Implement legacy display manager for system with no Mutter

lutris/sysoptions.py

@@ -2,12 +2,17 @@
 import os
 from collections import OrderedDict
 
+from gi.repository import GLib
+
 from lutris import runners
 # from lutris.util.log import logger
 from lutris.util import display, system
 
 
-DISPLAY_MANAGER = display.DisplayManager()
+try:
+    DISPLAY_MANAGER = display.DisplayManager()
+except GLib.Error:
+    DISPLAY_MANAGER = display.LegacyDisplayManager()
 
 
 def get_resolution_choices():

lutris/util/display.py

@@ -193,6 +193,16 @@ def get_providers():
     return providers
 
 
+class LegacyDisplayManager:
+    @staticmethod
+    def get_resolutions():
+        return get_resolutions()
+
+    @staticmethod
+    def get_display_names():
+        return get_output_names()
+
+
 class DisplayManager(object):
     def __init__(self):
         self.screen = Gdk.Screen.get_default()