Re: [XeTeX] Handling of combining and variant selector characters in math
> http://blogs.msdn.com/b/murrays/archive/2016/02/05/unicode-math-calligraphic-alphabet.aspx >> >> As explained in the article at least two possible suggestions are >> being considered: adding the new alphabet in a new code block range, >> or defining "variant selector" characters that would force one > or >> other interpretation. >> In Asana-Math I have both alphabets. The default is the one with the fancy letters while the second can be used by enabling the salt property. A.S. -- Apostolos Syropoulos Xanthi, Greece -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
Re: [XeTeX] Handling of combining and variant selector characters in math
On 2/10/2016 5:34 PM, David Carlisle wrote: Note I was using Khaled's xits-math variant not the original stix version, xits-math has many improvements to the opentype internals. The VS1 combinations in xits-math work for example in firefox. David Thanks, David. I downloaded the XITS fonts today from github, so I assume I have the most recent. I will poke around some more and see if I can figure out how Firefox is accessing the variants. -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
Re: [XeTeX] Handling of combining and variant selector characters in math
Thanks for the reply, Will. On 2/10/2016 4:52 PM, Will Robertson wrote: My understanding here is that Variant Selector acts like a character to produce a difference glyph (analogous to a ligature), so doesn’t need shaping/positioning information. That's true, but the fonts that I am familiar with have a substitution lookup (similar indeed to a ligature) that says "replace character X followed by VS1 with character Y." I saw nothing like that in XITS. For maths typesetting, this is activated with “script=math”, and there are a bunch of (~50, too tired to look up the number now) font parameters stored directly within the font to handle most spacing needs. Yes, I saw a bunch of OT features in the font but nothing that looked familiar in terms of accent positioning and the like. Which may be my own ignorance, of course. However, I am not sure about the technical side of applying maths accents like \ddots. These are placed not as combining marks but with the XeTeX primitive \Umathaccent (which can also place the accent below the letter, etc.). I can only assume that a font designer can provide additional details to fine-tune the spacing for certain cases; to me it would seem necessary. I wonder how this is done (and I agree it seems needed). It doesn't seem to be with the usual OT mechanisms. -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
Re: [XeTeX] Handling of combining and variant selector characters in math
On 10 February 2016 at 21:36, David J. Perry wrote: > I know nothing whatsoever about math, so perhaps I shouldn't even join this > discussion, but I am curious. I do have considerable experience in font > development and supporting things like the use of combining marks and > variation selectors outside of math contexts. > > I looked in a font editor at the font (XITS) that was used to produce the > sample PDF. As far as I can see, it has no support for combining marks or > variation selectors of the sort that I would expect, based on my non-math > experience. (For instance, fonts that support combining marks usually have > a Mark to Base lookup.) Is there an expectation that in TeX the math > typesetting can properly position combining characters and handle variation > selectors without support from the font? > > David > Note I was using Khaled's xits-math variant not the original stix version, xits-math has many improvements to the opentype internals. The VS1 combinations in xits-math work for example in firefox. David > > On 2/9/2016 8:54 AM, David Carlisle wrote: > > Sending this separately to xetex luatex lists... > > The current Unicode math alphabets in U+1D400 ...include a "script" > alphabet this was intended to cover both "caligraphic/chancery" and > "script/roundhand" as font variants, in the hope that no document > would need both. > > Unicode is considering adding separate markup for the two forms, see > Murray's blog here > > http://blogs.msdn.com/b/murrays/archive/2016/02/05/unicode-math-calligraphic-alphabet.aspx > > As explained in the article at least two possible suggestions are > being considered: adding the new alphabet in a new code block range, > or defining "variant selector" characters that would force one or > other interpretation. > > Unicode combining characters following the base have always been a bit > tricky in TeX so I wondered whether the engine (or font) developers > (as opposed to macro level hacker like myself) have a view on what is > a reasonable input form here. > > You could either reply here or as a comment on the above Blog. > > I attach a (latex) text file that produces more or less the same > output in xetex and luatex showing that by default neither a simple > combining character like e-acute nor VS1 work but the combining acute > at least can perhaps be made to work but VS1 seems tricky as the base > is a \mathop atom so it's not really amenable to being combined with > the