为什么 display: block 和 display: flex 以不同的高度渲染相同的元素? [英] Why do display: block and display: flex render the same element with a different height?

问题描述

所以我有一个里面有一个跨度的 div.我在 div 上设置 display:block 或 display:flex，在 span 上设置小字体.令人惊讶的是，这在 div 上给出了不同的高度.参见示例.

如果我在 body 或 div 上设置较小的字体大小，则两者的高度相等.但是，如果我像示例中那样在跨度上设置较小的字体大小，则 div 会获得不同的高度.怎么来的?我能做些什么吗?

span {字体大小:0.8rem；边框:1px 红色实心；}div {边框:1px 蓝色实心；}

<div style="display:block;"><span>测试文本 1</span>

<div style="display: flex;"><span>测试文本 2</span>

解决方案

In a 块格式上下文，line-height 属性有所不同.

这是因为 line-height 为块级容器内的行内元素和行框建立了最小高度.

在块格式上下文中，span 是行内级元素，并且 line-height 适用.

在代码示例中，span 上低于 1rem 的任何字体大小都会改变 font-size，但不会改变 line-height，保持不变.这就是您在 font-size: .8rem 中看到的.div 的高度不会改变.除非字体大小超过1rem，否则它不会改变.

在 flex 格式上下文，span 是一个弹性项.弹性项目始终是块级元素(无论元素类型如何).根据 flexbox 规范，Flex 项目被屏蔽".因为没有行内元素，line-height 不适用.

此外，弹性容器的初始设置是align-items:stretch.这意味着 span 设置容器的高度.

总结，通过display:block，line-height 保持div 高度固定.使用display:flex，没有line-height干扰，div自由跟踪span的高度.

一种解决方案:在span中添加display:block，消除line-height问题.

So I have a div with a span inside. And I'm setting display:block or display:flex on the div, and a small font-size on the span. Surprisingly, this is giving different heights on the div. See the example.

If I set the smaller font-size on the body or div then the height of both is equal. But if I set the smaller font-size on the span like in the example, then the divs get different heights. How come? And can I do anything about it?

span {
  font-size: 0.8rem;
  border: 1px red solid;
}

div {
  border: 1px blue solid;
}

<div style="display: block;">
  <span>test text 1</span>
</div>

<div style="display: flex;">
  <span>test text 2</span>
</div>

解决方案

In a block formatting context, the line-height property makes a difference.

This is because line-height establishes the minimum height for inline-level elements and line boxes inside block-level containers.

In a block formatting context a span is an inline-level element and line-height applies.

In the code sample, any font size on the span below 1rem will change the font-size, but not the line-height, which remains fixed. That's what you're seeing with font-size: .8rem. The height of the div doesn't change. And it won't change unless the font size exceeds 1rem.

In a flex formatting context, the span is a flex item. A flex item is always a block-level element (regardless of the element type). Flex items are "blockified", according to the flexbox spec. Because there are no inline-level elements, line-height doesn't apply.

Also, an initial setting of a flex container is align-items: stretch. This means that the span sets the height of the container.

In summary, with display: block the line-height keeps the div height fixed. With display: flex, there is no line-height interference and the div tracks the height of the span freely.

One solution: Add display: block to the span, which eliminates the line-height issue.

这篇关于为什么 display: block 和 display: flex 以不同的高度渲染相同的元素?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！