css - 为什么浏览器不呈现由 "white-space: pre"元素内的尾随换行符引起的换行符？

Question

这两个 div 渲染相同。为什么呈现前导换行符而不是尾随换行符(在第二个 div 中)？我读了Line Breaking and Word Boundaries CSS3 规范中的部分，但它没有解释这种行为。

.pre {
  white-space: pre;
  border: 1px solid red;
  margin-bottom: 10px;
}

<div class="pre">
hello
world</div>

<div class="pre">
hello
world
</div>

Answer 1

为什么？好吧，显然是为了避免兼容性问题。

W3C说:

In order to avoid problems with SGML line break rules and inconsistencies among extant implementations, authors should not rely on user agents to render white space immediately after a start tag or immediately before an end tag.

and also :

Note that the white space processing rules have already removed any tabs and spaces after the segment break before these checks [on the value of the white-space property] take place.

现在尚不清楚如果允许浏览器在结束标记之前保留空格，那么哪些会引入不一致，但你知道了。