Re: [ft] iOS 7 system font Helvetica Neue horribly mis-hinted with FreeType 2.5.3

[Louis Semprini]

> Date: Thu, 14 Aug 2014 19:59:09 +0200
> To: address@hidden
> CC: address@hidden
> Subject: Re: [ft] iOS 7 system font Helvetica Neue horribly mis-hinted with FreeType 2.5.3
> From: address@hidden
>
>
> > So the conclusion so far is that FreeType may have a bug that shows
> > up with the Apple iOS system font when
> > TT_CONFIG_OPTION_SUBPIXEL_HINTING is not defined, but that
> > TT_CONFIG_OPTION_SUBPIXEL_HINTING is a workaround for now.
>
> I'm not sure that it counts as a bug. To really check that, it would
> be necessary to display the font on a Windows 98 box that don't have
> ClearType.
>
> > Werner, can you comment more about the description of that option as
> > "experimental?"
>
> `Experimental' means that the code has some rough edges (in
> particular, it doesn't behave well for all fonts, and sometimes
> produces results far inferior to Windows ClearType), and that it is
> quite slow. Its main author, Infinality, currently has no time to
> work on it, and I have no time either.
>
> > Should we be wary of using TT_CONFIG_OPTION_SUBPIXEL_HINTING in
> > production code?
>
> Well, the worst issue you can experience is bad good hinting...
>
> > If so, any ideas about how to fix the font in the
> > non-TT_CONFIG_OPTION_SUBPIXEL_HINTING code base?
>
> As mentioned above, displaying the font on Windows 98 can decide that
> (or maybe an environment like a font editor that uses the proper, old
> Windows libraries). It might also help to display the font on an old
> Mac running an OS version before OS X.

Unfortunately I don't have any access to Windows 98 or Macs with <OSX, or any font editors except FontForge, which presumably does not use any Windows libraries at all.  Does anyone on this mailing list have one of these?  You can try to download and use the following test .ttf font at 39 pixel size:  http://s000.tinyupload.com/index.php?file_id=45029700711604489984 and see if it is distorted like the attachment in my original post.

More generally though, while it has some diagnostic value, I am not sure the 98/Mac test is key to the issue at hand....I am quite sure that large numbers of iOS developers who write their apps using OpenGL and FreeType will encounter this problem, because of course the first font one is likely to try is the system font so that one's app fits in visually with the rest of iOS world.  I haven't tried other iOS fonts but I suspect the problem is not just limited to the system font either.

So, regardless of the Windows 98 results, it seems like at the very least we need to inform folks that there are 3 possible workarounds to problems encountered when using FreeType with iOS and Mac OS fonts:

1. disable hinting by passing FT_LOAD_NO_HINTING to FT_Load_Glyph ... at a COST of no hinting

2. change from TrueType bytecode-based hinting to FreeType autohinting by passing FT_LOAD_FORCE_AUTOHINT to FT_Load_Glyph ... at a COST of possibly worse hinting

3. define TT_CONFIG_OPTION_SUBPIXEL_HINTING in ftoption.h and recompile FreeType ... at a COST of using code that is known to be slower and doesn't work with all fonts

Perhaps it would be useful to place this advice in some of the dox, since many (most) developers may not be aware of the mailing list?

I would say that since each of these three workaround options comes with a cost, it would be reasonable to figure out why the font doesn't work with TrueType bytecode hinting regardless of the results of a test with Windows 98.

Perhaps that investigation might reveal that the iOS system font is indeed truly broken, but it seems worthwhile to look into it EVEN if the font looks ok in Windows 98, since it will be such a common case for iOS developers using OpenGL and FreeType.  Perhaps you might even find a reasonable workaround to make the font work.

I understand that you have limited time and I thank you for the massive time you have already spent on this great library.