emb — Flutter Embedder CLI

emb provisions a Flutter embedded-Linux development workspace and builds deployable app bundles for embedders such as ivi-homescreen. It's a Dart port of meta-flutter/workspace-automation (flutter_workspace.py + create_aot.py).

The whole flow is a handful of commands:

deps → repos → Flutter SDK → engine → AOT → ivi-homescreen bundle

• Host dependency install in one transaction (PackageKit on Linux), with WhatProvides resolution so pkg-config, libjpeg-devel, etc. just work.
• Prebuilt Flutter engine fetched from meta-flutter/flutter-engine releases (auto, keyed by the SDK's engine commit).
• Cross-compile AOT for arm64 / riscv64 from an x86_64 host using the engine's simulator gen_snapshot — no qemu (the artifact is self-contained).
• Self-describing packages: a package declares its build in a manifest and emb build <dir> does the rest.

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Requirements

• Dart SDK ≥ 3.10.1 (to run/build the emb tool itself).
• Linux for host dependency install (PackageKit — dnf/apt/zypper). The macOS (Homebrew) and Windows (WinGet) backends are stubbed in this build; all other commands are cross-platform.
• git, tar, curl on PATH.
• Cross-compiling to a device arch is supported from an x86_64 host.

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Install

# From the package root:
dart pub get
dart pub global activate --source=path .   # puts `emb` on PATH

emb --help

Make sure the pub-global bin dir ($PUB_CACHE/bin, e.g. ~/.pub-cache/bin) is on PATH. You can also run without activating:

dart run bin/emb.dart <command>     # from the package root

The Linux backend loads packagekit_dart's native bridge (libpackagekit_nc.so). emb locates it automatically — from the package's own build, or from the package:hooks build-hook output under .dart_tool/. Override with PK_NC_LIB=/path/to/libpackagekit_nc.so.

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Quick start

# 0. Check host detection + package backend
emb doctor

# 1. Provision the workspace (host deps + repos + Flutter SDK + engine)
emb setup --config ../configs --yes

# 2. Load the environment it wrote (Flutter/Dart on PATH, FLUTTER_WORKSPACE, …)
. ./setup_env.sh

# 3. Build an ivi-homescreen bundle for a Raspberry Pi (arm64), release AOT
emb bundle --app-path ./app/my_app --arch arm64 --build

# 4. Run it on the target
#    ivi-homescreen --b=<workspace>/bundle/my_app-release-arm64

emb setup runs every phase; you can also run them individually (emb deps, emb sync, emb flutter, emb engine).

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Workspace & path resolution

Every command that touches the workspace resolves its root in this order:

1. --workspace <dir> (explicit flag), else
2. the $FLUTTER_WORKSPACE environment variable, else
3. the current working directory.

<workspace>/                              # the resolved root
  app/                                    # cloned source repositories
  flutter/                                # Flutter SDK
  bundle/                                 # built bundles (default output)
  setup_env.sh                            # generated environment script
  .config/flutter_workspace/
    flutter-engine/<commit>/...           # downloaded + extracted engine SDKs
    flutter-engine/bundle-<mode>-<arch>/  # staged engine halves (icudtl + .so)

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Command reference

emb <command> [arguments]

Global options

Option	Description
-h, --help	Print usage. Works at the top level and per command (emb <cmd> --help).
-v, --version	Print the CLI version.
--[no-]verbose	Noisy logging, including every shell command executed.

--workspace (-w), shown on most commands, follows the resolution order above. --mode/--arch defaults and value sets differ per command — see each entry.

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emb doctor

Report host detection (os / arch / distro) and package-manager backend availability. No options. Exit code is non-zero if the backend is unavailable.

emb doctor

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emb setup

One-shot provision: deps → repos → Flutter SDK → engine, then writes setup_env.sh. Each phase is individually skippable.

