etherpad-lite/src/static/js/cssmanager.js

/**
 * This code is mostly from the old Etherpad. Please help us to comment this code.
 * This helps other people to understand this code better and helps them to improve it.
 * TL;DR COMMENTS ON THIS FILE ARE HIGHLY APPRECIATED
 */

/**
 * Copyright 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

function makeCSSManager(emptyStylesheetTitle, doc) {
  if (doc === true) {
    doc = 'parent';
  } else if (!doc) {
    doc = 'inner';
  }

  function getSheetByTitle(title) {
    if (doc === 'parent') {
      win = window.parent.parent;
    } else if (doc === 'inner') {
      win = window;
    } else if (doc === 'outer') {
      win = window.parent;
    } else {
      throw 'Unknown dynamic style container';
    }
    const allSheets = win.document.styleSheets;

    for (let i = 0; i < allSheets.length; i++) {
      const s = allSheets[i];
      if (s.title == title) {
        return s;
      }
    }
    return null;
  }

  const browserSheet = getSheetByTitle(emptyStylesheetTitle);

  function browserRules() {
    return (browserSheet.cssRules || browserSheet.rules);
  }

  function browserDeleteRule(i) {
    if (browserSheet.deleteRule) browserSheet.deleteRule(i);
    else browserSheet.removeRule(i);
  }

  function browserInsertRule(i, selector) {
    if (browserSheet.insertRule) browserSheet.insertRule(`${selector} {}`, i);
    else browserSheet.addRule(selector, null, i);
  }
  const selectorList = [];

  function indexOfSelector(selector) {
    for (let i = 0; i < selectorList.length; i++) {
      if (selectorList[i] == selector) {
        return i;
      }
    }
    return -1;
  }

  function selectorStyle(selector) {
    let i = indexOfSelector(selector);
    if (i < 0) {
      // add selector
      browserInsertRule(0, selector);
      selectorList.splice(0, 0, selector);
      i = 0;
    }
    return browserRules().item(i).style;
  }

  function removeSelectorStyle(selector) {
    const i = indexOfSelector(selector);
    if (i >= 0) {
      browserDeleteRule(i);
      selectorList.splice(i, 1);
    }
  }

  return {
    selectorStyle,
    removeSelectorStyle,
    info() {
      return `${selectorList.length}:${browserRules().length}`;
    },
  };
}

exports.makeCSSManager = makeCSSManager;