question: public void undoableEditHappened ( mxUndoableEdit undoableEdit ) { if ( enabled ) { if ( undoableEdit . getTransparent ( ) ) { } else if ( ! undoableEdit . getUndoable ( ) ) { notUndoableEditHappened ( ) ; } else if ( collection ) { collected . add ( undoableEdit ) ; fireEvent ( new mxEventObject ( mxEvent . ADD , "edit" , undoableEdit ) ) ; } else { collected . add ( undoableEdit ) ; addEventList ( ) ; fireEvent ( new mxEventObject ( mxEvent . ADD , "edit" , undoableEdit ) ) ; } } }
target:  Method to be called to add new undoable edits to the history.