Flutter
about the nightmare of cross platform development targetting Linux mobile
Hej, I'm The one with the braid
- alleged Flutter toucher since 2018
- working in healthcare IT for a couple of years
- healthcare be like : [matrix]
- I use arm btw.
- @braid:alsace.hair (oops, location leaked)
- Yes, I'm from France btw.
Flutter, but why ?
- Decent cross-platform ecosystem
- Native plugin system
- Advanced mobile UI optimization
- Fancy animation
- Fast rendering
- No JS, no XML
Linux (mobile) as a Flutter target
- Adopting existing software
- Less development effort
- Biiiig players into it
Keys in targetting mobile
- Runtime issues
- Debugging
- Redistribution
Flutter redistribution
- Building the Flutter toolchain
- Packaging (let's check this first)
The Flutter tool
A nightmare for packaging
Downloading Linux x64 Dart SDK from Flutter engine f40e976bedff57e69e1b3d89a7c2a3c617a03dad...
# [...]
Building flutter tool...
Resolving dependencies... (1.8s)
Got dependencies.
Downloading Material fonts... 296ms
Downloading Gradle Wrapper... 18ms
Downloading android-arm-profile/linux-x64 tools... 237ms
Downloading android-arm-release/linux-x64 tools... 213ms
Downloading android-arm64-profile/linux-x64 tools... 247ms
Downloading android-arm64-release/linux-x64 tools... 217ms
Downloading android-x64-profile/linux-x64 tools... 238ms
Downloading android-x64-release/linux-x64 tools... 215ms
Downloading android-x86 tools... 1,807ms
Downloading android-x64 tools... 1,919ms
Downloading android-arm tools... 1,750ms
Downloading android-arm-profile tools... 607ms
Downloading android-arm-release tools... 416ms
Downloading android-arm64 tools... 6.9s
Downloading android-arm64-profile tools... 732ms
Downloading android-arm64-release tools... 482ms
Downloading android-x64-profile tools... 679ms
Downloading android-x64-release tools... 489ms
Downloading android-x86-jit-release tools... 852ms
Downloading Web SDK... 5.4s
Downloading package sky_engine... 116ms
Downloading flutter_patched_sdk tools... 326ms
Downloading flutter_patched_sdk_product tools... 326ms
Downloading linux-x64 tools... 3.9s
Downloading linux-x64-debug/linux-x64-flutter-gtk tools... 1,998ms
Downloading linux-x64-profile/linux-x64-flutter-gtk tools... 845ms
Downloading linux-x64-release/linux-x64-flutter-gtk tools... 713ms
Downloading linux-x64/font-subset tools... 164ms
Likely to some user directory ?
Even better : to the installation directory - hardcoded location
Step by step
- get Flutter tool sources
- downloads Dart SDK snapshot
- builds Flutter tool snapshot
- downloads Flutter engine
- download platform dependencies
- fonts (Material Icons, Roboto)
- android
- profile, jit and release toolchain
- all per architecture
- web SDK
- skia
- Flutter SDK tools
- platform compiler
- Windows / Linux / macOS
- font renderer
- platform embedding
- (e.g. GTK on Linux)
Platform dependencies
Origin of these downloads
- GitHub releases ?
- Some package registry ?
- Even better : Chromium CI !
This is not very open source of you !
Back to topic :
How to package this bloat ?
Packaging these downloads
- From Chromium CI
- pre-cache at package time
- patch : user directory - rejected in upstream
- Even better - let's build them ourselves
Building Flutter
Special thanks to lauren n. liberda !
Issues on FLOSS builds
- Vendored packages
- Chromium CI ✨
- Unhappy musl and *BSD noises
Toolchain for Flutter builds
- gclient solution + generate ninja
- blobs downloaded from Chromium CI
Alpine's patch set
Waaaaiiiit ?
What's about upstream work ?
Mostly rejected.
Getting Flutter to build FOSS
- Buildroot patches
- use local libraries
- Engine
- make build e.g. with musl
- Flutter tool
- use local artifacts, engine and Dart SDK
Cross-compiling
The moment I wished Flutter was written in go.
But wait a second ?
$ flutter build linux --target-platform linux-arm64 \
--target-sysroot ~/flutter-aarch64-sysroot
> Cross-build from Linux x64 host to Linux arm64 target is
> not currently supported.
docker run --privileged --rm tonistiigi/binfmt --install all
> [...]
docker run -ti --rm --platform linux/arm64 -v "$(pwd):/build" -w /build \
registry.gitlab.com/theonewiththebraid/flutter-dockerimages:3.16.8 \
flutter build linux --target-platform linux-arm64
> [...]
file build/linux/arm64/release/bundle/test_project
> build/linux/arm64/release/bundle/test_project: ELF 64-bit LSB pie executa
ble, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld
-linux-aarch64.so.1, BuildID[sha1]=759d1251987321485b7f93787a32312871e7c618
, for GNU/Linux 3.7.0, not stripped
Flutter cross-compiling
- No built-in way
- Compiler toolchain goes QEMU
- Standalone aarch64 build server
- custom-devices
- flutter-elinux or flutter-pi
- no built-in way again
-> Dev environment on target device way easier
You should hopefully see an image^w
Notable runtime issues
- Linux embedder considers touch as mouse
- Scaling
- gtk_header_bar
- Multi window
But there
is the momentum.
Let's get Linux
mobile ready as a
cross-platform target !
All Rosahaj emojis based on the works of heatherhorns, CC BY-SA.
<- these slides
Flutter on Linux mobile
By The one with the braid
Flutter on Linux mobile
Flutter - about the nightmare of cross platform development targetting Linux mobile
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