CSS: Understanding and adjusting leading / line-he

问题:

A very similar question was asked here but the really answered sufficiently...

The CSS line-height property controls the amount of white space above the letters. Making it bigger/smaller spaces rows of text farther/closer together. But if you set the line height to the exact same value as the font-size, the text will still have white space above them.

So this DOESN'T quite work...

div { height: 80px; }
span { font-size : 80px; line-height : 80px; }
<div>
<span>Foo</span>
</div>

http://jsfiddle.net/s_d_p/yMHVs/

The degree to which the enclosed text actually matches the container height seems to differ from font to font.

So my question is two parts:

1. What are we actually adjusting when we set line-height?

2. Is there a way to remove it entirely so that letter fit precisely inside their container?

回答1:

Note that the remaining/extra space is typically a symptom of the font being used, as designated by its designer.

Thus, the 80px includes the allocated white space above and/or below. Additional white space above is typically provided to allow for accented characters, which would otherwise require the letter itself to be compressed- producing an inconsistent typeface.

See here & here for further information.

Line height refers to the total height of the typeface, inclusive of any allocated whitespace.

回答2:

i'm sure that space is reserved for some characters that need more space. like this one:

Fj╛

character "j" need more space that "F" and i'm sure again that there is other characters (like "╛") that needs some space in above and bottom. so font designer reserved this space for that characters.

jsFiddle