[backport humble] fix threading shutdown (#1122)

Backport from #792

Co-authored-by: Christian Rauch <Rauch.Christian@gmx.de>

Author: jangeliniara

camera_calibration/src/camera_calibration/camera_calibrator.py

@@ -86,7 +86,7 @@ def __init__(self, queue, function):
         self.function = function
 
     def run(self):
-        while True:
+        while rclpy.ok():
             m = self.queue.get()
             self.function(m)
 
@@ -262,18 +262,17 @@ def __init__(self, *args, **kwargs):
 
     def spin(self):
         sth = SpinThread(self)
-        sth.setDaemon(True)
         sth.start()
 
-        while True:
+        while rclpy.ok():
             if self.queue_display.qsize() > 0:
                 self.image = self.queue_display.get()
                 cv2.imshow("display", self.image)
             else:
                 time.sleep(0.1)
             k = cv2.waitKey(6) & 0xFF
             if k in [27, ord('q')]:
-                rclpy.shutdown()
+                return
             elif k == ord('s') and self.image is not None:
                 self.screendump(self.image)
 

camera_calibration/src/camera_calibration/nodes/cameracalibrator.py

@@ -224,6 +224,7 @@ def main():
                                  checkerboard_flags=checkerboard_flags, max_chessboard_speed=options.max_chessboard_speed,
                                  queue_size=options.queue_size)
     node.spin()
+    rclpy.shutdown()
 
 if __name__ == "__main__":
     try: