[MPlayer-dev-eng] Font hinting in libass

[Vladimir Mosgalin]

Hi Uoti Urpala!

 On 2007.04.19 at 02:30:27 +0300, Uoti Urpala wrote next:

> Why? Wouldn't that just mean some of the hinting options fall back to
> others?

Well, results will be different at least when regular hinting or
autohinting aren't used.

> At least current Debian ships FreeType with the bytecode interpreter
> fully enabled by default.

Well that's nice..

> No, I meant those fonts produce bad results when "native" hinting is
> enabled. I do not have a reason to believe things would be any different
> if I'd extract them and then use a different load method.

But then this bug will always be present on windows and os x systems,
and the font should be considering quite broken. "Fixing" this by
disable native hinting doesn't seem like a good idea.

> Try the font I posted earlier. The most easily verifiable problem I
> noticed is that with "native" hinting 'i' and 'j' are too tall compared
> to other small letters. If you try rendering a string like "ririri" it
> should be pretty clear.

True. It has many problems. However, disabling hinting won't cure this.
And while it solves problems with some characters, it introduces problem
with few others. Check out ÑÙÚÛ (tilde above Ñ looks awful without
native hinting, middle Ú looks taller than both characters around it
without native hinting).

> Why do you think it has to be a FreeType bug? Surely there are at least
> a few fonts floating around that really have incorrect hinting
> information and render badly if it's used?

Well, if windows renders these fonts slightly better than freetype with
native hinting, most likely it's freetype bug. I don't think you can
turn off native hinting in windows - there is no point in it, the idea
is absurd (well, unless you are trying to use Type1 fonts on your
desktop and want autohinting-similar effect - but who cares about Type1
on desktop).

Anyway, one can check what exactly native hinting does on this font,
with mensis (http://mensis.sourceforge.net/overview.html). I can't right
now because mensis fails to build with fontforge and my fontforge isn't
new enough to include mensis (you might have better luck - debian's
fontforge seems to be up-to-date).

-- 

Vladimir