(Solve) Maya MEL: batch undo history?

bitinn

Is it possible programmatically merge/modify command history queue?

I want this really for an UNDO operation: If my script performs a series of commands to create some meshes, what's the best way to "group" my commands together, so that UNDO can clean up the changes?

(In some query languages this is also called a transaction, which can be rollbacked.)

(I understand some commands are not undo-able, so an alternative would be to delete the result instead, but then how do I wire the delete to UNDO??)

Froyok

You can't edit the undo operations, that would be too risky.
However you can indeed group them, take a look at undoInfo, especially the openChunk parameter : http://download.autodesk.com/global/docs/maya2013/en_us/Commands/undoInfo.html

bitinn

Froyok said:

You can't edit the undo operations, that would be too risky.
However you can indeed group them, take a look at undoInfo, especially the openChunk parameter : http://download.autodesk.com/global/docs/maya2013/en_us/Commands/undoInfo.html

Thing is, I already put them in one proc (it contains multiple sub-routines, of course), so I have only 1 chunk of undo history. But undo-ing that doesn't return to the initial state. It ends somewhere in the middle...

I don't think I am messing with the history though, so my question is now: what could have caused my undo problem?

For instance: is there a limited length of commands on each undo chunk? (Not the undo history queue length, but how many commands a undo chunk can remember...)

bitinn

OK so it looks like the main trouble maker is pathAnimation, many had problem undo-ing it (for years really), it's still not fixed in 2017

To be precise: pathAnimation is itself can be undo, but any commands before it are no longer undo-able.

EDIT: also some "forced" operations such as connectAttr -lock 1, Maya doesn't know how to go back? so undo is broken.

Froyok

Yes it's probable some actions can broke the undo. Importing something in a scene is one of them.