Function drop_range_op

src/app/document_range_ops.cpp:28–333

enum Op { Move, Copy };

static DocumentRange drop_range_op(
  Document* doc, Op op, const DocumentRange& from,
  DocumentRangePlace place, const DocumentRange& to)
{
  if (place != kDocumentRangeBefore &&
      place != kDocumentRangeAfter) {
    ASSERT(false);
    throw std::invalid_argument("Invalid 'place' argument");
  }

  Sprite* sprite = doc->sprite();

  // Check noop/trivial/do nothing cases, i.e., move a range to the same place.
  // Also check invalid cases, like moving a Background layer.
  switch (from.type()) {
    case DocumentRange::kCels:
      if (from == to)
        return from;
      break;
    case DocumentRange::kFrames:
      if (op == Move) {
        if ((to.frameBegin() >= from.frameBegin() && to.frameEnd() <= from.frameEnd()) ||
            (place == kDocumentRangeBefore && to.frameBegin() == from.frameEnd()+1) ||
            (place == kDocumentRangeAfter && to.frameEnd() == from.frameBegin()-1))
          return from;
      }
      break;
    case DocumentRange::kLayers:
      if (op == Move) {
        if ((to.layerBegin() >= from.layerBegin() && to.layerEnd() <= from.layerEnd()) ||
            (place == kDocumentRangeBefore && to.layerBegin() == from.layerEnd()+1) ||
            (place == kDocumentRangeAfter && to.layerEnd() == from.layerBegin()-1))
          return from;

        // We cannot move the background
        for (LayerIndex i = from.layerBegin(); i <= from.layerEnd(); ++i)
          if (sprite->indexToLayer(i)->isBackground())
            throw std::runtime_error("The background layer cannot be moved");
      }

      // Before background
      if (place == kDocumentRangeBefore) {
        Layer* background = sprite->indexToLayer(to.layerBegin());
        if (background && background->isBackground())
          throw std::runtime_error("You cannot move or copy something below the background layer");
      }
      break;
  }

  const char* undoLabel = NULL;
  switch (op) {
    case Move: undoLabel = "Move Range"; break;
    case Copy: undoLabel = "Copy Range"; break;
    default:
      ASSERT(false);
      throw std::invalid_argument("Invalid 'op' argument");
  }
  DocumentRange resultRange;