void start() {
_redoStack.clear();
if (_undoStack.size() == _undoLevels) {
_undoStack.pop_front();
}
startUndo();
trackersBegin();
}
// Sets the size of the undoStack
void setLevels(std::size_t levels) {
if (levels > MAX_UNDO_LEVELS) {
levels = MAX_UNDO_LEVELS;
}
while (_undoStack.size() > levels) {
_undoStack.pop_front();
}
_undoLevels = levels;
}