[ft-devel] Fwd: Possible FontForge (and FreeType) OTF issues

[Richard COOK]

FYI, forwarding the exchange below in case anyone wants to follow up.

Begin forwarded message:

> From: Ken Lunde
> Date: March 21, 2011 9:58:37 AM PDT
> To: Richard Cook, Williams George
> Cc: Wenlin Institute Tom Bishop, James Cloos, Werner Lemberg
> Subject: Re: Possible FontForge (and FreeType) OTF issues
> 
> Richard (and George),
> 
> To back up my recommendation that the limit on the number of hint 
> dictionaries (aka subfonts) should be increased to 256, please see the 
> following on page 37 of the CIDFont and CMap Specification (Adobe Tech Note 
> #5014):
> 
>> The value for FDBytes determines how many bytes are used as an index into 
>> the FDArray and, hence, the range of font dictionaries that can be 
>> referenced. For example, With an FDBytes value of 1, a CIDFont's FDArray can 
>> have up to 256 referenced font dictionaries (numbered 0 to 255).
> 
> It is the FDArray that holds the hint dictionaries, so this is key.
> 
> Regards...
> 
> -- Ken
> 
> On Mar 21, 2011, at 9:20 AM, Richard COOK wrote:
> 
>> On Mar 21, 2011, at 7:57 AM, Ken Lunde wrote:
>> 
>>> George,
>>> 
>>> I am not a FontForge user (mainly because we have our own font development 
>>> tools, many of which are in AFDKO), but I received a report from Richard 
>>> Cook that it is silently failing to recognize the 'cmap' table for some 
>>> OpenType fonts, specifically when the number of mappings seems to be above 
>>> a certain threshold. Based on the fonts that work, meaning that the 'cmap' 
>>> table is recognized and used, the threshold may be 16K, which is one of 
>>> those magic numbers when setting limits. We have OpenType fonts which 
>>> include more than 20K mappings, and even four that have over 30K mappings.
>>> 
>>> If you have access to any of our CS5 applications, the following OpenType 
>>> fonts have over 30K mappings in each of their UTF-32 and BMP-only UTF-16 
>>> 'cmap' subtables:
>>> 
>>> AdobeHeitiStd-Regular.otf
>>> AdobeSongStd-Light.otf
>>> AdobeFangsongStd-Regular.otf
>>> AdobeKaitiStd-Regular.otf
>>> 
>>> The fonts may not install by default, but should be on one of the product 
>>> DVDs as additional fonts.
>>> 
>>> Regards...
>>> 
>>> -- Ken
>>> 
>> 
>> hi George,
>> 
>> There's another OTF issue too. Last December on the FreeType dev list 
>> address@hidden we (Tom) reported an issue with CFF_MAX_CID_FONTS being set 
>> arbitrarily low to 32, which Werner Lemberg kindly bumped up to 64 in git.
>> 
>>> #define CFF_MAX_CID_FONTS  64
>> 
>> FontForge itself seems to have a built-in max of 42 CID sub-fonts: the 
>> pull-down menu under CID displays at most 42 (in builds of 20090224 and 
>> 20100501; not sure about the current source, since I'm still trying to get 
>> it to build on Mac OS X 10.6.6).
>> 
>> Anyway, maybe FontForge should match FreeType's CFF_MAX_CID_FONTS. 
>> 
>> But, Ken just suggested the CFF_MAX_CID_FONTS might really like to be 
>> something like 256. 
>> 
>> I think James Cloos on the FT list said that CFF_MAX_CID_FONTS simply 
>> determined the size of an array of pointers, and that it was no big deal to 
>> increase it to 64. So maybe 256 would also be no problem for FT either.
>> 
>> -Richard
>>