feat: wacom tablet integration

This is.. filled with hacks. But it works, and is in the `blueplum.nix`
file, which is specialized for my machine anyways.

blueplum.nix

@@ -7,9 +7,45 @@
 
 let
     concat = strings: builtins.concatStringsSep " " strings;
+    wacom.src =
+        let
+            xsetwacom = "${pkgs.xf86_input_wacom}/bin/xsetwacom";
+            awk = lib.getExe pkgs.gawk;
+        in
+        ''
+            #!/bin/sh
+
+            # Wait for X socket
+            for i in $(seq 30); do
+            	[ -S /tmp/.X11-unix/X0 ] && break
+            	sleep 0.5
+            done
+
+			# Just to be sure that the displays are ready...
+			sleep 5
+
+            export DISPLAY=:0
+            export XAUTHORITY="$HOME/.Xauthority"
+
+            for i in $(seq 10); do
+            	if ${xsetwacom} list devices | grep -q Wacom; then
+            		break
+            	fi
+            	sleep 1
+            done
+
+            stylus=$(${xsetwacom} list devices | ${awk} -F' \t' '/stylus/{print $1}')
+
+            if [ -z "$${stylus}" ]; then
+            	exit 0
+            fi
+
+            ${xsetwacom} set "$stylus" MapToOutput HEAD-0
+        '';
 in
 {
     services.xserver.videoDrivers = [ "nvidia" ];
+    services.xserver.wacom.enable = true;
 
     hardware.nvidia = {
         modesetting.enable = true;
@@ -37,4 +73,19 @@ in
             "--rate 144"
         ]}"
     ];
+
+    systemd.user.services.wacom = {
+        enable = true;
+        description = "Configure my Wacom (One) tablet";
+        wantedBy = [ "default.target" ];
+        after = [ "graphical-session.target" ];
+        serviceConfig = {
+            Type = "oneshot";
+            ExecStart = pkgs.writeShellScript "wacom.sh" wacom.src;
+        };
+    };
+
+    services.udev.extraRules = ''
+        ACTION=="add", SUBSYSTEM=="usb", ATTRS{idVendor}=="056a", TAG+="systemd", ENV{SYSTEMD_USER_WANTS}+="wacom.service"
+    '';
 }