The hope is to have this eventually work with almost any GOG game, but that is probably a ways off.
You will need flatpak 0.9.7 or later, and python3. Both should be available in your repository if not already installed. 64-bit OS only, but building and playing 32-bit games works.
This all uses the Freedesktop runtime. If you haven't already got it, add the repo like this:
flatpak --user remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
then install the runtime plus SDK:
flatpak --user install flathub org.freedesktop.Platform/x86_64/19.08
flatpak --user install flathub org.freedesktop.Sdk/x86_64/19.08
For x86 games additionally install the required compatibility packages:
flatpak --user install flathub org.freedesktop.Platform.Compat.i386/x86_64/19.08
flatpak --user install flathub org.freedesktop.Platform.GL32/x86_64/19.08
flatpak --user install flathub org.freedesktop.Sdk.Compat.i386/x86_64/19.08
flatpak --user install flathub org.freedesktop.Sdk.Extension.toolchain-i386/x86_64/19.08
To prepare a game, you can use the provided "json-maker.py" script, e.g.
./json-maker.py ~/Downloads/gog_baldur_s_gate_2_enhanced_edition_2.6.0.11.sh
which will create a new json in the current dir based on the com.gog.Template.json file, with a name like gen_com.gog.BaldursGate2EnhancedEdition.json .
You can then build and install it directly thus:
flatpak-builder --user --install build gen_com.gog.BaldursGate2EnhancedEdition.json --force-clean --arch=x86_64
(see also the suggested command in the output of json-maker.py)
After installation you can start it like this, or use the desktop/menu icon that should have also been created.
flatpak run com.gog.BaldursGate2EnhancedEdition
flatpak-builder leaves some caching in .flatpak-builder, and the prepared Build/GAMENAME directory. These can be safely removed once you have the game running.
Sometimes the start.sh script provided from GOG does not work right in our flatpak. You can "override" this by placing a custom start-script in overrides/starter-GAMENAME .
This has not been tested with many GOG games yet, and it is extremely likely that a lot of further work will be needed to cover more games.
See the compatibility list for details.
Things that would be nice to implement:
