Pure CL terminal UI framework. No ncurses, no FFI, no external dependencies.

```lisp (ql:quickload :cl-tty) ```

## Quick start

The simplest possible cl-tty program — detect the terminal, draw some text, read a key, and shut down:

```lisp (sb-posix:with-raw-terminal (let* ((be (cl-tty.backend:detect-backend)) (w 80) (h 24)) (cl-tty.backend:initialize-backend be) (unwind-protect (progn (cl-tty.backend:draw-text be 0 0 "Hello, terminal!" :green nil :bold t) (cl-tty.backend:draw-border be 0 1 30 5 :style :single) (finish-output) ;; Read one key (blocks) (cl-tty.input:read-event be)) (cl-tty.backend:shutdown-backend be)))) ```

Or run the full interactive demo:

```bash sbcl –script demo.lisp ```

## Architecture

Two backends, one protocol:

• modern-backend — truecolor 24-bit, OSC 8 hyperlinks, DECICM sync, SGR mouse, kitty keyboard, bold/italic/underline, box-drawing chars
• simple-backend — ASCII art, no color, universal compatibility (pipe-safe)

Everything is pure escape sequences (no curses, no terminfo, no FFI).

### Backend protocol

Every drawing operation is a CLOS generic function dispatched on the backend class. Programs never call terminal codes directly:

```lisp ;; Lifecycle (initialize-backend backend) (shutdown-backend backend)

;; Drawing (draw-text backend x y string fg bg &key bold italic underline reverse dim) (draw-border backend x y width height &key style fg bg title) (draw-rect backend x y width height &key bg) (draw-link backend x y string url &key fg bg)

;; Input (read-event backend &key timeout) → key-event or mouse-event (backend-size backend) → (values columns lines)

;; Cursor (cursor-move backend x y) (cursor-hide backend) (cursor-show backend) (cursor-style backend shape &key blink) ;; :bar :block :underline ```

### Event loop pattern

```lisp (let ((be (detect-backend))) (initialize-backend be) (loop with running = t while running do (backend-clear be) ;; … draw frame … (finish-output standard-output) (let ((event (read-event be))) (typecase event (key-event (when (eql (key-event-key event) :escape) (setf running nil))) (mouse-event ;; handle mouse )))) (shutdown-backend be)) ```

### Layout system

Pure CL flexbox layout engine. No C dependencies, no Yoga FFI.

```lisp ;; Macros build layout-trees: (vbox (:gap 1 :padding 1) (header "Title") (hbox (:grow 1) (sidebar (:width 30) …) (content …))) ```

Layout properties: `:direction` (`:row` / `:column`), `:grow`, `:shrink`, `:basis`, `:gap`, `:padding`, `:margin`, `:width`, `:height`, `:wrap`.

See `layout/layout.lisp` or `org/layout-engine.org` for the full API.

### Rendering pipeline

Component trees render through a coordinated pipeline:

1. Layout pass — `compute-layout` traverses dirty branches, solves flex constraints
2. Render dispatch — `render` generic dispatches per component type
3. Framebuffer — (optional) `make-framebuffer-backend` captures to a cell array, `diff-framebuffers` computes minimal changes, `flush-framebuffer` writes only changed cells

```lisp ;; Full pipeline with framebuffer (let* ((fb-be (make-framebuffer-backend :width 80 :height 24)) (fb (fb-framebuffer fb-be))) (render my-component fb-be) (flush-framebuffer prev-fb fb real-backend)) ```

## Components

Component	What it does	Status
Box	Bordered container with background, title	stable
Text	Styled text with word-wrap, spans	stable
ScrollBox	Scrollable viewport with scrollbars	stable
TabBar	Horizontal tab navigation	stable
Select	Dropdown with fuzzy filter, category headers	stable
TextInput	Single-line text input with readline keybindings	stable
TextArea	Multi-line input with undo/redo, cursor movement	stable
Markdown	Renders markdown with syntax highlighting + diffs	stable
Dialog	Modal overlays with stack management	stable
Toast	Transient notifications (info/success/warning/error)	stable
Mouse	Event handlers, hit-testing, text selection	stable
Slot	Plugin system — named slots for extensible UI	stable

Each component follows a consistent pattern:

```lisp ;; 1. Create — factory function returns instance (let ((input (make-text-input :placeholder "Type here…")) (box (make-box :border-style :single :title "My Box")))

;; 2. Layout — macros compose components (vbox (:gap 1) box (hbox (:grow 1) input (make-select :options '((:title "Option A") (:title "Option B")))))

;; 3. Render — dispatches through the component protocol (render my-component backend)) ```

### Box

Bordered container. Draws borders using Unicode box-drawing characters (modern) or ASCII `+`/`-`/`|` (simple). Supports background fill, titled borders. See `org/box-renderable.org`.

```lisp (make-box &key (border-style :single) title (title-align :left) fg bg width height) ```

### Text

Styled text with inline spans and word wrapping. Spans support per-run attributes (bold, italic, underline, fg, bg). See `org/box-renderable.org`.

```lisp (make-text content &key fg bg wrap-mode width height spans) ;; Span example: (span "hello" :bold t :fg :bright-yellow) ```

### TextInput

Single-line text editor with emacs-style keybindings. Supports placeholder, max-length, on-submit callback. See `org/text-input.org`.

```lisp (make-text-input &key value cursor placeholder max-length on-submit) ;; Widget logic (input-level, no backend needed): (handle-text-input input (make-key-event :key :a :code (char-code #\a))) ```

### TextArea

Multi-line text editor. Supports undo/redo (Ctrl+Z/Y), cursor movement, line joining on backspace. See `org/text-input.org`.

