Undo without dirtying document, take 10.5

FROM : Christiaan Hofman
DATE : Sun Nov 04 01:32:10 2007

Hi,

I have some undoable changes that do not change and savable state, 
but rather some display state. Therefore, the document should not be 
marked dirty for those changes. However undoManager in a document 
based app automatically dirties the document. This could be avoided 
by "undoing" the change count using an explicit -updateChangeCount: 
call. However, in Leopard this does not seem to work anymore. Could 
anyone here explain why it fails to work, something changed in 
Leopards undo architecture or in document change count? Or is this a 
bug? Also would there be an alternative workaround to this problem 
that works on Leopard?

thanks,
Christiaan