Backport PR #18584: Fix setting 0-timeout timer with Tornado.

jklymak · meeseeksmachine · commit c5506744d3f1 · 2020-10-13T20:26:38.000Z
diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
@@ -517,7 +517,7 @@ def _timer_start(self):
         else:
             self._timer = tornado.ioloop.PeriodicCallback(
                 self._on_timer,
-                self.interval)
+                max(self.interval, 1e-6))
             self._timer.start()
 
     def _timer_stop(self):