Option	Default	Description
-c, --config <dir>	configs	Legacy JSON config directory.
-p, --packages <dir>	—	Directory to discover self-describing emb manifests.
--enable <id>	—	Force-load the config with this id (overrides load: false). Repeatable; unmatched ids ignored.
--disable <id>	—	Skip the config with this id (overrides load: true). Repeatable; unmatched ids ignored.
-w, --workspace <dir>	resolution order	Workspace root.
--flutter-version <ref>	globals.json flutter_version	Flutter version/tag/branch.
--arch <arch>	host arch	Engine arch to prefetch.
-m, --mode <mode>	release	Engine runtime modes to prefetch (repeatable): release, profile, debug.
-y, --yes	off	Skip the deps confirmation prompt (CI).
--skip-deps	off	Skip host dependency install.
--skip-sync	off	Skip repository sync.
--skip-flutter	off	Skip Flutter SDK install.
--skip-engine	off	Skip engine artifact fetch.

emb setup --config ../configs --yes
emb setup --config ../configs --skip-deps --skip-sync   # SDK + engine only
emb setup --config ../configs --enable weston --disable agl-compositor

Config selection (applies to setup, deps, and sync): legacy --config components apply only when their load flag is logically true. --enable <id> / --disable <id> override that per component, matched by id; ids matching nothing are ignored, and load order is preserved.

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emb deps

Coalesce host dependencies across all selected manifests, filter to what's missing on this host, and install the union in one transaction.

Option	Default	Description
-c, --config <dir>	configs	Legacy JSON config directory. Repeatable.
-p, --packages <dir>	—	Directory to discover self-describing emb manifests. Repeatable.
--enable <id>	—	Force-load the config with this id (overrides load: false). Repeatable; unmatched ids ignored.
--disable <id>	—	Skip the config with this id (overrides load: true). Repeatable; unmatched ids ignored.
--dry-run	off	Resolve and print the install plan without changing the system.
-y, --yes	off	Skip the confirmation prompt (CI).

emb deps --config ../configs --dry-run      # plan only
emb deps --config ../configs --yes          # install in one transaction

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emb sync

Clone/update source repositories into <workspace>/app (bounded concurrency).

Option	Default	Description
-c, --config <dir>	configs	Legacy JSON config directory. Repeatable.
-p, --packages <dir>	—	Directory to discover self-describing emb manifests.
--enable <id>	—	Force-load the config with this id (overrides load: false). Repeatable; unmatched ids ignored.
--disable <id>	—	Skip the config with this id (overrides load: true). Repeatable; unmatched ids ignored.
--repos <file>	—	A JSON file containing a bare array of repo entries. Repeatable.
-w, --workspace <dir>	resolution order	Workspace root.
-j, --concurrency <n>	4	Maximum concurrent git operations.

emb sync --config ../configs -j 8

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emb flutter

Install the Flutter SDK into <workspace>/flutter.

Option	Default	Description
-w, --workspace <dir>	resolution order	Workspace root.
--flutter-version <ref>	globals.json flutter_version	Version/tag/branch to check out.
-c, --config <dir>	configs	Directory to read globals.json from.
--configure	off	Run flutter config (desktop + custom devices) and flutter doctor after install.

emb flutter --flutter-version 3.44.2 --configure

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emb engine

Fetch prebuilt Flutter engine artifacts (auto fetch-else-build). Modes you don't fetch here are auto-fetched on demand by emb bundle/emb build.

Option	Default	Description
-w, --workspace <dir>	resolution order	Workspace root.
--commit <sha>	<workspace>/flutter/bin/internal/engine.version	Engine commit to fetch.
--arch <arch>	host arch	Engine arch token (see Architectures).
-m, --mode <mode>	release	Runtime modes to fetch (repeatable): release, profile, debug.
--clean	off	Re-stage bundles even when already present.
--check	off	Only check prebuilt availability; do not download.

emb engine --arch arm64 --mode release --mode profile
emb engine --arch riscv64 --check       # is a prebuilt available?

