Function up

static/editor.md/lib/codemirror/lib/codemirror.js:4024–4030

(e)

    addClass(lineDiv, "CodeMirror-crosshair");

    function up(e) {
      if (e.keyCode == 18 || !e.altKey) {
        rmClass(lineDiv, "CodeMirror-crosshair");
        off(document, "keyup", up);
        off(document, "mouseover", up);
      }
    }
    on(document, "keyup", up);
    on(document, "mouseover", up);
  }