Hi Peter,
On Fri, May 8, 2009 at 8:33 AM, Peter Verswyvelen
If you work with a text editor like Microsoft Visual Studio (maybe also Eclipse, don't know), each text editor has its own undo/redo history. However, when you perform refactoring - like renaming a function - this becomes an undo/redo on multiple files together, so in a sense these changes are part of a global history. You can combine these two different kinds of mutations, and undo/redo still works as expected. I don't know how hard this is to implement, but it looks like this problem is somehow is related to Darcs theory of patches (which I don't know yet :-)
I have thought about applications of patch theory like this as well. I could imagine applying it to the undo stack in GIMP. Allowing you to undo things on different layers. I think one of the things you need for this to work, is a graphical representation of the undo history. You could commute the change you want to undo to the top of the stack, undo it, and then you have a branch in the history. Because this could get complicated, you need to display this branched history to the user so they are able to continue working with it. If you wanted to work on this, I would encourage you to read more about patch theory[1,2,3,4] and also try out libdarcs[5]. Thanks, Jason [1] http://darcs.net/manual/node9.html [2] http://en.wikibooks.org/wiki/Understanding_darcs/Patch_theory [3] http://files.codersbase.com/thesis.pdf (see chapter 3) [4] http://wiki.darcs.net/DarcsWiki/Talks [5] http://bugs.darcs.net/issue1149