RE: SVG Text elements within glyphs

Hi Rob,

I agree about “unintuitive”, in this context I was using it more like a measure of common sense, as in
“it doesn’t make sense to allow font data, which is intended to be used a resource to visualize text content, utilize textual content to be used as a fill for rendering the glyphs”

Regarding the UA style sheet – if we agree that the use of text elements as part of the SVG glyph description doesn’t make sense and should be disallowed, the solution you proposed would be one a way to implement the restriction; however I would imagine that in some cases the SVG-enabled OFF implementations may not support the concept of UA style sheet and would have to do something else to restrict the use of text elements. BTW, is there a chance that font-size value defined as part of the SVG text element would override UA style sheet definition?

I think that regardless of _how_ the restriction can be implemented it needs to be mentioned as part of the spec proper, similar to e.g. how we specify limitations on rendering of animated content [using secure animation mode]. This would be useful for both rendering engine implementers and for tool vendors.

Thank you,
Vlad


From: rocallahan@gmail.com [mailto:rocallahan@gmail.com] On Behalf Of Robert O'Callahan
Sent: Monday, February 03, 2014 4:33 PM
To: Levantovsky, Vladimir
Cc: Chris Lilley; Daniel Flassig; Sairus Patel; public-svgopentype@w3.org
Subject: Re: SVG Text elements within glyphs

On Tue, Feb 4, 2014 at 10:01 AM, Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com<mailto:Vladimir.Levantovsky@monotype.com>> wrote:
My primary concern is that it seems counter-intuitive to allow font data, which is intended to be used a resource to visualize text content, utilize textual content to be used as a fill for rendering the glyphs. Considering that the "SVG in OpenType" was proposed to become part of the generic font format standard usable in different environments and different applications both as a web font as well as a local font - even a hypothetical possibility to enter the endless loop of a font referencing itself to render the text content is unsettling.

I'm not worried about the intuitions here. "It's unintuitive to combine X and Y" is not generally a good enough reason on its own to disallow the combination of X and Y. But preventing recursive fonts does seem like a good idea for safety reasons.

I think the simplest thing might just be to specify that the UA style sheet for a SVG glyphs document must contain "font-size:0 !important". This will ensure that no text needs to be measured or rendered.
The alternatives of blacklisting certain SVG elements (and foreignObject I guess) are a bit more complicated and would probably have to be extended over time, which isn't good.

Rob
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