Re: ascender, descender, cap-height and x-height

Jelle Bosma wrote:
> 
> It is the type designer who decides on how large the font
> is in the EM square. There are no rules. In TrueType
> (and OpenType) you can get some measurements such
> as the Typographic ascend and descend as explained by Greg.
> These values are in the OS/2 table of the font.
> In Monotype fonts these are set to top f and bottom g
> for the font family. Whether fonts of other foundries
> contain reliable values I am not sure. Many foundries didn't
> bother much about these things until recently.

Do you also happen to know why those "many" foundries are now more
concerned about these things? I'd really like to know.

The reason I'm concerned is because the Internet has caused many
different platforms and many different document types to come into
direct contact. In the past, we had various word processing programs
like MS Word, WordPerfect, etc, and users cursed the software industry
for all of the (in)compatibility problems. These problems were
compounded by differences between the OSes (platforms).

However, now that we are using documents formats like HTML and XML
together with style sheets like CSS's on the Web, we need to standardize
font sizes. It is impossible to predict what kind of platform the user
is using, and which fonts they have available. So, CSS provides for font
substitution. You still want to have a "reasonable" font size, even when
substitution takes place.

But what exactly is "reasonable"? This is kind of subjective, but it
seems like we have some agreement that the size of a "bicameral" font
(one with both upper and lower case) is mostly dependent on the
x-height.

That is why CSS defines font-size-adjust. But for font-size-adjust to
work well, the underlying font-size must also be specified and
implemented well. Any help that www-font experts can provide is most
appreciated.

Erik

Received on Wednesday, 26 January 2000 19:54:08 UTC