Build rich terminal UIs from Java. jatatui is a faithful port of ratatui — same widgets, same buffer model, same Crossterm backend — translated to idiomatic modern Java (records, sealed interfaces, switch expressions). Plus an optional React-style component layer on top.

The non-React stack (crossterm + jatatui-core + jatatui-widgets + jatatui-crossterm) is a complete library on its own. The React layer is opt-in.

Coordinates: com.olvind.jatatui.

Maven:

<dependency>
  <groupId>com.olvind.jatatui</groupId>
  <artifactId>jatatui-core</artifactId>
  <version>0.30.0</version>
</dependency>
<dependency>
  <groupId>com.olvind.jatatui</groupId>
  <artifactId>jatatui-widgets</artifactId>
  <version>0.30.0</version>
</dependency>
<dependency>
  <groupId>com.olvind.jatatui</groupId>
  <artifactId>jatatui-crossterm</artifactId>
  <version>0.30.0</version>
</dependency>

Gradle:

implementation("com.olvind.jatatui:jatatui-core:0.30.0")
implementation("com.olvind.jatatui:jatatui-widgets:0.30.0")
implementation("com.olvind.jatatui:jatatui-crossterm:0.30.0")

The version tracks the upstream ratatui release jatatui ports from. JVM target is Java 21.

import jatatui.core.style.*;
import jatatui.core.text.Line;
import jatatui.core.widgets.Widget;
import jatatui.crossterm.Jatatui;
import jatatui.widgets.Borders;
import jatatui.widgets.block.Block;
import jatatui.widgets.paragraph.Paragraph;
import tui.crossterm.CrosstermJni;
import tui.crossterm.Event;
import tui.crossterm.KeyCode;

public class Hello {
  public static void main(String[] args) throws java.io.IOException {
    var ct = new CrosstermJni();
    Jatatui.runIo(terminal -> {
      while (true) {
        terminal.draw(frame -> {
          Block block = Block.empty()
              .withTitle(Line.from(" Hello "))
              .withBorders(Borders.ALL)
              .withBorderStyle(Style.empty().withFg(new Color.Yellow()));
          Widget content = Paragraph.of("Press q to quit.")
              .withStyle(Style.empty().withFg(new Color.White()));
          block.render(frame.area(), frame.bufferMut());
          content.render(block.inner(frame.area()), frame.bufferMut());
        });
        Event event = ct.read();
        if (event instanceof Event.Key key
            && key.keyEvent().code() instanceof KeyCode.Char c
            && c.c() == 'q') {
          return;
        }
      }
    });
  }
}

For something more substantive, see the demos in jatatui-demo/ (porting of the upstream examples/apps/*) and the React-style demos in jatatui-demo-react/.

jatatui-react and jatatui-components add a React-shaped API: components as pure functions, hooks for state, focus management, event bubbling, portals for overlays. Same buffer underneath — just different ergonomics.

import static jatatui.react.Components.*;

import jatatui.core.style.Color;
import jatatui.core.style.Style;
import jatatui.react.ReactApp;
import jatatui.widgets.Borders;
import java.util.Optional;
import tui.crossterm.KeyCode;

public class Counter {
  public static void main(String[] args) throws java.io.IOException {
    ReactApp.run(component(ctx -> {
      var count = ctx.useState(() -> 0);
      boolean focused = ctx.useFocus(Optional.of("counter"), true);

      if (focused) {
        ctx.onKey(new KeyCode.Up(),   () -> count.update(n -> n + 1));
        ctx.onKey(new KeyCode.Down(), () -> count.update(n -> n - 1));
      }

      return box(
          focused ? " Counter * " : " Counter ",
          Borders.ALL,
          text(
              "Count: " + count.get(),
              Style.empty().withFg(focused ? Color.YELLOW : Color.CYAN)),
          row(
              button("[ + ]", Style.empty().withFg(Color.GREEN), () -> count.update(n -> n + 1)),
              button("[ - ]", Style.empty().withFg(Color.RED),   () -> count.update(n -> n - 1))),
          text(
              "(↑/↓ when focused, click ± buttons, Ctrl+C to quit)",
              Style.empty().withFg(Color.GRAY)));
    }));
  }
}

