These are the build rules that are used to create docker images to build Proton. The automated creation of the official images lives in https://gitlab.steamos.cloud/proton/steamrt4/sdk, but this can be used to create local images too.

Local Changes And Testing

Make changes to the .Dockerfile.in

Just run make proton in this directory. To use Podman instead run make DOCKER=podman proton.

This will create container image tagged both as registry.gitlab.steamos.cloud/proton/steamrt4/sdk:$SOME_VERSION-0-dev and registry.gitlab.steamos.cloud/proton/steamrt4/sdk:latest

Look for lines successfully tagged at the bottom of the output.

To use the just built container image for Proton build you can pass the following argument to ./configure.sh (assuming you are using the same container engine, Podman or Docker, for both): --proton-sdk-image=registry.gitlab.steamos.cloud/proton/steamrt4/sdk:latest

ARM64 Containers

To build:

make BUILD_ARCH=aarch64 proton-llvm

To use:

$PROTON_SRC/configure.sh --proton-sdk-image=registry.gitlab.steamos.cloud/proton/steamrt4/sdk/arm64:latest

Official Images

To update the official Proton SDK images:

Update the image build rules and the base STEAMRT_VERSION numbers in files in this directory, test locally, commit and push the changes.
Update .gitlab-ci.yml in the Proton SDK repository to point to the new commit, commit and push to trigger a new build of -dev images.
Once the images are satisfying, tag the version in Proton SDK repository and push the tag, this will trigger a new build of the images and version them with the same tag as the Git tag.
Once the images have been published, update the default STEAMRT_IMAGE version number in the top-level Makefile.in to use the newly built images by default.

Any change or addition to GPL-ed source first requires to update or add the corresponding source to https://repo.steampowered.com/proton-sdk. The SOURCES_URLBASE variable must be used to download the sources from there, and its SHA256 must be added to validate the sources in the same way the existing code does.

Technical Details

The images are built incrementally, with intermediate images created for each component of the toolchain, then assembled together in a single proton image.

The reason behind this is to optimize the use of docker cache, so that components that didn't change do not require to be rebuilt every time, saving a lot of time in the build process, when only small additions are made.

It also lets us build several components of the toolchain separately, in parallel. This is especially the case when building the images on the https://gitlab.steamos.cloud CI.

Because the ARG parameter in Dockerfile doesn't behave nicely with docker caches it is avoided, and Dockerfile.in are used with variable replacements done using sed.

The https://gitlab.steamos.cloud CI uses Kaniko instead of Docker, with a bit of script conversion to generate commands usable there. More details are available in Proton SDK.