Viet+

Vietnamese Input Method for Linux
_{Zero underline • Native X11 • Backspace-Replay sync • Built in Rust}

About Viet+

Viet+ is a modern Vietnamese input method for Linux that eliminates the underline hell common in other Vietnamese IMEs. Unlike traditional solutions that use pre-edit buffers with ugly underlines and duplicate text, Viet+ implements a Direct Input approach:

• No pre-edit buffer — keystrokes are instantly converted to Unicode
• No underline — clean, distraction-free typing
• No text duplication — just pure Vietnamese
• Backspace-Replay sync — engine state never desyncs from what's on screen

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Features

Feature	Description
Direct Input Engine	No pre-edit buffer, no underline, no text duplication
Backspace-Replay	Replays entire keystroke history through a fresh engine on every keypress — eliminates state desync
Telex & VNI	Both input methods fully supported
Flexible Diacritic Placement	Type modifiers/tone marks at end of syllable (e.g., tranaf -> trần)
Auto-Restore English	Hit space/ESC to undo accidental Vietnamese conversion
ESC Undo	Strip all tones from the current word instantly
Smart App Memory	Remembers Vietnamese/English per application
Macro Expansion	Custom shortcuts (e.g., ko -> không)
Focus Reset	Automatically clears engine state on focus change between apps
Casing Preservation	Syllable substitutions preserve your exact casing (e.g. Saa -> Sả, SAA -> SẢ)
CPU Priority	Pins daemon to P-cores + nice(-10) for low-latency input
Zero Telemetry	No keylogging, no network calls, fully FOSS

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Why Viet+?

Most Vietnamese input methods on Linux suffer from underline hell — pre-edit buffers that duplicate text, show ugly underlines, and break your flow. Viet+ takes a different approach:

Direct Input — keystrokes are instantly converted to Unicode. No pre-edit buffer. No underline. No text duplication. Just pure Vietnamese.

The Backspace-Replay pattern keeps the engine perfectly in sync: instead of tracking state incrementally (which can desync), Viet+ replays the entire keystroke history through a fresh engine on every keypress. The screen output is always recomputed from scratch.

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Quick Start

# Clone and build
git clone https://git.khoavo.myds.me/vndangkhoa/vietc.git
cd vietc
make build-all

# Test the engine interactively
cargo run --bin vietc-cli

# Run the daemon
cargo run --bin vietc

# Or download a package from the releases page
#   AppImage: ./Viet+-0.1.0-x86_64.AppImage
#   Debian:   sudo dpkg -i vietc_0.1.0-1_amd64.deb

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Input Methods

Telex

Key	Result	Example
aa	â	tan -> tân
aw	ă	tan -> tăn
ee	ê	men -> mên
oo	ô	to -> tô
ow	ơ	to -> tơ
uw	ư	tu -> tư
s	á (sắc)	as -> á
f	à (huyền)	af -> à
r	ả (hỏi)	ar -> ả
x	ã (ngã)	ax -> ã
j	ạ (nặng)	aj -> ạ
dd	đ	dd -> đ

VNI

Key	Result
a1	á
a2	à
a3	ả
a4	ã
a5	ạ
a6	â
a8	ă
e6	ê
o6	ô
o7	ơ
u7	ư

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Configuration

Config file: ~/.config/vietc/config.toml or ./vietc.toml

input_method = "vni"
toggle_key = "space"
start_enabled = false
grab = true

[auto_restore]
enabled = true
trigger_keys = ["space", "escape"]

[app_state]
enabled = true
english_apps = ["code", "vim", "kitty", "foot"]
vietnamese_apps = ["telegram", "discord", "firefox"]

[macros]
ko = "không"
dc = "được"
vs = "với"
lm = "làm"

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Architecture

┌──────────────────┐     ┌──────────────────┐     ┌────────────────┐
│  X11 Keyboard    │────▶│  Viet+ Daemon    │────▶│  X11/XTEST     │
│  Grab (XGrabKb)  │     │                  │     │  Injection     │
│                  │     │  Backspace-Replay│     │                │
│  FocusIn/Out     │     │  Engine          │     │  Direct        │
│  Detection       │     │  (Telex/VNI)     │     │  Clipboard     │
└──────────────────┘     └──────────────────┘     └────────────────┘
                                │
                          ┌─────┴─────┐
                          │  App State │
                          │  Manager   │
                          └───────────┘

How Backspace-Replay Works

1. All keystrokes in the current word are stored in keystroke_history
2. On each keypress, a fresh engine is created and the entire history is replayed through it
3. The engine's buffer IS what should be on screen
4. Viet+ calculates the diff: backspaces to erase old text + new text to type
5. On flush (space/period/etc.), history is cleared for the next word

This eliminates the state desync bugs that plague incremental engines.

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Installation

Debian/Ubuntu Package

sudo dpkg -i vietc_0.1.0-1_amd64.deb

Recommends: libxtst6, xclip (for clipboard injection)

AppImage

./Viet+-0.1.0-x86_64.AppImage

No special permissions needed on X11 — uses XGrabKeyboard + XTest injection.

Manual Install

make build-all
sudo make install

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Building

# Build all backends (X11 + Wayland)
make build-all

# Run tests (255+ tests)
make test

# Run interactive test harness
cargo run --bin vietc-cli

# Build packages
make deb        # .deb package
make appimage   # AppImage

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Project Structure

vietc/
├── engine/              # Core IME engine (Telex + VNI)
│   ├── src/
│   │   ├── engine.rs    # Main engine + replay_keystrokes()
│   │   ├── telex.rs     # Telex state machine
│   │   ├── vni.rs       # VNI engine
│   │   ├── english.rs   # English auto-restore dictionary
│   │   └── tests/       # 255+ unit tests
│   └── Cargo.toml
├── protocol/            # Injection backends
│   ├── src/
│   │   ├── inject.rs         # KeyInjector trait
│   │   ├── x11_capture.rs    # X11 keyboard capture (XGrabKeyboard)
│   │   ├── x11_inject.rs     # Direct X11 clipboard + XTest injection
│   │   └── wayland_im.rs     # Wayland IM protocol
│   └── Cargo.toml
├── daemon/              # Background daemon
│   ├── src/
│   │   ├── main.rs      # Event loop, Backspace-Replay integration
│   │   ├── config.rs    # TOML config loader
│   │   ├── app_state.rs # Per-app state manager
│   │   └── display.rs   # Display server detection
│   └── Cargo.toml
├── cli/                 # Interactive test harness
├── ui/                  # Tray icon application
├── packaging/           # Distribution packages
│   ├── appimage/        # AppImage build scripts
│   └── deb/             # .deb package build scripts
├── vietc.toml           # Default configuration
├── vietc.service        # Systemd user service
├── Makefile             # Build targets
└── README.md

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Changelog

See CHANGELOG.md for release history.

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License

MIT License - see LICENSE for details.

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_{Made with love for the Vietnamese Linux community}