[mpeg-OTspec] comments re SVG table in the OFF draft

[Jonathan Kew]

On 11/3/14 15:53, Levantovsky, Vladimir wrote:
> Thank you Jonathan,
>
> What you're proposing makes perfect sense but I also wonder if, in
> light of the changes proposed by Cameron for UA style sheet we should
> also extend the language of your proposed second sentence to say that
> "The use of SVG text elements _and/or SVG foreign objects_ within
> these glyph descriptions is prohibited."

Sounds good to me. We should certainly mention the foreignObject 
prohibition somewhere, and this seems a logical place to include it.

JK

>
> Best regards, Vladimir
>
>
>> -----Original Message----- From: mpeg-OTspec at yahoogroups.com
>> [mailto:mpeg-OTspec at yahoogroups.com] On Behalf Of Jonathan Kew
>> Sent: Tuesday, March 11, 2014 11:37 AM To: OTspec
>> <mpeg-OTspec at yahoogroups.com> Subject: [mpeg-OTspec] comments re
>> SVG table in the OFF draft
>>
>> A few comments on the current 3rd ed. working draft:
>>
>> - - - - -
>>
>> First, the opening sentence in section "5.5.1 SVG - The SVG
>> (Scalable Vector Graphics) table" seems problematic to me:
>>
>> <quote> This table contains SVG [16] descriptions for some or all
>> of the glyphs in the font, the use of SVG text elements for outline
>> fill is prohibited. </quote>
>>
>> This would read much better if split into two sentences, not joined
>> by a comma. And second, shouldn't the use of SVG text elements be
>> prohibited for -any- purpose within the glyphs (not only for
>> outline fill)? If we want to avoid glyph descriptions referring to
>> external fonts, we can't allow SVG text elements to be stroked or
>> used as clipping paths, for example.
>>
>> So I suggest changing this to something like:
>>
>> <proposed> This table contains SVG [16] descriptions for some or
>> all of the glyphs in the font. The use of SVG text elements within
>> these glyph descriptions is prohibited. </proposed>
>>
>> - - - - -
>>
>> Further, we should specify what happens if an SVG text element is
>> found (despite being prohibited): is that element ignored, but the
>> remainder of the glyph rendered normally, or do we consider the
>> entire glyph description invalid, and ignore it, falling back to a
>> TrueType or CFF glyph?
>>
>> Offhand, I'm inclined to favor the former: require the renderer to
>> ignore the SVG text element(s), but proceed to do its best to
>> render any other content. So I'd suggest an additional sentence
>> such as:
>>
>> <proposed> If any SVG text element is encountered within a glyph
>> description, it MUST be ignored by the renderer. </proposed>
>>
>> - - - - -
>>
>> Finally, forwarding a comment from Cameron McCormack regarding the
>> description of "Glyph Rendering":
>>
>> <forwarded> I don't think that added rule in the UA style sheet,
>>
>> :root { font-size: 0 !important; }
>>
>> is sufficient, since font-size can be specified on an element in
>> the document.  The importance of the rule doesn't inherit.
>>
>> Instead, I think this would work:
>>
>> @namespace svg url(http://www.w3.org/2000/svg);
>>
>> svg|text, svg|foreignObject { display: none !important; }
>>
>> Using |display: none| seems like a clearer description of what's
>> going on, and should have the same effect as |font-size: 0|.
>> </forwarded>
>>
>> This seems like a good change we should make to the draft.
>>
>>
>> JK
>>
>>
>> ------------------------------------