Function updateLineBackground

src/codemirror.js:920–930

(lineView)

  }

  function updateLineBackground(lineView) {
    var cls = lineView.bgClass ? lineView.bgClass + " " + (lineView.line.bgClass || "") : lineView.line.bgClass;
    if (cls) cls += " CodeMirror-linebackground";
    if (lineView.background) {
      if (cls) lineView.background.className = cls;
      else { lineView.background.parentNode.removeChild(lineView.background); lineView.background = null; }
    } else if (cls) {
      var wrap = ensureLineWrapped(lineView);
      lineView.background = wrap.insertBefore(elt("div", null, cls), wrap.firstChild);
    }
  }

  // Wrapper around buildLineContent which will reuse the structure
  // in display.externalMeasured when possible.