Re: A proposal for units in GTK+

[Shahms King <shahms shahms com>]

On Mon, 2003-02-03 at 14:30, Noah Levitt wrote:
> CSS seems to define an em as the font's height.
> http://www.w3.org/TR/REC-CSS1#length-units
> 
> H1 { margin: 0.5em }      /* ems, the height of the element's font */
> 
> Noah

Then that comment is wrong.  en's and em's should not be the same, but
using the "height" measure, they would be. CSS2, however defines them
as:

Relative units are:

      * em: the 'font-size' of the relevant font
      * ex: the 'x-height' of the relevant font
      * px: pixels, relative to the viewing device
Example(s):


H1 { margin: 0.5em }      /* em */
H1 { margin: 1ex }        /* ex */
P  { font-size: 12px }    /* px */

The 'em' unit is equal to the computed value of the 'font-size' property
of the element on which it is used. The exception is when 'em' occurs in
the value of the 'font-size' property itself, in which case it refers to
the font size of the parent element. It may be used for vertical or
horizontal measurement. (This unit is also sometimes called the
quad-width in typographic texts.)

The 'ex' unit is defined by the font's 'x-height'. The x-height is so
called because it is often equal to the height of the lowercase "x".
However, an 'ex' is defined even for fonts that don't contain an "x".

_________________________________

To me, this definition implies that 'ex' directly relates to font height
and 'em' (more) directly relates to font width.

my $0.02

-- 
Shahms King <shahms shahms com>