About

The class GeListNode is based on C4DAtom and is a base class for many entities of the classic Cinema 4D API. It mostly provides the functionality to organize elements in linked lists and trees.

GeListNode objects are an instance of Tgelistnode.

Access

NodeData::Get(): Returns the GeListNode connected with a NodeData instance.

NodeData::Get() is rarely needed, as a pointer to a GeListNode is typically handed over to virtual functions of NodeData and derived classes:

  // This example shows a primitive implementation of Message().
 
  virtual Bool Message(GeListNode* node, Int32 type, void* data)
  {
    switch (type)
    {
      case (MSG_UPDATE):
      {
        break;
      }
 
      // more cases
 

GeListNode is also used in the context of object hierarchies with GeListHead elements.

Allocation/Deallocation

It is possible to create a GeListNode instance of a RegisterNodePlugin() registered node with

AllocListNode(): Returns an allocated GeListNode that was registered with RegisterNodePlugin().
AllocSmallListNode(): Returns an allocated GeListNode that was registered with RegisterNodePlugin() and the PLUGINFLAG_SMALLNODE flag.

Note: These functions are typically not used with third party plugins. They are only useful to handle custom NodeData plugins.

  // This example allocates a node of the type ID_PYTHONSCRIPT.
  // This node can be used to execute a Python script.
 
  String python;
  python += "print(\"this is python\")";
 
  BaseList2D* op = static_cast<BaseList2D*>(AllocListNode(ID_PYTHONSCRIPT));
  if (op == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  BaseContainer& data = op->GetDataInstanceRef();
  data.SetString(PYTHONSCRIPT_TEXT, python);
 
  op->Message(MSG_SCRIPT_EXECUTE, nullptr);
 
  blDelete(op);

Lists and Trees

Navigation in Lists and Trees

GeListNode based elements can be organized in lists and trees. A GeListNode based entity can reference the accompanying elements in that hierarchy. If no element is referenced, nullptr is returned.

GeListNode::GetNext(): Returns the next GeListNode in the list.
GeListNode::GetPred(): Returns the previous GeListNode in the list.
GeListNode::GetDown(): Returns the child GeListNode.
GeListNode::GetUp(): Returns the parent GeListNode.
GeListNode::GetDownLast(): Returns the last child GeListNode.

Note: Derived classes often provide overwritten versions of these functions for convenience.

The typical Cinema 4D workflow would be:

  // This example iterates over a linked list.
  // In this case it is the list of all tags of the given BaseObject.
 
  // loop through all tags
  for (BaseTag* tag = object->GetFirstTag(); tag; tag = tag->GetNext())
  {
    ApplicationOutput("Tag: " + tag->GetName());
  }

and

// This function walks recursively over the tree of nodes.
 
static void WalkTreeRec(GeListNode* node)
{
  while (node != nullptr)
  {
    // check if the current node is a BaseList2D object
    if (node->IsInstanceOf(Tbaselist2d))
    {
      const BaseList2D* const baseList2d = static_cast<BaseList2D*>(node);
      ApplicationOutput("Name: " + baseList2d->GetName());
    }
 
    // check child objects
    WalkTreeRec(node->GetDown());
 
    // check next objects in the list
    node = node->GetNext();
  }
}

Note: Avoid unnecessary recursion to prevent a stack overflow.

Edit Lists and Trees

A given GeListNode can be inserted into a list or tree or it can be removed from that list or tree:

GeListNode::InsertBefore(): Inserts the element before the given GeListNode in the list.
GeListNode::InsertAfter(): Inserts the element after the given GeListNode in the list.
GeListNode::InsertUnder(): Inserts the element under the given GeListNode.
GeListNode::InsertUnderLast(): Inserts the element as the last child element under the given GeListNode.
GeListNode::Remove(): Removes the element from the list or tree.

Note: If a GeListNode is supposed to be deleted it must be removed from its list before.; At any given time a GeListNode can only be inserted into one single list or tree. Before inserting a node into a new list, make sure to remove it from the old one.

  // This example switches the position of the given object
  // and its parent object in the object tree.
 
  BaseObject* const parentObject = selectedObject->GetUp();
  if (parentObject == nullptr)
    return maxon::IllegalArgumentError(MAXON_SOURCE_LOCATION);
 
  // the parent object may or may not have a parent itself
  BaseObject* const parentParent = parentObject->GetUp();
 
  // remove both objects from the tree
  selectedObject->Remove();
  parentObject->Remove();
 
  // insert the selected object
  doc->InsertObject(selectedObject, parentParent, nullptr);
 
  // insert the parent object as a child
  parentObject->InsertUnder(selectedObject);

Heads and Branches

A GeListHead element is used as the root of a list or tree:

GeListNode::GetListHead(): Returns the GeListHead root of the element's list or tree.

See GeListHead Manual.

A given GeListNode can host multiple internal lists and trees by storing multiple GeListHead objects, called branches. For example the list of tags is a branch of BaseObject. These branches can be accessed with this function:

GeListNode::GetBranchInfo(): Fills the given array with information about the element's internal branches.

