DP Code - Unicode/Greek

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Unicode and Greek have a troubled relationship. This relationship makes supporting Greek at DP in Unicode difficult.

Overview

Given extensive research and conversation, we chose to support tonos Greek letterforms during the proofreading arounds at DP, leaning on the Post-Processors to convert back to the oxia/accute ones. This page discusses why but it really boils down to Unicode forcing our hand.

Background

There are two forms of Greek: polytonic and monotonic. Monotonic Greek is very new, officially, having been imposed by law in 1982, though the simplification started much earlier in the 20th century.

Greek has two vowel accent forms: oxia (aka: acute) and tonos. Monotonic Greek uses the tonos forms, and is limited to the acute accent (´) and the diaeresis (¨). Polytonic Greek uses the oxia forms -- this is where we find not only the above two, but also, the grave accent, the circumflex, and rough and smooth breathing marks. Each of these have their own set of Unicode codepoints.

From the above it seems obvious that at DP we would want to use the oxia Unicode characters, as most of the books we are likely to run into will be using the polytonic Greek. But alas, technology is not on our side.

Normalizing Strings

Unicode has the idea of canonical equivalence, where two characters are considered "the same". Because there are multiple ways to encode a single character in Unicode, Unicode supports normalizing strings. This enables things like normalizing "a + umlaut" into ä. Normalization, specifically NFC normalization, is critical to how DP has implemented Unicode.

At DP we don't want to enable proofreaders to put literally any Unicode character into a page. Instead we want to add guide rails for each project to limit the possible characters used. This ensures that proofreaders don't pull in similar-looking, but not identical, characters. We have implemented this by allowing projects to specify the character suites they support (note: initially this will just be the Basic Latin character suite). Characters that aren't in these character suites will never be saved into the project. On project load the characters are filtered out. On page save in the proofreading interface the proofreader is notified of invalid characters before they save the page. To make this restriction work we need to NFC normalize strings so we have a small and known set of characters to restrict down to. Without normalization we would have no way to say ä is supported but ẍ is not.

For Greek, Unicode specifies that the oxia and tonos versions of the characters are canonically equivalent and when canonically normalized, oxia codepoints are replaced with their tonos equivalents. This means that anytime we NFC normalize a string containing oxia codepoints we will get a string with tonos instead. Many view this as incredibly shortsighted of the Unicode Consortium, but here we are. To support oxia we would have to not normalized strings which, as mentioned above, is a key piece of the DP Unicode design philosophy.

Normalizing strings means we need to use tonos and not oxia.

Keyboard input

When considering whether to support oxia or tonos we also evaluated how keyboards input these accented characters.

Based on the testing done, detailed below, the current conclusion is that we should not jump through exotic hoops to keep from using the normalized (tonos) forms of the accented vowels listed in the oxia & tonos codepoints section below, but should provide the information necessary for the PPers who wish to use those forms to convert the normalized forms back to the oxia forms.

Soft & Virtual Keyboards

Soft keyboards, such as on Android and iPadOS devices, allow selecting accented Greek characters. In addition, macOS (and presumably Windows), allows configuring a keyboard to type in Greek characters. What we found was that the vast majority of the keyboards input the tonos versions of the characters:

  • GBoard keyboard on Android: tonos
  • iPadOS built-in keyboard, both soft keyboard and hardware keyboard stand: tonos
  • Hoplite Polytonic keyboard on iPadOS: tonos and oxia (tonos only using hardware keyboard stand)
  • iPolytonic on iPadOS: tonos & oxia (tonos only using hardware keyboard stand)
  • AGK keyboard on iPadOS: tonos and oxia -- probably not a good choice, as it allows any accents to be put on any letter (tonos only using hardware keyboard stand)

On all three of the tested iPadOS soft keyboards, the oxia-only characters must be entered using the soft keyboard. Where physically similar accented vowels are in both the "Greek and Coptic" Unicode block (U+0370 +) and the "Greek Extended" block (U+1F00 +), all three tested will use the tonos versions (see the "oxia & tonos codepoints" section below).

Computer Keyboards

Various operating systems have different approaches to inserting characters from the keyboard.

