CMakeLists.txt

#
# MIT License
#
# Original work Copyright (c) 2020 Joel Winarske
# Modified work Copyright     2021 Hannes Winkler
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
#

cmake_minimum_required(VERSION 3.10.2)

if(NOT CMAKE_BUILD_TYPE)
    set(CMAKE_BUILD_TYPE "Release" CACHE STRING "Choose the type of build, options are: Debug, Release, or MinSizeRel." FORCE)
    message(STATUS "CMAKE_BUILD_TYPE not set, defaulting to Release.")
endif()

project(flutter-pi LANGUAGES C VERSION "1.0.0")

message(STATUS "Generator .............. ${CMAKE_GENERATOR}")
message(STATUS "Build Type ............. ${CMAKE_BUILD_TYPE}")

# configure options
option(BUILD_TEXT_INPUT_PLUGIN "Include the text input plugin in the finished binary. Enables text input (to flutter text fields, for example) via attached keyboards." ON)
option(BUILD_RAW_KEYBOARD_PLUGIN "Include the raw keyboard plugin in the finished binary. Enables raw keycode listening in flutter via the flutter RawKeyboard interface." ON)
option(BUILD_TEST_PLUGIN "Include the test plugin in the finished binary. Allows testing platform channel communication." OFF)
option(BUILD_GSTREAMER_VIDEO_PLAYER_PLUGIN "Include the gstreamer based video plugins in the finished binary. Allows for more stable, hardware accelerated video playback in flutter using gstreamer." ON)
option(BUILD_GSTREAMER_AUDIO_PLAYER_PLUGIN "Include the gstreamer based audio plugins in the finished binary." ON)
option(TRY_BUILD_GSTREAMER_VIDEO_PLAYER_PLUGIN "Don't throw an error if the gstreamer libs aren't found, instead just don't build the gstreamer video player plugin in that case." ON)
option(TRY_BUILD_GSTREAMER_AUDIO_PLAYER_PLUGIN "Don't throw an error if the gstreamer libs aren't found, instead just don't build gstreamer audio plugin." ON)
option(BUILD_CHARSET_CONVERTER_PLUGIN "Include the charset converter plugin in the finished binary." OFF)
option(ENABLE_OPENGL "Build with EGL/OpenGL rendering support." ON)
option(TRY_ENABLE_OPENGL "Don't throw an error if EGL/OpenGL aren't found, instead just build without EGL/OpenGL support in that case." ON)
option(ENABLE_VULKAN "Build with Vulkan rendering support." OFF)
option(TRY_ENABLE_VULKAN "Don't throw an error if vulkan isn't found, instead just build without vulkan support in that case." OFF)
set(VULKAN_DEBUG "AUTO" CACHE STRING "Enable vulkan validation layers and verbose vulkan logging. (ON/OFF/AUTO)")
set_property(CACHE VULKAN_DEBUG PROPERTY STRINGS ON OFF AUTO)
option(ENABLE_SOFTWARE "Build with software rendering support." ON)
option(DUMP_ENGINE_LAYERS "True if flutter-pi should dump the list of rendering layers that the flutter engine sends to flutter-pi on each draw." OFF)
option(WARN_MISSING_FIELD_INITIALIZERS "True of the compiler should be instructed to warn about missing field initializers. This needs some hacky workarounds in the code so gcc won't report spurious warnings, so this should only be enabled if the warnings are explicitly required." OFF)
option(ENABLE_TSAN "True to build & link with -fsanitize=thread" OFF)
option(ENABLE_ASAN "True to build & link with -fsanitize=address" OFF)
option(ENABLE_UBSAN "True to build & link with -fsanitize=undefined" OFF)
option(ENABLE_MTRACE "True if flutter-pi should call GNU mtrace() on startup." OFF)
option(ENABLE_TESTS "True if tests should be built. Requires Unity to be checked out at third_party/Unity." OFF)
option(ENABLE_SESSION_SWITCHING "True if flutter-pi should be built with session switching support. Requires libseat-dev to be installed." ON)
option(TRY_ENABLE_SESSION_SWITCHING "Don't throw an error if libseat isn't found, instead just build without session switching support in that case." ON)
option(LTO "Check for IPO/LTO support and enable, if supported. May require gold/lld when building with clang. (Either using `-fuse-ld` in CMAKE_C_FLAGS or by setting as the default system linker.) Only applies to Release or RelWithDebInfo build types." ON)
option(LINT_EGL_HEADERS "Set an define that'll make the egl.h only export the extension definitions, prototypes that are explicitly marked as required." OFF)
option(DEBUG_DRM_PLANE_ALLOCATIONS "Add logging in modesetting.c for debugging the process of choosing a fitting DRM plane for a framebuffer layer." OFF)
option(USE_LEGACY_KMS "Force the use of legacy KMS." OFF)

