Write a home-screen widget once in Dart. Ship it on iOS and Android.

Mosaic turns a Flutter-style Dart tree into real native widgets — SwiftUI/WidgetKit on iOS, RemoteViews/Kotlin on Android. Your app pushes data; the OS draws the tile. No Swift, no Kotlin, no per-platform widget code.

import 'package:mosaic_widgets/dsl.dart';

MosaicDefinition buildNews() => MosaicDefinition(
  name: 'News',
  root: MContainer(
    background: const MColor.hex('#111827', dark: '#000000'),
    radius: 16,
    child: MPadding(
      const MInsets.all(12),
      MText(MBind('title'), style: const MTextStyle(bold: true)),
    ),
  ),
);

Quick start

# pubspec.yaml
dependencies:
  mosaic_widgets: ^0.3.0

dart run mosaic_widgets:mosaic init          # writes mosaic.yaml from your real bundle ids
dart run mosaic_widgets:mosaic add widget News
dart run mosaic_widgets:mosaic build         # generates the native code
dart run mosaic_widgets:mosaic doctor        # checks the native wiring

Then push data from your app:

import 'package:mosaic_widgets/mosaic_widgets.dart';

await MosaicBridge.setAppGroupId('group.com.example.app.widgets'); // iOS only
await MosaicBridge.saveString('title', 'Markets rally');
await MosaicBridge.refreshAll();

One-time native wiring (an Xcode Widget Extension target, one line in your AppDelegate / MainActivity) is in iOS Setup and Android Setup. doctor tells you exactly what is missing.

What you get

Home-screen widgets	iOS 14+ WidgetKit · Android AppWidget
Lock Screen	iOS 16+ accessory families
Live Activities	Dynamic Island, and Apple Watch with watch: true
Controls	iOS 18 Control Center · Android Quick Settings tiles
Interactive	Buttons, toggles, deep links, background callbacks
Live data	MBind for text, images, progress, visibility, timers, colours
Refresh with the app closed	Declare an endpoint; the widget fetches it itself
Per-size layouts	compactRoot: gives small tiles their own tree
Theming	Light/dark, Material You (MColor.system), iOS tinted mode
Device metrics	Battery, storage and RAM, read in the widget process
Render any Flutter widget	renderFlutterWidget rasterises to a PNG for what the DSL cannot express
Or drop to native	MRaw inserts your own SwiftUI / layout XML, keeping the generated plumbing
Per-platform trees	MAdaptive when one tree genuinely cannot serve both
Typography	MTextRole semantic scale, MFontWeight w100–w900, italic, copyWith
macOS & watchOS	One extension target compiles for both, watch complications included
Android TV	Home-screen channels of preview cards — TV hosts no widgets at all
Accessibility	MSemantics → VoiceOver / TalkBack
Localised text	Real values-<locale>/ and .lproj resources

Widgets are static snapshots on both platforms, so there is no general animation and no Lottie. What exists: a spinner and self-cycling content on Android, digit-roll transitions on iOS 17+, and live timers on both — each documented with its limits rather than failing quietly.

Docs

DSL Reference — every node, with its platform notes · iOS Setup · Android Setup · Live Activities · Roadmap

A runnable app using every feature lives in examples/demo_app.

Using an AI assistant?

Mosaic is newer than most training data, so it ships a skill that teaches assistants the real API:

cp -r skills/mosaic-widgets ~/.claude/skills/

Assistants then load it automatically on seeing a mosaic.yaml or a *.widget.dart file. See also llms.txt and AGENTS.md.

Support

If Mosaic helped you, consider supporting the author: