What exactly does 'Undo' undo?

[Alex Rice]

On Wednesday, June 4, 2003, at 01:08  AM, Jeanne A. E. DeVoto wrote:

> The undo command only works on certain actions: specifically, painting
> actions (using the paint tools to paint in an image), deletion of 
> objects
> (using the Pointer tool to select an object, then deleting it), moving 
> of
> controls (with the Pointer tool), and editing actions in a field (such 
> as
> typing, cutting, and pasting).
>
> The undo command also only works on user actions, as opposed to 
> scripted
> actions. For example, if you use a script to edit text, the undo 
> command
> cannot undo that change, but if the user edits text, you can use undo.
> Similarly, if you use the delete command to remove a control, the undo
> command cannot be used to restore the control, but if the user chooses 
> the
> control and presses Delete, the undo command will undo the action.

Has anyone written an undo architecture for messages and functions and 
made the code available? I don't see anything in User Contributions.

I have written shareware in Cocoa* which has a terrific undo 
architecture. I can't imagine it would be too difficult in Transcript 
because of it's send, do and value features. But I haven't been using 
RR long enough to really have a good feel for how it would be done just 
right. I could explain how it's done in the Cocoa frameworks, if anyone 
is curious.

*Cocoa is an Objective-C object-oriented framework that was formerly 
called OPENStep, before Apple bought NEXTStep.

As much as I love the Cocoa frameworks, I get terribly sick of waiting 
for compiles, and  it's not cross platform. It can be ported to Unix, 
but not Windows. So I'll be buying a RR license for my shareware 
development sometime soon. :-) But I diverge...

Thanks,

Alex Rice, Software Developer
Architectural Research Consultants, Inc.
alrice at ARCplanning.com
alrice at swcp.com