add a undo_redo lib

[QJesus]

1. fabric.Text.text cannot be null\undefined
2. undo_redo extension

[ShaMan123]

fabric.Text.text cannot be null\undefined

Can be a standalone PR

[melchiar]

Suggested change

	const ___setupCanvas = fabric.canvas.prototype.__setupCanvas;
	fabric.canvas.prototype.__setupCanvas = function (serialized, enlivenedObjects, renderOnAddRemove, callback) {
	const ___setupCanvas = fabric.Canvas.prototype.__setupCanvas;
	fabric.Canvas.prototype.__setupCanvas = function (serialized, enlivenedObjects, renderOnAddRemove, callback) {

Nice lib idea! fabric.canvas should have uppercase C though

[melchiar]

Can we improve some of these variable names. Names like t, v, and h aren't very human readable.

Some comments would be helpful as well to explain the purpose of each function and variables like undoredo.escape

[ShaMan123]

I don't think history should be part of core.
IMO history is something that is heavily customized between different apps.
If it is hard to build such functionality I would suggest PRing to make fabric easier to develop such functionalities. That makes sense to me.
Regardless, saveObjectTransform isn't good enough. What about skewing? cacheProperties? stateProperties?
This re-introduces state management which we have decided to deprecate in #7920
And of course we are in the midst of TS migration, so the PR lockdown should be enforced. After that it might be very simple to develop this kind of functionality.

[ShaMan123]

@QJesus I am very for contributions, hope I didn't put you down.
We are migrating to TS if you want to join the effort. And that should eventually open up a better way to write extensions for fabric.

[asturur]

Actually we wanted to think about a more simple way to tackle this, both on core and an external lib. We have to move forward with our schedule and as soon as the rollup pr is merged, we can get back to this.

change of direction

[melchiar]

@QJesus Thanks for the pr, however as asturur explained this isn't quite the direction we want to take with an undoredo library. I'm going to close this PR for now, but we can revisit adding an official undoredo component once v6 is out of the gate.