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emb aot

Build the AOT image (libapp.so) for a Flutter app — the AOT primitive used by emb bundle --build. Debug is not AOT, so only release/profile apply.

Option	Default	Description
-a, --app-path <dir>	mandatory	Path to the Flutter application to build.
-w, --workspace <dir>	resolution order	Workspace root.
-m, --mode <mode>	release	Runtime modes to build (repeatable): release, profile.
--arch <arch>	host arch	Target arch for gen_snapshot (e.g. arm64 for a Pi).
--gen-snapshot <path>	auto-resolved	Explicit gen_snapshot path (overrides resolution).
--glibc-sysroot <dir>	artifact's bundled clang_x64/lib64	Directory with ld-linux + libc to run gen_snapshot under.

emb aot --app-path ./app/my_app --arch arm64 --mode release --mode profile

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emb bundle

Assemble an ivi-homescreen bundle from app + engine artifacts. With --build it runs emb aot first; the engine SDK for the (mode, arch) is fetched implicitly if not already cached.

Option	Default	Description
-a, --app-path <dir>	mandatory	Path to the Flutter application.
-w, --workspace <dir>	resolution order	Workspace root.
-m, --mode <mode>	release	Single mode: debug (JIT, no AOT), profile, or release (AOT).
--arch <arch>	host arch	Target arch (e.g. arm64).
-o, --output <dir> (alias --out)	<workspace>/bundle/<app>-<mode>-<arch>	Output bundle directory — any path.
--build	off	Run emb aot first to (re)build flutter_assets + libapp.so.

emb bundle --app-path ./app/my_app --arch arm64   --build                # release
emb bundle --app-path ./app/my_app --arch arm64   --build --mode debug   # JIT
emb bundle --app-path ./app/my_app --arch riscv64 --build --mode profile
emb bundle --app-path ./app/my_app --build                               # host
emb bundle --app-path ./app/my_app --arch arm64 --output /tmp/out        # custom path

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emb build

Build a self-describing package — a directory with an emb.yaml (or an emb: key in pubspec.yaml) — into bundles, using the manifest's build: matrix. The package directory is a positional argument (mandatory; omitting it prints a usage error).

emb build <package-dir> [options]

Option	Default	Description
<package-dir>	mandatory (positional)	Directory containing emb.yaml or a pubspec.yaml with an emb: key.
-w, --workspace <dir>	resolution order	Workspace root.
--arch <arch>	manifest's archs	Override target arch(es). Repeatable.
-m, --mode <mode>	manifest's modes	Override mode(s): debug, profile, release. Repeatable.
--no-build	off	Assemble from existing artifacts; skip compiling.

emb build ./app/my_app                              # full manifest matrix
emb build ./app/my_app --arch arm64 --mode release  # override the matrix
emb build ./app/my_app --no-build                   # assemble only

Manifest (emb.yaml)

id: my_app
type: app
build:
  app_path: .              # Flutter app dir, relative to this manifest (default ".")
  archs: [arm64, x86_64]   # target architectures (default: host)
  modes: [release, debug]  # default: [release]
  output: bundles          # optional output dir, relative to the workspace
deps:                      # optional host packages, by OS / distro
  linux:
    fedora: [pkg-config, freetype-devel]
    ubuntu: [pkg-config, libfreetype-dev]
  macos: [pkg-config, freetype]
  windows: [Kitware.CMake]

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emb cross

Cross-compile a native embedder (e.g. ivi-homescreen) for an arm64 / riscv64 target from an x86_64 host, driven by the manifest's cross: block. This is the C/C++ toolchain + sysroot path — distinct from the Dart AOT cross used by emb build / emb bundle. Three providers: arm-gnu (a downloaded ARM GNU toolchain plus a sysroot unpacked from a distro image or rsync'd from a device), yocto-recipe (a located OE recipe-sysroot), and yocto-sdk (a populate_sdk install). The input is a positional package dir (with emb.yaml) or an explicit manifest file.

