Sorry for a late reply. I found a couple typos and it actually needs to be updated.
I actually have a working polytonic Greek setup for LaTeX; (more accurately, XeLaTeX and LuaLaTeX); send me a message and I'll send you a minimum working preamble :)
yes, I think putting it in greek.el would be a better option, but I
don't have contributor rights, and so far this has been the easier way
for me to distribute it. I'd be happy to if someone can help me with that.
> It seems to go against the intent of whoever is
> typing the text: they do want the decomposed characters to appear in
> the text. Emacs will automatically (by default) compose them on
> display (and if it doesn't, that's a bug that should be reported and
> fixed), per Unicode requirements, and if the font supports the
> precomposed glyph, you will actually see that glyph on display.
> Replacing characters with their NFC equivalents should IMO be a
> separate feature, not something an input method does.
In an ideal world... yeah. De facto, polytonic Greek online and presumably in most digital systems use the precomposed forms, and /all/ polytonic fonts I'm aware of do not gracefully handle the placement of decorations on greek letters. Some fonts don't display the accents, some fonts have them overlap, and probably all fonts don't place the combining breathings (single-quotation-commas) in the right place. When writing this I found that my favorite programming font on emacs actually crashes my Linux system when using these combining characters!
This is the most prevalent compromise I've found online. greek-polytonic.el gives the most graceful fallback, compositing into precomposed forms whenever available.
: I think this is in fact the case, de facto, for most Latin/Greek/Cyrillic documents. For example, I've observed that in movement in emacs, decomposed characters count as two characters, but all the documents so far I've opened have their accented characters count as one. Korean... is similar in its poor de facto support for decomposed characters. The only natural language that I know writes in decomposed characters de facto are the Indic languages!
: This is a bug on emacs or the window system, but I don't even know where to begin diagnosing it.