Periodcentered

Nick Shinn
Nick Shinn Posts: 2,207
in Technique and Theory
1. Should it be an identical glyph to period?

2. Should it be the same character width as period?

3. Should it be centred vertically on the cap height (with suitable “optical” adjustment)?

4. Where a type is “high- (or low-) waisted” in the caps, should it be aligned with the waist?

5. Where ascenders overshoot cap height, which should it be (vertically) centred on?

6. Where ascenders overshoot cap height, would it make sense to (vertically) align it with the ascender, and provide a “case” alternate aligned to the caps?

Comments

  • Craig Eliason
    Craig Eliason Posts: 1,436
    4. Where a type is “high- (or low-) waisted” in the caps, should it be aligned with the waist?
    Does anybody do that with hyphens or dashes?
  • James Puckett
    James Puckett Posts: 1,992
    Is this glyph still in use? Or has it been made obsolete since /ldot became common in fonts?
    Does anybody do that with hyphens or dashes?
    It happens in fonts that have alternate all-caps punctuation.
  • Nick Shinn
    Nick Shinn Posts: 2,207
    edited July 2013
    It is used for some math functions, James.
    And in dictionaries to indicate syllable breaks.
    I often used it in all cap settings as a spacer, similar to the way people use the bar.

    I believe that in Catalan, manuscripts are more often keyboarded with /l followed by /periodcentered, rather than using /ldot. With this in mind, I create a glyph “periodcentered.ldot” which substitutes in the local feature. AFAIK, the only drawback would be in a Catalan dictionary.
  • Sandy Cerovich
    Sandy Cerovich Posts: 17
    ...and in line with what Chris said, I always center it vertically with the bullet.
  • John Hudson
    John Hudson Posts: 3,186
    edited July 2013
    I typically make it lower, aligned with the hyphen, because it gets used between lowercase letters sometimes, e.g. as a syllable separator in dictionaries. I provide a raised version for use in all caps, accessed via the {case} feature.

    Following discussion with Catalan colleagues, I think it is best to provide either a {locl} alternate as Nick suggests, or ligate

    l periodcentered -> ldot

    The best height of the dot for Catalan is going to depend on the typeface, and the proportions of the x-height to the ascender height. Generally speaking, it is going to be somewhere around the mid-height of the l, but it should be looked at in sample words to determine what looks best for a particular design.
  • Nick Shinn
    Nick Shinn Posts: 2,207
    The ligature method becomes uneven when anything other than zero tracking is applied.
    When tracking is beyond the “fail” amount, and the ligature ceases to be substituted, the spacing is even, but disproportionately large.
  • [Deleted User]
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  • Chris Lozos
    Chris Lozos Posts: 1,458
    James, I'll bet you "like the smell of Napalm in the morning", too ;-)
  • [Deleted User]
    [Deleted User] Posts: 0
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  • Chris Lozos
    Chris Lozos Posts: 1,458
    It wasn't soon enough for me.
  • Georg Duffner
    Georg Duffner Posts: 3
    Just for completeness about periodcentered in catalan: it’s always at a syllable boundary (only occuring in the combination l·l), so in a dictionary you wouldn’t need to add an extra symbol, however all my catalan dictionaries (mono- and bilingual ones) don’t show any syllable boundaries. The only comparable symbol in one of them is a vertical bar that shows boundaries between the word’s root and affixes.

    To add to John’s comment: it’s also necessary that the localised periodcentered doesn’t take up much space because the distance between the two "l" in "l·l" should be similar to the one in "ll".

    One further observation: a similar case exists in occitan where you might find the combinations s·h, n·h and l·h. They’d probably need a similarly localised glyph.
  • Nick Shinn
    Nick Shinn Posts: 2,207
    @Goerge: To add to John’s comment: it’s also necessary that the localised periodcentered doesn’t take up much space because the distance between the two "l" in "l·l" should be similar to the one in "ll".

    Right, a feature of this method is that no kerning is required, just adjust the sidebearings until width of the combination of glyphs = the ldot width.
    But you will probably need separate “periodcentered.catalan” glyphs for UC, lc and small caps.
  • Georg Duffner
    Georg Duffner Posts: 3
    @Nick: But you will probably need separate “periodcentered.catalan” glyphs for UC, lc and small caps.

