Systems and emulators

#What comes built in

Tandem knows 104 systems. The common ones:

The built-in platforms.json lists every system, folder name and file type. Tandem offers each installed emulator that fits, and a system appears only when its folder has at least one game.

#Using your own platforms.json

The built-in list is app/src/main/assets/platforms.json. To change it:

1. Copy that file to ROMs/tandem/platforms.json on your device.
2. Edit it: add a system, add an emulator, change a folder name.
3. In Tandem, Settings › Library › Rescan games.

When ROMs/tandem/platforms.json exists, Tandem uses it instead of the built-in list, entirely. Start from a copy of the built-in file, so you keep the systems you didn't mean to change.

#The format

The file is one object with a platforms list. Each entry is a system:

{
  "platforms": [
    {
      "id": "gba",
      "name": "Game Boy Advance",
      "short": "GBA",
      "folders": ["gba"],
      "extensions": ["gba", "zip", "7z"],
      "skipDirs": [],
      "art": ["gba"],
      "players": [
        {
          "name": "RetroArch",
          "component": "com.retroarch.aarch64/com.retroarch.browser.retroactivity.RetroActivityFuture",
          "action": "android.intent.action.MAIN",
          "game": "extra-path:ROM",
          "extras": {
            "LIBRETRO": "/data/data/com.retroarch.aarch64/cores/mgba_libretro_android.so",
            "CONFIGFILE": "/storage/emulated/0/Android/data/com.retroarch.aarch64/files/retroarch.cfg"
          }
        }
      ]
    }
  ]
}

#System fields

#Emulator fields

Each entry in players describes how to start one emulator.

The game field takes one of three forms:

A content link points into the ROMs folder you picked on first launch, and Tandem grants the emulator access to that one file. That is why the second setup step matters for emulators that use data or extra-uri.

#Finding an emulator's component and action

Most emulator projects document how frontends should launch them; look for "frontend", "intent" or "ES-DE" in their docs. ES-DE's own configuration (its es_find_rules.xml and es_systems.xml for Android) lists the activity and action for many emulators, and translates directly:

With a computer and adb, you can also list an installed app's activities:

adb shell cmd package resolve-activity --brief -a android.intent.action.VIEW <package>
adb shell dumpsys package <package> | grep -i activity

#Several emulators for one system

Add more entries to players. The first is the default, and any game can use another from its game menu (Y › Emulator). For example, to offer a standalone mGBA alongside RetroArch for the GBA, add it as a second player.

#Sharing what works

If you get an emulator working, please share it: open a new emulator request with your entry, or a pull request that adds it to the built-in file.