From: Vinod Kumar (rigvinod@gmail.com)
Date: Thu Oct 14 2010 - 21:04:45 CDT
On Fri, Oct 15, 2010 at 3:44 AM, Andrew Cunningham
<lang.support@gmail.com>wrote:
>
>
> I've been monitoring solutions for mobile devices esp smart phones in
> south east asia, and there seems to be a growing trend to implement
> legacy encodings for pseudo-Unicode solutions that aren't dependent on
> complex rendering that's missing on mobile devices.
>
> Unicode compliance does not mean that complex text support must be on Open
Font format or its Feature tag based shaping technique. There is no doubt
that the mobile phone community has accepted Unicode as the standard for
text representation, and for what the text should look like when
displayed. How the text should transform to the shapes is not under
the purview of Unicode. If people find simpler or elegant ways of
transforming Unicode text to shapes, these are not pseudo-Unicode solutions.
For example, India had a font standard called INSFOC for Devanagari. A
shaping engine that will convert Devanagari text in Unicode to INSFOC glyph
code sequence would be completely Unicode compliant with respect to
rendering of Devanagari. Some of my contacts have already extended this
approach for Gujarati and plan to bring all the nine Indian scripts too
under the same Unicode text to font glyph code standard.
Open Font (OpenType) is mistakenly considered to be the unique and only
Unicode compliant solution for complex scripts. The OT Feature tag based
complex text shaping, introduced by Microsoft Typography is not the only
method for using Open Fonts. This method is based upon the idea of Digital
fonts- fonts that can change size, slant or boldness computationally
depending on Tags embedded into the text manually or through a page
layout style. The transformations possible with Digital fonts have been
extended to complex shape formation. Thus Devanagari text <Ka Halant Pa> is
tagged essentially as ( <half> Ka Halant </half> Pa ) by a Devanagari text
analysis program (not manually). Lower layers of the shaping pipeline
convert this to <halfKaGlyph PaGlyph>. (With INSFOC standard, the Devanagari
text would be converted to (<halfKaINSFOCGlyphCode
halfPaINSFOCGlyphCode verticalRightStemINSFOCGlyphCode> ). The INSFOC
pipeline and font is much more simple than the OpenType Feature based
shaping. It is not a surprise that mobile platforms would go for it.
Moreover Feature based technique is not the only way Open Fonts can be
employed for complex text shaping. In our IndiX-II project, we have treated
Open Fonts as concrete Intelligent fonts (and not as Digital fonts) espoused
in the recommendation ISO/IEC 15285. ISO/IEC 15285 deals with transforming
sequence of characters to shapes. We have demonstrated that an ordered
sequence of context sensitive glyph substitutions as implemented by the GSUB
tables in Open Fonts are necessary and sufficient for shaping all the
nine Indian scripts. In IndiX-II, the layer handling the Open Font will not
tag the text with any tags like <half>. The substitution table in the
font will transform (<KaGlyph HalantGlyph> <PaGlyph>) to (<HalfKaGlyph>
<PaGlyph>). <Ka Halant> followed by <PA> should shape as <HalfKa><Pa>
without question or tags. Some developers (mobile platforms) have seen
that the text and font handling layers as well as the font itself have
become much more simpler and robust. Shaping complex text treating Open
Fonts as an Intelligent font cannot be considered as pseudo-Unicode. Both
methods of using Open Fonts are Unicode compliant for rendering the text,
but one is better.
and in some cases there is retrograde movement
>
> Finding alternate and better implementations under the framework of a
standard is one of the stated advantages of any standard, not only Unicode.
There is scope for diversity and innovation in the implementations.
Standards (especially Unicode) strive to separate the implementation issues
from the core representational and interface issues. We should not mistake
particular implementation choices as a stipulation of the standard.
Specifically, Feature tag based Open Fonts, or even Open Fonts themselves,
cannot be propagated as the essence of the Unicode standard for complex
text shaping.
> Andrew
> --
> Andrew Cunningham
> Senior Project Manager, Research and Development
> Vicnet
> State Library of Victoria
> Australia
>
> <andrewc@vicnet.net.au>
>
>
Vinod Kumar
Project IndiX
-- पृथिवी सस्यशालिनी the earth be green
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