Function EdgeLines

graph-ui/src/components/EdgeLines.tsx:54–154

({
  nodes,
  edges,
  highlightedIds,
  opacity = 1.0,
  brightness = 1.0,
  targetNodes,
}: EdgeLinesProps)

const DEFAULT_EDGE_COLOR = "#1C8585";

export function EdgeLines({
  nodes,
  edges,
  highlightedIds,
  opacity = 1.0,
  brightness = 1.0,
  targetNodes,
}: EdgeLinesProps) {
  const geometry = useMemo(() => {
    /* Shrink per-edge glow as the edge count grows so the additively-blended
     * center doesn't saturate to white; the user multiplier rides on top. */
    const densityScale = edgeIntensityScale(edges.length) * brightness;
    const srcMap = new Map<number, number>();
    for (let i = 0; i < nodes.length; i++) {
      srcMap.set(nodes[i].id, i);
    }
    const tgtArr = targetNodes ?? nodes;
    const tgtMap = targetNodes ? new Map<number, number>() : srcMap;
    if (targetNodes) {
      for (let i = 0; i < targetNodes.length; i++) {
        tgtMap.set(targetNodes[i].id, i);
      }
    }

    const hasHighlight = highlightedIds && highlightedIds.size > 0;
    const positions = new Float32Array(edges.length * 6);
    const colors = new Float32Array(edges.length * 6);
    let validCount = 0;

    for (const edge of edges) {
      const si = srcMap.get(edge.source);
      const ti = tgtMap.get(edge.target);
      if (si === undefined || ti === undefined) continue;

      const s = nodes[si];
      const t = tgtArr[ti];

      const sHL = !hasHighlight || highlightedIds.has(s.id);
      const tHL = !hasHighlight || highlightedIds.has(t.id);
      if (hasHighlight && !sHL && !tHL) continue;

      const sameCluster =
        getClusterKey(s.file_path) === getClusterKey(t.file_path);

      /* Intensity based on cluster membership and highlight.
       * With additive blending + dark background, these glow nicely. */
      let intensity = sameCluster ? 0.25 : 0.06;
      if (hasHighlight) {
        /* A selection stays at full strength (never density-scaled) so it
         * pops against the dimmed rest; only the un-selected bulk is scaled. */
        intensity = sHL && tHL ? 0.5 : 0.04 * densityScale;
      } else {
        intensity *= densityScale;
      }

      const off = validCount * 6;
      positions[off] = s.x;
      positions[off + 1] = s.y;