    Exactly. The glyphs for UC and sc will be of zero width and have a negative left sidebearing.
  • Nick Shinn
    Nick Shinn Posts: 2,207
    I give the l.c. Catalan dot zero sidebearings. That seems to work quite well, and makes it easy to calculate so that it implements with the same metrics as the /ldot glyph, for what it’s worth.
  • Wei Huang
    Wei Huang Posts: 98
    edited May 2016
    What size is a good periodcentered compared to the lowercase letter weight or the period? I had read from some Catalan readers that it shouldn't be the same size in certain cases but I can't find the reference again.
  • Wei Huang
    Wei Huang Posts: 98
    edited June 2018
    Reviving this long dead thread, is there a difference between dot operator U+22C5 ⋅ and bullet operator U+2219 ∙ 

    ⋅∙
  • Eli Heuer
    Eli Heuer Posts: 3
    edited June 2018
    U+22C5 is used as a multiplication symbol when typesetting math, there are many usage examples here: https://tex.stackexchange.com/questions/19180/which-dot-character-to-use-in-which-context



  • Kent Lew
    Kent Lew Posts: 937
    These two characters, and their relationships to similar punctuation, are discussed in Chapter 22 of the Unicode Standard — specifically Section 22.5 in the subsection on Disunifications, with the corresponding Table 22-5, pages 807–8.

  • Kent Lew
    Kent Lew Posts: 937
    I just re-read something I wrote above almost five years ago, and realized I mistyped.

    What I believe I would have meant was:
    So, theoretically, the periodcentered can be aligned on lowercase to work as syllable separator, with a .case variant for use in all-caps, while the uni2219 can be aligned to work with figures.
    The periodcentered should be encoded as U+00B7. Which makes the second half of my original statement contradictory. It’s U+2219 which is used for math and should align with figures.

  • Wei Huang
    Wei Huang Posts: 98
    edited June 2018
    @Kent Lew Thanks Kent, I read the section and I'm still not sure at what height, size and what spacing is ideal for these glyphs:

    Mathematical operators render on the math centerline, rather than the text baseline. 

    The distinction between middle dot and dot operator deserves special consideration. dot operator is preferred for mathematical use, where it signifies multiplication. This allows for rendering consistent with other mathematical operators, with unambiguous character properties and mathematical semantics. middle dot is a legacy punctuation mark, with multiple uses, and with quite variable layout in different fonts. For the typographical convention of a raised decimal point, in contexts where simple layout is the priority and where automated parsing of decimal expressions is not required, middle dot is the preferred representation

    So I gather from this that the 22c5 Dot Operator, should be designed to work between figures and letters, and that 00b7 middle dot should align with lowercase letters (?) but in practise, in the following examples, it is inconsistent. Mostly designers make 00b7 middle dot, 22c5 dot operator the same.

    Menlo:



    Cambria Math:


    Georgia:


    Apple Symbol:


    Arial Unicode MS:


  • Kent Lew
    Kent Lew Posts: 937
    but in practise, in the following examples, it is inconsistent. Mostly designers make 00b7 middle dot, 22c5 dot operator the same.
    Yes, that’s the reality. Partly, I believe, due to the fact that users aren’t consistent with their use of 0x22C5 and 0x2219.

    Or are users inconsistent because font manufacturers have often made them the same, so there’s no visual distinction? ;-)

  • Michel Boyer
    Michel Boyer Posts: 120
    If you want to see what the math symbols are expected to look like for publishers that heavily use math fonts, you can have a look at the STIX fonts.
  • Mark Simonson
    Mark Simonson Posts: 1,732
    edited June 2018
    In the STIX fonts, all four are positioned the same, slightly above the center of the x-height.


  • Michel Boyer
    Michel Boyer Posts: 120
    edited June 2018
    Here is how they render with XeLaTeX with \setmathfont{STIX Two Math} and equation   \[ x\cdotp x\cdot x\bullet x\smblkcircle x\]
    \smblkcircle belongs to a series of black circles of various sizes.
  • Michel Boyer
    Michel Boyer Posts: 120
    edited June 2018
    Here are the relative positions of periodcentered, hyphen and cdot in commonly used LaTeX packages. 

    Notice that the  vertical positioning of cdot relative to periodcentered (on any text on the current line) does not seem to be affected by the surrounding equations as suggests the following test:

    (I did not check the specs). It is the whole line that moved down with the equation. Here I used Fourier (and three cdots).
  • Claudio Piccinini
    Claudio Piccinini Posts: 681
    I bookmark this old discussion as I am making final decisions on how to align these various glyphs (punctuation ones and mathematical equivalents) in my own typefaces. :)

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