undo method

void undo()

Undoes the last drawing modification.

Implementation

void undo() {
  if (!canUndo) return;
  _redoStack.add(_drawings.map((d) => d.copyWith()).toList());
  _drawings
    ..clear()
    ..addAll(_undoStack.removeLast());
  notifyListeners();
  triggerAutoSave();
}