ReCast

Automatic English ↔ Hebrew keyboard-layout correction, as you type.

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ReCast is a lightweight background daemon that watches what you type, checks each finished word against embedded English and Hebrew dictionaries, and — when it detects that a word was typed in the wrong layout — switches the keyboard layout and retypes the word correctly. It runs quietly in the tray, menubar, or as a system service, and stays out of your way until a mistyped word actually needs fixing.

• Cross-platform — Linux, macOS, and Windows share one correction engine.
• Self-contained — both dictionaries are compiled into the binary, so there are no data files to install and it runs identically from any directory.
• Conservative by design — it anchors on your live keyboard layout and only intervenes when it is confident, so valid words are never mangled.

Contents

• How it works
• Supported platforms
• Requirements
• Installation
  • Linux
  • macOS
  • Windows
• Usage
  • Command-line options
  • Environment variables
• Tuning correction behaviour

How it works

1. Capture — ReCast reads global key events and builds up the current word from your key presses. The buffer resets on cursor- and focus-shifting keys (Tab, Escape, arrows, Home/End, PgUp/PgDn, Insert, Delete) and on mouse clicks (macOS / Windows).
2. Evaluate — when you press Space or Enter, ReCast interprets the typed key sequence as both an English word and a Hebrew word, and looks each up in the matching dictionary.
3. Decide — it anchors on your live keyboard layout (queried from the OS, with any English or Hebrew regional variant recognised). A sequence that already reads as a real word in your current layout is left untouched — including prefixed Hebrew forms (ו/ה/ל/ב/כ/מ/ש) and words whose other-layout reading also happens to be a dictionary word. ReCast switches only when the other layout yields a confident word and the current one yields nothing real. This is what keeps valid and prefixed words intact.
4. Correct — on a switch, ReCast erases the mistyped word and retypes it (followed by the original Space/Enter), waiting until the layout change has actually propagated first.

Missing-space splitting (carving helloעולם into two words) is opt-in via RECAST_SPLIT=1. It is off by default because it cannot reliably distinguish a word that simply isn't in the dictionary from two run-together words.

Supported platforms

OS	Capture	Layout switch
Linux	evdev	hyprctl switchxkblayout (Hyprland only)
macOS	rdev	Carbon TISSelectInputSource
Windows	rdev	LoadKeyboardLayoutW + WM_INPUTLANGCHANGEREQUEST

Requirements

• Rust toolchain (rustup, cargo).
• Both English and Hebrew layouts installed in your OS keyboard settings. On Linux/Hyprland, the xkb config must list English as layout 0 and Hebrew as layout 1.
• Linux only: membership in the input group (for evdev read access). ReCast creates a uinput virtual device named recast-injector to replay corrected words.

Installation

Linux

One-shot setup: adds your user to the input group, builds in release mode, installs the binary to ~/.local/bin/recast, and registers a systemd --user unit that starts ReCast at login.

sudo usermod -aG input $USER && exec newgrp input <<< 'make service'

newgrp applies the new group to the current shell so you don't have to log out; omit it and re-login instead if you prefer. Ensure ~/.local/bin is on your PATH.

Manage the service:

systemctl --user status  recast    # health check
systemctl --user restart recast    # apply a rebuild
journalctl  --user -u    recast -f  # follow logs
make service-uninstall             # stop and remove the unit

Common Make targets:

Target	Action
make	cargo build --release
make install	build + copy binary to ~/.local/bin
make deploy	clean + build + install
make uninstall	remove the installed binary
make run ARGS=-g	cargo run with a flag (here, the TUI)
make help	full target list

Override the install root with PREFIX=, e.g. make install PREFIX=/opt/recast.

macOS

make service

This writes a launchd LaunchAgent at ~/Library/LaunchAgents/org.recast.plist and starts it. The first time it runs, grant the binary Input Monitoring and Accessibility permissions in System Settings → Privacy & Security.

To reset ReCast's permissions:

tccutil reset All com.recast.app

Once installed, recast is on your PATH and supports the same flags as every other platform (see Usage) — e.g. recast -h, recast -g, recast -s. Note that the LaunchAgent runs with KeepAlive, so recast -s stops a manually-launched instance but the service will be relaunched by launchd; to stop the service, run make service-uninstall.

Windows

In PowerShell:

.\deploy.ps1 -Target service

This builds, installs to %USERPROFILE%\.local\bin, and registers a Scheduled Task that runs ReCast at logon. Run .\deploy.ps1 -Target help to list every target.

Usage

You don't need the service — you can run the binary (or cargo run --release) directly from any shell. On Linux it daemonizes into the background by default (under systemd this is detected automatically); on macOS and Windows it lives in the tray/menubar.

Command-line options

Option	Description
(none)	Start ReCast (Linux: forks into the background and writes a pidfile)
-s, --stop	Stop a running daemon (via its pidfile)
-g, --gui	Foreground terminal dashboard (TUI): status, live log, toggle
-w, --window	Foreground control window (Linux only)
-f, --foreground	Don't daemonize (Linux; implied under systemd)
-h, --help	Show the full option list

The TUI (-g, Linux/Windows) shows the enabled state, the fixed-word counter, and a live log; press e or Space to toggle correction on and off, and q to quit. The control window (-w) offers the same toggle and counter in a small GUI window. On macOS, use the menubar menu instead.

Environment variables

Variable	Effect
RECAST_DEBUG=1	Print every word check and switch decision
RECAST_SPLIT=1	Enable the opt-in missing-space splitting fallback
RECAST_SHORT=0	Never auto-switch on short (≤3 char) words

RECAST_DEBUG=1 recast   # verbose decision logging

Tuning correction behaviour

Short words are the most collision-prone: many 2–3 letter abbreviations are valid in one dictionary while also spelling a real word in the other layout. RECAST_SHORT=0 is the knob for "never switch incorrectly" — at the cost of no longer fixing short mistyped words.