Re: Unified draft of SVG-in-OT

Let's take animation out of the picture for the moment – that has all sorts of other issues that need discussion.

Can we agree that for static glyphs that they should be clipped – OR at least that the box needs to be pre-defined somewhere?

Zapfino and other fancy swatches work because only the glyphs shape/outline is provided back to the rendering context, so it can then draw/render them as it needs to. And if we were to assume that all  rendering of SVG-in-OT glyphs were onto a web canvas, then we could probably get away with the same thing.

HOWEVER, there are a myriad of use cases for these glyphs where these glyphs are rendered OUTSIDE of a web context.  Whether it is an OS platform (Windows, iOS, etc.), a non-web-based file format (Word, iWork, PDF, etc.), or print – these glyphs will need to be rendered by SVG into a separate context and then "copied back" into the primary context.  That requires knowing the size & shape of the destination – at least to do it optimally.

Make sense?

Leonard

From: Robert O'Callahan <robert@ocallahan.org<mailto:robert@ocallahan.org>>
Reply-To: "robert@ocallahan.org<mailto:robert@ocallahan.org>" <robert@ocallahan.org<mailto:robert@ocallahan.org>>
Date: Thursday, July 25, 2013 11:45 PM
To: Leonard Rosenthol <lrosenth@adobe.com<mailto:lrosenth@adobe.com>>
Cc: Nikos Andronikos <nikos.andronikos@cisra.canon.com.au<mailto:nikos.andronikos@cisra.canon.com.au>>, "public-svgopentype@w3.org<mailto:public-svgopentype@w3.org>" <public-svgopentype@w3.org<mailto:public-svgopentype@w3.org>>
Subject: Re: Unified draft of SVG-in-OT

On Fri, Jul 26, 2013 at 2:57 PM, Leonard Rosenthol <lrosenth@adobe.com<mailto:lrosenth@adobe.com>> wrote:
Whether authors may want it isn't the issue – the fact is that it would completely inappropriate to have a glyph that is placed at at a specific location on a page drawing outside it's given "box" - not just slightly, but even worse, somewhere completely different.

If you don't clip – what is to prevent a glyph from doing its own translate transform and ending up somewhere else on the canvas/page?!?!

Nothing.

Clipping to a static box makes things difficult in the presence of animated glyphs. It's impossible in general to automatically calculate a single ink bounding box that will contain every frame of an SVG animation, so we can't fully automate this in font design tools. Authors will sometimes have to do it manually. Either way it's unnecessary work, compared to the approach of just not clipping in the renderer. (Computing the ink bounding box of a single frame of an animation is easy.)

Opentype already has fonts whose glyphs extend far outside the box used for layout --- Zapfino for example --- so I think allowing SVG glyphs to extend arbitrarily far is also reasonable. Of course it can be used for aesthetically displeasing effects, but we can't legislate aesthetics.

Rob
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