Re: Padding is not zero
- From: "Jukka K. Korpela" <jkorpela@xxxxxxxxx>
- Date: Sat, 8 Nov 2008 15:04:29 +0200
Bergamot wrote:
Inside the borders, that extra space above and
below the text is part of the default line-height - space reserved for
character ascenders (e.g. Ñ) and descenders (y).
That's probably a helpful informal description, but it's not technically quite correct.
Consider an element like <div>N</div> with border: solid 1px and with padding not set (or, for definiteness, padding explicitly set to 0). A naive assumption might be that the border touches "N" both at the top and at the bottom. But as you note, it turns out that this would be pragmatically all wrong.
But even if you consider <div>Ñy</div>, you probably see (depending on font etc.) that there is still some space above the tilde and below the descender of "y".
Next, if you set line-height: 1 (making line height equal to the size of the font, i.e. the nominal height of the font), you will see variation: there might still be spacing, or the tilde or the descender might cross the border. This is simply a matter of font design.
There is fairly popular belief saying that font size is the overall height of the font, including ascenders and descenders and diacritic marks. It is second-best approximation to truth in this matter and surely much better than most of what we see written about font size. But it really cannot be the whole truth. A simple proof is that by character code standards, diacritic marks can be stacked with no pre-set limitation, and apparently you go out of bounds at _some_ point.
The truth is that font size is a property assigned to the font by the font designer, normally expected to provide sufficient height for all characters including the fancy stuff, but the designer may design otherwise. One can also say that a font designer works inside a square, the em square, and designs glyphs inside it but not necessary utilizing the full height (and hardly ever the full width, for Latin letters at least) and, on the other hand, feeling free to cross the limits occasionally when he decides so. A typical example is the letter Å, A with a ring above, occurring in Scandinavian languages. Due to the nature of the ring, the letter very often extends beyond the "upper limit" of the font - and there might even be another diacritic, like the acute, above the circle, in some languages.
When you have set line-height: 1 (which I mention for a frame of reference only - it is almost always too small, but sometimes suitable when you really know and understand your text and context and their stability) and padding: 0, then there is no space between a border and the font height, though of course individual letters almost always consume less than the full height of the font.
And of course, in a more common situation, there are different types of spacing between, say, your letter "a" and the bottom and top border of the box where it resides: spacing cause by the fact that "a" is not as tall as the height of the font; the leading, i.e. spacing caused by line-height being larger than 1 as it usually is and should be; and padding, if set to a nonzero value.
--
Yucca, http://www.cs.tut.fi/~jkorpela/
.
- References:
- Padding is not zero
- From: rodeored
- Re: Padding is not zero
- From: Johannes Koch
- Re: Padding is not zero
- From: rodeored
- Re: Padding is not zero
- From: Bergamot
- Padding is not zero
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