How to Swap location in Object Manager

pchg

Hello colleagues, I used C++ to write the C4D S26 plugin on Windows 10. Swap the positions of 2 and 10 in the Object Manager. I cannot find the relevant API.

BaseDocument* doc = GetActiveDocument();
Int32 count = selection->GetCount();
AutoAlloc<AtomArray> selection;
doc->GetActiveObjects(selection, GETACTIVEOBJECTFLAGS::CHILDREN);
BaseObject* obj_2 = static_cast<BaseObject*>(selection->GetIndex(count - obj_10));
BaseObject* obj_10 = static_cast<BaseObject*>(selection->GetIndex(count - obj_2));

What should we do next？Thanks in advance!

ferdinand

Hey @pchg,

Thank you for reaching out to us. There is no dedicated "Swap" function for node hierarchies. All the relevant tools can be found on cinema::GeListNode. The general drill would be here to either get the node before or after the nodes you want to swap, remove the nodes, and then use GeListNode::InsertBefore or InsertAfter to insert the nodes. Please note that other than in the Python API, there is no fail safe which prevents you from inserting nodes multiple times into a scene graph (which is not allowed and will lead to crashes).

Cheeers,
Ferdinand

Code

I wrote this 'blind' in a text editor, i.e., this is uncompiled code to demonstrate the principle:

BaseObject* const a = static_cast<BaseObject*>(selection->GetIndex(count - obj_10));
BaseObject* const b = static_cast<BaseObject*>(selection->GetIndex(count - obj_2));
if (!a || !b)
  return maxon::UnexpectedError(MAXON_SOURCE_LOCATION, "a or b is nullptr"_s);

// Get the predecessor of the objects a and b which can be a null pointer when either a or b is the 
// first object in the hierarchy. We could then use either the next object as the insertion point or
// use GeListNode::InsertUnder or BaseDocument::InsertObject to insert the object at the top of its
// hierarchy local hierarchy. I went here for the latter as for the next object you also have to deal
// with the case that there is neither a predecessor nor a next object.
BaseObject* const predA = a->GetPred();
BaseObject* const predB = b->GetPred();
BaseObject* const parentA = a->GetUp();
BaseObject* const parentB = b->GetUp();

// Remove both objects from the hierarchy.
a->Remove();
b->Remove();

// Insert the objects back into the hierarchy, either after the predecessor, under the parent, 
// or at the top of the document hierarchy.
if (predA) 
  b->InsertAfter(predA);
else if (parentA)
  b->InsertUnder(parentA); // Will insert at the top of the hierarchy.
else
  doc->InsertObject(b, nullptr, nullptr); // Will insert at the top of the hierarchy.

if (predB)
  a->InsertAfter(predB);
else if (parentB)
  a->InsertUnder(parentB);
else
  doc->InsertObject(a, nullptr, nullptr);

pchg

@ferdinand Thank you very much for your reply