[mpeg-OTspec] Re: [OpenType] Typo in CFF2 specification?

Ken Lunde lunde at adobe.com
Tue Apr 23 14:18:18 CEST 2019 

Done → https://github.com/MicrosoftDocs/typography-issues/issues/209

> On Apr 22, 2019, at 11:18 PM, Peter Constable via OpenType <opentype-listmaster at indx.co.uk> wrote:
> 
> Message from OpenType list:
> 
> 
> I suggest that somebody leave feedback on this page
> 
> https://docs.microsoft.com/en-us/typography/opentype/spec/cff2
> 
> stating clearly what changes are required. Each feedback item left on any given page of the OT spec is recorded as an issue in the github issue tracking system for the project.
> 
> 
> Peter
> 
> -----Original Message-----
> From: listmaster at indx.co.uk <listmaster at indx.co.uk> On Behalf Of Ken Lunde via OpenType
> Sent: Thursday, April 11, 2019 1:22 PM
> To: listmaster at indx.co.uk
> Subject: Re: [mpeg-OTspec] Re: [OpenType] Typo in CFF2 specification?
> 
> Message from OpenType list:
> 
> 
> Behdad,
> 
> Right. I clicked "send" on my reply to your reply at the same time as your followup to your reply came in, hence the apparent disconnect, which was made further confusing by the lag in the mailing lists. Thank you for clarifying.
> 
> Will someone take an action to correct this in both versions of the spec?
> 
> Regards...
> 
> -- Ken
> 
>> On Apr 11, 2019, at 1:15 PM, Behdad Esfahbod <behdad at behdad.org> wrote:
>> 
>> Hi Ken,
>> 
>> As I said, you are right.  All instances of 65536 should be 65535.  Not because of the sentinel you mention.  But because the "number of items" encoded in 16bits maxes out at 65535.
>> 
>> On Thu, Apr 11, 2019 at 2:10 PM Ken Lunde lunde at adobe.com [mpeg-OTspec] <mpeg-OTspec-noreply at yahoogroups.com> wrote:
>> Behdad,
>> 
>> To clarify, would that mean that the valid GID range for Table 12 FDSelect Format 3 and Table 13 Range3 Record Format is 0 through 65535 (and not 0 through 65534)? Given that there is a sentinel CID, I would think that the usable GID range would be 0 through 65534 (65,535 glyphs), not 0 through 65535 (65,536 glyphs). To quote from the "Table 13 Range3 Record Format" section: 
>> 
>> "A sentinel GID follows the last range element and serves to delimit the last range in the array. The sentinel GID is set equal to the number of glyphs in the font. That is, its value is 1 greater than the last GID in the font." 
>> 
>> Regards... 
>> 
>> -- Ken
>> 
>>> On Apr 11, 2019, at 10:08 AM, Behdad Esfahbod via OpenType <opentype-listmaster at indx.co.uk> wrote: 
>>> 
>>> Message from OpenType list: 
>>> 
>>> 
>>>> ****** Attachments to this email message have been removed ******
>>> 
>>> I think only the second instance in this quote is wrong: 
>>> 
>>> *Note:* While FDSelect format 4 allows for more than 65536 glyphs, 
>>> other parts of the OpenType format, such as the numGlyphs field of the 'maxp'
>>> table, are still constrained to 65536 glyphs. 
>>> 
>>> 
>>> 
>>> On Thu, Apr 11, 2019 at 12:37 PM Ken Lunde via OpenType < 
>>> opentype-listmaster at indx.co.uk> wrote:
>>> 
>>>> Message from OpenType list: 
>>>> 
>>>> 
>>>> All,
>>>> 
>>>> Can someone double check to make sure that all instances of "65536" 
>>>> in the
>>>> CFF2 specification are correct? See: 
>>>> 
>>>> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fd
>>>> ocs.microsoft.com%2Fen-us%2Ftypography%2Fopentype%2Fspec%2Fcff2&amp
>>>> ;data=02%7C01%7Cpetercon%40microsoft.com%7C3b2551db2b924809b69f08d6
>>>> bebb8c0d%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6369061100618
>>>> 79769&sdata=btDoUKIwPW%2BCu8bbv8gJGP6IvAjLcQyoa5h6hOYfCGw%3D&am
>>>> p;reserved=0
>>>> 
>>>> Given that the valid GID range for CFF is 0 through 65534 (65,535 
>>>> glyphs), my understanding is that "65536" should instead be 
>>>> "65535," unless CFF2 was architected in a way that allows 65,536 glyphs.
>>>> 
>>>> Regards... 
>>>> 
>>>> -- Ken
>>>> 
>>>> 
>>>> 
>>>> 
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>>> 
>>> --
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>> 
>> 
>> 
>> 
>> 
>> --
>> behdad
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