set(FILESYSTEM_LAYOUTS default meta-flutter)
set(FILESYSTEM_LAYOUT "default" CACHE STRING "Where to look for the icudtl.dat, app.so/libapp.so, flutter asset bundle.")
set_property(CACHE FILESYSTEM_LAYOUT PROPERTY STRINGS ${FILESYSTEM_LAYOUTS})

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

include(ExternalProject)
include(CheckCCompilerFlag)
include(FetchContent)

# Those libraries we definitely need.
include(FindPkgConfig)
pkg_check_modules(DRM REQUIRED IMPORTED_TARGET libdrm)
pkg_check_modules(GBM REQUIRED IMPORTED_TARGET gbm)
pkg_check_modules(LIBSYSTEMD REQUIRED IMPORTED_TARGET libsystemd)
pkg_check_modules(LIBINPUT REQUIRED IMPORTED_TARGET libinput)
pkg_check_modules(LIBXKBCOMMON REQUIRED IMPORTED_TARGET xkbcommon)
pkg_check_modules(LIBUDEV REQUIRED IMPORTED_TARGET libudev)

# find pthreads
set(THREADS_PREFER_PTHREAD_FLAG ON)
find_package(Threads REQUIRED)

add_library(
  flutterpi_module OBJECT
  src/flutter-pi.c
  src/platformchannel.c
  src/pluginregistry.c
  src/texture_registry.c
  src/modesetting.c
  src/util/collection.c
  src/util/bitscan.c
  src/util/vector.c
  src/cursor.c
  src/keyboard.c
  src/user_input.c
  src/locales.c
  src/notifier_listener.c
  src/pixel_format.c
  src/filesystem_layout.c
  src/compositor_ng.c
  src/surface.c
  src/render_surface.c
  src/tracer.c
  src/dmabuf_surface.c
  src/frame_scheduler.c
  src/window.c
  src/dummy_render_surface.c
  src/plugins/services.c
)

target_link_libraries(flutterpi_module PUBLIC
  PkgConfig::DRM
  PkgConfig::GBM
  PkgConfig::LIBSYSTEMD
  PkgConfig::LIBINPUT
  PkgConfig::LIBXKBCOMMON
  PkgConfig::LIBUDEV
  Threads::Threads
  ${CMAKE_DL_LIBS}
  rt m atomic
)

target_include_directories(flutterpi_module PUBLIC
  ${CMAKE_SOURCE_DIR}/third_party/flutter_embedder_header/include
  ${CMAKE_SOURCE_DIR}/src
  ${CMAKE_BINARY_DIR}
)

target_compile_options(flutterpi_module PUBLIC
  $<$<CONFIG:Debug>:-O0 -Wall -Wextra -Wno-sign-compare -Werror -ggdb -U_FORTIFY_SOURCE -DDEBUG>
  $<$<CONFIG:RelWithDebInfo>:-O3 -Wall -Wextra -Wno-sign-compare -ggdb -DNDEBUG>
  $<$<CONFIG:Release>:-O3 -Wall -Wextra -Wno-sign-compare -DNDEBUG>
)

# GCC prior to 11.3 reports false positives for missing-field-initializers warning.
if (CMAKE_C_COMPILER_ID STREQUAL "GNU")
  if (CMAKE_C_COMPILER_VERSION VERSION_LESS "11.3")
    target_compile_options(flutterpi_module PUBLIC -Wno-missing-field-initializers)
  endif()
endif()

# libinput stuff
# There's no other way to query the libinput version (in code) somehow.
# So we need to roll our own libinput version macro
string(REPLACE "." ";" LIBINPUT_VERSION_AS_LIST ${LIBINPUT_VERSION})
list(GET LIBINPUT_VERSION_AS_LIST 0 LIBINPUT_VERSION_MAJOR)
list(GET LIBINPUT_VERSION_AS_LIST 1 LIBINPUT_VERSION_MINOR)
list(GET LIBINPUT_VERSION_AS_LIST 2 LIBINPUT_VERSION_PATCH)

