Re: SVG Text elements within glyphs

Hello Daniel,

Saturday, January 25, 2014, 11:59:33 PM, you wrote:

> Dear SVG in OpenType community,

> Interesting Spec Proposal. I know that the train has already left the
> station, still I was wondering about two questions related to possible text
> elements in the Glyph-SVG:

Firstly, bear in mind that what is being standardized for SVG Glyphs
in OpenType is the use of SVG graphics as OpenType glyph outlines. Not
the SVG 'glyph' element and related elements (collectively, "SVG
Fonts").

> - I didn't see any restrictions on text-content elements (like "text") in
> the SVG glyph description. Does this imply, that text rendering will
> possibly be a recursive process in which the software component that renders
> (SVG-) glyphs will have to perform additional text layout for the contained
> text-content elements?

In theory, yes. And this would have the expected performance hit, just
as in theory you could specify an outline with millions of points
which again, would be slow to render.

Speaking of text layout, recall that SVG supports only a single
unwrapped line of text, with no auto-wrapping; although absolute and
relative shift are allowed which can be used to produce a fixed
layout.

Thus, in practice, if someone makes a glyph which contains textual
elements, this would likely contain a very small amount (otherwise the
effect is not visible) and then only on display type likely to be used
at large sizes.

It is also worth pointing out that for SVG Glyphs in OpenType, the
glyphs are rendered using the "secure animated" security model which
means that there is no user interaction with the contents (and thus,
no opportunity to select the text being used as a fill). In turn, this
means that there is no accessibility drawback, and a performance gain,
from deigning with textual fill but then converting those textual
elements to curves. Accessibility is retained in that the text used to
set the SVG in OpenType glyphs is still there in whatever application
is laying out the text, using the accessibility features of that
application, if any (be it HTML, a wordprocessor, page layout program, etc).

> - I read the SVG Spec as making a certain commitment to a whole list of font
> formats

No, it does not (although I can see how you would think that; but
please check on the use of the words "must", "should" and "may" in
this context).

SVG 1.1 lists examples of the formats mentioned by CSS2, none of which
CSS2 requires to be supported. In terms of requirements, SVG specifies
that the SVG font format must be supported and any other format may be
supported.

In SVG2, SVG Fonts are going away so that requirement is
being dropped, and SVG2 references CSS3 Fonts rather than CSS2, which
has a different list of example formats (again, none of which are
mandatory). SVG2 mandates that WOFF must be supported. WOFF is a
wrapper used to contain 'sfnt' fonts (of which TrueType and OpenType
are the two formats in actual widespread use.

Thanks for your review and I hope this answers the questions you
raised.


-- 
Best regards,
 Chris                            mailto:chris@w3.org

Received on Monday, 27 January 2014 01:11:35 UTC