[mpeg-OTspec] FW: [Proposal] Improve the definition of the 'CFF ' table

[Ken Lunde]

Vladimir,

I believe that the CFF specification refers to multiple font instances  
as FontSets. While it is true that a CFF can contain up to 65,535  
FontSets, and each FontSet can include up to 64,000 (for name-keyed)  
or 65,535 (for CID-keyed) glyphs, it is useful to clarify that in the  
context of an OTF/OFF that only one FontSet can be included. The  
various tables that depend on GIDs have no way to index multiple CFF  
FontSets, thus the practical limit of one.

In any case, I agree that clarifying this limitation in the  
specification is a good thing.

-- Ken

On 2009/12/02, at 10:40, Levantovsky, Vladimir wrote:

> Dear all,
>
> A proposal to improve the definition of the CFF table was submitted  
> to the public OpenType email list (see below). I would like to ask  
> for your opinion - I believe that the proposed clarification is  
> useful and since it attempts to clarify the existing ambiguity in  
> the standard it can be done by corrigendum to the current text of  
> ISO standard.
>
> Thank you,
> Vladimir
>
>
> -----Original Message-----
> From: listmaster at indx.co.uk [mailto:listmaster at indx.co.uk] On Behalf  
> Of Manlio Perillo
> Sent: Sunday, November 29, 2009 1:21 PM
> To: multiple recipients of OpenType - sent by
> Subject: [OpenType] [Proposal] Improve the definition of the 'CFF '  
> table
>
> Message from OpenType list:
>
>
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>
> Hi.
>
> In the current Open Font Format specification, I think that the
> definition of the CFF table is not complete.
>
> The current text is:
>
> This table contains a compact representation of a PostScript Type 1,  
> or
> CIDFont and is structured according
> to Adobe Technical Note #5176: "The Compact Font Format Specification"
> [5] and Adobe Technical Note
> #5177: "Type 2 Charstring Format" [4].
> Existing TrueType fonts use a glyph index to specify and access glyphs
> within a font, e.g. to index the loca
> table and thereby access glyph data in the glyf table. This concept is
> retained in OFF PostScript fonts except
> that glyph data is accessed through the CharStrings INDEX of the CFF  
> table.
>
>
>
> I propose the following text to be added:
>
> Although CFF enables multiple font or CIDFont programs to be bundled
> together in a single file, the CFF table must consist of exactly one
> font or CIDFont (as appropriate for the associated font dictionary).
>
>
> Note that this text come from the PDF 1.7 Reference, section 5.8,  
> page 468.
>
>
> I think that other restrictions should be placed on the CFF data
> embedded in the CFF table; I have posted a message some time ago.
>
>
>
> Manlio Perillo
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