# TODO: Just unconditionally define those, make them optional later
set(HAVE_KMS ON)
set(HAVE_GBM ON)
set(HAVE_FBDEV ON)

# OpenGL support
set(HAVE_EGL OFF)
set(HAVE_GLES2 OFF)
set(HAVE_EGL_GLES2 OFF)

pkg_check_modules(EGL IMPORTED_TARGET egl)
pkg_check_modules(GLES2 IMPORTED_TARGET glesv2)
if (ENABLE_OPENGL)
  if (EGL_FOUND AND GLES2_FOUND)
    target_sources(flutterpi_module PRIVATE
      src/egl_gbm_render_surface.c
      src/gl_renderer.c
    )
    target_link_libraries(flutterpi_module PUBLIC
      PkgConfig::EGL
      PkgConfig::GLES2
    )

    set(HAVE_EGL ON)
    set(HAVE_GLES2 ON)
    set(HAVE_EGL_GLES2 ON)
  elseif (TRY_ENABLE_OPENGL)
    message("EGL and/or OpenGL was not found. Flutter-pi will build without EGL/OpenGL rendering support.")
  else()
    message(SEND_ERROR "EGL and/or OpenGL was not found. Try building with `-DTRY_ENABLE_OPENGL=On` if you want to just disable EGL/OpenGL support in that case.")
  endif()
endif()

message(STATUS "EGL/GLES support ....... ${HAVE_EGL_GLES2}")

message(STATUS "Lint EGL headers ....... ${LINT_EGL_HEADERS}")

# Vulkan support
set(HAVE_VULKAN OFF)

pkg_check_modules(VULKAN IMPORTED_TARGET vulkan)
if (ENABLE_VULKAN)
  if (VULKAN_FOUND)
    target_sources(flutterpi_module PRIVATE
      src/vk_gbm_render_surface.c
      src/vk_renderer.c
    )
    target_link_libraries(flutterpi_module PUBLIC
      PkgConfig::VULKAN
    )

    set(HAVE_VULKAN ON)
  elseif (TRY_ENABLE_VULKAN)
    message("Vulkan was not found. Flutter-pi will build without vulkan rendering support.")
  else()
    message(SEND_ERROR "Vulkan was not found. Try building with `-DTRY_ENABLE_VULKAN=On` if you want to just disable vulkan support in that case.")
  endif()
endif()

message(STATUS "Vulkan support ......... ${HAVE_VULKAN}")

# We need at least one renderer
if (NOT HAVE_VULKAN AND NOT HAVE_EGL_GLES2)
  message(SEND_ERROR "At least one of the EGL/GLES2 and Vulkan backends must be enabled.")
endif()

# Filesystem Layout
# meta-flutter or normal flutter-pi.
# see src/filesystem_layout.c for details.
if(NOT FILESYSTEM_LAYOUT IN_LIST FILESYSTEM_LAYOUTS)
  message(FATAL_ERROR "FILESYSTEM_LAYOUT must be one of ${FILESYSTEM_LAYOUTS}")
endif()

message(STATUS "Filesystem Layout ...... ${FILESYSTEM_LAYOUT}")

# config.h takes the defines in form of #cmakedefine FILESYSTEM_LAYOUT_DEFAULT, ...
if(FILESYSTEM_LAYOUT STREQUAL default)
  set(FILESYSTEM_LAYOUT_DEFAULT ON)
elseif(FILESYSTEM_LAYOUT STREQUAL meta-flutter)
  set(FILESYSTEM_LAYOUT_METAFLUTTER ON)
endif()

# Session switching support (using libseat)
set(HAVE_LIBSEAT OFF)

if (ENABLE_SESSION_SWITCHING)
  if (TRY_ENABLE_SESSION_SWITCHING)
    pkg_check_modules(LIBSEAT IMPORTED_TARGET libseat)
  else()
    pkg_check_modules(LIBSEAT REQUIRED IMPORTED_TARGET libseat)
  endif()

  if (LIBSEAT_FOUND)
    target_link_libraries(flutterpi_module PUBLIC PkgConfig::LIBSEAT)
    set(HAVE_LIBSEAT ON)
  else()
    message("libseat was not found. flutter-pi will be built without session switching support.")
  endif()
endif()

message(STATUS "Session switching ...... ${HAVE_LIBSEAT}")

