[mpeg-OTspec] AHG on Font Format Kick-off

[Ken Lunde]

Vladimir,

I am very glad to see that WG11 is pushing us toward a standard.

With that said, the highest priority for the AHG, in my opinion, is to determine whether Apple's "Spliced Font Format" is suitable as the basis for CFS. Apple confirmed that they are open to this, and they are also open to adding support for any additional elements or attributes, as long as they are considered optional. (The vast majority of elements and attributes are optional, so I don't anticipate any issues.)

To help with this effort, please reference/re-read my 01/15/2010 email to the AHG that summarized Apple's Spliced Font Format.

Secondly, I once brought up the issue of nesting in the context of CFS, and stated that it should not be allowed due to recursion and complexity issues. However, I now believe that this should be allowed in a specific context, because I believe that we can now distinguish CFS objects that serve as composite fonts versus as fallback fonts. Let me explain.

CFS objects can serve two main purposes or functions, specifically as composite fonts or as fallback fonts. I started going into this distinction in my 01/08/2010 post to the mailing list. Specifically, a CFS object functioning as a composite font requires a unique name, meaning a name that is unique from any installed font, and unique from any other CFS object that is functioning as a composite font. However, a CFS object that functions as a fallback font takes on the name of an existing font, which may be a standard font or potentially a CFS object that functions as a composite font. This means that CFS-savvy OSes and applications need to be prepared to deal with a CFS object and an installed font with the same name, and to prioritize the CFS object for obvious reasons.

If you consider how fallback fonts work today, they take on the name of an existing font resource, and describe composite font-like behavior, such as referencing other font resources to provide glyphs for characters that are not supported by the parent font resource.

Getting back to the nesting of CFS objects, I now believe that this can be allowed in CFS objects as long as what is being nested is a CFS object that is functioning as a composite font. Furthermore, I propose that the nesting depth should be one, meaning a top-level CFS object that functions as a fallback font can reference one or more CFS objects that function as composite fonts, but that those "nested" CFS objects that function as composite fonts cannot reference any CFS objects themselves.

Regards...

-- Ken

On 2010/01/28, at 12:39, Levantovsky, Vladimir wrote:

> 
> Dear AHG,
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> 
> First of all, I’d like to welcome many new members who have recently joined the group – just for the past couple of weeks our group grew stronger by 20+ members.
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> At this time, the mandate for the AHG has been extended with new work items – to produce the report summarizing the results of the exploration activities and to propose and develop a timeline for WG11 to achieve stated goals of CFS standardization.
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> The timeline should include the following steps that are part of the ISO standards development process:
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> -        Finalization of complete list of requirements for Composite Font Standard – these should include any and all features that we believe should be part of the CFS (expected to be finished by the next WG11 meeting in April 2010);
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> -        Creation and publication of the Call for Proposals for either existing or developing technical solutions that would address indentified list of requirements.
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> -        Review and analysis of responses to the Call for Proposal, and publication of a working draft specification;
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> -        Creation of the Committee Draft (Proposed Draft Amendment if applicable);
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> -        Final Committee Draft ;
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> -        Final Draft International Standard.
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> As part of the requirements work, I suggest that we should identify and document both features that are already supported by known / existing technical solutions (such as features proposed by Adobe), as well as features / capabilities implemented in Apple’s Spliced Font format and other technologies.
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> We should also review and discuss the text of the draft corrigendum for ISO OFF standard that was prepared at the WG11 meeting last week. If there are any changes or corrections that need to be made – we should review them and bring to the attention of the respective National Bodies to be included as part of the ballot comments. I have uploaded the draft to the AHG files.
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> Thank you,
> 
> Vladimir
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