@Override
	protected void decoratePrimaryViewer(GraphViewer<FGVertex, FGEdge> viewer,
			VisualGraphLayout<FGVertex, FGEdge> layout) {

		super.decoratePrimaryViewer(viewer, layout);

		// the edge renderer was set by the parent call; get the renderer to add our painter
		Renderer<FGVertex, FGEdge> renderer = viewer.getRenderer();
		RenderContext<FGVertex, FGEdge> renderContext = viewer.getRenderContext();

		// for background colors when we are zoomed to far to render the listing
		PickedState<FGVertex> pickedVertexState = viewer.getPickedVertexState();
		FGVertexRenderer vertexRenderer = new FGVertexRenderer();
		vertexRenderer.setVertexFillPaintTransformer(new FGVertexPickableBackgroundPaintTransformer(
			pickedVertexState, PICKED_COLOR, START_COLOR, END_COLOR));
		renderer.setVertexRenderer(vertexRenderer);

		// edge label rendering
		com.google.common.base.Function<FGEdge, String> edgeLabelTransformer = e -> e.getLabel();
		renderContext.setEdgeLabelTransformer(edgeLabelTransformer);

		// note: this label renderer is the stamp for the label; we use another edge label
		//       renderer inside of the VisualGraphRenderer
		VisualGraphEdgeLabelRenderer edgeLabelRenderer = new VisualGraphEdgeLabelRenderer(
			new GColor("color.fg.plugin.functiongraph.label.picked"));
		edgeLabelRenderer.setNonPickedForegroundColor(
			new GColor("color.fg.plugin.functiongraph.label.non.picked"));
		edgeLabelRenderer.setRotateEdgeLabels(false);
		renderContext.setEdgeLabelRenderer(edgeLabelRenderer);

		viewer.setGraphOptions(vgOptions);
		Color bgColor = vgOptions.getGraphBackgroundColor();
		if (vgOptions.isDefaultBackgroundColor(bgColor)) {

			// Give user notice when seeing the graph for a non-function (such as an undefined
			// function), as this is typical for Ghidra UI widgets.
			// Don't do this if the user has manually set the background color (this would require
			// another option).
			Function function = functionGraphData.getFunction();
			if (function instanceof UndefinedFunction) {
				viewer.setBackground(UNDEFINED_FUNCTION_COLOR);
			}
			else {
				viewer.setBackground(new GColor("color.bg.plugin.functiongraph"));
			}
		}

	}
A somewhat arbitrary value that is used to signal a 'big' graph, which is one that will
slow down the system during the rendering process.
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/FGComponent.java