FluXTeX

A native desktop LaTeX editor written in Rust, built around two pieces of custom infrastructure:

1. A from-scratch pure-Rust LaTeX engine (aldutex, tracked here as a submodule). FluXTeX compiles through aldutex by default. An optional Tectonic CLI fallback handles constructs aldutex hasn't grown into yet, so the rendered PDF stays faithful while the engine matures. See document/compiler.rs.

2. Real-time collaborative editing on a CRDT + WebRTC stack. A small signaling server (fluxtex-signal) brokers SDP and ICE between peers; once the WebRTC data channel is open, peers sync directly using cola operations. The demo also runs a shared-file watcher in parallel as a belt-and-suspenders path for single-machine verification.

Plus the usual editor surface: floem-based UI, custom LaTeX syntax highlighting against the editor's rope, multi-page PDF preview via pdfium, and a native macOS menu bar.

Architecture

                   ┌──────────────────┐
                   │  fluxtex-signal  │  WebSocket relay; rooms keyed by
                   │  (rooms + relay) │  6-char codes; forwards SDP/ICE.
                   └─────┬────────┬───┘
                         │        │
                  WS     │        │     WS
                         ▼        ▼
                   ┌──────────┐  ┌──────────┐
                   │  Peer A  │  │  Peer B  │
                   │ fluxtex- │  │ fluxtex- │
                   │   app    │  │   app    │
                   └────┬─────┘  └────┬─────┘
                        └────────────┘
                       WebRTC DataChannel
                  (cola CRDT ops, snapshots)

    Each peer:
      ┌──────────────┐    ┌────────────────────┐    ┌─────────────────┐
      │ Floem editor │ ── │ DocumentBuffer     │ ── │ Compile pipe:   │
      │  (rope-based)│    │  (cola Replica +   │    │  aldutex first, │
      │              │    │   String mirror)   │    │  tectonic on    │
      └──────────────┘    └────────────────────┘    │  fallback.      │
                                                    └────────┬────────┘
                                                             ▼
                                                   ┌─────────────────┐
                                                   │ pdfium-render → │
                                                   │ multi-page PNG  │
                                                   │ preview         │
                                                   └─────────────────┘

Layout

Path	What's there
crates/fluxtex-app	Editor binary: floem UI, compile pipeline, syntax highlighting, PDF preview, collaboration glue, macOS menu bar
crates/fluxtex-signal	Signaling server (lib for the wire types, bin for the relay)
vendor/aldutex	Pure-Rust LaTeX engine, as a Git submodule and the primary compiler
vendor/pdfium	Pdfium headers + license; the .dylib is fetched out-of-band (see Setup)
vendor/tectonic	Optional fallback compiler location

Setup

Prerequisites

• Rust 1.78+
• macOS (the menu bar code uses objc2-app-kit; the rest is portable)
• vendor/aldutex initialized as a submodule (see below)

Clone with the submodule

git clone --recurse-submodules https://github.com/danielsuit/fluxtex
cd fluxtex

If you've already cloned without --recurse-submodules:

git submodule update --init --recursive

Fetch the pdfium dylib

The Pdfium headers are vendored; the dylib isn't (it's ~7 MB and platform- specific). Fetch the macOS arm64 build:

curl -L -o /tmp/pdfium-mac-arm64.tgz \
  https://github.com/bblanchon/pdfium-binaries/releases/download/chromium/7802/pdfium-mac-arm64.tgz
tar -xzf /tmp/pdfium-mac-arm64.tgz -C vendor/pdfium

document/pdf_render.rs walks up from the executable looking for vendor/pdfium/lib/libpdfium.dylib, falling back to bind_to_system_library.

Build

cargo build

Optional: install Tectonic for the fallback compiler

When aldutex declines a document, FluXTeX can hand it to Tectonic so the preview still renders. If you don't install Tectonic, aldutex-only documents still compile — you'll just see an error pane for anything aldutex can't handle.

To enable the fallback, install Tectonic via Homebrew:

brew install tectonic

…or drop a binary at vendor/tectonic/bin/tectonic, or point FLUXTEX_TECTONIC_BIN at one. Bundle lookup order is documented at the bottom of this README.

Running

The editor takes per-instance flags so two copies can run side-by-side:

cargo run -p fluxtex-app -- \
    --signaling 127.0.0.1:9000 \
    --autosave path/to/doc.tex \
    --label "My Peer"

Demo: two peers + signaling server

A scripted launcher boots the signaling server and two app instances pointed at the same shared file:

./run-demo.sh

Click Host in one window, type the displayed 6-character code into the other window's Room code field, and click Join. The status pill turns green when the WebRTC data channel is established; edits flow either way through the CRDT.

The demo additionally watches the shared autosave path on disk, which is useful for sanity-checking edit propagation without involving the network stack.

Iterating on the LaTeX engine

vendor/aldutex is a Git submodule. To pull the latest revision, rebuild, and verify it still drives the editor cleanly:

./update-aldutex.sh

Tests

cargo test -p fluxtex-app -p fluxtex-signal

Covers the wire-format round-trip for SyncMessage (Insert/Delete/Snapshot), the snapshot-seed-the-joiner round-trip end-to-end through the CRDT, and the shape of the signaling JSON protocol.

Lints

cargo fmt -p fluxtex-app -p fluxtex-signal -- --check
cargo clippy -p fluxtex-app -p fluxtex-signal --all-targets --no-deps -- -D warnings

(--no-deps skips clippy on the aldutex submodule, which has its own lint budget I don't try to enforce here.)

Tectonic fallback lookup order

When the dispatcher falls back to Tectonic, document/compiler.rs locates the binary and optional bundle in this order:

Resource	Sources, in priority
Binary	FLUXTEX_TECTONIC_BIN, vendor/tectonic/bin/tectonic, vendor/tectonic/tectonic, tectonic on PATH
Bundle	FLUXTEX_TECTONIC_BUNDLE, vendor/tectonic/bundles/{default.zip,default.bundle,tectonic-default.bundle}, vendor/tectonic/default.bundle

If no bundle is configured, Tectonic uses its default network bundle on the first fallback compile, then caches it.

License

MIT.