A functional, Elm-architecture TUI framework written in GALA (which transpiles to Go).
Built ground-up around immutability, exhaustive sealed types, and pure-data widgets. Includes everything you'd expect from a serious TUI library — and several things you wouldn't.
Core architecture
Program[M, T]— Elm-style Model / Update / View tripleCmd[T]— pure data side effects (NoCmd / QuitCmd / MsgCmd / BatchCmd / FutureCmd)Sub[T]— subscriptions: KeySub / BatchSub / MapSub / TickSub (timer)RunRich/RunFull— async-aware runtimes (futures + tickers + mouse + resize + diff render)
Layout & rendering
- Constraint solver (Length, Fill, Percent)
- Row, Column, Stack, Overlay, Padding, Align, Border (5 glyph kinds)
- Differential renderer (
Buffer.DiffString) — only changed cells go on the wire - Grapheme-aware cell widths (CJK, emoji, combining marks)
Widgets
- Text · Paragraph (word-wrap) · Input · Button · Spinner
- List · Table · DataTable (sort + filter + frozen header) · Tree
- Progress · Gauge · Sparkline · BarChart · LineChart (sub-cell resolution)
- Tabs · Menu · Dropdown · Modal (ConfirmDialog / AlertDialog) · Scrollbar · Viewport
- Toast · StatusBar · LogPanel · Form (multi-field with validators)
- Markdown rendering (headings, bold, italic, code spans, links, lists, rules)
- Command palette with fuzzy search (à la VS Code Cmd-Shift-P)
- Auto-generated help screen from key-binding declarations
Modern terminal integration
- SGR mouse mode (
\x1b[?1006h) — clicks, scroll, drag - OSC 8 hyperlinks · OSC 52 clipboard · OSC 2 terminal title
State helpers
ScreenStack— multi-screen routing with breadcrumbsFocusManager— pane-cycle ring with Tab/Shift-Tab semanticsAnimation— interpolated tweens with 5 easings (Linear, EaseInCubic, EaseOutCubic, EaseInOutCubic, Bounce, StepEasing)Snapshottesting utilities — render a Widget to a string for golden-file assertions
Themes
- Default · Dark · Light · HighContrast (palette + border kind + style overrides)
Cmd helpers
AfterDelay(d, msg)·Async(compute, onResult)·AsyncTry(compute, onOk, onErr)ReadFileCmd(path, …)·WriteFileCmd(path, content, …)
Key spec DSL
KeyBind[T]("ctrl+c", Quit())— human-readable shortcut strings, no boilerplate
gala build ./demo
./gala_tui.exeThe bundled demo is a build-server dashboard that exercises every widget on screen at once — sortable DataTable, collapsible Tree, command palette, confirm modal, line/bar/sparkline charts, themes, and the log drawer.
| Key | Action |
|---|---|
Ctrl-P |
command palette (fuzzy search) |
↑ / ↓ |
cycle screens (overview ↔ builds ↔ pipelines ↔ logs); on builds screen, moves the row cursor |
PgUp / PgDn |
scroll the log drawer when it's open |
End |
jump to the latest log entry |
Tab |
cycle focus pane; in the confirm modal, flips Yes ↔ No |
Enter |
confirm; in the confirm modal, picks the focused button |
Esc |
close overlay / go back |
? |
toggle help (markdown overlay) |
/ |
toggle log drawer |
t |
cycle theme (default → dark → light → high-contrast) |
c |
copy the selected build row to clipboard |
d |
open the deploy-to-prod confirm dialog |
q / Ctrl-C |
quit |
| Mouse wheel | scroll up/down in the focused list/table |
- Getting Started — build a counter, an input form, and a fetcher app from scratch
- Widget catalog — every widget the framework ships, grouped by purpose
- Cookbook — confirm-on-quit, debounced search, virtualized lists, draggable splitters, async fan-out
- Testing —
StepAll/Harness/Snapshotand the focus-contract helpers - Project structure — where each file lives in this repo
Small, focused, single-file apps that show one feature without the noise of the full demo:
examples/counter/— the smallest possible gala-tui app. One field, three messages,+/-to mutate,qquits. Read end-to-end in 30 seconds.examples/clickable_list/— mouse + keyboard on a 4-item nav list. Click any row OR press↑/↓+Enter; both paths produce the same model. DemonstratesRunSimpleWithMouse,SelectListOfPick, andKeyMatchesAnyin <90 lines.examples/chat/— Claude-Code-style chat TUI usingTextArea+ConversationLog+StreamingText. Multi-line composer with history (↑/↓), scrollable message log with auto-stick to bottom, fake streaming response demonstrates theStreamingTextcursor + token-by-token append. ~250 lines.examples/custom_widget/— author your own widget (a clickable star-rating row) with its own event vocabulary. Shows the recommended composition pattern: take typed callbacks, attach them to inner widgets via the fluent.OnClick(msg)method, callers compose the result like a built-in.
- 564 tests passing
- Builds against GALA 0.34.1+
Source-code contributions and bug reports welcome.
APACHE 2.0