Re: [ft-devel] ttfautohint / Oxygen / infinality

[vern adams]

Many thanks for this Erik,

You seem to have recreated the glitchy rendering that earlier versions of 
ttfautohint created on iOS and when adobe apps converted ttfautohinted fonts to 
outlines. That's very interesting i think, as it probably points to something 
important still going on.

First though i think we should check that the issue is not with a particular 
buggy build of Oxygen; very occasionally a nightly build of an oxygen font has 
been sent to the git repo with weird extra points that could upset ttf 
instructions. I'll mail you some Oxygen fonts to test with and confirm that you 
get same rendering?

Many thanks

vernon




On 21 Apr 2012, at 03:15, Infinality wrote:

> Hi guys,
> 
> Today I tested out the TT-instructed Oxygen font from the KDE repo with my TT 
> subpixel hinting patches.  This is the result:
> http://www.infinality.net/files/oxygen-infinality-problems.png
> 
> Yikes!!!  After examining the TT instructions in the instructed version of 
> the Oxygen fonts, it looks like the way that ttfautohint is generating 
> instructions is substantially different than typical TT-instructed fonts.  
> Since my patches are attempting to do what the MS rasterizer does (at least 
> with legacy fonts), I'm curious how these render on Windows.  Unfortunately I 
> don't have a Windows system available to test that on at the moment, however 
> my guess is that it renders just fine on Windows.
> 
> I have a way to exclude certain fonts or individual glyphs within a font from 
> using the tweaks that my patches employ (i.e. render it the way Freetype TT 
> hinter does by default), but I'd rather not build up a giant hard-coded 
> exclusion list of fonts generated by ttfautohint if at all possible.  And, 
> given that the TT subpixel hinting patches may soon land into Freetype, I'd 
> like make them work nicely with other Freetype-related software.  :D   So, 
> I'd like to adapt my TT hinting patches to gracefully handle fonts that have 
> been hinted with ttfautohint.
> 
> My question is this:  Is there something unique about ttfautohint-ed fonts 
> that indicates they are already taking into account subpixel-hinting?  I know 
> there is the "ready for Cleartype" flag, but it never seems to be set in any 
> fonts I've seen (including Oxygen), even the MS ones.  Also, the Microsoft 
> Cleartype fonts seem to behave well with my patches just as they are.  They 
> are designed for Cleartype/subpixel just as the ttfautohint fonts are.  I 
> guess I'm trying to reconcile what exactly ttfautohint is doing differently 
> that causes these issues.  Can any of you provide any insight?
> 
> Thanks,
> Erik / Infinality
>