边界块启动 | border-block-start (Logical Properties) - CSS 中文开发手册

这是一项实验技术

由于该技术的规格不稳定，请查看兼容性表以了解各种浏览器的使用情况。还请注意，随着规范的变化，实验技术的语法和行为在未来版本的浏览器中可能会发生变化。

border-block-start CSS 属性是在样式表一个单一的地方设置单独的逻辑块开始 border 属性值的速记属性。

border-block-start: 1px;
border-block-start: 2px dotted;
border-block-start: medium dashed blue;

border-block-start可用于对一个或多个的设置的值border-block-start-width，border-block-start-style和border-block-start-color。它映射的物理边界取决于元素的写入模式，方向性和文本方向。它对应于border-top，border-right，border-bottom，或border-left属性根据为定义的值writing-mode，direction和text-orientation。

相关属性是border-block-end，border-inline-start和border-inline-end，它们定义了元素的其他边界。

border-width：作为速记的每个属性：

-  [`border-top-width`](border-top-width): `medium` 
-  [`border-right-width`](border-right-width): `medium` 
-  [`border-bottom-width`](border-bottom-width): `medium` 
-  [`border-left-width`](border-left-width): `medium` 

border-style：作为速记的每个属性：

-  [`border-top-style`](border-top-style): `none` 
-  [`border-right-style`](border-right-style): `none` 
-  [`border-bottom-style`](border-bottom-style): `none` 
-  [`border-left-style`](border-left-style): `none` 

color：因浏览器而异

Applies to all elements   [Inherited](inheritance) no   Media visual   [Computed value](computed_value) as each of the properties of the shorthand:

border-width：作为速记的每个属性：

-  [`border-bottom-width`](border-bottom-width): the absolute length or `0` if [`border-bottom-style`](border-bottom-style) is `none` or `hidden` 
-  [`border-left-width`](border-left-width): the absolute length or `0` if [`border-left-style`](border-left-style) is `none` or `hidden` 
-  [`border-right-width`](border-right-width): the absolute length or `0` if [`border-right-style`](border-right-style) is `none` or `hidden` 
-  [`border-top-width`](border-top-width): the absolute length or `0` if [`border-top-style`](border-top-style) is `none` or `hidden` 

border-style：作为速记的每个属性：

-  [`border-bottom-style`](border-bottom-style): as specified
-  [`border-left-style`](border-left-style): as specified
-  [`border-right-style`](border-right-style): as specified
-  [`border-top-style`](border-top-style): as specified

color：如果该值是半透明的，则计算出的值将是rgba()相应的值。如果不是，那将是rgb()相应的一个。该transparent关键字映射到rgba(0,0,0,0)。

Animation type discrete   Canonical order the unique non-ambiguous order defined by the formal grammar  

语法

值

在border-block-start与一个或多个以下的规定，以任何顺序：

<‘border-width‘>边框的宽度。看border-width。

<‘border-style‘>边框的线条样式。看border-style。

<‘color‘>边框的颜色。看color。

形式语法

<‘border-width‘> || <‘border-style‘> || <‘color‘>where <color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>where <rgb()> = rgb( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )<rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )<hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )<hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )where <alpha-value> = <number> | <percentage><hue> = <number> | <angle>

例子

HTML 内容

<div>
  <p class="exampleText">Example text</p>
</div>

CSS 内容

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

.exampleText {
  writing-mode: vertical-rl;
  border-block-start: 5px dashed blue;
}

规范

浏览器兼容性