CaretCode

Xossip CaretCode
Versión del día 27/7/2017. Echa un vistazo a la versión más reciente.
Este script no debería instalarse directamente. Es una biblioteca que utilizan otros scripts mediante la meta-directiva de inclusión // @require https://update.greasyfork.org/scripts/31785/208318/CaretCode.js
Pregunta tus dudas, ponle nota o notifica una posible infracción de las normas.
Ajuste de línea
// ==UserScript==
// @name         CaretCode
// @description  Xossip CaretCode
// ==/UserScript==
var properties = [
  'direction',  // RTL support
  'boxSizing',
  'width',  // on Chrome and IE, exclude the scrollbar, so the mirror div wraps exactly as the textarea does
  'height',
  'overflowX',
  'overflowY',  // copy the scrollbar for IE

  'borderTopWidth',
  'borderRightWidth',
  'borderBottomWidth',
  'borderLeftWidth',

  'paddingTop',
  'paddingRight',
  'paddingBottom',
  'paddingLeft',

  // https://developer.mozilla.org/en-US/docs/Web/CSS/font
  'fontStyle',
  'fontVariant',
  'fontWeight',
  'fontStretch',
  'fontSize',
  'fontSizeAdjust',
  'lineHeight',
  'fontFamily',

  'textAlign',
  'textTransform',
  'textIndent',
  'textDecoration',  // might not make a difference, but better be safe

  'letterSpacing',
  'wordSpacing'
];

function CaretCoordinates(element) {
  var self = this;

  this.element = element;

  // mirrored div
  this.div = document.createElement('div');
  // this.div.id = 'input-textarea-caret-position-mirror-div';
  element.parentNode.insertBefore(this.div, element);

  var style = this.div.style;
  this.computed = window.getComputedStyle? getComputedStyle(element) : element.currentStyle;  // currentStyle for IE < 9

  // default textarea styles
  style.whiteSpace = 'pre-wrap';
  if (element.nodeName !== 'INPUT')
    style.wordWrap = 'break-word';  // only for textarea-s

  // position off-screen
  style.position = 'absolute';  // required to return coordinates properly
  style.visibility = 'hidden';  // not 'display: none' because we want rendering

  // transfer the element's properties to the div
  properties.forEach(function (prop) {
    style[prop] = self.computed[prop];
  });

  style.overflow = 'hidden';  // for Chrome to not render a scrollbar; IE keeps overflowY = 'scroll'

  this.divText = document.createTextNode('');
  this.div.appendChild(this.divText);
  this.span = document.createElement('span');
  this.spanText = document.createTextNode('');
  this.span.appendChild(this.spanText);
  this.div.appendChild(this.span);

  function resize() {
    style.width = self.computed.width;
  }

  window.addEventListener('resize', resize);
}


CaretCoordinates.prototype.get = function(positionLeft, positionRight) {
  // calculate left offset
  this.divText.nodeValue = this.element.value.substring(0, positionLeft);

  // the second special handling for input type="text" vs textarea: spaces need to be replaced with non-breaking spaces - http://stackoverflow.com/a/13402035/1269037
  if (this.element.nodeName === 'INPUT')
    this.divText.nodeValue = this.divText.nodeValue.replace(/\s/g, "\u00a0");

  // Wrapping must be replicated *exactly*, including when a long word gets
  // onto the next line, with whitespace at the end of the line before (#7).
  // The  *only* reliable way to do that is to copy the *entire* rest of the
  // textarea's content into the <span> created at the caret position.
  // for inputs, just '.' would be enough, but why bother?
  this.spanText.nodeValue = this.element.value.substring(positionLeft) || '.';  // || because a completely empty faux span doesn't render at all

  var left = this.span.offsetLeft + parseInt(this.computed['borderLeftWidth'], 10);

  // calculate right offset
  this.divText.nodeValue = this.element.value.substring(0, positionRight);

  // the second special handling for input type="text" vs textarea: spaces need to be replaced with non-breaking spaces - http://stackoverflow.com/a/13402035/1269037
  if (this.element.nodeName === 'INPUT')
    this.divText.nodeValue = this.divText.nodeValue.replace(/\s/g, "\u00a0");

  this.spanText.nodeValue = this.element.value.substring(positionRight) || '.';  // || because a completely empty faux span doesn't render at all
  var right = this.span.offsetLeft + parseInt(this.computed['borderLeftWidth'], 10);

  // special case where right position is not be calculated correctly (full line selected)
  if (right <= left) {
    right = this.div.offsetWidth + parseInt(this.computed['borderLeftWidth'], 10);
  }

  var coordinates = {
    top: this.span.offsetTop + parseInt(this.computed['borderTopWidth'], 10),
    left: left,
    right: right
  };

  return coordinates;
};

module.exports = CaretCoordinates;