Valid flags are:

GETBRANCHINFO::NONE : None.
GETBRANCHINFO::ONLYWITHCHILDREN : Only return a branch if it is in use, i.e. has content.

The used BranchInfo struct has the following members:

BranchInfo::head: Pointer to the GeListHead element.
BranchInfo::name: Pointer to a String with the branch name. May be nullptr.
BranchInfo::id: The ID of the branch.
BranchInfo::flags: Branch flags

The branch flags are:

BRANCHINFOFLAGS::NONE : None.
BRANCHINFOFLAGS::ANIMATE : Animate the nodes in this branch.
BRANCHINFOFLAGS::HIDEINTIMELINE : If set, this branch will not show up in the timeline.

  // This example loops through all branches of a given BaseDocument.
  // If possible the name of the first branch child object is printed.
 
  BranchInfo  info[20]; // 20 is just an arbitrary number, that should be enough to catch all branches
  const Int32 branchCount = doc->GetBranchInfo(info, 20, GETBRANCHINFO::NONE);
 
  for (Int32 i = 0; i < branchCount; ++i)
  {
    ApplicationOutput("Branch " + String::IntToString(i));
 
    const String branchName = info[i].name;
    ApplicationOutput(" - Name: " + branchName);
 
    GeListHead* const branchHead = info[i].head;
    if (branchHead != nullptr)
    {
      GeListNode* const child = branchHead->GetFirst();
 
      // check if the child is a BaseList2D object
      if (child && child->IsInstanceOf(Tbaselist2d))
      {
        BaseList2D* const child2D = static_cast<BaseList2D*>(child);
        ApplicationOutput(" - First Child Element: " + child2D->GetName());
      }
    }
  }

NodeData

The base class for most classic plugins is NodeData. NodeData based plugin classes build the "core" of any plugin based entity of the classic Cinema 4D API. This "core" class can be obtained with:

GeListNode::GetNodeData(): Gets the internal NodeData based plugin class.

  // This example checks if the given object has the type of a custom plugin class.
  // If so, GetNodeData<T>() can be used to get the pointer to the plugin class.
 
  // check if the selected object is an "ExampleGenerator"
  if (selectedObject->GetType() == g_exampleGeneratorID)
  {
    ExampleGenerator* const exampleGenerator = selectedObject->GetNodeData<ExampleGenerator>();
    if (exampleGenerator)
    {
      exampleGenerator->MemberFunction();
    }
  }

Warning: It is only possible to cast the retrieved object into a specific class in the module where this class is defined.; Some components of Cinema 4D are not implemented as a plugin so there is no NodeData instance to access.

Document

GeListNode based objects can also be part of a BaseDocument:

GeListNode::IsDocumentRelated(): Returns true if the element can be inserted directly into a document.
GeListNode::GetDocument(): Returns the BaseDocument that owns this element. Usually this function should be used in NodeData based plugins.

Warning: Always check the returned document pointer for nullptr, as the element might not be part of any document.

          // This example from a NodeData::Message() function uses
          // the BaseDocument of the given GeListNode.
 
          // get the document that hosts the given node
          const BaseDocument* doc = node->GetDocument();
          if (doc)
          {
            GeData geData;
 
            // read the BaseLink parameter from the node
            if (node->GetParameter(EXAMPLE_GENERATOR_LINK, geData, DESCFLAGS_GET::NONE))
            {
              // resolve the link using the received document
              C4DAtom* const atom = geData.GetLinkAtom(doc, Tbaselist2d);
              if (atom)
              {
                BaseList2D* const baseList2D = static_cast<BaseList2D*>(atom);
                ApplicationOutput(baseList2D->GetName());
              }
            }
          }

Infos

Additional information can be accessed:

GeListNode::GetNodeID(): Returns the ID of a multinode with the given index. In most cases it just returns the type ID.
GeListNode::GetInfo(): Returns the flags defined with the "Register" function. See Registration.

  // This example casts the given BaseObject into SplineObject
  // if it is a spline or if it is a spline generator.
 
  SplineObject* spline = nullptr;
 
  // check if the object is a "Spline" object
  if (object->IsInstanceOf(Ospline))
    spline = ToSpline(object);
  // check if the object is a spline generator
  else if (object->GetInfo() & OBJECT_ISSPLINE)
    spline = object->GetRealSpline();
 
  if (spline != nullptr)
    ApplicationOutput("Spline Object: " + spline->GetName());

NBits

Various settings of an element can be configured by changing a corresponding bit. A list of available bits is defined in NBIT.

GeListNode::GetNBit(): Returns true if the given bit is set.
GeListNode::ChangeNBit(): Changes the given bit.

The change operations are:

NBITCONTROL::SET : Sets the bit.
NBITCONTROL::CLEAR : Clears the bit.
NBITCONTROL::TOGGLE : Toggles the bit.

  // This example toggles the NBIT_EHIDE of the active object.
 
  BaseObject* const object = doc->GetActiveObject();
  if (object == nullptr)
    return maxon::IllegalArgumentError(MAXON_SOURCE_LOCATION);
 
  object->ChangeNBit(NBIT::EHIDE, NBITCONTROL::TOGGLE);

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