Italic punctuation in a font with both right slanted Latin and left slanted Hebrew/Arabic

Michael Rafailyk
Michael Rafailyk Posts: 171
in Technique and Theory
I want to try to work on left-slanted italics for RTL scripts, in the same font file where Latin italics are right-slanted. The problem is that punctuation (and numerals) is shared between LTR and RTL scripts. So if RTL scripts have left-slanted italics, then right-slanted punctuation can't be used.

It seems like I need to duplicate all the punctuation (and numerals for Hebrew) and substitute their right-slanted versions with left-slanted versions for RTL scripts (perhaps, in a locl feature). But there are about 100 punctuation characters and 44 numerals (including lnum, onum, pnum, tnum, zero). It is quite large set of glyphs to duplicate to make their left-slanted versions. This seems like either a problem or a challenge.
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Comments

  • Khaled Hosny
    Khaled Hosny Posts: 298
    Using language or script-specific substitutions here is not reliable especially for numerals. Since numerals are strong LTR characters, they are always processed in separate BiDi run when inside RTL text, and some implementations do script itemization on individual BiDi runs which means that the numerals are seen outside of the full context and don’t get the RTL script, and the substitution will not be applied.
    Similar things happen to punctuation. It gets even more complicated, for example in a “RTL (LTR) RTL” text, should the parenthesis get RTL script or LTR script? They are likely to get RTL script, but they will be slanted in the wring direction for the enclosed LTR text.
    The solution I ended up with is keeping the numerals and punctuation upright. It looks a bit odd to the modern reader, but IMO it is better than numerals and punctuation being slanted in the wrong direction.
  • Michael Rafailyk
    Michael Rafailyk Posts: 171
    Khaled, thanks for the explanation about scripts blocks in a text flow. So the substitution is not an option here. It seems more complicated than I thought.

    I also thought about upright punctuation and numerals. It's a choice that's not easy to make. Another possible issue with upright punctuation/numerals is that when a user changes the font from Regular to Italic, they may be confused as to why the punctuation and numerals remain upright. But of course, it all depends on the design (amount of straight lines) and the inclination level of italic.

    Probably, this issue, along with the vertical metrics issue, is the reason why different scripts are often published in different subfamilies.
  • Khaled Hosny
    Khaled Hosny Posts: 298
    edited April 17
    Michael Rafailyk said:
    Probably, this issue, along with the vertical metrics issue, is the reason why different scripts are often published in different subfamilies.
    These are some of the reasons indeed.
    Also in some scripts, like Arabic, slanted text has no much typographic use, since for many designs (especially the more traditional ones) it does not provide enough contrast unlike Latin. Arabic typography usually uses bold or quotation (or other typographic or calligraphic treatments) for emphases.

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