[Feature request] Add pre-1918 Russian as the input language option

[nalsuriv]

Legacy and aesthetics

Pre-1918 Russian orthography saw widespread use in the state and society, both of which no longer exist in the modern (let alone post-modern) world. However, as the Unicode standard includes the characters retired from the Russian alphabet by a set of spelling reforms in 1918-1920, I think it might prove useful for some to include it as a separate input language option, whether as an exercise in creative anachronism, or a literary fashion statement.

Alternatives

The Google Keyboard does include the legacy Cyrillic characters in its "Old church Slavonic" keyboard, however their placement is somewhat counter-intuitive In addition, the spelling suggestions are way off.

AnySoftKeyboard provides a better solution in terms of spell-checking and auto-completion, but it also struggles to place the additional characters in their more appropriate places. However, it does allow to extend the keyboard to four rows, thereby assigning each character its own separate key, with no need for long presses. Another drawback is that it totally excludes the letter Ё (ё), making it available only in the modern Russian keyboard layout, not the legacy one.

Suggested implementation

This layout introduces 8 additional characters (4 uppercase and 4 lowercase ones), with should be regarded as additional input options, available upon long pressing the respective main key:

• І (і) and Ѵ (ѵ) (placed here in order of frequency) should be additional options for the letter И (и);
• Ѣ (ѣ) should be an additional option for the letter Е (е);
• Ѳ (ѳ) should be an additional option for the letter Ф (ф).

In addition, the letter Ё (ё), relatively common in the modern Russian language but barely used before the spelling reforms, should be kept as an additional option for the letter Е (е) for the ease of its explicit input.

Note that the letters described in the above passages belong to the Cyrillic character set, and should not be confused with their similar-looking Latin counterparts!

The word list JSON for the autocompletion dictionary can be generated from a Hunspell dictionary, freely available from http://slavenica.com/za/?za=ru-petr1708-hunspell-3.1.tar.bz2 (© 2013-2015 Danslav Slavenskoj, MIT-license).

The suggested label for this keyboard layout is "Russian (pre-1918)" (default locale) and "Русскій (до 1918)" (ru locale).