[Reland2] Implements UISceneDelegate dynamically w/ FlutterLaunchEngine (#169276) ## **BREAKING CHANGE** Adopting Apple's UISceneDelegate protocol shifts the initialization order of apps. For the common cases we've made sure they will work without change. The one case that will require a change is any app that in `-[UIApplicateDelegate didFinishLaunchingWithOptions:]` assumes that `UIApplicationDelegate.window.rootViewController` is a `FlutterViewController` instance. This is sometimes done to register platform channels directly on the `FlutterViewController`. Instead users should use the `FlutterPluginRegistry` API's to create platform channels in `-[UIApplicateDelegate didFinishLaunchingWithOptions:]`, like `FlutterPlugin`s do. An example can be seen here: https://github.com/flutter/flutter/pull/168914/files#diff-9f59c5248b58124beca7e290a57646023cda3ca024607092c6c6932606ce16ee In extreme cases, like bespoke test harnesses, the startup logic can be moved to `-[FlutterViewController awakeFromNib]` in a FlutterViewController subclass. An example can be seen here: https://github.com/flutter/flutter/pull/169276/files#diff-dbe39c23a0a380447b90b7559a878dae8564616e0875c4ef0d9e99e02b91adac ## Changes since revert I changed the init in `//dev/integration_tests/external_textures` from the UIApplicationDelegate to the FlutterViewController's awakeFromNib. This is a more appropriate place for initialization post-UISceneDelegate since it avoids the launch engine altogether. I tried avoiding to make the big change to prove we could do a small change to migrate that project. I don't think this big refactor is indicative of what users will experience. There was a timing assumption in the integration test that required not using the launch engine at all. ## Description fixes: https://github.com/flutter/flutter/issues/167267 design doc: https://docs.google.com/document/d/1ZfcQOs-UKRa9jsFG84-MTFeibZTLKCvPQLxF2eskx44/edit?tab=t.0 relands https://github.com/flutter/flutter/pull/168396 relands https://github.com/flutter/flutter/pull/168914 ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. https://dart.googlesource.com/external/github.com/flutter/flutter/+/4226470eb66a524a9e96a58db5db96ce8d279745
Monorepo is:
With depot_tools installed and on your path, create a directory for your monorepo checkout and run these commands to create a gclient solution in that directory:
mkdir monorepo cd monorepo gclient config --unmanaged https://dart.googlesource.com/monorepo gclient sync -D
This gives you a checkout in the monorepo directory that contains:
monorepo/ DEPS - the DEPS used for this gclient checkout commits.json - the pinned commits for Dart, flutter/engine, and flutter/flutter tools/ - scripts used to create monorepo DEPS engine/src/ - the flutter/buildroot repo flutter/ - the flutter/engine repo out/ - the build directory, where Flutter engine builds are created third_party/ - Flutter dependencies checked out by DEPS dart/ - the Dart SDK checkout. third_party - Dart dependencies, also used by Flutter flutter/ - the flutter/flutter repo
Flutter's instructions for building the engine are at Compiling the engine
They can be followed closely, with a few changes:
goma_ctl ensure_start is sufficient.Example build commands that work on linux:
MONOREPO_PATH=$PWD if [[ ! $PATH =~ (^|:)$MONOREPO_PATH/flutter/bin(:|$) ]]; then PATH=$MONOREPO_PATH/flutter/bin:$PATH fi export GOMA_DIR=$(dirname $(command -v gclient))/.cipd_bin goma_ctl ensure_start pushd engine/src flutter/tools/gn --goma --no-prebuilt-dart-sdk --unoptimized --full-dart-sdk autoninja -C out/host_debug_unopt popd
The Flutter commands used to build and run apps will use the locally built Flutter engine and Dart SDK, instead of the one downloaded by the Flutter tool, if the --local-engine option is provided.
For example, to build and run the Flutter spinning square sample on the web platform,
MONOREPO_PATH=$PWD cd flutter/examples/layers flutter --local-engine=host_debug_unopt \ -d chrome run widgets/spinning_square.dart cd $MONOREPO_PATH
To build for desktop, specify the desktop platform device in flutter run as -d macos or -d linux or -d windows. You may also need to run the command
flutter create --platforms=windows,macos,linux
on existing apps, such as sample apps. New apps created with flutter create already include these support files. Details of desktop support are at Desktop Support for Flutter
Tests in the Flutter source tree can be run with the flutter test command, run in the directory of a package containing tests. For example:
MONOREPO_PATH=$PWD cd flutter/packages/flutter flutter test --local-engine=host_debug_unopt cd $MONOREPO_PATH
Please file an issue or email the dart-engprod team with any problems with or questions about using monorepo.
We will update this documentation to address them.
flutter commands may download the engine and Dart SDK files for the configured channel, even though they will be using the local engine and its SDK.gclient sync needs to be run in an administrator session, because some installed dependencies create symlinks.