> See the Undo Engine item.
>
> Robert
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