Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated)
At 12:43 PM 1/27/02 -0800, Mark Davis \(jtcsv\) wrote: It sounds like what you are saying, in concrete terms, is that Font #6 at the bottom of: http://www.macchiato.com/utc/variation_selection/variation_selection_f ollowup.htm is conformant. If that is so, then we would have to have an additional VS to select the closed form of the glyph. In that case, one could only depend on a visual distinction based upon the description if the font supported both of the VS sequences. I can see your point. In your posting you wrote: Number 6 is the decisive one. If we say that it is conformant, then we are required to have another VS sequence (if, of course, we need to distinguish a determinant closed form). If we say that it is not, then we are not required to have another VS to distinguish the closed form. I am saying #6 is definitely conformant (but it does not serve well the community that asked for the open form at a separate location ;-) Adding an explicit VS2 (or whatever VS) mechanism to ask for the distinct form of the plain character code, gives everyone more choices: If you are a user that needs the distinction, then you would have two choices: a) get a font that makes the distinction, and enforce its presence b) try asking for the distinction using VS2 (or whichever VS) The latter allows you to make distinctions that can always be recovered from your source data with fidelity, even if the 'try asking' didn't pan out. If you are a font vendor wanting to support the distinction, then you would have two choices: a) have your font always make the distinction (and VS2 gets ignored silently) b) don't make the distinction, unless asked to do so explicitly The latter allows you to serve users not needing the distinction w/o compromising the typographical aesthetics of your font in *their* context. That directly translates into market choices. A./
Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated)
At 12:33 AM 1/27/02 -0800, Mark Davis \(jtcsv\) wrote: I find it fairly pointless to say that a font supports the variation selection sequence U+03B8, U+FE00 if it does not provide a visual distinction from U+03B8; and such a distinction should be based on the entry description. Thus, of the following four fonts, only number 4 correctly supports the sequence U+03B8, U+FE00. (Of course, any real font would have designs for the two glyphs that were a bit more harmonious!) I couldn't view your examples, but guessing at what they might have been, I'll risk an answer. The problem is that some of the distinctions for which variant selectors are used, are *needed only by a minority of users*. Some of the math variants (not PHI, or THETA, but the ones in StandardizedVariants) may only be needed by *some* math authors. Any requirement that by supporting VS1, one must restrict the glyph range of the unmarked symbol forces either a) the tail to wag the dog or b) many dogs to do without tail Case a is where fonts assume the most restrictive glyph choice for the unmarked symbol, so that they can be used by all users. This is bad since the restricted glyph range for the unmarked symbol may be a somewhat unnatural one. Given the expense of creating a math font, it may not make sense to do one that is not usable by all math authors. Case b is where fonts assert their choice of unmarked glyph and (because of the required contrast) choose not to support the VS1 form, since that's the form they want to use as the unmarked default. Given the expense of creating a math font, the sub-set of math authors may not have the werewithal to source a font for their needs, since most of the market can be covered by something that is 'good enough'. By explicitly defining a way to restrict the glyph range (via coding another character, or another VS sequence) it becomes easier to support groups with related needs, but different requirements in the face of variants. A./
Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated)
Sorry, I guess not all mailers handle embedded graphics in HTML messages. I posted it so that you could see the graphics, on http://www.macchiato.com/utc/variation_selection/variation_selection_followu p.htm It is *not* exactly the same. I added and rearranged the concrete examples at the very end. I think those last examples of the font are key to this issue: depending on which we say conformantly support the variation sequence will help determine how we handle this issue. I also posted my previous paper, although my thinking has changed a bit since then, particularly on the 'tightness' of the description -- the paragraph containing Suppose a glyph has a slash with an angle of 32° from vertical. http://www.macchiato.com/utc/variation_selection/variation_selection.htm Mark — Πόλλ’ ἠπίστατο ἔργα, κακῶς δ’ ἠπίστατο πάντα — Ὁμήρου Μαργίτῃ [For transliteration, see http://oss.software.ibm.com/cgi-bin/icu/tr] http://www.macchiato.com - Original Message - From: Asmus Freytag [EMAIL PROTECTED] To: Mark Davis (jtcsv) [EMAIL PROTECTED] Sent: Sunday, January 27, 2002 01:36 Subject: Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated) Now this message was clear as mud. Literally. As in totally opaque in the pure visual sense: All the examples show as nice gray boxes in my mailer - please make sure whatever you are sending is an attachment, and not in-line. Thanks, A./ (PS: They may well arrive in viewable condition when this reply gets back to you..., but I can't read it) — Πόλλ’ ἠπίστατο ἔργα, κακῶς δ’ ἠπίστατο πάντα — Ὁμήρου Μαργίτῃ [For transliteration, see http://oss.software.ibm.com/cgi-bin/icu/tr] http://www.macchiato.com - Original Message - From: Asmus Freytag [EMAIL PROTECTED] To: Mark Davis (jtcsv) [EMAIL PROTECTED] Sent: Sunday, January 27, 2002 01:36 Subject: Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated) Now this message was clear as mud. Literally. As