src/utils/viewportTooltip.js

/**
 * Place a tooltip near (clientX, clientY) without jumping left unless the
 * default below-right placement would overflow the viewport.
 *
 * @param {number} clientX
 * @param {number} clientY
 * @param {{ estWidth?: number; estHeight?: number; gap?: number; pad?: number }} [opts]
 *   Pass measured width/height from the tooltip element when possible; defaults
 *   that are larger than the real box cause early horizontal clamping.
 */
export function viewportTooltipPosition(clientX, clientY, opts = {}) {
  const vw = typeof window !== "undefined" ? window.innerWidth : 1200;
  const vh = typeof window !== "undefined" ? window.innerHeight : 800;
  const W = opts.estWidth ?? 236;
  const H = opts.estHeight ?? 92;
  const gap = opts.gap ?? 12;
  const pad = opts.pad ?? 8;

  let left = clientX + gap;
  let top = clientY + gap;

  if (left + W + pad > vw) {
    left = vw - W - pad;
  }
  if (left < pad) {
    left = pad;
  }

  if (top + H + pad > vh) {
    top = vh - H - pad;
  }
  if (top < pad) {
    top = pad;
  }

  return { left, top };
}