checkpoint ()

Finish current history and add to undo stack (also, clear redo stack, and if current history isn't undoable, clear the undo stack too.)

has_delta_for ( key )

True if a delta with key key is in current history

record ( delta )

Record delta as part of the current history (see IDelta.merge()) (Should clear redo history)

redoNext ()

Pop a history from the redo stack and redo it (while moving it to the undo stack). Raise an error if deltas recorded.

revert ()

Roll back current history to last checkpoint or undo/redo

Undo and discard all deltas recorded since the last checkpoint, revert, or undo/redo operation. Undo/redo histories do not change.

undoLast ()

Undo the last history added to the undo stack (while moving it to the redo stack). Raise an error if deltas recorded.