flutter_embedded

This repo is used for CI automation to build flutter-engine embedder for Linux.

Project Status

x86_86 and aarch64 functional

No external toolchain is required, it uses toolchain pulled as part of engine build - Clang Toolchain.

If your are using a sysroot different than that included as default, you will need to override a few variables. See examples below.

The original Yocto Layer to build Engine with variety of Flutter embedders: meta-flutter

Build Example

See CI build jobs here: https://github.com/jwinarske/flutter_embedded/blob/ci/.github/workflows/blank.yml

Switching channels

To switch channels add variable CHANNEL to cmake invocation. Like this

cmake .. -DCHANNEL=beta
make package -j8

To build all channels of Engine/GLFW shell for Raspberry Pi armv7 in your nightly CI build job, you could do this

git clone https://github.com/jwinarske/flutter_embedded
cd flutter_embedded
mkdir build && cd build
cmake ..
make package -j8
cmake .. -DCHANNEL=beta
make package -j8
cmake .. -DCHANNEL=dev
make package -j8
cmake .. -DCHANNEL=master
make package -j8
cmake .. -DCHANNEL=stable -DENGINE_RUNTIME_MODE=release
make package -j8
cmake .. -DCHANNEL=beta
make package -j8
cmake .. -DCHANNEL=dev
make package -j8
cmake .. -DCHANNEL=master
make package -j8

Override Variables

To use the override variables, pass them in with the cmake command. One example

cmake -DTOOLCHAIN_DIR=~/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64 -DTARGET_SYSROOT=~/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot  -DENGINE_REPO=https://github.com/jwinarske/engine -DCMAKE_BUILD_TYPE=Release

TARGET_SYSROOT

This is the location of the target sysroot. The default value is "${CMAKE_SOURCE_DIR}/sdk/sysroot". One approach would be to download target image such as a Raspberry Pi image, and mount it. Setting TARGET_SYSROOT to the rootfs directory.

TARGET_ARCH

This is the target architecture of your build. It must match your toolchain, and that which the flutter engine build supports.

ENGINE_REPO

This is the repo of the flutter engine. The default value is https://github.com/flutter/engine.git. If you want to use your own fork, set this variable to point to your fork's url.

ENGINE_UNOPTIMIZED

Unoptimized flag, defaults to OFF

ENGINE_RUNTIME_MODE

If ENGINE_RUNTIME_MODE is not set to debug, profile, or release, it defaults to debug.

ENGINE_SIMULATOR

Enable simulator, defaults to OFF

ENGINE_INTERPRETER

Enable interpreter, defaults to OFF

ENGINE_DART_DEBUG

Enable dart-debug, defaults to OFF

ENGINE_CLANG

Enable clang, defaults to ON

ENGINE_GOMA

Enable goma, defaults to OFF

ENGINE_LTO

Enable link-time optimization, defaults to ON

ENGINE_EMBEDDER_FOR_TARGET

Embedder for Target, defaults to ON

ENGINE_ENABLE_VULKAN

Enable Vulkan, defaults to OFF

Native Flutter Target Debug

I am successfully able to single step the Flutter Embedder using Host Side gdb-multiarch, and latest Eclipse release. Target side requires gdbserver installed. LLDB will be at a later date.

sudo apt-get install gdbserver

Change build flags in this file

{build folder}/engine-prefix/src/engine/src/build/config/compiler/BUILD.gn

To include

if (is_linux) {
    if (current_cpu != "x86") {
        cflags_cc += [ 
        "-ggdb",
        "-ggdb3",

Rebuild Engine

Copy Artifact

scp {absolute build folder}/engine-prefix/src/engine/src/out/linux_debug_arm/so.unstripped/libflutter_engine.so pi@raspberrypi.local:/home/pi/lib

Inside Eclipse - Import C/C++ Executable, and select the Flutter binary.

Configuration - via Debugger Dialog

Main / C/C++ Application: flutter

Main / Connection: Remote Host

Main / Remote Absolute File Path for C/C++ Application: /home/pi/bin/flutter

Main / Commands to execute before application

    export LD_LIBRARY_PATH=/home/pi/lib

Main / Skip download to target path [TRUE]

Arguments: /home/pi/build/flutter_assets/

Debugger / Main / GDB Debugger

    gdb-multiarch

Debugger / Shared Libraries

    {absolute build folder}/engine-prefix/src/engine/src/out/linux_debug_arm/so.unstripped
    {absolute sdk folder}/sysroot/lib
    {absolute sdk folder}/toolchain/lib

Debugger / Shared Libraries / Load shared library symbols automatically [TRUE]  

Set breakpoint at FlutterEngineRun().

Run the debugger, once breakpoint hits, change to the Debugger Console window, and issue

set step-mode on

Step into FlutterEngineRun()