RE: Updated WOFF2 spec is uploaded

Okay, check the (new-ish) updated version and let me know if this would do it for you. I think it is pretty clear why DSIG has to go – I just added a bit more explanatory text to emphasize the uncertainty of the decoder actions and certainty of getting a binary mismatch between input and output font data.

Cheers,
Vlad


From: Roderick Sheeter [mailto:rsheeter@google.com]
Sent: Monday, April 06, 2015 10:57 AM
To: Levantovsky, Vladimir
Cc: w3c-webfonts-wg (public-webfonts-wg@w3.org)
Subject: Re: Updated WOFF2 spec is uploaded

I actually like what you just wrote: We don't know ahead of time what the decoder will do. We know it is very likely to change something, therefore remove DSIG because it is very unlikely to remain valid. I agree the spec already tells you this but I think it could be more direct about it.

So ... maybe we could put something more like that in? (but in more spec-ish language :D)

If the spec more directly pointed out the reasoning (improbability of DSIG working + inability to predict decoder behavior ahead of time), I think I would understand why DSIG MUST go away on first reading. Currently I think I'd have to read it a few times if it was my first pass through the spec.

Ultimately it's fine as is; just trying to make it easier on the reader.

Cheers, Rod S

PS - just noticed a typo in: "between the editros draft used to prepare the First Public Working Draft and the editors draft used to prepare"



On Mon, Apr 6, 2015 at 7:41 AM, Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com<mailto:Vladimir.Levantovsky@monotype.com>> wrote:
Thank Rod.
Not sure I completely understand your point here – what the spec is saying is that there can be many things changed as a result of the WOFF2 encoding/decoding process besides glyf/loca conversion – table order is among them, which can be changed by either an encoder or a decoder, with the obvious effect on the table directory and table offsets. Not knowing ahead of time what the specific changes will be on the decoder side (but knowing that changes are very likely to happen) we are mandating that the DSIG to be removed by the encoder and indicate the modifying transform by setting the flag in the ‘head’ table.

Again, we are mandating DSIG removal _before_ the modifying transform is applied [knowing that it will be applied], and the rest of the language in that paragraph is the justification for it – I am not sure what else can be said to make it more explicit. If you have any specific language to suggest, please do.

Thank you,
Vlad


From: Roderick Sheeter [mailto:rsheeter@google.com<mailto:rsheeter@google.com>]
Sent: Monday, April 06, 2015 10:30 AM
To: Levantovsky, Vladimir
Cc: w3c-webfonts-wg (public-webfonts-wg@w3.org<mailto:public-webfonts-wg@w3.org>)
Subject: Re: Updated WOFF2 spec is uploaded

Small comment, it (diff<http://email.monotype.com/wf/click?upn=uA1u4oo8eyOFJ-2BcXH8sLkshuSA44ALP-2F0s9AodVupvecwkqKp048x1R2FhW-2Fo-2B79lRjfnyQjetY-2F6qxELXqai13-2FsAcexzPpt5vAAmwqvDm-2F-2FJP1hHOnR4IiNxq872N-2F_1G-2FjDAr7rgTstemRC6HwN-2F5kG9-2FqEkBGAZI-2BeK4lw-2BcbZ0p1LrE4rbHBf736K4l5m-2F0u8jeO8LzIgmTj-2BmqFwrbWWhVex6X5o-2B51V8dRVyHp-2BkpAVRAVdVO4raHC5UgwtDFJcORYhraFuPclQ7kI0vUNZyJfeAT475OHH9MI3ywCYfYfAlTBbIDWhhoDmnu2dtGsmOviYk33N2prRyzBKQ-3D-3D>) says several things may change and therefore we MUST remove DSIG. If I was reading it for the first time I think I would wonder why DSIG is removed when none of those things had changed.

Presumably it is unlikely nothing would change and it keeps things simple to just kill DSIG; I wonder if we should be more explicit about this?

Rod S.

On Thu, Apr 2, 2015 at 12:29 PM, Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com<mailto:Vladimir.Levantovsky@monotype.com>> wrote:
Folks,

I have added the details about table reordering and how changes in table order and their corresponding offsets affect DSIG table (to justify its removal for CFF fonts), and fixed a couple of typos along the way.
The new version is uploaded for your reviewing pleasure!
http://dev.w3.org/webfonts/WOFF2/spec/<http://email.monotype.com/wf/click?upn=uA1u4oo8eyOFJ-2BcXH8sLkkZYEmDWlVONg6AVPNmy5M4Wk06JKOopu3DF5Gd6MVmc_1G-2FjDAr7rgTstemRC6HwN-2F5kG9-2FqEkBGAZI-2BeK4lw-2BcbZ0p1LrE4rbHBf736K4l5F0HnLCjtRWW8Pww6ff63WiC-2FA4gQ2g4jcTqkeiysmu8dxpyOcURR0pEkCxKdj8PJmzUiaJPe27Ia3qLGMLs9hpj7sSNMSz-2FD-2BuIUFLXZrV3HyTmYDTy96ca1F4w3vl6-2BwoRkmg9S0lhIAJeRMtkJdQ-3D-3D>

Cheers,
Vlad