css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003.html

<!DOCTYPE html>
<title>text-box-trim should only be applied on the first/last formatted line</title>
<link rel="help" href="https://drafts.csswg.org/css-inline-3/#text-box-trim">
<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#first-formatted-line">
<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
<link rel="match" href="text-box-trim-half-leading-block-box-003-ref.html">

<style>
.div-parent {
  outline: 1px solid orange;
  font: 20px/3 Ahem;
  text-box-trim: trim-both;
  text-box-edge: text;
}
span {
  border-block: solid red;
}
</style>

<!-- The SPANs here will be wrapped inside anonymous blocks. #div-parent will
     thus start with an anonymous block (for the first SPAN). When looking for a
     first formatted line, it will have to be inside this anonymous block (or it
     doesn't exist at all).

     To quote the spec:

     The first formatted line of a block container [...] that contains
     block-level content [...] is the first formatted line of its first in-flow
     block-level child. If no such line exists, it has no first formatted
     line. -->
<div class="div-parent">
  <span>    </span>
  <div>Testline1<br>Testline2<br>Testline3</div>
  <span>	</span>
</div>