File: editor/codemirror/src/util/feature_detection.js

import { elt, range, removeChildren, removeChildrenAndAdd } from "./dom.js"
import { ie, ie_version } from "./browser.js"

// Detect drag-and-drop
export let dragAndDrop = function() {
  // There is *some* kind of drag-and-drop support in IE6-8, but I
  // couldn't get it to work yet.
  if (ie && ie_version < 9) return false
  let div = elt('div')
  return "draggable" in div || "dragDrop" in div
}()

let zwspSupported
export function zeroWidthElement(measure) {
  if (zwspSupported == null) {
    let test = elt("span", "\u200b")
    removeChildrenAndAdd(measure, elt("span", [test, document.createTextNode("x")]))
    if (measure.firstChild.offsetHeight != 0)
      zwspSupported = test.offsetWidth <= 1 && test.offsetHeight > 2 && !(ie && ie_version < 8)
  }
  let node = zwspSupported ? elt("span", "\u200b") :
    elt("span", "\u00a0", null, "display: inline-block; width: 1px; margin-right: -1px")
  node.setAttribute("cm-text", "")
  return node
}

// Feature-detect IE's crummy client rect reporting for bidi text
let badBidiRects
export function hasBadBidiRects(measure) {
  if (badBidiRects != null) return badBidiRects
  let txt = removeChildrenAndAdd(measure, document.createTextNode("A\u062eA"))
  let r0 = range(txt, 0, 1).getBoundingClientRect()
  let r1 = range(txt, 1, 2).getBoundingClientRect()
  removeChildren(measure)
  if (!r0 || r0.left == r0.right) return false // Safari returns null in some cases (#2780)
  return badBidiRects = (r1.right - r0.right < 3)
}

// See if "".split is the broken IE version, if so, provide an
// alternative way to split lines.
export let splitLinesAuto = "\n\nb".split(/\n/).length != 3 ? string => {
  let pos = 0, result = [], l = string.length
  while (pos <= l) {
    let nl = string.indexOf("\n", pos)
    if (nl == -1) nl = string.length
    let line = string.slice(pos, string.charAt(nl - 1) == "\r" ? nl - 1 : nl)
    let rt = line.indexOf("\r")
    if (rt != -1) {
      result.push(line.slice(0, rt))
      pos += rt + 1
    } else {
      result.push(line)
      pos = nl + 1
    }
  }
  return result
} : string => string.split(/\r\n?|\n/)

export let hasSelection = window.getSelection ? te => {
  try { return te.selectionStart != te.selectionEnd }
  catch(e) { return false }
} : te => {
  let range
  try {range = te.ownerDocument.selection.createRange()}
  catch(e) {}
  if (!range || range.parentElement() != te) return false
  return range.compareEndPoints("StartToEnd", range) != 0
}

export let hasCopyEvent = (() => {
  let e = elt("div")
  if ("oncopy" in e) return true
  e.setAttribute("oncopy", "return;")
  return typeof e.oncopy == "function"
})()

let badZoomedRects = null
export function hasBadZoomedRects(measure) {
  if (badZoomedRects != null) return badZoomedRects
  let node = removeChildrenAndAdd(measure, elt("span", "x"))
  let normal = node.getBoundingClientRect()
  let fromRange = range(node, 0, 1).getBoundingClientRect()
  return badZoomedRects = Math.abs(normal.left - fromRange.left) > 1
}