return old value of PyMac_DoYieldEnabled; -1 means do not even check for interrupts

Mac/Modules/macosmodule.c

@@ -197,13 +197,13 @@ MacOS_SetScheduleTimes(PyObject *self, PyObject *args)
 static PyObject *
 MacOS_EnableAppswitch(PyObject *self, PyObject *args)
 {
-	int enable;
+	int old, new;
 	
-	if (!PyArg_ParseTuple(args, "i", &enable))
+	if (!PyArg_ParseTuple(args, "i", &new))
 		return NULL;
-	PyMac_DoYieldEnabled = enable;
-	Py_INCREF(Py_None);
-	return Py_None;
+	old = PyMac_DoYieldEnabled;
+	PyMac_DoYieldEnabled = new;
+	return Py_BuildValue("i", old);
 }
 
 
@@ -246,3 +246,4 @@ MacOS_Init()
 	if (MacOS_Error == NULL || PyDict_SetItemString(d, "Error", MacOS_Error) != 0)
 		Py_FatalError("can't define MacOS.Error");
 }
+

Mac/Python/macglue.c

@@ -115,7 +115,12 @@ static long yield_bg = 12;
 static long lastyield;
 static int in_foreground;
 
-int PyMac_DoYieldEnabled = 1;	/* Don't do eventloop when false */
+/* 
+** When > 0, do full scanning for events (program is not event aware)
+** when == 0, only scan for Command-period
+** when < 0, don't do any event scanning 
+*/
+int PyMac_DoYieldEnabled = 1;
 
 /* Convert C to Pascal string. Returns pointer to static buffer. */
 unsigned char *
@@ -238,6 +243,8 @@ scan_event_queue(flush)
 int
 PyOS_InterruptOccurred()
 {
+	if (PyMac_DoYieldEnabled < 0)
+		return 0;
 #ifdef THINK_C
 	scan_event_queue(1);
 #endif
@@ -882,3 +889,4 @@ PyMac_InitApplication()
 	}
 	Py_Main(argc, argv);
 }
+