Viet+
Vietnamese Input Method for Linux
Zero underline • No pre-edit buffer • Backspace-Replay sync • Built in Rust
---
## What is Viet+?
Viet+ is a Vietnamese input method for Linux that takes a fundamentally different approach from every other IME: **Direct Input**.
Most Vietnamese IMEs use a **pre-edit buffer** — you type into a temporary buffer with an ugly underline, and the text only becomes real Vietnamese when you commit it. This causes:
- Duplicate text (buffer + committed)
- Underline distraction
- Broken copy/paste
- Desync between engine state and what's on screen
Viet+ eliminates all of this. Keystrokes are **instantly converted to Unicode** — what you type is what you see. No buffer. No underline. No duplication.
---
## How It Works
### Data Flow: Keypress to Screen
```
Physical Keyboard
│
▼
┌──────────────────────────────────────────────────────────────┐
│ Stage 1: KEY CAPTURE │
│ │
│ evdev: /dev/input/event* grabs keyboard (primary, reliable) │
│ X11: XRecord passive monitoring (fallback) │
│ │
│ ┌─────────────┐ ┌──────────────┐ ┌──────────────────┐ │
│ │ evdev grab │ │ X11Capture │ │ FocusIn/FocusOut │ │
│ │ (libevdev) │ │ (XRecord) │ │ detection │ │
│ └─────────────┘ └──────────────┘ └──────────────────┘ │
└──────────────────────────────────────────────────────────────┘
│
▼
┌──────────────────────────────────────────────────────────────┐
│ Stage 2: KEY ROUTING │
│ │
│ Modifier keys (Ctrl/Alt/Super) → forward directly │
│ Ctrl+Space → toggle Vietnamese ON/OFF │
│ Backspace → replay_backspace() │
│ Characters → replay_and_inject(ch) │
│ VNI/Telex control keys → consume when no match │
└──────────────────────────────────────────────────────────────┘
│
▼
┌──────────────────────────────────────────────────────────────┐
│ Stage 3: BAMBOO ENGINE │
│ │
│ Transformation model: keystrokes produce composition │
│ changes. Marks and tones modify existing characters. │
│ Flexible backtracking scans up to 5 chars for vowels. │
│ Smart uo→ươ cluster with backtrack. │
│ Only emits Replace events when output actually changes. │
└──────────────────────────────────────────────────────────────┘
│
▼
┌──────────────────────────────────────────────────────────────┐
│ Stage 4: KEY INJECTION │
│ │
│ ASCII: direct Linux keycodes via /dev/uinput │
│ Backspace: Linux keycode 14 via uinput │
│ Vietnamese Unicode: clipboard paste + trailing ASCII via │
│ uinput (split only at whitespace/punctuation boundary) │
│ Persistent X11 connection for Ctrl+V (no per-call overhead) │
│ │
│ Fallback: vietc-uinputd Unix socket daemon (privileged) │
└──────────────────────────────────────────────────────────────┘
│
▼
Application receives keystrokes
and renders Vietnamese text on screen
```
### Event Sourcing + Backspace-Replay
This is Viet+'s core innovation. Traditional IMEs track state incrementally — each keystroke updates an internal buffer. But this buffer can **desync** from what's actually on screen (due to focus changes, external pastes, etc.).
Viet+ uses **Event Sourcing**: every input action is recorded as a typed `InputEvent` (`KeyTyped`, `Backspace`, `Flush`, `Paste`) in an `EventStore`. On every keystroke, the entire event history is **replayed from scratch** through a fresh engine to compute the correct diff — no incremental state to desync.
```
Traditional IME:
keystroke → update buffer → emit event → hope it matches screen
Viet+ (Event Sourcing):
keystroke → append InputEvent → replay ALL events in fresh engine → compute diff
```
On every keystroke:
1. The keystroke is appended as an `InputEvent` to the `EventStore`
2. A **brand new** `Engine` is created
3. The **entire** event history is replayed through it via `Engine::replay_events()`
4. The engine's buffer is the **correct** screen output
5. Viet+ computes the diff: `Engine::replay_events_to_commands()` returns Type/Backspace commands
This means:
- **Zero state desync** — always recomputed from scratch
- **Self-healing** — if anything goes wrong, the next keystroke fixes it
- **Privacy-safe** — `EventStore::pattern_hash()` provides a sha256 of the event type sequence for pattern detection without any ability to recover original text
- **Simple** — no complex state tracking or synchronization
---
## Architecture
```
vietc/
├── engine/ # Vietnamese composition engine (bamboo-core Rust port)
│ ├── engine.rs # Orchestrator + replay_events(), replay_events_to_commands()
│ ├── event.rs # Event Sourcing: InputEvent, EventStore, Command
│ ├── bamboo.rs # Bamboo engine: transformation model, composition, tone placement
│ ├── input_method.rs # Telex/VNI rule definitions
│ └── spelling.rs # Vietnamese syllable validation
│
├── protocol/ # Keyboard capture & injection
│ ├── inject.rs # KeyInjector trait
│ ├── x11_capture.rs # XRecord keyboard capture via C helper
│ ├── x11_inject.rs # XTest injection + direct clipboard
│ ├── uinput_monitor.rs # /dev/uinput injection for ASCII + Unicode
│ ├── uinput_client.rs # Unix socket client for vietc-uinputd