in totally opaque in the pure visual sense: All the examples show as nice gray boxes in my mailer - please make sure whatever you are sending is an attachment, and not in-line. Thanks, A./ (PS: They may well arrive in viewable condition when this reply gets back to you..., but I can't read it) At 12:33 AM 1/27/02 -0800, you wrote:  The other possibility is to say that to be strictly Unicode-conformant, fonts should always use the reference glyph for unmarked characters (ignoring differences only of style). I think this is actually a better Boy, great minds to think alike. Mark Davis just proposed that in a paper to the UTC this week. I would like to thank you for the compliment, but I must not have been clear in my paper, since that is not really what I was proposing. Let me try again, with a concrete case. Since I don't have a variety of math fonts, I will use the example of U+03B8 greek small letter theta. This character can be represented by the following glyphs (collected on my system) and many more. Any of these are acceptable, conformant representations of the theta, depending on the design of the font. 1f908bf2.jpg Now, there is already a presentation form for the open form of the theta, at U+03D1 greek theta Symbol. A presentation form of a character represents the same abstract character, but is restricted in format to a subset of the possible glyphs that could represent the character, such as the following: 1f908db5.jpg But suppose there were no such character. In that case, we might add an encoded variant, expressed as an entry in the StandardizedVariants.html file in the UCD, looking something like: Ref Glyph Character Sequence Alt Glyph Description of variant appearance 1f908e05.jpg 03B8, FE00 1f908e4b.jpg Open Theta, unconnected on the left side Now there are four key facts that we need to keep in mind: * This does not, at all, prevent the character alone U+03B8 from having the same appearance as what is titled as the Alt Glyph. It is still a perfectly acceptable representation of that character in normal text. * What is titled Alt Glyph in this entry is also merely a representative, one of many possible glyphs that can represent the variant. Thus both of the glyphs are representative: they do not, and cannot, encompass all of the possible glyphs that can represent either the character alone, or the variant. (It would be a good idea for us to change the title of this column, since it may mislead some into thinking that that precise glyph must be used: it should be Variant Ref Glyph.) * A key feature of the entry is the description; it provides the limitation on the set of glyphs that can be used to represent the sequence, if the sequence is supported by a font. * If a font does not support the variation sequence given by this entry, that it is also perfectly acceptable to ignore the U+FE00, and thus render the sequence U+03B8, U+FE00 with precisely the same glyph as the single character U+03B8. So the open
Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated)
It sounds like what you are saying, in concrete terms, is that Font #6 at the bottom of: http://www.macchiato.com/utc/variation_selection/variation_selection_f ollowup.htm is conformant. If that is so, then we would have to have an additional VS to select the closed form of the glyph. In that case, one could only depend on a visual distinction based upon the description if the font supported both of the VS sequences. I can see your point. Mark — Πόλλ’ ἠπίστατο ἔργα, κακῶς δ’ ἠπίστατο πάντα — Ὁμήρου Μαργίτῃ [For transliteration, see http://oss.software.ibm.com/cgi-bin/icu/tr] http://www.macchiato.com - Original Message - From: Asmus Freytag [EMAIL PROTECTED] To: Mark Davis (jtcsv) [EMAIL PROTECTED]; David Hopwood [EMAIL PROTECTED]; [EMAIL PROTECTED]; Unicore [EMAIL PROTECTED]; [EMAIL PROTECTED] Sent: Sunday, January 27, 2002 01:49 Subject: Re: Variation Selection (Was Re: Unicode 3.2: BETA files updated) At 12:33 AM 1/27/02 -0800, Mark Davis \(jtcsv\) wrote: I find it fairly pointless to say that a font supports the variation selection sequence U+03B8, U+FE00 if it does not provide a visual distinction from U+03B8; and such a distinction should be based on the entry description. Thus, of the following four fonts, only number 4 correctly supports the sequence U+03B8, U+FE00. (Of course, any real font would have designs for the two glyphs that were a bit more harmonious!) I couldn't view your examples, but guessing at what they might have been, I'll risk an answer. The problem is that some of the distinctions for which variant selectors are used, are *needed only by a minority of users*. Some of the math variants (not PHI, or THETA, but the ones in StandardizedVariants) may only be needed by *some* math authors. Any requirement that by supporting VS1, one must restrict the glyph range of the unmarked symbol forces either a) the tail to wag the dog or b) many dogs to do without tail Case a is where fonts assume the most restrictive glyph choice for the unmarked symbol, so that they can be used by all users. This is bad since the restricted glyph range for the unmarked symbol may be a somewhat unnatural one. Given the expense of creating a math font, it may not make sense to do one that is not usable by all math authors. Case b is where fonts assert their choice of unmarked glyph and (because of the required contrast) choose not to support the VS1 form, since that's the form they want to use as the unmarked default. Given the expense of creating a math font, the sub-set of math authors may not have the werewithal to source a font for their needs, since most of the market can be covered by something that is 'good enough'. By explicitly defining a way to restrict the glyph range (via coding another character, or another VS sequence) it becomes easier to support groups with related needs, but different requirements in the face of variants. A./
