PartyDeck and gamescope

Run several Roblox windows side by side, one profile each, from PartyDeck or from a gamescope you start yourself.

Cordial can start a game straight from the command line, with no launcher window, and each such start is a Cordial of its own. That is what PartyDeck needs to run several players on one machine, and it is also all gamescope needs.

cordial --profile P1 --play --fullscreen

Sign every profile in before you use it here. Inside gamescope the game opens on X11, which has no in-app web window, so the Sign In button cannot finish. Sign each profile in once from a normal Cordial window, then start it from PartyDeck.

Set it up with PartyDeck

1. Create and sign in one profile per player

   Open Cordial normally. In the header bar, open the profile menu, choose New Profile…, name it with letters, digits, - and _ (P1, couch-left), and sign in. Repeat for each player, then close Cordial. A profile is one account’s storage, and two windows cannot share one.

2. Add the handler to PartyDeck

   PartyDeck reads handler folders from ~/.local/share/partydeck/handlers/. Copy the one that matches how you installed Cordial from packaging/partydeck/ in this repository.

   For the deb, rpm and Arch packages, which put cordial in /usr/bin:

   cp -r packaging/partydeck/Cordial ~/.local/share/partydeck/handlers/
   

   For the Flatpak, which runs flatpak run and so works for a user or a system install (read the Flatpak note under What is broken first):

   cp -r packaging/partydeck/Cordial-Flatpak ~/.local/share/partydeck/handlers/
   
3. Give each PartyDeck player a profile of the same name

   In PartyDeck, create a profile named exactly like each Cordial profile (P1, P2) and pick it for that player. The name is what Cordial runs, so it must exist in both places.

4. Start

   Pick Cordial in PartyDeck and start. Each player gets a Cordial window running their own profile.

Start a game from the command line

Everything PartyDeck does is these options, so you can use them from a script, a shortcut or your own gamescope.

Option	What it does
--profile NAME	Run this profile in this process only. It is not remembered as your profile and it does not hand over to a Cordial that is already open.
--play	Start Roblox at once with no launcher window. Exits when the game does.
--place-id N	Join experience N instead of the home screen. Implies --play.
--fullscreen	Fill the display the window opens on. gamescope wants this.
--set KEY=VALUE	Override one setting from Settings for this run, for example --set present_mode=fifo. Nothing is saved. A wrong KEY lists the right ones.

Without --play and --profile, cordial behaves as it always has: one launcher, and a second start hands over to it.

Exit status, for a program that starts games: 0 the game ended normally, 1 it could not start (the reason is on stderr), 2 the command line was wrong, 3 the profile is already open in another Cordial, 4 there is no Roblox build to run, 5 the game could not open a window.

Plain gamescope

gamescope -W 1280 -H 720 -- cordial --profile P1 --play --fullscreen

Add --backend headless to run with no display at all. --expose-wayland is not needed and makes no difference: Cordial uses the X11 display gamescope provides either way.

What is broken

No sign-in inside gamescope. The game opens on X11 there (gamescope’s own Wayland server cannot host the engine’s surface), and X11 has no web window. Sign in from a normal Cordial window first. A profile that does not exist yet starts signed out and says so on the console.

PartyDeck guests do not work. A guest is named .Name, which Cordial refuses as a profile name, and a fresh profile could not sign in anyway. Give every player a named profile.

• Controllers. Cordial reads /dev/input/js*, and PartyDeck leaves each instance only its own pad, so each player’s controller reaches only their window. This was tested with a stand-in device node, not with PartyDeck and real pads. The Flatpak sandbox held no input devices until --device=input was added to its manifest, so a Flatpak older than the release after 0.27.0 cannot see a pad; see Controllers. Whether PartyDeck’s one-pad-per-instance binding carries into a Flatpak is untested; Use the native package for split-pad play.
• Mouse look. Pointer capture under gamescope has not been tested, because the test sessions had no pointer. INFERRED: it works as on any X11 window. If the camera drifts, gamescope --force-grab-cursor is the first thing to try.
• Flatpak. The handler is untested. INFERRED: a Flatpak reaches gamescope’s X11 display through --socket=fallback-x11. If you started gamescope with --expose-wayland, add --env=CORDIAL_X11=1 right after run in the handler’s arguments, because the Flatpak does not see gamescope’s variables.
• Starting together. PartyDeck starts instances half a second apart unless a handler says otherwise, and these ask for three seconds. Two instances started half a second apart on one build store ran side by side in the one test made, which used a stand-in for PartyDeck’s command line and not PartyDeck itself.

Why it works this way, and what was measured: ADR-058.