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CSS-背景附件 | background-attachment

日期：2018-09-11点击：578收藏

如果指定了 background-image ，那么 background-attachment 决定背景是在视口中固定的还是随包含它的区块滚动的。

/* Keyword values */
background-attachment: scroll;
background-attachment: fixed;
background-attachment: local;

/* Global values */
background-attachment: inherit;
background-attachment: initial;
background-attachment: unset;

初始值	scroll
适用元素	all elements. It also applies to ::first-letter and ::first-line.
是否是继承属性	no
适用媒体	visual
计算值	as specified
Animation type	discrete
正规顺序	the unique non-ambiguous order defined by the formal grammar

语法

background-attachment属性被指定为下面列表中的一个关键字值。

值

fixed——此关键字表示背景相对于视口固定。即使一个元素拥有滚动机制，背景也不会随着元素的内容滚动。

local——此关键字表示背景相对于元素的内容固定。如果一个元素拥有滚动机制，背景将会随着元素的内容滚动，并且背景的绘制区域和定位区域是相对于可滚动的区域而不是包含他们的边框。

scroll——此关键字表示背景相对于元素本身固定，而不是随着它的内容滚动（对元素边框是有效的）。

正式语法

<attachment>#where 
<attachment> = scroll | fixed | local

示例

简单例子

HTML

<p>
  There were doors all round the hall, but they were all locked; and when
  Alice had been all the way down one side and up the other, trying every
  door, she walked sadly down the middle, wondering how she was ever to
  get out again.
</p>

CSS

p {
  background-image: url("https://mdn.mozillademos.org/files/12057/starsolid.gif");
  background-attachment: fixed;
}

结果

多背景图支持

此属性支持多张背景图片。你可以用逗号分隔来为每一张背景图片指定不同的<attachment>。每一张背景图片顺序对应相应的attachment 类型。

HTML

<p>
  There were doors all round the hall, but they were all locked; and when
  Alice had been all the way down one side and up the other, trying every
  door, she walked sadly down the middle, wondering how she was ever to
  get out again.

  Suddenly she came upon a little three-legged table, all made of solid
  glass; there was nothing on it except a tiny golden key, and Alice's
  first thought was that it might belong to one of the doors of the hall;
  but, alas! either the locks were too large, or the key was too small,
  but at any rate it would not open any of them. However, on the second
  time round, she came upon a low curtain she had not noticed before, and
  behind it was a little door about fifteen inches high: she tried the
  little golden key in the lock, and to her great delight it fitted!
</p>

CSS

p {
  background-image: url("https://mdn.mozillademos.org/files/12057/starsolid.gif"),
      url("https://mdn.mozillademos.org/files/12059/startransparent.gif");
  background-attachment: fixed, scroll;
  background-repeat: no-repeat, repeat-y;
}

结果

规范

Specification	Status	Comment
CSS Backgrounds and Borders Module Level 3The definition of 'background-attachment' in that specification.	Candidate Recommendation	The shorthand property has been extended to support multiple backgrounds and the local value.
CSS Level 2 (Revision 1)The definition of 'background-attachment' in that specification.	Recommendation	No significant change.
CSS Level 1The definition of 'background-attachment' in that specification.	Recommendation	No significant change.