Representation of Undoinfo	The Undo Mechanism	The Undo API

Combining Undoinfo

The SetFillStyle method of the Group class has to return undoinfo that describes how to undo several operations at once. To achieve this, one can define a function UndoList as follows:

def UndoList(infos): undoinfo = map(Undo, infos) undoinfo.reverse() return (UndoList, undoinfo)

Here, Undo is a function that executes a single undoinfo (defined in undo.py).

Given a list `infos' of undoinfos, Group.SetFillStyle can return (UndoList, infos).

Calling reverse in UndoList is essential, as some operations must be undone in exactly the reverse order in which they were performed.

For more complex cases where several undoinfos have to be executed in a certain order one can easily define similar functions. See for instance UndoAfter in undo.py

Representation of Undoinfo	The Undo Mechanism	The Undo API