GeListNode Manual

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() 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

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\")";
if (op == nullptr)
return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
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.

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)
{
// check if the current node is a BaseList2D object
{
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:

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)
return maxon::OK;
// 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:

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:

Valid flags are:

The used BranchInfo struct has the following members:

The branch flags are:

// 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)
{
const String branchName = info[i].name;
ApplicationOutput(" - Name: " + branchName);
GeListHead* const branchHead = info[i].head;
if (branchHead)
{
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:

See also Basic Classes and Plugin Classes.

// 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:

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);
GePrint(baseList2D->GetName());
}
}
}

Infos

Additional information can be accessed:

// 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)
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.

The change operations are:

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

Further Reading