emb cross <package-dir|manifest.yaml> [options]

Option	Default	Description
<package-dir|manifest>	mandatory (positional)	Dir with emb.yaml, or a manifest file.
-w, --workspace <dir>	resolution order	Workspace root.
-t, --target <name>	local if cross.targets defined	Select a platform from cross.targets (e.g. rpi5, radxa-zero3), or local/host for a native build on this machine. When the manifest defines cross.targets, omitting --target defaults to local.
--list-targets	off	List the platforms defined under cross.targets (plus the built-in local), then exit.
--dry-run	off	Report the resolution plan (provider, toolchain, sysroot, preflight, augment, backends) with no download / mount / ssh.
--prepare	off	After resolving, build the augment libraries into the overlay.
--build	off	Configure + build the embedder under the resolved profile, one build per cross.backends entry.
--backend <name>	all	Build only the named cross.backends entries. Repeatable.
--deb	off	With --build: package each backend binary into a root-free .deb (Depends auto-derived from the binary's needed libraries).
--clean	off	Remove this target's build + overlay dirs (keeps the toolchain + sysroot), then exit.
--clean-all	off	Also remove the downloaded / extracted toolchain + sysroot and the apt / deb caches, then exit.

emb cross ./app/ivi-homescreen --dry-run      # plan only, no side effects
emb cross ./app/ivi-homescreen --build        # toolchain + sysroot + build
emb cross ./app/ivi-homescreen --build --deb  # ...and package a .deb
emb cross ./app/ivi-homescreen --clean        # drop build dirs (keep toolchain)
emb cross ./app/ivi-homescreen --clean-all    # drop everything for this target

Everything is root-free: the sysroot is extracted with debugfs / dpkg-deb, and -dev packages are resolved against the image's own apt sources — no apt, no chroot, no sudo. Validated end-to-end on Raspberry Pi (arm-gnu, raspios bookworm): --build --deb produces an aarch64 ELF and an installable .deb. See examples/cross/ for one manifest per board (pi5 is the validated end-to-end example) and the full schema.

Manifest (cross: block)

cross:
  provider: arm-gnu               # arm-gnu | yocto-recipe | yocto-sdk
  toolchain_version: 12.3.rel1    # pinned ARM GNU release (or version_policy: derive)
  image_url: https://.../raspios-bookworm-arm64-lite.img.xz
  cpu_flags: [-mcpu=cortex-a76]   # pi5; pi4=cortex-a72, pi-zero-2=cortex-a53
  sysroot:
    partition: 2                  # rootfs partition in the image (default 2)
    dev_packages: [libdrm-dev, libegl-dev, libgbm-dev, libinput-dev]
  augment:                        # libs built from source when the sysroot is too old
    - { pkg: libdisplay-info, min: "0.2.0", url: https://.../libdisplay-info-0.2.0.tar.gz, build: meson, static: true }
  defines:                        # -D<name>=<value> applied to every build
    CMAKE_INSTALL_PREFIX: /usr
  cmake_args: [-Wno-dev]          # raw cmake configure flags (cmake only)
  backends:                       # one build per entry; -D<key>=<value> each
    drm-kms-egl: { BUILD_BACKEND_DRM_KMS_EGL: 'ON', DISABLE_PLUGINS: 'ON' }
  package:                        # optional, consumed by --deb
    name: ivi-homescreen
    version: 1.0.0
    bin: shell/homescreen         # binary, relative to each backend build dir
    install_dir: /usr/bin

Multiple platforms in one manifest (cross.targets)

