SDL3 porting to emscripten wasm

Надіслав: Admin , дата: Sun, 29 Mar 2026 - 01:11

Some time ago I've started to porting my SDL2 based angine to SDL3. There were some issues I was struggled with, but one day I woke up with a thing in my head to test if current build could be ported to emscripten.

Previous version of my engine was ported and everything went almost smooth. I've used emsdk and it's commands like 'emcmake cmake ..' and 'emmake make -j4' to build the project.

But this time I wanted to try something interesting and another way of handling the project. I'm using VSCode with "CMake tools" extension, which allows me to build the app from the IDE.

Using cmake-variants.yaml file I can have more build types! For example

buildType:
  default: debug
  choices:
    debug:
      short: Debug
      long: Emit debug information
      buildType: Debug
    release:
      short: Release
      long: Optimize generated code
      buildType: Release
    release_emscipten:
      short: Release Emscipten
      long: Build for web
      buildType: Release_Emscripten

First get emsdk build. https://emscripten.org/docs/tools_reference/emsdk.html

Then install latest emscripten core.

emsdk install latest
emsdk activate latest

emcmake is the wrapper for cmake for emscripten. There is a Emscripten.cmake file which is used to generate build configs, so I'm just using it. It's not correct way though but it works.

if (CMAKE_BUILD_TYPE STREQUAL "Release_Emscripten")
    set(EMSDK_PATH $ENV{HOME}/SDK/emsdk)
    include("${EMSDK_PATH}/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake")

    set( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/bin/html )
    add_executable(${PROJECT_NAME} ${all_SRCS})

    set(USE_FLAGS "-sUSE_SDL=3 -sUSE_SDL_MIXER=3 -sUSE_FREETYPE -sUSE_SDL_TTF=3 -sUSE_ZLIB=1 -Wno-experimental")
    set(CMAKE_CXX_FLAGS "${USE_FLAGS}")
    set(CMAKE_C_FLAGS "${USE_FLAGS}")
    set(CMAKE_EXECUTABLE_SUFFIX .html)
    set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")

    # Fix error with unrecognized option in wasm
    set(CMAKE_C_LINK_DEPENDS_USE_LINKER FALSE)
    set(CMAKE_CXX_LINK_DEPENDS_USE_LINKER FALSE)

    set_target_properties(${PROJECT_NAME} PROPERTIES LINK_FLAGS "--no-check-features --use-preload-plugins --preload-file ../assets -s WASM=0 -sALLOW_MEMORY_GROWTH=1 -sMAXIMUM_MEMORY=1gb -sPTHREAD_POOL_SIZE_STRICT=100")

endif()

Build was failed at first time because of [build] wasm-ld: error: unknown argument: --dependency-file=CMakeFiles/database-backup-recovery.dir/link.d

It was fixed with

    set(CMAKE_C_LINK_DEPENDS_USE_LINKER FALSE)
    set(CMAKE_CXX_LINK_DEPENDS_USE_LINKER FALSE)

Next thing is that SDL3_mixer was not ported yet! Gosh... It was the time to figure out if I can port it)

First of all SDL3 should be updated to the latest version https://github.com/emscripten-core/emscripten/pull/26572

Then I've spent lots of time to figure out the correct way to implement the port and tests for it. It was fun. I've added wav support by default and ogg/mp3 as optional.

https://github.com/emscripten-core/emscripten/pull/26571

To check the port build use commands from ${EMSDK_PATH}/upstream/emscripten folder. for any port

./embuilder clear sdl3_mixer
./embuilder build sdl3_mixer

For tests use

test/runner browser.test_sdl3_mixer_wav
test/runner browser.test_sdl3_mixer_music
test/runner other.test_sdl3_mixer

There is an option to setup Task in VSCode to execute compiled project in the browser. but for me it's fine to use nodes http-server . from the build folder.

Теґи

coding

python