```lisp (make-textarea &key value on-submit) ```

### ScrollBox

Scrollable viewport with a list of children. Only renders children intersecting the visible area (viewport culling). Scrollbars drawn at the right/bottom edges. See `org/scrollbox-tabbar.org`.

```lisp (make-scroll-box &key children scroll-y scroll-x sticky-scroll-p) (scroll-by sb dy dx) ```

### TabBar

Horizontal tab navigation. Renders tab labels, highlights active tab. Left/right arrows cycle through tabs. See `org/scrollbox-tabbar.org`.

```lisp (make-tab-bar &key tabs active) (tab-bar-add tb id title) (tab-bar-next tb) / (tab-bar-prev tb) (tab-bar-handle-key tb event) ```

### Select

Dropdown/filter widget. Options can have categories (rendered as non-selectable headers). Fuzzy fallback: matching > 30% character overlap. Arrow keys navigate, Enter selects. See `org/select.org`.

```lisp (make-select &key options filter on-select) ;; Options format: (:title "Name" :category "Group") or (:title "Name") ```

### Markdown

Parsed markdown AST with rendering. Supports headings, paragraphs, bold, italic, inline code, links, code blocks with syntax highlighting, diff blocks, blockquotes, lists, thematic breaks. See `org/markdown-renderer.org`.

```lisp (render-markdown "# Hello\n\nThis is bold.") ```

### Dialog + Toast

Modal dialog stack. `alert-dialog`, `confirm-dialog`, `select-dialog`, `prompt-dialog` are convenience constructors. Toasts are transient notifications that auto-dismiss. See `org/dialog.org`.

```lisp (push-dialog (make-instance 'dialog :size :medium)) (alert-dialog "Notice" "Operation complete") (toast "Saved!" :variant :success) ```

### Mouse

Mixin class providing mouse event handler slots. `hit-test` finds the deepest component at a coordinate. Text selection tracks drag gestures. Scrollboxes integrate wheel events. See `org/mouse.org`.

```lisp (defclass my-panel (mouse-mixin) …) (handle-mouse-event component mouse-event) (hit-test root x y) → deepest matching component ```

### Slot system

Plugin system for extensible rendering slots. Register named rendering functions, then render them by slot name. Useful for toolbars, status bars, and plugin architectures.

```lisp (defslot :status-bar :order 0 (lambda (&rest args) (draw-text backend 0 0 "Ready" :text-muted nil))) (slot-render :status-bar) ```

## Backend features

Feature	modern	simple
Truecolor (24-bit)	Yes	No
Bold/italic	Yes	No
OSC 8 hyperlinks	Yes	No
DECICM sync	Yes	No
SGR mouse	Yes	No
Kitty keyboard	Yes	No
Box drawing chars	Unicode	ASCII
Pipe-safe	No	Yes

Backend selection happens automatically via `detect-backend`. It checks:

1. Is stdout a TTY? (if not → simple-backend)
2. Does `COLORTERM` contain "truecolor" or "24bit"?
3. Send DA1 query — does the terminal respond with modern feature codes?

Result is cached in `*detected-backend*`.

## Development

```bash

sbcl –script run-all-tests.lisp

sbcl –script demo.lisp

for f in org/*.org; do emacs –batch –eval "(progn (require 'org) (find-file \"$f\") (org-babel-tangle) (kill-buffer))" 2>&1 done ```

Literate programming: `.org` files in `org/` are the source of truth for the input system, scrollbox/tabbar, dialog, mouse, select, slot, framebuffer, and markdown modules. The backend (`modern.lisp`, `simple.lisp`) and basic components (`box.lisp`, `text.lisp`, `render.lisp`, `theme.lisp`, `dirty.lisp`) are written directly.

Project structure:

``` cl-tty/ ├── cl-tty.asd # ASDF system definition ├── demo.lisp # Interactive demo ├── run-all-tests.lisp # Test runner ├── backend/ # Backend protocol + implementations │ ├── package.lisp │ ├── classes.lisp # Generic definitions │ ├── simple.lisp # ASCII fallback backend │ ├── modern.lisp # Truecolor escape backend │ └── detection.lisp # Auto-detect backend from env ├── layout/ # Flexbox layout engine │ └── layout.lisp ├── src/ │ ├── rendering/ # Framebuffer backend + diff + flush │ │ └── framebuffer.lisp │ └── components/ # Widgets │ ├── box.lisp, text.lisp, render.lisp, theme.lisp │ ├── dirty.lisp, input-package.lisp, input.lisp │ ├── text-input.lisp, textarea.lisp, keybindings.lisp │ ├── scrollbox.lisp, tabbar.lisp, container-package.lisp │ ├── select.lisp, select-package.lisp │ ├── markdown.lisp, markdown-package.lisp │ ├── dialog.lisp, dialog-package.lisp │ ├── mouse.lisp, mouse-package.lisp │ └── slot.lisp, slot-package.lisp ├── tests/ # Test files ├── org/ # Literate source files │ ├── text-input.org │ ├── scrollbox-tabbar.org │ ├── dialog.org │ ├── mouse.org │ ├── select.org │ ├── slot.org │ ├── framebuffer.org │ ├── markdown-renderer.org │ ├── detection.org │ ├── modern-backend.org │ ├── box-renderable.org │ └── layout-engine.org └── docs/ ├── ROADMAP.org # Versioned roadmap └── ARCHITECTURE.org # Design docs ```

## License

GNU General Public License v3.0