[mpeg-OTspec] Re: OFF "cv01"-"cv99", and a more general question

[Peter Constable]

There's no reason a cvXX feature couldn't be applied to entire paragraphs, if that's what the user wants. I could see that being a common scenario, particularly when it's used to achieve for the effects that the locl feature is intended for but that the font developer could not implement since they could not anticipate all the languages that use particular variants. Indeed, that's the kind of scenario that originated the idea for this feature.

Peter

From: mpeg-OTspec at yahoogroups.com [mailto:mpeg-OTspec at yahoogroups.com] On Behalf Of karstenluecke
Sent: Friday, March 13, 2009 11:26 AM
To: mpeg-OTspec at yahoogroups.com
Subject: [mpeg-OTspec] Re: OFF "cv01"-"cv99", and a more general question


Hello Mr Constable and Thomas,

thank you for the clarification regarding "cvXX" and "ssXX".
I have ignored the mention of lookup type 3 in the spec. So this means that "cvXX" features are applied only to single selected characters/glyphs rather than entire paragraphs. Then it makes sense indeed that no more than one "cvXX" feature would address a specific character/glyph.
(My earlier interpretation was that it would really behave like "ssXX": Select a string of text in the application, then choose "cv01" to replace all "a"s by a variant, choose "cv02" to replace all "n"s by a variant, etc.)

* * *

> Also, the comparison at this point is not an apples-to-apples
> comparison: [...]
> I think a more even comparison with GX layout and ATSUI
> would be GDI text, WPF, DirectWrite or similar APIs

This is true, and possibly helps me make my point clear:
GX aims at a single platform for which an according engine/API is available. So within this limited realm the couple of font format and engine/API exists.
OpenType claims to be platform independent (this is how it was sold to foundries and end users, and only then it makes sense to turn it into a standard), but there is no cross-platform engine/API nor a specification which would ensure that OT fonts, built after the spec, behave the same on a variety of platforms.
(No intentions to play out GX vs OT. GX just helps me illustrate what I consider as important missing bit.)

Best wishes,
Karsten

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