CSS transition auto width

Question

I have an element whose width I\'d like to animate when its contents change. It has width: auto, and this never changes. I\'ve seen this trick, but that\'s for

Answer 1

As I commented, one can't animate auto (yet), so either use the max-width/max-height trick, or, if you need it to be more exact, set the width using a script.

With the max-width/max-height trick, give it a value big enough to accommodate the widest.

Stack snippet

.myspan {
  display: inline-block;
  font-size: 30px;
  background-color: #ffffd;
  vertical-align: bottom;
}
.myspan::after {
  content: " \00a0\f12a ";
  font-family: ionicons;
  font-size: 80%;  
  display: inline-block;
  max-width: 0;
  transition: max-width .6s;
  vertical-align: bottom;
  overflow: hidden;
}
.myspan:hover::after {
  max-width: 80px;
  transition: max-width 1s;
}

<link href="https://code.ionicframework.com/ionicons/2.0.1/css/ionicons.min.css" rel="stylesheet" />

<span class="myspan">Hello!</span>