[embedder] Use engine in third_party.

This changes the Flutter Engine workflow in the
embedder repo to use a checkout of Flutter Engine
at third_party/engine instead of $ENGINE_DIR. This
makes it easier to juggle working on the engine code
with working on the embedder code, because the hacks
live in third_party/engine instead of your

- Renames sync_engine_artifacts_to_revision.sh -->
  sync_engine_to_revision.sh and drops the building and
  copying logic. This lets the script be used in contexts
  where we just want to fetch the Flutter Engine (for
  example during initial setup).

- Adds setup_engine.sh script that fetches third_party/engine.
  This isn't necessary for all workflows in the embedder, so
  it's separate from bootstrap.sh.

- Updates the instructions for working with the Flutter Engine.

Change-Id: I03cfb00c85f346452de9ff11cbdb217fa403e0c2
Reviewed-on: https://fuchsia-review.googlesource.com/c/flutter-embedder/+/743590
Reviewed-by: Ben Bergkamp <benbergkamp@google.com>
14 files changed
tree: 6c54ecc277edd3c013652df030919f90325e3713
  1. .vscode/
  2. docs/
  3. hooks/
  4. scripts/
  5. src/
  6. third_party/
  7. tools/
  8. .bazelrc
  9. .clang-format
  10. .editorconfig
  11. .gitignore
  12. .gitmodules
  16. OWNERS
  18. README.md
  20. WORKSPACE.bazel


The Flutter Embedder for Fuchsia is a new in-progress runtime for Flutter apps on Fuchsia. This runtime is built on top of Flutter's embedder platform.

This repository is a work in progress and should be considered experimental.


If you're using WSL2 (Windows Subsystem for Linux), see SETUP_WINDOWS.md first.

  1. Set $FUCHSIA_EMBEDDER_DIR to your flutter-embedder.git checkout location, for example ~/flutter-embedder.

    export FUCHSIA_EMBEDDER_DIR=$HOME/flutter-embedder
  2. Bootstrap the repository's dependencies:


    This script initializes tools (including bazel and ffx), installs some Git hooks and downloads the workstation_eng.qemu-x64 product bundle, which you can use to run the examples below.

Run an example app

  1. Start the emulator.

    If running in a graphical environment:

    $FUCHSIA_EMBEDDER_DIR/tools/ffx emu start workstation_eng.qemu-x64

    If running in a terminal environment:

    $FUCHSIA_EMBEDDER_DIR/tools/ffx emu start --headless workstation_eng.qemu-x64

    The workflow below also supports Fuchsia builds from source that are within Fuchsia's SDK compatibility window (six weeks).

  2. Set the default target in ffx to be fuchsia-emulator:

    $FUCHSIA_EMBEDDER_DIR/tools/ffx target default set fuchsia-emulator
  3. Run an example component:

    $FUCHSIA_EMBEDDER_DIR/scripts/build_and_run_example.sh hello_flutter
    • To watch logs for the example component, run:

      $FUCHSIA_EMBEDDER_DIR/scripts/build_and_run_example.sh hello_flutter --log

      If you want to watch all logs, run $FUCHSIA_EMBEDDER_DIR/tools/ffx log in a separate terminal.

    • To watch FIDL calls for the example component, run:

      $FUCHSIA_EMBEDDER_DIR/scripts/build_and_run_example.sh hello_flutter --fidl


      • --fidl currently requires setting $FUCHSIA_DIR to a Fuchsia source checkout with a build in $FUCHSIA_DIR/out/default. This directory is only used to read IR files for FIDL, you can still use the workstation_eng.qemu-x64 product bundle with --fidl.

      • --fidl attaches after the component has been run, so it does not pick up FIDL calls made when the component starts.

    • To attach a debugger to the example component, see debugging.md

      TODO(akbiggs): Work with Bazel SDK team to get proper support for --fidl.

Making Flutter Engine changes

Running the Flutter app is handled by the Flutter Engine's embedder platform code. This code is compiled into a shared library called libflutter_engine.so, which we can interact with using the embedder.h header.

If you need to make changes to this Flutter Engine code (for example for testing a new API in embedder.h with this embedder) see making_engine_changes.md for instructions. This isn‘t required for changes to only flutter-embedder.git’s source code.

Uploading changes for review.

See git_workflow.md.