[thelist] Re: other CSS2 question

Matt Patterson ltu97mp at reading.ac.uk
Tue May 22 06:41:15 CDT 2001

On 22/5/01 at 6:29 am, web at master.gen.in.us (deke ) wrote:

> Line height and leading are *not* the same thing. In 
> this example, 18 points is the line-height, and the 
> leading is 6 points.

You're absolutely right, which is why Quark chose to call line-height (or
line-feed from photo-typesetting, or interlinear space (baseline-to-baseline) if
you're in my department) leading. Typographic terminology is hacked together: it
still hasn't quite recovered from the switch away from bits of metal. If you
think that leading is odd, you should read about the history of the point, which
has had many different values in different places. It was only standardised by
Adobe, who made it different to everyone else's and didn't tell anyone...


Anyway, points in screen typography are kind of an odd concept. Use relative
units instead.

<tip>With relative units and line heights you may find that specifying a
line-height in ems does something very strange indeed. The font-size of an
element specified in ems is derived relative to its parent, so a font-size of
1.2em equates to 12pt when the parent's font-size is 10pt. But, the size of all
other lengths in ems is derived from its own font-size. So, a line-height of 2em
in an element with a font-size of 1.2em is actually 2x1.2, or 2.4 times the
original size (10pt -> 24pt) rather than 2x (10pt -> 20pt). 

Are you confused yet? I am. However, you can specify line-height with just a
numeral, which has the exact same effect as specifying in ems, but doesn't have
the attendant confusion of thinking that the unit is relative to something it

If you want a line-height of 1.2em (compared to a para's parent) when it has a
font-size of 1.2em, i.e. you want the line 'set solid' where the font-size and
line-height are the same font: 1.2em/1 looks a lot more sensible than font:
1.2em/1em, IMHO. Since I started doing this i've stopped wondering why my
headings (font-size: 2.5em;) with a line-height of 2.5em (thinks - 2.5em = 2.5em
= set solid) have huge gaps between lines... (thinks - 2.5em/2.5 = big gaps
between lines). Well, it works for me anyway...</tip>

Matt Patterson:
   Reading University
   Department of Typography & Graphic Communication

   ltu97mp at reading.ac.uk

   'Yes,' said Eeyore. 'However,' he said, brightening up a little, 
'we haven't had an Earthquake lately.'

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