Module engine 

Vietnamese IME engine — Letter-based accumulator model. Each keystroke produces a Letter struct. Modifier keys (w, tone, z) mutate the last matching vowel in place. UTF-8 output via precomputed tables.

Functions

convert_teip_vni

Combined Telex + VNI mode. Accepts BOTH Telex and VNI keystrokes in one stream:

convert_telex

convert_telex_auto_restore

Telex conversion with auto-restore: if the composed output is not valid Vietnamese and differs from the raw input, return the raw input instead. Skips auto-restore when the input has Vietnamese composition markers (dd, vowel+w, double vowels) — those signal intentional IME transforms.

convert_viqr

VIQR (Vietnamese Quoted-Readable) conversion.

convert_vni