task: Restore previous interrupt handler after `taskMgr.step()`

Related to #1180

direct/src/task/Task.py

@@ -130,6 +130,8 @@ class TaskManager:
         self.destroyed = False
         self.fKeyboardInterrupt = False
         self.interruptCount = 0
+        if signal:
+            self.__prevHandler = signal.default_int_handler
 
         self._frameProfileQueue = []
 
@@ -171,7 +173,7 @@ class TaskManager:
         print('*** allowing mid-frame keyboard interrupt.')
         # Restore default interrupt handler
         if signal:
-            signal.signal(signal.SIGINT, signal.default_int_handler)
+            signal.signal(signal.SIGINT, self.__prevHandler)
         # and invoke it
         raise KeyboardInterrupt
 
@@ -487,25 +489,30 @@ class TaskManager:
         chains that are in sub-threads or that have frame budgets
         might execute their tasks differently. """
 
+        startFrameTime = self.globalClock.getRealTime()
+
         # Replace keyboard interrupt handler during task list processing
         # so we catch the keyboard interrupt but don't handle it until
         # after task list processing is complete.
         self.fKeyboardInterrupt = 0
         self.interruptCount = 0
+
         if signal:
-            signal.signal(signal.SIGINT, self.keyboardInterruptHandler)
+            self.__prevHandler = signal.signal(signal.SIGINT, self.keyboardInterruptHandler)
 
-        startFrameTime = self.globalClock.getRealTime()
+        try:
+            self.mgr.poll()
 
-        self.mgr.poll()
+            # This is the spot for an internal yield function
+            nextTaskTime = self.mgr.getNextWakeTime()
+            self.doYield(startFrameTime, nextTaskTime)
 
-        # This is the spot for an internal yield function
-        nextTaskTime = self.mgr.getNextWakeTime()
-        self.doYield(startFrameTime, nextTaskTime)
+        finally:
+            # Restore previous interrupt handler
+            if signal:
+                signal.signal(signal.SIGINT, self.__prevHandler)
+                self.__prevHandler = signal.default_int_handler
 
-        # Restore default interrupt handler
-        if signal:
-            signal.signal(signal.SIGINT, signal.default_int_handler)
         if self.fKeyboardInterrupt:
             raise KeyboardInterrupt