recharts/src/util/DOMUtils.ts

import { CSSProperties } from 'react';
import { Global } from './Global';
import { Size } from './types';

interface StringCache {
  widthCache: Record<string, any>;
  cacheCount: number;
}

const stringCache: StringCache = {
  widthCache: {},
  cacheCount: 0,
};
const MAX_CACHE_NUM = 2000;
const SPAN_STYLE = {
  position: 'absolute',
  top: '-20000px',
  left: 0,
  padding: 0,
  margin: 0,
  border: 'none',
  whiteSpace: 'pre',
};
const MEASUREMENT_SPAN_ID = 'recharts_measurement_span';

function removeInvalidKeys(obj: Record<string, any>) {
  const copyObj = { ...obj };
  Object.keys(copyObj).forEach(key => {
    if (!copyObj[key]) {
      delete copyObj[key];
    }
  });
  return copyObj;
}

export const getStringSize = (text: string | number, style: CSSProperties = {}): Size => {
  if (text === undefined || text === null || Global.isSsr) {
    return { width: 0, height: 0 };
  }

  const copyStyle = removeInvalidKeys(style);
  const cacheKey = JSON.stringify({ text, copyStyle });

  if (stringCache.widthCache[cacheKey]) {
    return stringCache.widthCache[cacheKey];
  }

  try {
    let measurementSpan = document.getElementById(MEASUREMENT_SPAN_ID);
    if (!measurementSpan) {
      measurementSpan = document.createElement('span');
      measurementSpan.setAttribute('id', MEASUREMENT_SPAN_ID);
      measurementSpan.setAttribute('aria-hidden', 'true');
      document.body.appendChild(measurementSpan);
    }
    // Need to use CSS Object Model (CSSOM) to be able to comply with Content Security Policy (CSP)
    // https://en.wikipedia.org/wiki/Content_Security_Policy
    const measurementSpanStyle: Record<string, any> = { ...SPAN_STYLE, ...copyStyle };
    Object.assign(measurementSpan.style, measurementSpanStyle);

    measurementSpan.textContent = `${text}`;

    const rect = measurementSpan.getBoundingClientRect();
    const result = { width: rect.width, height: rect.height };

    stringCache.widthCache[cacheKey] = result;

    if (++stringCache.cacheCount > MAX_CACHE_NUM) {
      stringCache.cacheCount = 0;
      stringCache.widthCache = {};
    }

    return result;
  } catch {
    return { width: 0, height: 0 };
  }
};