On Thu, Feb 22, 2018 at 6:32 PM, Ken Whistler wrote: > > If you override the normal left-to-right ordering with bidi override > controls, then the layout order is reversed, but what is actually laid out > is those two glyphs. So you just reverse the order of the two syllables for > display, in either case. >
My confusion stems from Unicode’s online bidi utility. Compare https://unicode.org/cldr/utility/bidi.jsp?a=%E2%80%AE%EB%B3%B4%EA%B8%B0 (NFC) to https://unicode.org/cldr/utility/bidi.jsp?a=%E2%80%AE%E1%84% 87%E1%85%A9%E1%84%80%E1%85%B5 (NFD). Concatenating each one’s characters in reordered display position order produces canonically different results. Here is more practical example. A sequence of an emoji modifier base and an emoji modifier in an RTL run will be display-reordered such that the modifier is to left of the base. Clearly, the right thing is to not reorder them, because they should ligate to form a single glyph. Contrast this with “fl” in an RTL run, which will be display-reordered to “lf”: it would be wrong to apply the previous rationale here just because “fl” may have a single glyph. It sounds like the UBA doesn’t specify how to reorder the glyphs of the characters within a level run. That’s about what I expected. I was just worried it might require an easily implemented but wrong order, so thanks for the reassurance.