[XeTeX] Diacritics in color

Khaled Hosny khaledhosny at eglug.org
Wed Nov 30 22:14:37 CET 2011


On Wed, Nov 30, 2011 at 09:47:31PM +0100, Keith J. Schultz wrote:
> Hi Khaled,
> 
> I am afraid you are completely misconceived about what the subject matter is here.
> 	1) adding a diacritic mark(glyph) is composing a a glyph, You are able to output it
> 	    on its own.
> 
> 	2) There is a difference between the glyph ä and adding the diactirc mark of umlaut to
>              an a. 
>              a) in the first case you can use two different colors because it is one glyph. 
>              b) in the second you can use two different colors because you two glyph in order
> 	          two compose the ä glyph.
> 
> 	So we are talking about composed glyphs whether you realize it or not.

No we are not:
1) adding a mark to a glyphs is one thing, and composing them into a
   single glyph is another thing (in Latin fonts the later is a common
   result of the former, but that is mere implementation detail). The
   fully vowelled Arabic word مُحَمَّدٌ have a mark (or even two) in each
   character but no font will compose each <base><mark> into a single
   glyph (not a font build by a sane person). The same is even true for
   versatile Latin fonts that allow proper positioning of arbitrary
   <base><mark> combinations (e.g. many fonts from SIL).
2) the OP is developing his own font, which is neither covering Latin
   glyphs nor using precomposed glyphs.

Regards,
 Khaled

> 
> regards
> 	Keith.
> 
> 
> Am 30.11.2011 um 13:56 schrieb Khaled Hosny:
> 
> > On Wed, Nov 30, 2011 at 11:10:11AM +0100, Keith J. Schultz wrote:
> >> Hi All, 
> >> 
> >> I jump back in. I will cite anybody because what has been said is correct.
> >> 
> >> But,
> >> 
> >> 	1) trying to compare a browser, XeTex engine and LuaTeX will not help
> >> 	    as they have different methods of composing their output.
> >> 	    That is how they compose and position their glyphs.
> > 
> > As far as OpenType processing is concerned they all should give the same
> > result, else there is a bug somewhere.
> > 
> >> 	2) Most important a composed Unicode glyph is supposed to be just one color!!
> > 
> > No one talked about composed glyphs (certainly not the OP), it was just
> > a marginal and unrelated issue to the problem being discussed; coloring
> > combining marks without breaking OpenType mark positioning.
> > 
> >> 	3) Once you start using color a Unicode composed glyph you no longer are positioning
> >> 	     a single composed glyph, but two or more glyphs.
> > 
> > So? Again, coloring components of composed glyphs is not what is being
> > discussed here.
> > 
> >> 	3.a) color designed in TeX at.al is designed be applied to a box and not glyphs!! 
> > 
> > I've hard time understanding what this mean or how the difference, if
> > any, is material. AFAIK, TeX knows nothing about color, it handled just
> > like any other driver special which TeX makes no effort to interpret not
> > to mention "applying" it.
> > 
> >> The question remains how to position the composed glyphs and where and how the color attribute
> >> is added to the output. 
> >> 
> >> There are therefore two solutions:
> >> 	1) The Tex way:
> >> 		create a macro to compose the glyph and do the positioning and coloring.
> >> 
> >> 	2) The developer way:
> >> 		change the engine so that it firsts generates the composed glyph and then goes back
> >> 		and then applies color to the different glyphs. 
> > 
> > 3) The post-2000s way; use/build an OpenType font with proper combining
> > mark positioning and apply the colors to individual glyphs à la what
> > FireFox/LuaTeX and may be many other does.
> > 
> > Regards,
> > Khaled
> > 
> > 
> > --------------------------------------------------
> > Subscriptions, Archive, and List information, etc.:
> >  http://tug.org/mailman/listinfo/xetex
> 
> 
> 
> 
> --------------------------------------------------
> Subscriptions, Archive, and List information, etc.:
>   http://tug.org/mailman/listinfo/xetex


More information about the XeTeX mailing list