I have another idea for the undo redo stack,

effectively being able to roll back, make a change at a point in history then roll forward again.

I think this would be most impressive in bitmap editing software such as krita.

For instance,

setting the stroke parameters, say colour to keep it simple.

Drawing a line, doing some other stuff.

Then deciding that you want to change the stroke parameters for everything from a point in history. This should be a simple roll back roll forward and performance can be achieved if snapshots are taken. I don't think snapshots are such a requirement for vector graphics and DTP but would be needed for bitmap graphics along with GPU acceleration to make the whole things as smooth as possible.

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