我试图理解在 CSS/SASS 中创建一个坚实的基线网格背后的数学。
到目前为止，我可以将文本设置为给定页面的网格，但是一旦标题改变它的长度并换行，所有后续元素都将脱离网格。
使用这个简单的 HTML 代码：
<h1>A big greyish rounded bulk, the size, perhaps, of a bear, was</h1>
<p>A big greyish rounded bulk, the size, perhaps, of a bear, was rising slowly and painfully out of the cylinder. As it bulged up and caught the light, it glistened like wet leather.</p>
<p>Two large dark-coloured eyes were regarding me steadfastly. The mass that framed them, the head of the thing, was rounded, and had, one might say, a face. There was a mouth under the eyes, the lipless brim of which quivered and panted, and dropped saliva. The whole creature heaved and pulsated convulsively. A lank tentacular appendage gripped the edge of the cylinder, another swayed in the air.</p>
连同这个 SASS 代码：
@import url("http://fonts.googleapis.com/css?family=Open+Sans:400,600");
// These are the basic values to set up a baseline & vertical rhythm
$font-size: 16px;
$line-height: 24px;
$rhythm-unit: $line-height;
html {
background-image: url(http://basehold.it/i/24);
font-family: "Open Sans";
// Converting the font size to em
font-size: ($font-size / 16px) * 1em;
// Converting the line height to a unitless number
line-height: $line-height / $font-size;
}
// Vertical rhythm & single margin direction
h1,
p {
margin-top: 0;
margin-bottom: $rhythm-unit;
}
h1 {
// Arbitrary values that look good
font-size: 3.375em;
line-height: 1.3;
// To now restore the baseline grid, we need to apply
// a margin bottom value that accomodates for font size
// and line height.
//
// Font size in px: 3.375 * $font-size = 54px
// The next multiple of our $rhythm-unit is 56. That
// means 2px need to be shifted.
// 2px in em: 2 / 54px = 0.03703703704;
margin-bottom: 0.03703703704em;
// Now that we have accomodated for font size, we need
// to do the same with line height.
// Line height in px: 1.3 * 54px = 70.2px
// The next multiple of our $rhythm-unit is 72. That
// means 1.8px need to be shifted.
// 1.8px in em: 1.8 / 54px = 0.03333333333;
margin-bottom: 0.03703703704em + 0.03333333333em;
}
如您所见，我对它进行了大量评论，希望它更容易理解Live Example。
要查看所描述的行为，只需更改 的长度<h1>并查看以下段落会发生什么：
好的
不好
在这个例子中，效果可能很小，但对于较长的文本，它开始变得越来越强烈。
我真的不明白为什么它既适用于多行标题，也适用于单行标题。但更重要的是：是否可以按照我的要求设置基线网格：
- em 中所有与文本相关的测量值
font-size&line-height需要自由设置，不遵循一些倍数之类的line-height必须是无单位的- 我不知道标题或段落将换行多少行。