test for thread safety

richardsheridan · richardsheridan · commit 9180607cbe2d · 2020-10-24T07:59:07.000-04:00
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -54,11 +54,10 @@ def _blit(argsid):
     Thin wrapper to pass arguments to blit via tkapp.call
     """
     photoimage, dataptr, offsets, bboxptr, blank = _blit_args.pop(argsid)
-    args = (
-        photoimage.tk.interpaddr(), str(photoimage), dataptr, offsets, bboxptr)
     if blank:
         photoimage.blank()
-    _tkagg.blit(*args)
+    _tkagg.blit(
+        photoimage.tk.interpaddr(), str(photoimage), dataptr, offsets, bboxptr)
 
 
 def blit(photoimage, aggimage, offsets, bbox=None):
diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -72,6 +72,7 @@ def _get_testable_interactive_backends():
 import io
 import json
 import sys
+import threading
 from unittest import TestCase
 
 import matplotlib as mpl
@@ -146,6 +147,28 @@ def check_alt_backend(alt_backend):
     # FIXME: This should be enabled everywhere once Qt5 is fixed on macOS to
     # not resize incorrectly.
     assert_equal(result.getvalue(), result_after.getvalue())
+    
+# Test artists and drawing does not crash from thread (no other guarantees)
+fig, ax = plt.subplots()
+# plt.pause needed vs plt.show(block=False) at least on toolbar2-tkagg
+plt.pause(0.1)
+
+def thread_artist_work():
+    ax.plot([1,3,6])
+
+def thread_draw_work():
+    fig.canvas.draw()
+    fig.canvas.stop_event_loop()
+
+t = threading.Thread(target=thread_artist_work)
+t.start()
+# artists never wait for the event loop to run, so just join
+t.join()
+
+t = threading.Thread(target=thread_draw_work)
+t.start()
+fig.canvas.start_event_loop()
+t.join()
 """
 _test_timeout = 10  # Empirically, 1s is not enough on Travis.
 
