rustmd

A Typora-style WYSIWYG Markdown editor and reader, written in pure Rust.

No WebView, no JavaScript runtime, no bundled browser. Every extension beyond plain Markdown is rendered by code in this repository: the editor, the maths engine, the diagram renderer and the HTML renderer are all native egui drawing.

What it does

• Live preview, Typora style — the block under the caret shows its Markdown source, everything else renders. No split pane.
• Self-contained maths — $x^2$ and $$…$$, including \begin{…} environments (pmatrix, bmatrix, cases, aligned, array, …), typeset by a small box-model engine in src/math.rs.
• Self-contained diagrams — ```mermaid fences render as real vector graphics for eight diagram types: flowchart/graph, pie, sequenceDiagram, classDiagram, stateDiagram-v2, erDiagram, gantt and mindmap (src/mermaid.rs).
• HTML rendering — block-level HTML (<div>, <table>, <details>, <ul>, <pre>, <img>) is laid out as real structure, and inline tags (<b>, <i>, <u>, <code>, <span style="…">, <br>, comments, autolinks) take effect instead of being shown as source (src/html.rs). Markdown still works inside an HTML block.
• Syntax-highlighted code fences via syntect.
• Folders, tabs and a file picker built on rfd.
• Virtualised scrolling — only the blocks in the viewport are laid out, so a hundred-thousand-block document stays interactive.
• Standalone HTML export — --export in.md out.html writes a single file with everything inlined except the MathJax and mermaid CDN scripts.

Running

cargo run --release                       # open the editor
cargo run --release -- notes.md           # open a file
cargo run --release -- --export in.md out.html
cargo run --release -- --bench big.md     # parse + layout timings, no window

Building

macOS

scripts/make-app.sh          # -> dist/rustmd.app

Produces a real .app bundle, so it can be launched from Finder, found by Spotlight, and registered as a handler for .md files. It declares LSHandlerRank = Alternate, so installing it will not steal the default handler from whatever you already use.

Windows

cargo build --release        # -> target\release\rustmd.exe

Release builds carry windows_subsystem = "windows", so no console window is attached.

rustmd-windows-x64.zip is attached to every release, and the Windows workflow builds and tests the same .exe on every push.

Linux and other platforms

cargo build --release

The code is portable: libc is a unix-only dependency and the Apple-Event plumbing in src/macos.rs is compiled out elsewhere behind a stub.

Layout

Path	What lives there
src/app.rs	Application state, commands, menu bar
src/doc.rs	Document model and undo history
src/parser.rs	Markdown → blocks, inline spans
src/render.rs	Block drawing for every block kind
src/editor.rs	The live-preview widget, caret and selection
src/html.rs	Tolerant HTML subset renderer
src/html_export.rs	Static HTML export
src/math.rs	LaTeX layout engine
src/mermaid.rs	Diagram parsing, layout and drawing
src/code_hl.rs	Syntax highlighting
src/picker.rs	Folder listing and file open dialog
src/macos.rs	Apple Event handling for "open with"
src/smoke.rs	Headless end-to-end tests over samples/

samples/test-render.md is a stress document that exercises every syntax the renderer claims to support, with an "expected" note per section. Parts of the test suite read it directly with include_str!, so the fixtures cannot drift away from the document.

Tests

cargo test

The suite renders documents without opening a window, so layout regressions fail in CI rather than in the eye.

License

MIT — see LICENSE.