On Dec 6, 2009, at 04:36, Graham Cox wrote:
> On 06/12/2009, at 10:57 PM, Mike Abdullah wrote:
>
>> But why are you opening a group without registering an undo action? Why not
>> just wait until the first action actually needs to be registered?
>
> I tried it but it doesn't work. I forget the details now as this was my first
> approach and that was a long time ago, but basically the undo manager didn't
> tolerate having groups deferred until a task was actually received. It would
> crash, but without the code, I couldn't say why .
I'm not sure I understand this point. Are you talking about a situation with
'setGroupsByEvent:YES' or 'setGroupsByEvent:NO'? Either way, an explicit call
to 'beginUndoGrouping:' is *by definition* deferred, since it obviously can't
happen the instant an event is dequeued. The length of time between dequeuing
an event and invoking an undo manager method seems irrelevant. But I ask mainly
out of curiosity because ...
> My fourth approach is to write my own bloody undo manager and have done with
> it. Result so far - bliss.
I think that's a perfectly reasonably thing to have done. The functionality
described by the NSUndoManager docs certainly doesn't *seem* difficult to
re-implement. I haven't tried it, but now you have, and you've pretty much
verified that fact.
It's also interesting that the documentation:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/UndoArchitecture/Articles/UndoManager.html#//apple_ref/doc/uid/20000205-CJBDJCCJ
has this statement (in the overview):
> An undo manager collects all undo operations that occur within a single cycle
> of the run loop, so that performing an undo reverts all changes that occurred
> during the cycle.
Taken literally, that would seem to say that NSUndoManager's API contract
doesn't support undo actions that span events. FWIW.
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