C++ LayerList::front方法代码示例

static DocRange drop_range_op(
  Doc* doc,
  const Op op,
  const DocRange& from,
  DocRangePlace place,
  const TagsHandling tagsHandling,
  DocRange to)
{
  // Convert "first child" operation into a insert after last child.
  LayerGroup* parent = nullptr;
  if (to.type() == DocRange::kLayers &&
      !to.selectedLayers().empty()) {
    if (place == kDocRangeFirstChild &&
        (*to.selectedLayers().begin())->isGroup()) {
      place = kDocRangeAfter;
      parent = static_cast<LayerGroup*>((*to.selectedLayers().begin()));

      to.clearRange();
      to.startRange(parent->lastLayer(), -1, DocRange::kLayers);
      to.endRange(parent->lastLayer(), -1);
    }
    else {
      parent = (*to.selectedLayers().begin())->parent();
    }

    // Check that we're not moving a group inside itself
    for (auto moveThis : from.selectedLayers()) {
      if (moveThis == parent ||
          (moveThis->isGroup() &&
           has_child(static_cast<LayerGroup*>(moveThis), parent)))
        return from;
    }
  }

  if (place != kDocRangeBefore &&
      place != kDocRangeAfter) {
    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 DocRange::kCels:
      if (from == to)
        return from;
      break;

    case DocRange::kFrames:
      if (op == Move) {
        // Simple cases with one continuos range of frames that are a
        // no-op.
        if ((from.selectedFrames().ranges() == 1) &&
            ((to.firstFrame() >= from.firstFrame() &&
              to.lastFrame() <= from.lastFrame()) ||
             (place == kDocRangeBefore && to.firstFrame() == from.lastFrame()+1) ||
             (place == kDocRangeAfter && to.lastFrame() == from.firstFrame()-1)) &&
            // If there are tags, this might not be a no-op
            (sprite->frameTags().empty() ||
             tagsHandling == kDontAdjustTags)) {
          return from;
        }
      }
      break;

    case DocRange::kLayers:
      if (op == Move) {
        SelectedLayers srcSelLayers = from.selectedLayers();
        SelectedLayers dstSelLayers = to.selectedLayers();
        LayerList srcLayers = srcSelLayers.toLayerList();
        LayerList dstLayers = dstSelLayers.toLayerList();
        ASSERT(!srcLayers.empty());
        if (srcLayers.empty())
          return from;

        // dstLayers can be nullptr when we insert the first child in
        // a group.

        // Check no-ops when we move layers at the same level (all
        // layers with the same parent), all adjacents, and which are
        // moved to the same place.
        if (!dstSelLayers.empty() &&
            srcSelLayers.hasSameParent() &&
            dstSelLayers.hasSameParent() &&
            are_layers_adjacent(srcLayers) &&
            are_layers_adjacent(dstLayers)) {
          for (Layer* srcLayer : srcLayers)
            if (dstSelLayers.contains(srcLayer))
              return from;

          if ((place == kDocRangeBefore
               && dstLayers.front() == srcLayers.back()->getNext()) ||
              (place == kDocRangeAfter
               && dstLayers.back() == srcLayers.front()->getPrevious()))
            return from;
        }

//.........这里部分代码省略.........