Re: OT / OFF header info

On Tue, Apr 29, 2014 at 11:09 AM, Levantovsky, Vladimir
<Vladimir.Levantovsky@monotype.com> wrote:
> Brief update:
> I've got a response from MS regarding the OT spec changes for 'head' table flag. They think it's good idea and absolutely don't mind making changes to the description of this flag. Considering that the ballot is currently open for the 3rd edition ISO text - making this change in both OT and OFF text would be relatively easy and fast.
> No additional info yet about the current use of it, but the person who may have this information did not yet reply to my email.

Wow, that was fast!  Thank you Vlad and Microsoft.  The ability to
update the documentation would go a long way to reducing confusion
down the road in interpreting the bit.

Shall we discuss and decide in the working group meeting tomorrow?
Hopefully you will have heard back by then on the current use of the
bit.

Given that we are in the process of updating the reference
implementation for the known table tags, reserved bits and always
preprocess changes, it would be great time to tackle this one as well
(if the decision is to do so).
>
> Regards,
> Vlad
>
>
> -----Original Message-----
> From: David Kuettel [mailto:kuettel@google.com]
> Sent: Monday, April 28, 2014 4:58 PM
> To: Levantovsky, Vladimir
> Cc: w3c-webfonts-wg (public-webfonts-wg@w3.org)
> Subject: Re: OT / OFF header info
>
> On Mon, Apr 28, 2014 at 1:50 PM, Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com> wrote:
>> As I see it, one important benefit of setting this bit is that it informs the recipient that the font file was modified by a compliant encoder / decoder, and that this is the reason why e.g. DSIG table may no longer be valid or is missing from the transformed font file (but was present in the original file).
>>
>> I sent the email to MS folks and will let you know what their response is.
>
> Excellent, thank you Vlad.  Really eager to hear the response, in particular if the bit was helpful to tools/programs which consumed the fonts.
>>
>> Thank you,
>> Vlad
>>
>>
>> -----Original Message-----
>> From: David Kuettel [mailto:kuettel@google.com]
>> Sent: Monday, April 28, 2014 4:46 PM
>> To: Levantovsky, Vladimir
>> Cc: w3c-webfonts-wg (public-webfonts-wg@w3.org)
>> Subject: Re: OT / OFF header info
>>
>> On Mon, Apr 28, 2014 at 1:23 PM, Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com> wrote:
>>> Hi David,
>>>
>>> One reason I brought it up is because there is an open ballot for the ISO OFF document, and we wanted to suggest certain changes to the definition of the flag this can definitely be mentioned in ballot comments. I can ask MS folks if they don't mind changing the definition for this bit to make it more generic and not tied to MTX explicitly, but my gut feeling is that this should be a simple and non-controversial change since the meaning of the bit will not be affected.
>>
>> Given the opportunity to refine the documentation and the shared heritage between MTX and WOFF 2.0, it seems worth exploring a bit further.
>>
>> When/if you were to reach out to Microsoft, it would be really interesting to know whether they found the bit helpful.  For example, does Internet Explorer (or other programs) check the bit?
>>
>> Given that Chrome does not support EOT, it seems unlikely that it would check the bit.  The bit seems more like an "FYI" type bit.
>>
>>> Thank you,
>>> Vlad
>>>
>>>
>>> -----Original Message-----
>>> From: David Kuettel [mailto:kuettel@google.com]
>>> Sent: Monday, April 28, 2014 3:57 PM
>>> To: Levantovsky, Vladimir
>>> Cc: w3c-webfonts-wg (public-webfonts-wg@w3.org)
>>> Subject: Re: OT / OFF header info
>>>
>>> Interesting.
>>>
>>> Given that the documentation for the bit, explicitly refers to MicroType (MTX) compression, would it be confusing to directly reuse the bit for WOFF 2.0?
>>>
>>> To explore further, do you think Microsoft would be open to refining the text to make it more general?
>>>
>>> From the documentation (http://www.microsoft.com/typography/otspec/head.htm):
>>>
>>> "Bit 11: Font data is 'lossless,' as a result of having been compressed and decompressed with the Agfa MicroType Express engine."
>>>
>>> On Mon, Apr 28, 2014 at 11:20 AM, Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com> wrote:
>>>> Folks,
>>>>
>>>>
>>>>
>>>> I wanted to bring to your attention (and up for discussion) the
>>>> following
>>>> consideration:
>>>>
>>>>
>>>>
>>>> The OpenType / OFF font header table
>>>> (http://www.microsoft.com/typography/otspec/head.htm) has 16-bit
>>>> flags field where bit 11 is assigned to signal if a font has been
>>>> subjected to MTX transform. I believe that the original purpose of
>>>> allocating and setting the flag was to indicate that the font has
>>>> been transformed and, although it is functionally equivalent to the
>>>> original font, its binary representation differs from the original (hence invalid or absent DSIG table, etc.).
>>>>
>>>>
>>>>
>>>> I believe that the same would be true for WOFF2 transform, so it may
>>>> be appropriate to include a reference (e.g. in section 4.4 of the
>>>> WOFF2 spec) and suggest that the decoder should have this bit 11 of
>>>> the 'head' table flags set when the font is decompressed. Doing this
>>>> would be logical (and IMO consistent with the original intent of the
>>>> OpenType spec) but I really don't know if there are any engines out
>>>> there that would pay attention to this flag. It may not make any
>>>> difference in the end but rather be one extra bit of info that someone (anyone?) might find useful.
>>>>
>>>>
>>>>
>>>> Thought?
>>>>
>>>> Thank you,
>>>>
>>>> Vlad
>>>>
>>>>

Received on Tuesday, 29 April 2014 18:29:43 UTC