RE: SVG Text elements within glyphs

Hi Sairus,

I think that if the three options you mentioned were parts of the multiple-choice test the proper answer would have been "all of the above". ;-)
I think the spec needs to mention all the restrictions that are relevant for SVG glyphs in OpenType for the sake of many different audiences that will be using this spec - tool vendors, rendering implementations, etc. Simply adding font-size definition to the UA style sheet may not be sufficient since there may be some implementations that do not support the concept of user agent style sheet. And adding a new integration mode to SVG integration document is also a good idea, although I'd consider it complementary to (but not a substitute for) OT/OFF spec language - this document seems to be 'rendering-centric'.

And yes, we need to consider what other parts of SVG (such as e.g. foreignObject) may need to be trimmed for the purposes of 'SVG in OpenType' glyph description.

Thank you,
Vlad


From: Sairus Patel [mailto:sppatel@adobe.com]
Sent: Monday, February 03, 2014 6:51 PM
To: robert@ocallahan.org; Levantovsky, Vladimir
Cc: Chris Lilley; Daniel Flassig; public-svgopentype@w3.org
Subject: Re: SVG Text elements within glyphs

Vlad,

This thread has raised several concerns with allowing text elements. All these concerns can be dealt with by disallowing text elements, and that sounds good to me. (As an interesting side note, PDF's Type 3 font format explicitly allows for text object within its glyphs, and I don't see any language prohibiting self-references in that area of the spec.)

Disallowing text elements will generally not curtail the font designer artistically, since as Chris has pointed out, simple graphic paths can be used to simulate text within the SVG-in-OT glyph. If the designer wants the text-within-the-glyph to be displayed in system fonts that are typically unique to a platform, well something close to that may be able to be simulated by conditionals and graphic paths, but I would not prioritize making this kind of *non*-cross-platform effect possible.

As to how we disallow text elements, some options are:

1. Simply say so in the description of the 'SVG ' table.
2. Specify something in the UA style sheet as Rob has suggested.
3. Add a new integration mode to SVG Integration (https://svgwg.org/specs/integration), say, "OpenType glyph mode" and prohibit text elements there. Modify the OFF proposal to mention OT glyph mode instead of secure animated/static mode.

The nice thing about (3) is that this sort of thing is exactly what the SVG Integration document's purpose is: defining restrictions on allowable SVG when SVG is integrated into various other non-SVG specs (in our case, OpenType). It's one central place to go to see what parts of SVG are allowed or not in various environments.

foreignObject has been brought up before, and OT glyph mode would be the place to add the prohibition on foreignObject as well - we want SVG, not objects foreign to SVG, to be used for our glyph descriptions!

I'm interested in hearing from Cameron,Chris, and others on all the above.

Thanks,
Sairus