# TODO: We actually don't need the compile definitions anymore, except for
# text input and raw keyboard plugin (because those have special treatment
# in flutter-pi.c)
if (BUILD_TEXT_INPUT_PLUGIN)
  target_sources(flutterpi_module PRIVATE src/plugins/text_input.c)
endif()
if (BUILD_RAW_KEYBOARD_PLUGIN)
  target_sources(flutterpi_module PRIVATE src/plugins/raw_keyboard.c)
endif()
if (BUILD_TEST_PLUGIN)
  target_sources(flutterpi_module PRIVATE src/plugins/testplugin.c)
endif()
if (BUILD_GSTREAMER_VIDEO_PLAYER_PLUGIN)
  if (NOT HAVE_EGL_GLES2)
    message(NOTICE "EGL and OpenGL ES2 are required for gstreamer video player. Gstreamer video player plugin won't be build.")
  else()
    if (TRY_BUILD_GSTREAMER_VIDEO_PLAYER_PLUGIN)
      pkg_check_modules(LIBGSTREAMER IMPORTED_TARGET gstreamer-1.0)
      pkg_check_modules(LIBGSTREAMER_PLUGINS_BASE IMPORTED_TARGET gstreamer-plugins-base-1.0)
      pkg_check_modules(LIBGSTREAMER_APP IMPORTED_TARGET gstreamer-app-1.0)
      pkg_check_modules(LIBGSTREAMER_ALLOCATORS IMPORTED_TARGET gstreamer-allocators-1.0)
      pkg_check_modules(LIBGSTREAMER_VIDEO IMPORTED_TARGET gstreamer-video-1.0)
    else()
      pkg_check_modules(LIBGSTREAMER REQUIRED IMPORTED_TARGET gstreamer-1.0)
      pkg_check_modules(LIBGSTREAMER_PLUGINS_BASE REQUIRED IMPORTED_TARGET gstreamer-plugins-base-1.0)
      pkg_check_modules(LIBGSTREAMER_APP REQUIRED IMPORTED_TARGET gstreamer-app-1.0)
      pkg_check_modules(LIBGSTREAMER_ALLOCATORS REQUIRED IMPORTED_TARGET gstreamer-allocators-1.0)
      pkg_check_modules(LIBGSTREAMER_VIDEO REQUIRED IMPORTED_TARGET gstreamer-video-1.0)
    endif()

    if (LIBGSTREAMER_FOUND AND LIBGSTREAMER_PLUGINS_BASE_FOUND AND LIBGSTREAMER_APP_FOUND AND LIBGSTREAMER_ALLOCATORS_FOUND AND LIBGSTREAMER_VIDEO_FOUND)
      # There's no other way to query the libinput version (in code) somehow.
      # So we need to roll our own libinput version macro
      string(REPLACE "." ";" LIBGSTREAMER_VERSION_AS_LIST ${LIBGSTREAMER_VERSION})
      list(GET LIBGSTREAMER_VERSION_AS_LIST 0 LIBGSTREAMER_VERSION_MAJOR)
      list(GET LIBGSTREAMER_VERSION_AS_LIST 1 LIBGSTREAMER_VERSION_MINOR)
      list(GET LIBGSTREAMER_VERSION_AS_LIST 2 LIBGSTREAMER_VERSION_PATCH)

      target_sources(flutterpi_module PRIVATE
        src/plugins/gstreamer_video_player/plugin.c
        src/plugins/gstreamer_video_player/player.c
        src/plugins/gstreamer_video_player/frame.c
      )
      target_link_libraries(flutterpi_module PUBLIC
        PkgConfig::LIBGSTREAMER
        PkgConfig::LIBGSTREAMER_PLUGINS_BASE
        PkgConfig::LIBGSTREAMER_APP
        PkgConfig::LIBGSTREAMER_ALLOCATORS
        PkgConfig::LIBGSTREAMER_VIDEO
      )
    else()
      message(NOTICE "Couldn't find gstreamer libraries. Gstreamer video player plugin won't be build.")
    endif()
  endif()
endif()

