在CSS的font-size属性中使用分数em [英] Using fractional em's in CSS's font-size property

问题描述

说，我定义了以下CSS规则：

Say, I have the following CSS rule defined:

.className {
font-size:0.89em;
}

我的问题是， em对于浏览器实际上支持它，并且对于em的值中的小的分数变化，字体大小被不同地渲染。

My question is, how "deep" into fractions can I go while specifying 'em's for browsers actually to support it and for the font size to be rendered differently for a small fractional change in the em's value?

推荐答案

JohnB是对的。我们仍然以像素为单位渲染像素，无论我们使用的尺寸单位，ems中的小改变不会改变显示的大小：

JohnB is right. We're still rendering in pixels whatever the size unit we use, and small changes in ems will not change the displayed size:

例如，对于最初显示在高度为20px *，我们可以看到，当添加规则以使其成为它的原始高度的.99em时，没有有效的改变：

For example, for text originally displaying at a height of 20px*, we can see that there is no effective change when a rule is added to make it .99em of its original height:

20 * 0.99 = 19.8 

浏览器无法显示.8的像素，因此

The browser can't display .8 of a pixel, so (assuming it will round up) it will still display it as 20px high.

虽然看起来浏览器并不总是如预期那样四舍五入：

Though it appears that browsers do not always round off as expected:

http://meyerweb.com/eric/thoughts/ 2010/02/10 / rounding-off /

http://ejohn.org/blog/sub-pixel-problems-in-css/

*是的，我知道20px的font-size并不总是意味着它以20px显示！

*Yep, I know a font-size of 20px doesn't alway mean it's displayed at 20px!

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