Commands and Customization

NGT edits are command-driven. Use commands when a change should participate in undo, redo, model change tracking, and UI refresh.

Command Flow

Use graph-level hooks for policy tied to the graph type:

@Override
public boolean canExecuteCommand(IGraphCommand command) {
    return !(command instanceof GraphCommands.DeleteElementsCommand);
}

Use view-level interception for one editor instance:

graphView.setCommandInterceptor(command -> allowEditMode);

Both must allow the command.

Command Listeners

Use listeners for UI or tool behavior that should react after a command runs.

graphView.addCommandListener((view, graphModel, command) -> {
    refreshCustomPanel();
});

Use Graph.onCommandExecuted(...) when the reaction belongs to the graph definition itself.

Capabilities

Graph element models use capabilities to control user actions.

Common capabilities include:

Capability	Effect
MOVABLE	Can be moved on the canvas.
DELETABLE	Can be deleted.
COPIABLE	Can be copied and pasted.
RENAMABLE	Can be renamed.
COLORABLE	Can use color picker actions.
COLLAPSIBLE	Can collapse.
RESIZABLE	Can resize.
NEEDS_CONTAINER	Must live inside a container, used by block nodes.

Prefer capabilities when a rule applies to one element. Prefer command vetoes when a rule depends on a whole command.

Diagnostics

Use GraphLogger to show graph validation in the footer.

@Override
public void onGraphChanged(GraphLogger logger) {
    if (hasMissingOutput()) {
        logger.error(Component.literal("Output is not connected"));
    }
}

Supported message kinds are info, warning, and error.

Extra Elements

NGT includes more than nodes and wires:

• placemats for grouping visible graph areas,
• sticky notes for comments,
• wire portals for routing wires through named entry and exit portals,
• graph panels for docking tools,
• graph preview for custom preview UI.

These elements are normal graph models and participate in serialization and selection where supported by their capabilities.

Custom UI

Common customization points:

Target	Use
GraphResource.getGraphViewFactory()	Use a custom GraphView subclass.
GraphView.setLayers(...)	Change canvas layer order.
Node.getNodeIcon()	Custom node icon.
Node.getNodeWidth()	Minimum node width.
Node.hasNodePreview()	Add node preview panel.
IPortBuilder.withConnectorUI(...)	Custom port connector visuals.
IOptionBuilder.withConfigurable(...)	Custom option editor.
IInputPortBuilder.withConfigurable(...)	Custom input constant editor.