Undo/Redo about shadershop HOT 3 OPEN

What do you mean by nonlinear? And why 2 hotkeys for redo?

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Ctrl+Y is the classic Windows shortcut for redo (although less classic then F4), and Ctrl+Shift+Z is much better imo because it's physically related to Ctrl+Z, and easier to press with one hand.

Applications with linear history generally destroy it without telling you, if you undo and then do anything other than redo. That's the standard (history isn't considered important).
Nonlinear history means if you undo and then do something, you can still get back to where you were, because it's not two stacks of operations or states, it's a tree.
I guess the only software I know of that has it are emacs and vim (with the feature known as undo trees, or undo branches), but I've never used either program except for trying to exit them, and occasionally trying to edit text files, forgetting that nano exists. (I wish using GUI text editors over SSH was easier.)

Personally I have a lot of ideas about how undo/redo should work, for all creative/editing software. I think history should be stored along with the document, and made visible (like with history panels in some apps), and made more powerful and editable, like being able delete an operation in the middle of history and have the further actions play out on top, or to reorder operations, etc.

But anyways, just plain undo/redo would be nice.

Googling for some history on Ctrl+Shift+Z vs Ctrl+Y I found this. Man, I remember that happening, that probably lost me some work way back when. It illustrates the culmination of these two points. ␚

from shadershop.

I have since my last comment implemented non-destructive (nonlinear) undo history in my image editor JS Paint. You can get back to any state with Edit > History. And if you try to redo at the end of a branch in the history tree, it'll prompt you to open the history window.

from shadershop.