About

A maxon::GraphModelInterface contains a basic graph model containing a hierarchy of nodes and a collection of connections between these nodes. It is reused as a node material's node system with maxon::nodes::NodesGraphModel (see NodesGraphModelInterface Manual).

Nodes

The maxon::GraphNode nodes stored in the model are accessed with:

maxon::GraphModelInterface::GetRootPath(): Returns the maxon::NodePathInterface of the root node.
maxon::GraphModelInterface::GetRoot(): Returns the maxon::GraphNode root node.
maxon::GraphModelInterface::GetNode(): Returns the maxon::GraphNode for the given maxon::NodePathInterface.

  // This example accesses the root node of the given model in two different ways.
 
  // get root node
  const maxon::GraphNode rootNode = model.GetRoot();
 
  // or get root path
  const maxon::NodePath  rootPath = model.GetRootPath();
  const maxon::GraphNode rootNodeFromPath = model.GetNode(rootPath);

See GraphNodes Manual.

Edit

Editing a maxon::GraphModelInterface reference is done through transactions:

maxon::GraphModelInterface::BeginTransaction(): Starts a graph transaction. See maxon::GraphTransaction.
maxon::GraphModelInterface::Validate(): Validates the graph after editing. This is automatically done on commit.
maxon::GraphTransaction::Commit(): Ends a graph transaction. The changes made within this transaction become permanent in the graph.
maxon::GraphTransaction::Rollback(): Rolls back the graph to its state at the time this transaction has been started and ends the graph transaction.

Additionally, information relative to a maxon::GraphModelInterface reference can be retrieved with:

maxon::GraphModelInterface::GetModificationStamp(): Gets the maxon::TimeStamp of the graph.
maxon::GraphModelInterface::GetModificationsSince(): Gets all modifications which have been made since the given time step.
maxon::GraphModelInterface::IsReadOnly(): Returns true if this graph is read-only.

Note: A graph model may only be modified when there is an active transaction.

A change list stores changes and allows to reproduce these changes on a different graph.

maxon::GraphModelInterface::StartNewChangeList(): Starts a new change list.
maxon::GraphModelInterface::GetChangeList(): Returns the current change list.
maxon::GraphModelInterface::Apply(): Applies the given maxon::ChangeList to the graph.

  // This example obtains a node graph from a node material and inserts a new node.
 
  // get graph
  const maxon::nodes::NodesGraphModelRef& nodeGraph = nodeMaterial->GetGraph(nodeSpaceID) iferr_return;
 
  if (nodeGraph.IsReadOnly())
    return maxon::IllegalStateError(MAXON_SOURCE_LOCATION);
 
  // start a new change list if we want to apply the changes also to a different graph
  nodeGraph.StartNewChangeList() iferr_return;
 
  // start transaction
  maxon::GraphTransaction transaction = nodeGraph.BeginTransaction() iferr_return;
 
  // prepare for adding a new node
  const maxon::Id nodeAssetId { "net.maxonexample.noderenderer.usernode" };
  const maxon::AssetRepositoryRef& repository = maxon::AssetInterface::GetBuiltinRepository();
  maxon::nodes::NodeTemplate       nodeTemplate = maxon::nodes::NodesLib::LoadTemplate(repository, nodeAssetId) iferr_return;
 
  // add new node
  // leave the 'childId' parameter empty to create a UUID
  maxon::GraphNode userGraphNode = nodeGraph.AddChild(maxon::Id(), nodeTemplate) iferr_return;
  // set node name
  userGraphNode.SetValue(maxon::NODE::BASE::NAME, "My user node"_s) iferr_return;
 
  // commit transaction
  transaction.Commit() iferr_return;
 
  // this change list contains the latest changes
  const maxon::ChangeList& list = nodeGraph.GetChangeList();

Related observables are:

ObservableTransactionStarted: Informs about the start of a transaction.
ObservableTransactionCommitted: Informs about the commit of a transaction.
ObservableTransactionRolledBack: Informs about the rollback of a transaction.

  // This example stores the current modification stamp and registers a transaction observer.
 
  g_timeStamp = model.GetModificationStamp();
 
  model.ObservableTransactionCommitted(true).AddObserver(ObserveCommit) iferr_return;

// This observer function accesses all modifications since the last change
// and checks if a node has been added.
 
static void ObserveCommit(const maxon::GraphModelRef& graph, const maxon::DataDictionary& userData)
{
  iferr_scope_handler
  {
    DiagnosticOutput("Error @ in observer.", err);
    return;
  };
 
  graph.GetModificationsSince(g_timeStamp,
    [](const maxon::GraphNode& node, maxon::GraphModelInterface::MODIFIED mod) -> maxon::Result<maxon::Bool>
    {
// check if node was added
      if (mod & maxon::GraphModelInterface::MODIFIED::NODE_ADDED)
      {
        DiagnosticOutput("New Node: @", node.GetId());
        return false;
      }
 
      return true;
    }) iferr_return;
 
  // store time stamp
  g_timeStamp = graph.GetModificationStamp();
}

Attributes

A graph model can store attributes:

maxon::GraphModelInterface::GetGraphAttribute(): Returns the maxon::GraphAttribute for the given ID.
maxon::GraphModelInterface::GetGraphAttributeFlags(): Returns the maxon::GraphAttributeInterface::FLAGS to use for the given ID.
maxon::GraphModelInterface::ResetUserState(): Removes all values for the given user state attribute.

The attribute IDs can be found in graphattribs.h and portattributes.h.

Selection

Selection state can be retrieved with the maxon::GraphModelHelper interface and the next methods:

maxon::GraphModelHelper::IsNodeSelected(): Checks if the passed Port or True Node is selected.
maxon::GraphModelHelper::IsConnectionSelected(): Checks if a Wires between two port is selected. (GraphNode will be converted to nodePath)
maxon::GraphModelHelper::SelectNode(): Selects a node or a port.
maxon::GraphModelHelper::SelectConnection(): Selects the Wires between two Ports.
maxon::GraphModelHelper::DeselectNode(): Deselects a node or a port.
maxon::GraphModelHelper::DeselectConnection(): Deselects the Wire between two Ports.
maxon::GraphModelHelper::DeselectAll(): Deselects all True Nodes and ports based on the NODE_KIND passed as parameter.
maxon::GraphModelHelper::GetSelectedNodes(): Retrieves all selected Ports and/or True Node on the graph depending on the NODE_KIND passed as argument
maxon::GraphModelHelper::GetSelectedConnections(): Retrieves all selected Wires on the graph.

Miscellaneous

Further functions are:

maxon::GraphModelInterface::CreateCopyOfSelection(): Returns a new graph model which is a copy of the subgraph given by the selection.
maxon::GraphModelInterface::Merge(): Merges the given graph into this graph.
maxon::GraphModelHelper::ListAllNodes(): Retrieves all nodes having their stored data equals the ones in the passed DataDictionary.

Further utility functions are found in maxon::GraphLib.