pythongh-61698: Use launchctl to detect macOS window manager in tests (python#118390)

Author: erlend-aasland

Lib/test/support/__init__.py

@@ -253,22 +253,16 @@ class USEROBJECTFLAGS(ctypes.Structure):
         # process not running under the same user id as the current console
         # user.  To avoid that, raise an exception if the window manager
         # connection is not available.
-        from ctypes import cdll, c_int, pointer, Structure
-        from ctypes.util import find_library
-
-        app_services = cdll.LoadLibrary(find_library("ApplicationServices"))
-
-        if app_services.CGMainDisplayID() == 0:
-            reason = "gui tests cannot run without OS X window manager"
+        import subprocess
+        try:
+            rc = subprocess.run(["launchctl", "managername"],
+                                capture_output=True, check=True)
+            managername = rc.stdout.decode("utf-8").strip()
+        except subprocess.CalledProcessError:
+            reason = "unable to detect macOS launchd job manager"
         else:
-            class ProcessSerialNumber(Structure):
-                _fields_ = [("highLongOfPSN", c_int),
-                            ("lowLongOfPSN", c_int)]
-            psn = ProcessSerialNumber()
-            psn_p = pointer(psn)
-            if (  (app_services.GetCurrentProcess(psn_p) < 0) or
-                  (app_services.SetFrontProcess(psn_p) < 0) ):
-                reason = "cannot run without OS X gui process"
+            if managername != "Aqua":
+                reason = f"{managername=} -- can only run in a macOS GUI session"
 
     # check on every platform whether tkinter can actually do anything
     if not reason: