OpenTTD-patches/os/emscripten/README.md
Patric Stout d15dc9f40f Add: support for emscripten (play-OpenTTD-in-the-browser)
Emscripten compiles to WASM, which can be loaded via
HTML / JavaScript. This allows you to play OpenTTD inside a
browser.

Co-authored-by: milek7 <me@milek7.pl>
2020-12-15 15:46:39 +01:00

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## How to build with Emscripten
Building with Emscripten works with emsdk 2.0.10 and above.
Currently there is no LibLZMA support upstream; for this we suggest to apply
the provided patch in this folder to your emsdk installation.
For convenience, a Dockerfile is supplied that does this patches for you
against upstream emsdk docker. Best way to use it:
Build the docker image:
```
docker build -t emsdk-lzma .
```
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-lzma cmake .. -DOPTION_TOOLS_ONLY=ON
docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build-host emsdk-lzma make -j5 tools
```
Next, build the game with emscripten:
```
mkdir build
docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emcmake cmake .. -DHOST_BINARY_DIR=$(pwd)/build-host -DCMAKE_BUILD_TYPE=RelWithDebInfo -DOPTION_USE_ASSERTS=OFF
docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emmake make -j5
```
And now you have in your build folder files like "openttd.html".
To run it locally, you would have to start a local webserver, like:
```
cd build
python3 -m http.server
````
Now you can play the game via http://127.0.0.1:8000/openttd.html .