margin-block-start

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

* Some parts of this feature may have varying levels of support.

CSS 属性 margin-block-start 定义了元素的逻辑块首外边距，并根据元素的书写模式、行内方向和文本朝向对应至实体外边距。

尝试一下

margin-block-start: 20px;
writing-mode: horizontal-tb;

margin-block-start: 20px;
writing-mode: vertical-rl;

margin-block-start: 20%;
writing-mode: horizontal-tb;

margin-block-start: auto;
writing-mode: vertical-lr;

<section id="default-example">
  <div id="container">
    <div class="row">One</div>
    <div class="row transition-all" id="example-element">Two</div>
    <div class="row">Three</div>
  </div>
</section>

#container {
  width: 300px;
  height: 200px;
  display: flex;
  align-content: flex-start;
  flex-direction: column;
  justify-content: flex-start;
}

.row {
  height: 33.33%;
  display: inline-block;
  border: solid #ce7777 10px;
  background-color: #2b3a55;
  color: #ffffff;
  flex-shrink: 0;
}

#example-element {
  border: solid 10px #ffbf00;
  background-color: #2b3a55;
}

语法

css
/* <length> 值 */
margin-block-start: 10px; /* 绝对长度 */
margin-block-start: 1em; /* 相对于文本尺寸 */
margin-block-start: 5%; /* 相对于最近区块容器的宽度 */

/* 关键词值 */
margin-block-start: auto;

/* 全局值 */
margin-block-start: inherit;
margin-block-start: initial;
margin-block-start: revert;
margin-block-start: revert-layer;
margin-block-start: unset;

根据 writing-mode、direction 和 text-orientation 所定义的值，此属性对应于 margin-top、margin-right、margin-bottom 或 margin-left 属性。

与此属性相关的有 margin-block-end、margin-inline-start 和 margin-inline-end 等定义元素的其他外边距的属性。

取值

margin-block-start 属性的取值与 margin-left 属性相同。

形式定义

初始值0
适用元素same as margin
是否是继承属性否
Percentagesdepends on layout model
计算值if specified as a length, the corresponding absolute length; if specified as a percentage, the specified value; otherwise, auto
动画类型a length

形式语法

margin-block-start = 
  <'margin-top'>  

<margin-top> = 
  <length-percentage>  |
  auto                 |
  <anchor-size()>      

<length-percentage> = 
  <length>      |
  <percentage>  

<anchor-size()> = 
  anchor-size( [ <anchor-name> || <anchor-size> ]? , <length-percentage>? )  

<anchor-name> = 
  <dashed-ident>  

<anchor-size> = 
  width        |
  height       |
  block        |
  inline       |
  self-block   |
  self-inline

示例

设置块首外边距

HTML

html
<div>
  <p class="exampleText">示例文本</p>
</div>

CSS

css
div {
  background-color: yellow;
  width: 120px;
  height: 120px;
}

.exampleText {
  writing-mode: vertical-lr;
  margin-block-start: 20px;
  background-color: #c8c800;
}

结果

规范

Specification
CSS Logical Properties and Values Level 1
# margin-properties

浏览器兼容性

参见