From 69a7ab07fcbf9e7ee3a0b7d3ab73e1badefc78b4 Mon Sep 17 00:00:00 2001
From: CrystalSplitter <crystal@crystalwobsite.gay>
Date: Fri, 17 Jul 2026 00:05:08 -0700
Subject: [PATCH] nixos/opentabletdriver: Match OTD Upstream systemd
 environment checks

OTD requires WAYLAND_DISPLAY or DISPLAY to be set,
otherwise it assumes x11 which, on a WAYLAND display configuration,
leads to segfaults on OTD start up. Enforce an ordering
so that we wait until the session has initted before doing
anything.

Upstream has both a check for these environment variables,
as well as enforces a RestartSec=3 to prevent immediate
restarts.

Additionally, it's theoretically possible for DISPLAY to
be set before WAYLAND_DISPLAY, causing segmentation faults
on wayland set ups, so add an explicit polling condition for
that in the ExecStartPre script.
---
 nixos/modules/hardware/opentabletdriver.nix | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/nixos/modules/hardware/opentabletdriver.nix b/nixos/modules/hardware/opentabletdriver.nix
index aac29cac7f2f..44e28b31b387 100644
--- a/nixos/modules/hardware/opentabletdriver.nix
+++ b/nixos/modules/hardware/opentabletdriver.nix
@@ -61,16 +61,27 @@ in
       wantedBy = [ "graphical-session.target" ];
       partOf = [ "graphical-session.target" ];
 
+      unitConfig = {
+        After = "graphical-session.target";
+        ConditionEnvironment = [
+          "|WAYLAND_DISPLAY"
+          "|DISPLAY"
+        ];
+      };
+
       serviceConfig = {
         Type = "simple";
-        # workaround for https://github.com/NixOS/nixpkgs/issues/469340
-        ExecStartPre = pkgs.writeShellScript "disable-for-gdm-greeter" ''
-          if [[ "$USER" = "gdm-greeter"* ]]; then
+        # workaround for https://github.com/NixOS/nixpkgs/issues/469340 and
+        # https://github.com/OpenTabletDriver/OpenTabletDriver/issues/4885
+        ExecStartPre = pkgs.writeShellScript "poll-for-non-gdm-greeter-display" ''
+          if [[ "$USER" = "gdm-greeter"* \
+              || ( "$${XDG_SESSION_TYPE}" = wayland && -z "$${WAYLAND_DISPLAY}" ) ]]; then
             exit 1
           fi
         '';
         ExecStart = lib.getExe' cfg.package "otd-daemon";
         Restart = "on-failure";
+        RestartSec = 3;
       };
     };
   };