Installers can be downloaded from GOG.com, in the user's library page.
Installers use MojoSetup + makeself and are typically named gog_*.sh.
Some information could be extracted from the script at he head of the file, such as magic values or the game's title.
The default installation directory for GOG gGames is~/GOG Games/, each game can be installed anywhere.
Games are installed in a subdirectoy of the installation directory, named after the game.
The game's directory has a start.sh file, starting with: ` #!/bin/bash # GOG.com (www.gog.com) # The Game's Title `
The game's directory has a gameinfo file, containing the game's title on the first line, the game's version on the second line and the game's dev version (?) on the third line.
Gams installed that way should be runnable by executing their start.sh file.
Installing the Games
Games could try to autodetect the GOG installers and/or should let the users give the installer to the application.
So far, the best way to install the games would be to use Bastien's flatpak-games. Games installed that way are flatpacked and can be installed. That would make Games depend on Flatpak to install the GOG games, but it is an acceptable one as long as it is optionnal. This way, games would have the big advantage to run in an appropriate runtime and to be run sandboxd, for the user's security.