ragflow/web/src/components/artifact-force-graph/use-center-gravity.ts

import { forceX, forceY } from 'd3-force';
import { useEffect, type RefObject } from 'react';
import { type ForceGraphMethods } from 'react-force-graph-2d';
import { type ArtifactGraphNode } from './types';

// Weak gravity pulling every node toward the center so disconnected
// components and isolated nodes are not flung far away by charge repulsion.
const CenterGravityStrength = 0.08;

// Register weak center gravity once the graph is mounted; the forces live
// on the d3 simulation and persist across graphData changes.
export function useCenterGravity(
  fgRef: RefObject<ForceGraphMethods<ArtifactGraphNode> | undefined>,
  hasDimensions: boolean,
) {
  useEffect(() => {
    const fg = fgRef.current;
    if (!hasDimensions || !fg) return;
    fg.d3Force(
      'x',
      forceX<ArtifactGraphNode>(0).strength(CenterGravityStrength),
    );
    fg.d3Force(
      'y',
      forceY<ArtifactGraphNode>(0).strength(CenterGravityStrength),
    );
  }, [fgRef, hasDimensions]);
}