Battle.net on a Steam Gaming Mode PC

Problem: the PC boots into Steam Gaming Mode (gamescope). Lutris and other desktop installers can’t reliably show a window there, and whatever you install has to appear in the Steam library.

Approach: run the official installer once under Proton on a hidden virtual display, then register the result as a non-Steam game that uses the same Proton prefix.

1. Install into a Proton prefix on a virtual display

D=~/Games/battlenet; mkdir -p $D && cd $D
curl -fLo Battle.net-Setup.exe 'https://downloader.battle.net/download/getInstaller?os=win&installer=Battle.net-Setup.exe'
 
Xvfb :77 -screen 0 1600x900x24 & export DISPLAY=:77
export STEAM_COMPAT_DATA_PATH=$D STEAM_COMPAT_CLIENT_INSTALL_PATH=~/.steam/steam
~/.steam/steam/compatibilitytools.d/GE-Proton11-7-x86_64/proton run \
  Battle.net-Setup.exe --lang=enUS --installpath="C:\\Program Files (x86)\\Battle.net"

When pfx/drive_c/Program Files (x86)/Battle.net/Battle.net Launcher.exe exists, it’s done. The login window renders blank on the virtual display, which is expected because it has no GPU. Kill it with wineserver -k.

2. Add it to Steam as a non-Steam game

Steam overwrites shortcuts.vdf while it’s running, and in Gaming Mode steam-launcher respawns Steam within about a second of steam -shutdown. The trick is to wait for the old PID to exit and write immediately:

OLD=$(pgrep -x steam); steam -shutdown &
while kill -0 $OLD 2>/dev/null; do sleep 0.2; done
python add_shortcut.py   # uses the `vdf` package

The script does three things:

1. Appends a shortcut with Exe set to the quoted Battle.net Launcher.exe path. Its appid is crc32(exe + name) | 0x80000000, stored signed.
2. Adds CompatToolMapping["<appid>"] = {name: "GE-Proton11-7-x86_64"} to ~/.steam/steam/config/config.vdf.
3. Symlinks steamapps/compatdata/<appid> to ~/Games/battlenet, so Steam reuses the prefix that already has Battle.net installed.

Back up both .vdf files first.

3. Verify

steam "steam://rungameid/$(( (APPID<<32) | 0x02000000 ))"
pgrep -af 'Battle.net.exe'

Then sign in on the TV and install WoW from inside Battle.net.

Related: Sunshine and Moonlight on a Steam Gaming Mode PC