OpenTTD-patches/os/emscripten/README.md

How to build with Emscripten

Please use docker with the supplied Dockerfile to build for emscripten. It takes care of a few things:

• Use a version of emscripten we know works
• Patch in LibLZMA support (as this is not supported by upstream)
• Patch in nlohmann-json support (as this is not supported by upstream)

First, build the docker image by navigating in the folder this README.md is in, and executing:

  docker build -t emsdk-openttd .

Next, navigate back to the root folder of this project.

Now we build the host tools first:

  mkdir build-host
  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build-host emsdk-openttd cmake .. -DOPTION_TOOLS_ONLY=ON
  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build-host emsdk-openttd make -j$(nproc) tools

Finally, we build the actual game:

  mkdir build
  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-openttd emcmake cmake .. -DHOST_BINARY_DIR=../build-host -DCMAKE_BUILD_TYPE=Release -DOPTION_USE_ASSERTS=OFF
  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-openttd emmake make -j$(nproc)

In the build folder you will now see openttd.html.

To run it locally, you would have to start a local webserver; something like:

  cd build
  python3 -m http.server

You can now play the game via http://127.0.0.1:8000/openttd.html .