if (BUILD_GSTREAMER_AUDIO_PLAYER_PLUGIN)
  if (TRY_BUILD_GSTREAMER_AUDIO_PLAYER_PLUGIN)
    pkg_check_modules(LIBGSTREAMER IMPORTED_TARGET gstreamer-1.0)
    pkg_check_modules(LIBGSTREAMER_APP IMPORTED_TARGET gstreamer-app-1.0)
    pkg_check_modules(LIBGSTREAMER_AUDIO IMPORTED_TARGET gstreamer-audio-1.0)
  else()
    pkg_check_modules(LIBGSTREAMER REQUIRED IMPORTED_TARGET gstreamer-1.0)
    pkg_check_modules(LIBGSTREAMER_APP REQUIRED IMPORTED_TARGET gstreamer-app-1.0)
    pkg_check_modules(LIBGSTREAMER_AUDIO REQUIRED IMPORTED_TARGET gstreamer-audio-1.0)
  endif()

  if (LIBGSTREAMER_FOUND AND LIBGSTREAMER_APP_FOUND AND LIBGSTREAMER_AUDIO_FOUND)
    target_sources(flutterpi_module PRIVATE
      src/plugins/audioplayers/plugin.c
      src/plugins/audioplayers/player.c
    )
    target_link_libraries(flutterpi_module PUBLIC
      PkgConfig::LIBGSTREAMER
      PkgConfig::LIBGSTREAMER_APP
      PkgConfig::LIBGSTREAMER_AUDIO
    )
  else()
    message(NOTICE "Couldn't find gstreamer libraries. Gstreamer audio player plugin won't be build.")
  endif()
endif()

if (BUILD_CHARSET_CONVERTER_PLUGIN)
  target_sources(flutterpi_module PRIVATE src/plugins/charset_converter.c)
endif()

# Needed so dart VM can actually resolve symbols in the same
# executable. (For dart:ffi DynamicLibrary.executable / DynamicLibrary.process)
target_link_options(flutterpi_module PUBLIC -rdynamic)

# Define VULKAN_DEBUG if it was set to On, or if it was set to AUTO and we're using debug mode.
if (VULKAN_DEBUG MATCHES AUTO)
  if (CMAKE_BUILD_TYPE MATCHES DEBUG)
    set(VULKAN_DEBUG ON)
  else()
    set(VULKAN_DEBUG OFF)
  endif()
elseif (VULKAN_DEBUG MATCHES "OFF")
  set(VULKAN_DEBUG OFF)
elseif (VULKAN_DEBUG MATCHES "ON")
  set(VULKAN_DEBUG ON)
endif()

# Some sanitizer configs.
if (ENABLE_TSAN)
  target_link_options(flutterpi_module PUBLIC -fsanitize=thread)
  target_compile_options(flutterpi_module PUBLIC -fsanitize=thread)
endif()
if (ENABLE_ASAN)
  # when we use asan, we need to force linking against the C++ stdlib.
  # If we don't link against it, and load a dynamic library that's linked against the C++ stdlib (like the flutter engine),
  # and something in the dynamically loaded library triggers asan, it'll throw an error because it hasn't
  # intercepted stdc++ yet.
  # Also disable --as-needed so we _actually_ link against c++, even though we don't use any symbols from it.
  target_link_libraries(flutterpi_module PUBLIC stdc++)
  target_link_options(flutterpi_module PUBLIC -fsanitize=address -fno-omit-frame-pointer -Wl,--no-as-needed)
  target_compile_options(flutterpi_module PUBLIC -fsanitize=address)

  check_c_compiler_flag(-static-libasan HAVE_STATIC_LIBASAN)
  if (HAVE_STATIC_LIBASAN)
    target_link_options(flutterpi_module PUBLIC -static-libasan)
  endif()
endif()
if (ENABLE_UBSAN)
  target_link_options(flutterpi_module PUBLIC -fsanitize=undefined)
  target_compile_options(flutterpi_module PUBLIC -fsanitize=undefined)
endif()

configure_file(config.h.in config.h @ONLY)

# TODO: make mapping portable
# is mapping `../src/` to `` always gonna work?
check_c_compiler_flag(-fmacro-prefix-map=.=. COMPILER_SUPPORTS_MACRO_PREFIX_MAP)
if (COMPILER_SUPPORTS_MACRO_PREFIX_MAP)
  target_compile_options(flutterpi_module PRIVATE "-fmacro-prefix-map=../src/=")
  target_compile_options(flutterpi_module PRIVATE "-fmacro-prefix-map=${CMAKE_CURRENT_SOURCE_DIR}/src/=")
endif()

