父元素transform影响子元素fixed
问题
开发时发现当父元素有 transform 时,子元素position:fixed
效果同positon:absolute
参考
https://www.w3.org/TR/css-transforms-1/#containing-block-for-all-descendants
For elements whose layout is governed by the CSS box model, any value other than none for the transform property also causes the element to establish a containing block for all descendants. Its padding box will be used to layout for all of its absolute-position descendants, fixed-position descendants, and descendant fixed background attachments.
https://www.zhangxinxu.com/wordpress/2015/05/css3-transform-affect/