Re: [Devel] Fonts with glyphs containing zero contours

[Antoine Leca]

Hi Keith,

Keith Packard wrote on Thrusday:
> 
> Now I'm having trouble with msmincho.ttf (http://keithp.com/~keithp/fonts/
> msmincho.ttf).   This font has no fixed sizes; face->num_sbit_strikes is 0
> so there really aren't any bitmaps associated with the font.
> 
> Loading glyphs from this font, I discover that out of 12481 glyphs,
> I find some 4888 glyphs (other than space/nbsp) that load as outline
> glyphs, but with zero contours.  Most of these "broken" glyphs occur in
> the Unicode CJK space.

I can really guess that this is (loosely) trick to gain space.
I believe the missing glyphs are the Unicode codepoints that does not
exist in Shift-JIS encoding. Since they do not exist in the original
encoding, the missing glyphs are not used (except by special programs),
and users do not complain; on the other way, the fact there is only
one big range does speed both loading time and the time to search for
a glyphId given a charId.

There were a discussion back around August last year, with Brian Stell
raising the first question (so a good key to search the archives), about
a very similar problem he had with Netscape (at loading, he needed to
create a big dictionnary, and were forced to traverse the whole cmaps
to detect all the _possible_ use of fonts, which result of being
impossible if you have quite a number of fonts...)


> Scanning the 9364 .ttf font files I found on my machine, I note that many
> of them have glyphs of this form.  I presume there are additional Unicode
> glyphs which are supposed to be blank, but a hundred of these fonts
> have more than 100 "broken" glyphs.

Sorry I do not have a good Internet link, so I am not able to help more
by giving the references right now, but I am sure you could make profit
of visitin these discussions; the net result, as I can remember, is
that there is a very small number of fonts for which this is a problem,
but these fonts might be quite common.
An exception at processing time, as opposed as prevention to deal with
all cases as soon as possible, might be a way to investigate. But I am
not sufficientlky involved in the uses to be able to qualify it more
exactly.


Antoine