C++ (Cpp) Action::DrawnBefore примеры использования

Пример #1

// Undo last action
// Returns true if everything went fine
bool PlayGround::undo()
{
  ToDraw *newObject;
  Action *undone;
  int zOrder;

  if (!(undone = history.at(--currentAction)))
    return false;

  zOrder = undone->ZOrderAfter();
  if (zOrder != -1)
  {
    // Undo an "add" or a "move" action
    if (!toDraw.remove(zOrder)) return false;
  }

  zOrder = undone->ZOrderBefore();
  if (zOrder != -1)
  {
    // Undo a "delete" or a "move" action
    newObject = new ToDraw(undone->DrawnBefore());
    if (!toDraw.insert(zOrder, newObject))
      return false;
  }

  return true;
}