• Hooks: useState, useRef, useEffect, useFocus, useContext, useTimeout. Fiber-keyed semantics — order matters, deps arrays gate re-runs.
• Imperative focus: ctx.focus(id) and ctx.blur() for cross-component focus moves (e.g. opening a modal). autoFocus=true on useFocus eager-claims on mount so newly-mounted screens get a focused element same-frame.
• Reconciliation: when the component type at a given fiber slot changes (e.g. router screen swap), hook state under that slot is dropped — no state-bleed across screens.
• Events: onClick / onKey / onScroll are area-scoped and bubble through the focused-element chain; stopPropagation() halts them. onGlobalKey is window-level. ANY_KEY / ANY_CHAR predicates match by shape rather than equality.
• Portals: portal(area, child) renders into an arbitrary rect outside the parent layout — the mechanism behind modals, dropdowns, tooltips. Pairs with the Clear widget for opaque overlays.
• Layout primitives: column, row, box, stack; per-child length(n, ...) / fill(weight, ...) / min / max / percent / ratio constraints.
• Built-ins: text, paragraph, button, tabs, forEach, when / ifElse, memo, pureComponent. The widget(...) escape hatch wraps any jatatui-widgets widget into the tree.
• Two entry points:
  • ReactApp.run(element) — turnkey: terminal init, event loop, repaint on dirty. Best for whole-app jatatui-react programs.
  • Renderer — embeddable engine. Call renderer.render(frame, element) inside your own draw loop and pump events with dispatchKey / dispatchMouse. Best when integrating into an existing terminal app or a test harness (TestHarness is built on it).

• Input: textInput, titledTextInput, dropdown, picker (search + ranked list), selectableList (heterogeneous rows with double-click activation).
• Chrome: button, backButton, screenFrame, link, confirmDialog, modal, scrollable.
• Data: list, table, gauge, lineGauge, barchart, sparkline, scrollbar.
• Context providers: toastsProvider + useToasts, formProvider + useForm + useField, router + useRouter, themeProvider + Theme.useTheme.
• Search: FuzzyMatch — IntelliJ-style scoring with word-boundary bonuses for ranking lists/pickers.

Theme is a useContext-style provider; components don't currently auto-consume it — read the active theme with Theme.useTheme() and apply styles explicitly where you want them.

Design notes: jatatui-react/DESIGN.md.

bleep is the build tool. The version is pinned in bleep.yaml ($version: 1.0.0-M9); the bleep launcher picks it up automatically.

cd jatatui
bleep compile
bleep test jatatui-tests
bleep run jatatui-demo -- demo2
bleep run jatatui-demo-react -- counter

For consuming jatatui from other local projects without waiting for a release:

cd jatatui
bleep publish local-ivy

The version is derived from git describe via dynver — something like 0.30.0+14-shaabcdef. This publishes the six publishable modules (crossterm, jatatui-core, jatatui-widgets, jatatui-crossterm, jatatui-react, jatatui-components) to the local Ivy repo (~/.ivy2/local/). Pin the same identifier in the downstream build; re-publishing after new commits produces a fresh identifier — handy for picking up changes without a coordinate dance.

// in another project's build
implementation("com.olvind.jatatui:jatatui-widgets:0.30.0+14-shaabcdef")

Releases are tagged vX.Y.Z and published to Maven Central by the build workflow. The same tag doubles as the dynver base for in-between snapshot publishes. Required secrets in the repository: PGP_SECRET, PGP_PASSPHRASE, SONATYPE_USERNAME, SONATYPE_PASSWORD (see bleep's publish setup or sbt-ci-release docs for the GPG / Sonatype workflow — bleep's publish reuses the same env vars).

To cut a release: tag the head commit, push the tag.

git tag v0.30.0
git push origin v0.30.0

The workflow runs bleep publish sonatype --version 0.30.0 --assert-release, uploads native libraries from all 5 platforms, and creates a GitHub Release.

MIT (same as ratatui). See LICENSE.