add an examples app that has a gallery of pre-designed surfaces and allows editing/previewing A2UI JSON

examples/composer/.gitignore

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+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.build/
+.buildlog/
+.history
+.svn/
+.swiftpm/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins-dependencies
+.pub-cache/
+.pub/
+/build/
+/coverage/
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release

examples/composer/.metadata

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+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: "44a626f4f0027bc38a46dc68aed5964b05a83c18"
+  channel: "stable"
+
+project_type: app
+
+# Tracks metadata for the flutter migrate command
+migration:
+  platforms:
+    - platform: root
+      create_revision: 44a626f4f0027bc38a46dc68aed5964b05a83c18
+      base_revision: 44a626f4f0027bc38a46dc68aed5964b05a83c18
+    - platform: macos
+      create_revision: 44a626f4f0027bc38a46dc68aed5964b05a83c18
+      base_revision: 44a626f4f0027bc38a46dc68aed5964b05a83c18
+
+  # User provided section
+
+  # List of Local paths (relative to this file) that should be
+  # ignored by the migrate tool.
+  #
+  # Files that are not part of the templates will be ignored by default.
+  unmanaged_files:
+    - 'lib/main.dart'
+    - 'ios/Runner.xcodeproj/project.pbxproj'

examples/composer/README.md

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+# GenUI Composer
+
+An application for experimenting with and building A2UI surfaces.
+
+The composer allows you to:
+
+- Generate a UI surface from a text prompt using AI.
+- Browse a gallery of pre-designed surfaces.
+- View and edit the underlying A2UI JSON for any surface and see a live preview.

examples/composer/analysis_options.yaml

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+# Copyright 2025 The Flutter Authors.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+include: package:flutter_lints/flutter.yaml

examples/composer/lib/ai_client.dart

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+// Copyright 2025 The Flutter Authors.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:dartantic_ai/dartantic_ai.dart' as dartantic;
+
+import 'get_api_key.dart';
+
+/// An abstract interface for AI clients.
+abstract interface class AiClient {
+  /// Sends a message stream request to the AI service.
+  Stream<String> sendStream(
+    String prompt, {
+    required List<dartantic.ChatMessage> history,
+  });
+
+  /// Dispose of resources.
+  void dispose();
+}
+
+/// An implementation of [AiClient] using `package:dartantic_ai`.
+class DartanticAiClient implements AiClient {
+  DartanticAiClient({String? modelName}) {
+    final String apiKey = getApiKey();
+    _provider = dartantic.GoogleProvider(apiKey: apiKey);
+    _agent = dartantic.Agent.forProvider(
+      _provider,
+      chatModelName: modelName ?? 'gemini-3-flash-preview',
+    );
+  }
+
+  late final dartantic.GoogleProvider _provider;
+  late final dartantic.Agent _agent;
+
+  @override
+  Stream<String> sendStream(
+    String prompt, {
+    required List<dartantic.ChatMessage> history,
+  }) async* {
+    final Stream<dartantic.ChatResult<String>> stream = _agent.sendStream(
+      prompt,
+      history: history,
+    );
+
+    await for (final result in stream) {
+      if (result.output.isNotEmpty) {
+        yield result.output;
+      }
+    }
+  }
+
+  @override
+  void dispose() {}
+}

examples/composer/lib/ai_client_transport.dart

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+// Copyright 2025 The Flutter Authors.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:dartantic_ai/dartantic_ai.dart' as dartantic;
+import 'package:genui/genui.dart';
+import 'package:logging/logging.dart';
+
+import 'ai_client.dart';
+
+/// A [Transport] that wraps an [AiClient] to communicate with an LLM.
+class AiClientTransport implements Transport {
+  AiClientTransport({required this.aiClient});
+
+  final AiClient aiClient;
+  final A2uiTransportAdapter _adapter = A2uiTransportAdapter();
+  final List<dartantic.ChatMessage> _history = [];
+  final Logger _logger = Logger('AiClientTransport');
+
+  @override
+  Stream<A2uiMessage> get incomingMessages => _adapter.incomingMessages;
+
+  @override
+  Stream<String> get incomingText => _adapter.incomingText;
+
+  @override
+  Future<void> sendRequest(ChatMessage message) async {
+    final buffer = StringBuffer();
+    for (final dartantic.StandardPart part in message.parts) {
+      if (part.isUiInteractionPart) {
+        buffer.write(part.asUiInteractionPart!.interaction);
+      } else if (part is TextPart) {
+        buffer.write(part.text);
+      }
+    }
+    final text = buffer.toString();
+    if (text.isEmpty) return;
+
+    _history.add(dartantic.ChatMessage.user(text));
+
+    try {
+      final Stream<String> stream = aiClient.sendStream(
+        text,
+        history: List.of(_history),
+      );
+      final fullResponseBuffer = StringBuffer();
+
+      await for (final chunk in stream) {
+        if (chunk.isNotEmpty) {
+          fullResponseBuffer.write(chunk);
+          _adapter.addChunk(chunk);
+        }
+      }
+
+      _history.add(dartantic.ChatMessage.model(fullResponseBuffer.toString()));
+    } catch (e, stack) {
+      _logger.severe('Error sending request', e, stack);
+      rethrow;
+    }
+  }
+
+  @override
+  void dispose() {
+    _adapter.dispose();
+    aiClient.dispose();
+  }
+
+  /// Adds a system message to the history.
+  void addSystemMessage(String content) {
+    _history.add(dartantic.ChatMessage.system(content));
+  }
+}

examples/composer/lib/components_tab.dart

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+// Copyright 2025 The Flutter Authors.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert';
+
+import 'package:flutter/material.dart';
+import 'package:genui/genui.dart';
+
+/// The Components tab shows every component in the standard catalog using
+/// the built-in [DebugCatalogView].
+class ComponentsTab extends StatefulWidget {
+  const ComponentsTab({super.key});
+
+  @override
+  State<ComponentsTab> createState() => _ComponentsTabState();
+}
+
+class _ComponentsTabState extends State<ComponentsTab> {
+  late final Catalog _catalog;
+
+  @override
+  void initState() {
+    super.initState();
+    _catalog = BasicCatalogItems.asCatalog();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Padding(
+          padding: const EdgeInsets.fromLTRB(16, 16, 16, 0),
+          child: Text('Components', style: theme.textTheme.headlineSmall),
+        ),
+        const SizedBox(height: 8),
+        Expanded(
+          child: DebugCatalogView(
+            catalog: _catalog,
+            onSubmit: (message) {
+              ScaffoldMessenger.of(context).showSnackBar(
+                SnackBar(
+                  content: Text(
+                    'User action: '
+                    '${jsonEncode(message.parts.last)}',
+                  ),
+                ),
+              );
+            },
+          ),
+        ),
+      ],
+    );
+  }
+}