To target several boards from a single manifest, put the shared config at the cross: level and a per-board override under cross.targets, then pick one with --target:

cross:
  provider: arm-gnu               # shared by every target
  toolchain_version: 12.3.rel1
  sysroot: { dev_packages: [libdrm-dev, libegl-dev, libgbm-dev, libinput-dev] }
  backends: { drm-kms-egl: { BUILD_BACKEND_DRM_KMS_EGL: 'ON' } }
  targets:                        # per-board overrides
    rpi5:        { image_url: …raspios…, cpu_flags: [-mcpu=cortex-a76] }
    rpi4:        { image_url: …raspios…, cpu_flags: [-mcpu=cortex-a72] }
    rpi-zero-2w: { image_url: …raspios…, cpu_flags: [-mcpu=cortex-a53] }
    radxa-zero3: { image_url: …radxa…,   cpu_flags: [-mcpu=cortex-a55] }

emb cross . --list-targets
emb cross . --target rpi5 --build --deb
emb cross . --target radxa-zero3 --build

A target's fields shallow-merge over the shared block (a top-level image_url folds into sysroot). Working dirs are content-hash-keyed, so boards that share a sysroot (rpi4/rpi5/zero-2w — same image, only -mcpu differs) extract it once, while a different image (radxa) gets its own. A manifest with no cross.targets behaves exactly as before (one implicit target).

There's always a built-in local target (alias host): a native build on this machine — no cross toolchain or sysroot, host compiler + system libraries (install host dev deps via emb deps). It's the default when a manifest defines cross.targets and you don't pass --target, so emb cross . --build builds for the dev box while --target rpi5 cross-builds.

emb cross . --build            # native local build (default with cross.targets)
emb cross . --target local     # …the same, explicit (or --target host)
emb cross . --target rpi5 --build

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emb env

Write setup_env.sh (PATH for Flutter/Dart, FLUTTER_WORKSPACE, PUB_CACHE, XDG_CONFIG_HOME, the engine version, …).

Option	Default	Description
-w, --workspace <dir>	resolution order	Workspace root.
-o, --output <path>	<workspace>/setup_env.sh	Output file path.
--print	off	Print to stdout instead of writing a file.

emb env                 # write <workspace>/setup_env.sh
emb env --print         # preview on stdout

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emb update

Update the CLI itself (via pub). No options.

emb update

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Modes

--mode	How it builds	Bundle contents	Valid in
debug	JIT — flutter build bundle --debug	kernel_blob.bin, no libapp.so	bundle, build, engine, setup
profile	AOT (gen_snapshot)	libapp.so (+ profile engine)	all
release	AOT (gen_snapshot)	libapp.so (+ release engine)	all

emb aot only accepts release/profile (debug isn't AOT). Where a command takes multiple modes (aot, build, engine, setup), repeat the flag: --mode release --mode profile. emb bundle takes a single mode.

A bundle is the directory ivi-homescreen consumes:

<bundle>/
  data/flutter_assets/        # app code + assets
  data/icudtl.dat             # from the engine
  lib/libflutter_engine.so    # from the engine (per mode)
  lib/libapp.so               # AOT image (profile/release only)

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Architectures & cross-compiling

--arch accepts machine names or Flutter tokens; they normalize to one of four engine arch tokens used in paths and bundle names:

You pass	Normalized token
x64, x86_64, amd64	x86_64
arm64, aarch64	arm64
arm, armv7, armv7hf, armhf	armv7hf
riscv64	riscv64

Cross-compile is x86_64 host → target arch. The meta-flutter engine SDK ships a host-x86_64 simulator gen_snapshot that emits target code and carries its own loader/libc in clang_x64/lib64, so it runs on any host glibc — no qemu required. emb selects and runs it automatically; --gen-snapshot / --glibc-sysroot override if needed. Building on an arm64 host targets arm64 natively.

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Development

dart pub get
dart analyze
dart test

The macOS/Windows package backends live in lib/src/pkg/_platform/ and are excluded from the default (Linux) build — see that folder's README.md. Dart has no OS-conditional dependencies, so they're wired in only on per-OS builds that add brew_dart / winget_dart.