│ └── wayland_im.rs # Wayland IM protocol
│
├── daemon/ # Main daemon process
│ ├── main.rs # Event loops, Backspace-Replay, CPU pinning
│ ├── config.rs # TOML config loader + hot reload
│ ├── app_state.rs # Per-app Vietnamese/English memory
│ └── display.rs # X11/Wayland/compositor detection
│
├── uinputd/ # Privileged uinput backspace daemon (VMK-style)
│ └── main.rs # Unix socket server for /dev/uinput injection
│
├── ui/ # System tray icon
│ └── main.rs # Tray + daemon launcher
│
├── cli/ # Interactive test harness
├── packaging/ # AppImage + deb build scripts
└── vietc.toml # Default configuration
```
### Component Interaction
```
┌─────────────────────────────────────────────────────────────┐
│ vietc-tray │
│ (System tray icon, daemon launcher, password prompt) │
└───────────────────────┬─────────────────────────────────────┘
│ starts
▼
┌─────────────────────────────────────────────────────────────┐
│ vietc (daemon) │
│ │
│ ┌──────────────┐ ┌──────────────┐ ┌──────────────────┐ │
│ │ Config │ │ App State │ │ Display │ │
│ │ (hot reload) │ │ (per-app) │ │ (X11/Wayland) │ │
│ └──────┬───────┘ └──────┬───────┘ └────────┬─────────┘ │
│ │ │ │ │
│ └─────────────────┼────────────────────┘ │
│ │ │
│ ┌──────▼──────┐ │
│ │ Event Loop │ │
│ │ │ │
│ │ X11: grab │ │
│ │ keyboard │ │
│ │ │ │
│ │ Process │ │
│ │ keystroke │ │
│ │ │ │
│ │ Replay all │ │
│ │ history │ │
│ │ │ │
│ │ Inject │ │
│ │ diff │ │
│ └─────────────┘ │
│ │
│ ┌────────────────────────────────────────────────────────┐ │
│ │ vietc-engine │ │
│ │ TelexEngine / VniEngine / EnglishDict / Spelling │ │
│ └────────────────────────────────────────────────────────┘ │
│ │
│ ┌────────────────────────────────────────────────────────┐ │
│ │ vietc-protocol │ │
│ │ X11Capture / X11Injector / UinputInjector / Wayland │ │
│ └────────────────────────────────────────────────────────┘ │
└─────────────────────────────────────────────────────────────┘
```
---
## 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 | Example |
|-----|--------|---------|
| `1` | á (sắc) | `a1` → `á` |
| `2` | à (huyền) | `a2` → `à` |
| `3` | ả (hỏi) | `a3` → `ả` |
| `4` | ã (ngã) | `a4` → `ã` |
| `5` | ạ (nặng) | `a5` → `ạ` |
| `6` | â/ê/ô | `a6` → `â`, `e6` → `ê`, `o6` → `ô` |
| `7` | ơ/ư | `o7` → `ơ`, `u7` → `ư` |
| `8` | ă | `a8` → `ă` |
| `9` | đ | `d9` → `đ` |
Flexible typing: type the full syllable, then add marks/tone keys at the end. Example: `nguye6n4` → `nguyễn`. The engine scans backward up to 5 characters to find the target vowel.
---
## Features
| Feature | How It Works |
|---------|-------------|
| **Direct Input** | No pre-edit buffer. Keystrokes instantly become text via uinput/XTest injection |
| **Bamboo Engine** | Transformation model ported from bamboo-core — composition, marks, tones, flexible backtracking |
| **Flexible Backtrack** | Type tone/modifier at end of syllable (`tranaf` → `trần`). Scans up to 5 chars backward |
| **Smart Clusters** | `uo` → `ươ` with backtrack (`chuong7` → `chương`) |
| **Tone Placement** | Correct tone positioning for all Vietnamese diphthongs (io→gió, uâ→xuất, yê→nguyễn) |
| **Macro Expansion** | `ko` → `không`, `dc` → `được`, custom shortcuts |
| **Casing Preservation** | `Tieengs` → `Tiếng`, `TIEENGS` → `TIẾNG` |
| **App Memory** | Per-app Vietnamese/English state, saved to `overrides.toml` |
| **Hot Reload** | Config changes apply without restart (polls mtime every 1.5s) |
| **Focus Reset** | Focus change clears engine state — no stale injection on window switch |
| **CPU Priority** | Pins daemon to P-cores (0-3) + nice(-10) for low-latency input |
| **Uinput Daemon** | Privileged `vietc-uinputd` for clean backspace injection (Unix socket, VMK-style) |
---
## Installation
### Flatpak (recommended)
```bash
# Download from the release page, then:
flatpak install --user --bundle VietPlus-x86_64.flatpak
flatpak run io.github.vietc.VietPlus
```
Includes daemon + CLI + system tray + uinput daemon. Sandboxed — no system libraries are touched.
### Build from Source (Flatpak)
```bash
git clone https://github.com/vndangkhoa/vietc.git
cd vietc/packaging/flatpak
bash build-flatpak.sh [version]
```
Requires Flatpak runtimes: `org.gnome.Platform//50`, `org.gnome.Sdk//50`, `org.freedesktop.Sdk.Extension.rust-stable//25.08`
```bash
flatpak install --user flathub org.gnome.Platform//50
flatpak install --user flathub org.gnome.Sdk//50
flatpak install --user flathub org.freedesktop.Sdk.Extension.rust-stable//25.08
```
See `packaging/flatpak/FLATPAK_BUILD.md` for detailed build instructions.
---
## Configuration
Config file: `~/.config/vietc/config.toml` or `./vietc.toml`
```toml
input_method = "vni" # "vni" or "telex"
toggle_key = "space" # Ctrl+Space to toggle
start_enabled = false # English by default
grab = true # grab keyboard (evdev)
[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"
```
---
## License
MIT License — see [LICENSE](LICENSE) for details.
---
Made with love for the Vietnamese Linux community