following variant selector character. > > Since current combining character use seems tricky I'm worried about > the suggestion to use that method for selecting the entire script > alphabet. > > (The combining acute could be normalised away by running filter to NFC > form but don't do that as it's just standing in for a possible new > character to switch script forms:-) > > Tests 0 and A show that both combining forms work fine in text, but > math is the issue here > > David > > > > > -- > Subscriptions, Archive, and List information, etc.: > http://tug.org/mailman/listinfo/xetex > > > > > > -- > Subscriptions, Archive, and List information, etc.: > http://tug.org/mailman/listinfo/xetex > -- http://dpcarlisle.blogspot.com/ -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
Re: [XeTeX] Handling of combining and variant selector characters in math
On 11 Feb 2016, at 8:06 AM, David J. Perry wrote: > > I looked in a font editor at the font (XITS) that was used to produce the > sample PDF. As far as I can see, it has no support for combining marks or > variation selectors of the sort that I would expect, based on my non-math > experience. (For instance, fonts that support combining marks usually have a > Mark to Base lookup.) Is there an expectation that in TeX the math > typesetting can properly position combining characters and handle variation > selectors without support from the font? Hi David P, [My knowledge here is entirely as an end user of XeTeX maths features — I didn’t have any hand in implementing them.] My understanding here is that Variant Selector acts like a character to produce a difference glyph (analogous to a ligature), so doesn’t need shaping/positioning information. For maths typesetting, this is activated with “script=math”, and there are a bunch of (~50, too tired to look up the number now) font parameters stored directly within the font to handle most spacing needs. However, I am not sure about the technical side of applying maths accents like \ddots. These are placed not as combining marks but with the XeTeX primitive \Umathaccent (which can also place the accent below the letter, etc.). I can only assume that a font designer can provide additional details to fine-tune the spacing for certain cases; to me it would seem necessary. But these accents can be stretched over multiple glyphs, so perhaps not. Hope this helps, Will -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
Re: [XeTeX] Handling of combining and variant selector characters in math
I know nothing whatsoever about math, so perhaps I shouldn't even join this discussion, but I am curious. I do have considerable experience in font development and supporting things like the use of combining marks and variation selectors outside of math contexts. I looked in a font editor at the font (XITS) that was used to produce the sample PDF. As far as I can see, it has no support for combining marks or variation selectors of the sort that I would expect, based on my non-math experience. (For instance, fonts that support combining marks usually have a Mark to Base lookup.) Is there an expectation that in TeX the math typesetting can properly position combining characters and handle variation selectors without support from the font? David On 2/9/2016 8:54 AM, David Carlisle wrote: Sending this separately to xetex luatex lists... The current Unicode math alphabets in U+1D400 ...include a "script" alphabet this was intended to cover both "caligraphic/chancery" and "script/roundhand" as font variants, in the hope that no document would need both. Unicode is considering adding separate markup for the two forms, see Murray's blog here http://blogs.msdn.com/b/murrays/archive/2016/02/05/unicode-math-calligraphic-alphabet.aspx As explained in the article at least two possible suggestions are being considered: adding the new alphabet in a new code block range, or defining "variant selector" characters that would force one or other interpretation. Unicode combining characters following the base have always been a bit tricky in TeX so I wondered whether the engine (or font) developers (as opposed to macro level hacker like myself) have a view on what is a reasonable input form here. You could either reply here or as a comment on the above Blog. I attach a (latex) text file that produces more or less the same output in xetex and luatex showing that by default neither a simple combining character like e-acute nor VS1 work but the combining acute at least can perhaps be made to work but VS1 seems tricky as the base is a \mathop atom so it's not really amenable to being combined with the following variant selector character. Since current combining character use seems tricky I'm worried about the suggestion to use that method for selecting the entire script alphabet. (The combining acute could be normalised away by running filter to NFC form but don't do that as it's just standing in for a possible new character to switch script forms:-) Tests 0 and A show that both combining forms work fine in text, but math is the issue here David -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex -- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
