为什么 mozilla 和 webkit 在 CSS3 规则前添加 -moz- 和 -webkit- ?
CSS3 规则带来了许多有趣的功能。
取 border-radius ,例子。标准说,如果你写这个规则:
div.rounded-corners {
border-radius: 5px;
}
我应该得到 5px 的边框半径。
但 mozilla 和 webkit 都没有实现这一点。但是,它们使用相同的参数和不同的名称(分别为 -moz-border-radius
和 -webkit-border-radius
)实现相同的功能。
为了满足尽可能多的浏览器,你最终会得到这样的结果:
div.rounded-corners {
border-radius: 5px;
-moz-border-radius: 5px;
-webkit-border-radius: 5px;
}
我可以看到两个明显的缺点:
- 复制粘贴代码。这有明显的风险,我不会在这里讨论。
- W3C CSS 验证器不会验证这些规则。
同时,我并没有看到任何明显的优势。
我相信 mozilla 和 webkit 背后的人比我更聪明。必须有一些充分的理由以这种方式构建事物。只是我看不到他们。
所以,我必须问你们:这是为什么?
CSS3 rules bring lots of interesting features.
Take border-radius, for example. The standard says that if you write this rule:
div.rounded-corners {
border-radius: 5px;
}
I should get a 5px border radius.
But neither mozilla nor webkit implement this. However, they implement the same thing, with the same parameters, with a different name (-moz-border-radius
and -webkit-border-radius
, respectively).
In order to satisfy as many browsers as possible, you end up with this:
div.rounded-corners {
border-radius: 5px;
-moz-border-radius: 5px;
-webkit-border-radius: 5px;
}
I can see two obvious disadvantages:
- Copy-paste code. This has obvious risks that I will not discuss here.
- The W3C CSS validator will not validate these rules.
At the same time, I don't see any obvious advantages.
I believe that the people behind mozilla and webkit are more intelligent than myself. There must be some good reasons to have things structured this way. It's just that I can't see them.
So, I must ask you people: why is this?
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-moz-border-radius
描述了 Mozilla 的语义。如果 CSS3 以不同的语义发布,那么 Mozilla 始终可以使用这些语义来实现 border-radius,并且它们不会破坏任何人的网站。同时,如果他们直接使用 border-radius ,那么如果 CSS3 以不同的语义发布,Mozilla 必须在破坏人们的网站或永远支持非标准 CSS 之间做出选择。
The
-moz-border-radius
describes Mozilla's semantics. If CSS3 gets published with different semantics, then Mozilla can always implementborder-radius
using those semantics and they won't break anyone's website.Meanwhile, if they just used
border-radius
directly, then if CSS3 gets published with different semantics, Mozilla has to choose between breaking people's sites, or forever supporting nonstandard CSS.他们这样做是因为它没有得到完全支持。这很像在测试版中使用该代码。最终他们将添加对边界半径的支持。
当你观察线性渐变时,这一点更加明显。
请注意,它们不使用相同的语法。当他们最终就标准达成一致时,双方都会添加对线性渐变的支持并使用正确的语法。
They do this because its not fully supported. It much like having that code in beta. Eventually they will add support for border-radius.
It more obvious when you look at the linear gradients.
Notice they don't use the same syntax. When they finally agree on a standard then both with add support for linear-gradient and use the correct syntax.
简单的。专有变体
-moz
和-webkit
在border-radius
被写入 CSS3 推荐之前就已存在。他们有自己的实现,但不知道这些是否符合 W3C 的最终建议。因此,他们当时也没有使用现在的官方名称,以免以后破坏事情。Simple. The proprietary variants
-moz
and-webkit
were there before theborder-radius
became written into the CSS3 recommendation. They had their own implementations but didn't know whether these would match W3C's final recommendation. Thus, they didn't use the now-official name at that point, either, so as not to break things later on.请注意,自 2010 年 9 月 14 日起,-moz 前缀已更改为从边界半径中删除。这意味着 Firefox 4 将支持不带前缀的 border-radius。
Note that as of 2010-09-14, the -moz prefix has been removed from border-radius. This means that Firefox 4 will support border-radius with no prefix.