Description

This meta issue proposes an array of improvements to Flutter for supporting customers who want to use multiple Flutter instances in an app, focused on the Add-to-app use case. It includes improvements for performance and ease-of-use.

Design doc

http://flutter.dev/go/multiple-engines

Phase 1

Share Engine Components

iOS

• API - iOS - Shared Engine Components API - iOS - Lightweight Flutter Engines #72010
• Threads - iOS - iOS: Share engine thread hosts between multiple engines #72019
• Skia Contexts - iOS - iOS: Share Skia context between multiple engines #72021
• GPU Contexts - iOS - iOS: Share GPU contexts between lightweight engines #72022

Android

• API - Android - Shared Engine Components API for Android #72018
• Threads - Android - Android: Share engine thread hosts between multiple engines #72528
• Skia Contexts - Android - Android: Share Skia context between multiple engines #73597
• GPU Contexts - Android - Android: Share GPU contexts between lightweight engines #73599

Shared

• Fonts - Share font collections between multiple engines #72024
• Spawn -> Kill Spawner Integration test - Spawn -> Kill Integration Test #72319
• Documentation - Document the recommended way of producing multiple embedded Flutter UI / navigation states #37644
• Sample Code - Multiple Flutters Sample Code #74530 (written, not landed, waiting for API to hit stable)
• Handle thread merging (Crashing) - Handle thread merging (platform views) with engines that shared components #73620

Phase 2

Share Engine Components

• IsolateGroups - Use Dart's lightweight isolates between multiple engines #72025

More performance tightening

• Squeeze an extraneous 0.1MB per engine from Android embedding - Improve multiple Flutters Android embedding memory performance #74941
• Squeeze an extraneous 0.32MB per engine from Dart VM - Improve multiple Flutters Android dart VM memory performance #74942

FlutterView / FlutterEngine integration

• Android FlutterView ergonomics- Make integration via Android FlutterView easier website#7785

Tests

• Shared engine memory benchmark - Create multi-engine memory benchmark #72026
• Spawn->Kill Integration test for Android - Spawn->Kill Integration test for Android #72527

Cleanup

• Refactor Spawn-> Kill integration test - Refactor Spawn->Kill Integration test to be more independent #72525
• Handle thread merging (platform views) - Handle thread merging (platform views) with engines that shared components #73620
• InitialRoute missing in the API - FlutterEngineGroup does not support initialRoute #78931

Phase 3

• Async VM and Shell creation - Asynchronous Shell and VM creation #72028
• Easier engine↔engine interop - Easier FlutterEngine↔FlutterEngine interop #33288
• Signal garbage collection only when all isolates are idle - Garbage collect only when all isolates are idle #72031
• Cleanup non-visible view surfaces
• Shared image cache - Share image cache between multiple engines #72033
• Consider separate UI threads per engine
• Create lightweight engines from existing FlutterEngineGroup in FlutterActivity/FlutterViewController - Let FlutterEngineGroup be passed in proxy engine constructors in FlutterViewController/FlutterActivity #72742