Terminal user interfaces for OCaml.

This repository contains three packages that work together or independently:

Package	Description
Mosaic	High-level UI framework with The Elm Architecture
Matrix	Terminal toolkit: rendering, input, PTY, VTE
Toffee	CSS layout engine (Flexbox, Grid, Block) ported from Taffy

Mosaic provides a TEA runtime (model / update / view), 18 built-in widgets, and CSS layout via Toffee. Write your UI as a pure function of state.

Matrix is the terminal layer: double-buffered rendering that diffs cell changes to emit minimal ANSI output, Kitty keyboard, SGR mouse, bracketed paste, focus reporting, and a virtual terminal emulator. Usable on its own for immediate-mode terminal apps.

Toffee is a pure OCaml port of Taffy. It computes Flexbox, Grid, and Block layout with no C stubs and no runtime dependencies.

Two additional packages are included:

Package	Description
matrix-eio	Eio-based runtime for Matrix
tree-sitter	OCaml bindings for Tree-sitter

Quick start

Install via opam:

opam install mosaic

Or build from source:

dune build @install

Run a demo:

dune exec ./mosaic/examples/01-counter/main.exe

A minimal Mosaic app:

open Mosaic
type msg = Increment | Decrement | Quit
let init () = (0, Cmd.none)
let update msg model =
  match msg with
  | Increment -> (model + 1, Cmd.none)
  | Decrement -> (model - 1, Cmd.none)
  | Quit -> (model, Cmd.quit)
let view model =
  box ~flex_direction:Column
    ~size:{ width = pct 100; height = pct 100 }
    [
      box ~flex_grow:1. ~align_items:Center ~justify_content:Center
        [ text (Printf.sprintf "Count: %d" model) ];
      text "Press + / - to change, q to quit";
    ]
let subscriptions _model =
  Sub.on_key (fun ev ->
      match (Event.Key.data ev).key with
      | Char c when Uchar.equal c (Uchar.of_char '+') -> Some Increment
      | Char c when Uchar.equal c (Uchar.of_char '-') -> Some Decrement
      | Char c when Uchar.equal c (Uchar.of_char 'q') -> Some Quit
      | Escape -> Some Quit
      | _ -> None)
let () = run { init; update; view; subscriptions }

Examples

Mosaic ships with 25 examples and 4 showcase apps covering forms, tables, markdown, syntax highlighting, charts, async commands, tree widgets, CSS Grid layouts, and more. See mosaic/examples/.

Matrix has 15 examples and 1 showcase demonstrating rain animation, game of life, mandelbrot rendering, snake, a synthesizer, and a terminal emulator. See matrix/examples/.

Run any example from the repo root:

# Mosaic: form with focus management
dune exec ./mosaic/examples/12-form/main.exe
# Mosaic: ML dashboard showcase
dune exec ./mosaic/examples/x-dashboard/main.exe
# Matrix: rain animation
dune exec ./matrix/examples/01-rain/main.exe

License

ISC. See LICENSE.