Function onKeyDown

src/codemirror.js:4186–4205

(e)

  var lastStoppedKey = null;
  function onKeyDown(e) {
    var cm = this;
    cm.curOp.focus = activeElt();
    if (signalDOMEvent(cm, e)) return;
    // IE does strange things with escape.
    if (ie && ie_version < 11 && e.keyCode == 27) e.returnValue = false;
    var code = e.keyCode;
    cm.display.shift = code == 16 || e.shiftKey;
    var handled = handleKeyBinding(cm, e);
    if (presto) {
      lastStoppedKey = handled ? code : null;
      // Opera has no cut event... we try to at least catch the key combo
      if (!handled && code == 88 && !hasCopyEvent && (mac ? e.metaKey : e.ctrlKey))
        cm.replaceSelection("", null, "cut");
    }

    // Turn mouse into crosshair when Alt is held on Mac.
    if (code == 18 && !/\bCodeMirror-crosshair\b/.test(cm.display.lineDiv.className))
      showCrossHair(cm);
  }

  function showCrossHair(cm) {
    var lineDiv = cm.display.lineDiv;