Introduction

ashlar is a Rust library for building desktop apps (and, for its headless core, web apps) on egui. It gives an app the parts most apps rebuild by hand:

• Documents with undo: the document is an Arc snapshot with a revision number, every edit is an undo step, and the file format is versioned with migrations. Autosave and crash recovery come with it.
• Commands: one registry drives the menus, keyboard shortcuts, the command palette, a CLI, a control port and an MCP server. Anything a user can do, a script or an AI agent can do too.
• Background jobs with progress, cancellation and panic isolation, whose results land on the UI thread as one undo step.
• Files and settings: per-app folders, atomic writes, keyed settings, recent files.
• Native OS features: file dialogs, the menu bar, a tray icon, global shortcuts, notifications, drag and drop, single instance.
• UI components on egui: lists and tables that stay fast at any length, a sidebar, tabs, forms, dialogs and popovers, toasts, markdown, code and diff views, a chat kit, animated values.
• A runtime with crash safety, telemetry, and a headless mode for tests and agents.

Domain widgets (a timeline for a video editor, a canvas for a CAD tool) stay in the app. ashlar provides the general pieces they are built from.

The component gallery (cargo run -p ashlar-example-gallery), rendered headless.

Why

• Everything is a command. Menus, shortcuts, the palette, the CLI, the control port and MCP all go through one registry and one execute chokepoint.
• It does not crash. The library has no unwrap, panic! or unsafe outside tests. A panic in a view, a command or a job is caught, the session keeps running, and unsaved work is recovered on the next launch.
• An idle app does no work. Frames are drawn only when something asks for one: input, a document change, a finished job, a running animation.
• Apps can be tested and driven without a window. Every app takes --headless --snap out.png --tree tree.json, runs .ui scripts on a virtual clock, and serves golden screenshots and named scenes.

Status

The full API reference is on docs.rs/ashlar-rs. The source is on GitHub.

Where to start

1. Install the crate.
2. Build your first app.
3. Read the notes example in the repository (examples/notes): a complete app with typed commands, undo, autosave, a virtualized list, scenes and a notes-cli binary.