Mac OS

Mac OS comes with both a basic Greek keyboard and a Greek - Polytonic keyboard. The latter allows input of the vowels in the oxia range, but as with the soft keyboards mentioned above, normalizes the acute/oxia characters listed below to the tonos version.

Wiki & Forum software

MediaWiki and phpBB3, the DP wiki and forum software respectively, both NFC normalize their strings thereby converting any oxia character into a tonos character. If DP used oxia character, this would make communicating those to proofreaders very difficult. Any greek characters copied from the wiki or the forums would be tonos character.

PP conversion from tonos to oxia

After a book is finished, it's possible for Post-Processors to convert tonos codepoints back into oxia codepoints with a regular expression with three notable exceptions: · ; and ʹ

NFC normalization converts the GREEK ANO TELEIA into a MIDDLE DOT, GREEK QUESTION MARK into SEMICOLON, and GREEK NUMERAL SIGN into MODIFIER LETTER PRIME. Because there may be valid MIDDLE DOTs, SEMICOLONs and MODIFIER LETTER PRIMEs in a text, to convert a text from tonos to oxia a PPer would need to manually search and replace the characters as needed.

tonos: 

U+00B7 MIDDLE DOT
U+003B SEMICOLON
U+02B9 MODIFIER LETTER PRIME

oxia: 

U+0387 GREEK ANO TELEIA
U+037E GREEK QUESTION MARK
U+0374 GREEK NUMERAL SIGN

References

Sites

oxia & tonos codepoints

acute/oxia

Note: Because MediaWiki uses NFC normalization, the rendered characters will be tonos codepoints. You should use the U+ codepoint values below when referring to or searching for these codepoints in a text. 

ά U+1F71 GREEK SMALL LETTER ALPHA WITH OXIA
έ U+1F73 GREEK SMALL LETTER EPSILON WITH OXIA
ή U+1F75 GREEK SMALL LETTER ETA WITH OXIA
ί U+1F77 GREEK SMALL LETTER IOTA WITH OXIA
ό U+1F79 GREEK SMALL LETTER OMICRON WITH OXIA
ύ U+1F7B GREEK SMALL LETTER UPSILON WITH OXIA
ώ U+1F7D GREEK SMALL LETTER OMEGA WITH OXIA
Ά U+1FBB GREEK CAPITAL LETTER ALPHA WITH OXIA
Έ U+1FC9 GREEK CAPITAL LETTER EPSILON WITH OXIA
Ή U+1FCB GREEK CAPITAL LETTER ETA WITH OXIA
ΐ U+1FD3 GREEK SMALL LETTER IOTA WITH DIALYTIKA AND OXIA
Ί U+1FDB GREEK CAPITAL LETTER IOTA WITH OXIA
ΰ U+1FE3 GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND OXIA
Ύ U+1FEB GREEK CAPITAL LETTER UPSILON WITH OXIA
Ό U+1FF9 GREEK CAPITAL LETTER OMICRON WITH OXIA
Ώ U+1FFB GREEK CAPITAL LETTER OMEGA WITH OXIA

tonos

Ά U+0386 GREEK CAPITAL LETTER ALPHA WITH TONOS
Έ U+0388 GREEK CAPITAL LETTER EPSILON WITH TONOS
Ή U+0389 GREEK CAPITAL LETTER ETA WITH TONOS
Ί U+038A GREEK CAPITAL LETTER IOTA WITH TONOS
Ό U+038C GREEK CAPITAL LETTER OMICRON WITH TONOS
Ύ U+038E GREEK CAPITAL LETTER UPSILON WITH TONOS
Ώ U+038F GREEK CAPITAL LETTER OMEGA WITH TONOS
ΐ U+0390 GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS
ά U+03AC GREEK SMALL LETTER ALPHA WITH TONOS
έ U+03AD GREEK SMALL LETTER EPSILON WITH TONOS
ή U+03AE GREEK SMALL LETTER ETA WITH TONOS
ί U+03AF GREEK SMALL LETTER IOTA WITH TONOS
ΰ U+03B0 GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS
ό U+03CC GREEK SMALL LETTER OMICRON WITH TONOS
ύ U+03CD GREEK SMALL LETTER UPSILON WITH TONOS
ώ U+03CE GREEK SMALL LETTER OMEGA WITH TONOS
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