Module edit 

a vi line editor for the composer. insert and normal sub-modes, motions, operators, registers and history — the same muscle memory as everywhere else, rather than a handful of emacs control chords.

text is held as Vec<char> and the cursor is a CHAR index. chat is full of emoji and CJK, and byte offsets would put motions and deletes half-way through a glyph; at composer length the extra allocation is irrelevant.

no rendering and no app state here — main.rs asks what a key did and draws the result, which is what lets every motion below be tested directly.

Structs

Line

Enums

Act

what the caller should do after a key.

Mode

Constants

HISTORY_CAP

sent lines kept (in memory and on disk).