# Actual flutter-pi executable.
add_executable(
  flutter-pi
  src/main.c
)
target_link_libraries(
  flutter-pi
  flutterpi_module
)
install(TARGETS flutter-pi RUNTIME DESTINATION bin)

# Enable lto if supported.
cmake_policy(SET CMP0069 NEW)
include(CheckIPOSupported)
# include(CheckLinkerFlag)

set(USE_LTO OFF)
# set(NEEDS_GOLD OFF)
# set(NEEDS_LLD OFF)
if(LTO AND (CMAKE_BUILD_TYPE STREQUAL Release OR CMAKE_BUILD_TYPE STREQUAL RelWithDebInfo))
  # So people can specify `-fuse-ld=lld` in the CMAKE_C_FLAGS.
  # Otherwise check_ipo_supported will not use CMAKE_C_FLAGS.
  if (POLICY CMP0138)
    cmake_policy(SET CMP0138 NEW)
  endif()

  check_ipo_supported(RESULT IPO_SUPPORTED OUTPUT IPO_SUPPORT_OUTPUT)
  if (NOT IPO_SUPPORTED)
    message(WARNING "IPO/LTO was requested in the configure options, but is not supported by the toolchain. Check CMakeFiles/CMakeError.log for details.")
  endif()

  # Try to enable IPO with gold and lld.
  # Needs CMP0138.
  # (untested because CMP0138 required CMake 3.24, that's why it's commented out)
  # if (NOT IPO_SUPPORTED)
  #   check_linker_flag(C "-fuse-ld=gold" SUPPORTS_GOLD)
  #   if (SUPPORTS_GOLD)
  #     set(OLD_CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
  #
  #     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fuse-ld=gold")
  #     try_compile()
  #     check_ipo_supported(RESULT IPO_SUPPORTED_WITH_GOLD OUTPUT IPO_SUPPORT_OUTPUT)
  #     if (IPO_SUPPORTED_WITH_GOLD)
  #       set(IPO_SUPPORTED ON)
  #       set(NEEDS_GOLD ON)
  #     endif()
  #
  #     set(CMAKE_C_FLAGS "${OLD_CMAKE_C_FLAGS}")
  #   endif()
  #
  #   check_linker_flag(C "-fuse-ld=lld" SUPPORTS_LLD)
  #   if (SUPPORTS_LLD)
  #     set(OLD_CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
  #
  #     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fuse-ld=lld")
  #     check_ipo_supported(RESULT IPO_SUPPORTED_WITH_LLD OUTPUT IPO_SUPPORT_OUTPUT)
  #     if (IPO_SUPPORTED_WITH_LLD)
  #       set(IPO_SUPPORTED ON)
  #       set(NEEDS_LLD ON)
  #     endif()
  #
  #     set(CMAKE_C_FLAGS "${OLD_CMAKE_C_FLAGS}")
  #   endif()
  # endif()

  # clang doesn't support LTO when using GNU ld.
  if(IPO_SUPPORTED AND ("${CMAKE_C_COMPILER_ID}" STREQUAL "Clang"))
    execute_process(COMMAND ${CMAKE_C_COMPILER} -Wl,--version OUTPUT_VARIABLE LINKER_VERSION_OUTPUT ERROR_QUIET)
    if("${LINKER_VERSION_OUTPUT}" MATCHES "GNU ld")
      message(WARNING "IPO/LTO was requested, but is not supported when using clang with GNU ld as the linker. Try setting gold or lld as the system linker.")
      set(IPO_SUPPORTED OFF)
    endif()
  endif()

  if (IPO_SUPPORTED)
    set(USE_LTO ON)
  endif()
endif()

message(STATUS "IPO/LTO ................ ${USE_LTO}")
if (USE_LTO)
  set_property(TARGET flutterpi_module PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
  set_property(TARGET flutter-pi PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
  # if (NEEDS_GOLD)
  #   Technically specifying only for one would suffice.
  #   target_link_options(flutterpi_module PUBLIC "-fuse-ld=gold")
  #   target_link_options(flutter-pi PUBLIC "-fuse-ld=gold")
  # elseif (NEEDS_LLD)
  #   target_link_options(flutterpi_module PUBLIC "-fuse-ld=lld")
  #   target_link_options(flutter-pi PUBLIC "-fuse-ld=lld")
  # endif()
endif()

if(ENABLE_TESTS)
  include(CTest)

  add_subdirectory(third_party)
  add_subdirectory(test)
endif()