Add test for close_event.

anntzer · anntzer · commit a5a47a52be86 · 2020-03-26T16:04:25.000+01:00
Test that a single close_event is triggered when a window is closed.

This caught a bug in the gtk3 backends, which used to emit *two*
close_events (see comment there; a better fix would be welcome); and
another in the wx backends (which emit *no* close_events when the window
is closed by pressing "q") which I didn't see how to fix and is just
xfailed for now.
diff --git a/lib/matplotlib/backends/backend_gtk3.py b/lib/matplotlib/backends/backend_gtk3.py
@@ -367,6 +367,7 @@ def add_widget(child):
 
         self.window.set_default_size(w, h)
 
+        self._destroying = False
         self.window.connect("destroy", lambda *args: Gcf.destroy(self))
         self.window.connect("delete_event", lambda *args: Gcf.destroy(self))
         if mpl.is_interactive():
@@ -376,6 +377,13 @@ def add_widget(child):
         self.canvas.grab_focus()
 
     def destroy(self, *args):
+        if self._destroying:
+            # Otherwise, this can be called twice when the user presses 'q',
+            # which calls Gcf.destroy(self), then this destroy(), then triggers
+            # Gcf.destroy(self) once again via
+            # `connect("destroy", lambda *args: Gcf.destroy(self))`.
+            return
+        self._destroying = True
         self.vbox.destroy()
         self.window.destroy()
         self.canvas.destroy()
diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -111,6 +111,7 @@ def check_alt_backend(alt_backend):
 timer.add_callback(FigureCanvasBase.key_press_event, fig.canvas, "q")
 # Trigger quitting upon draw.
 fig.canvas.mpl_connect("draw_event", lambda event: timer.start())
+fig.canvas.mpl_connect("close_event", print)
 
 plt.show()
 """
@@ -120,12 +121,19 @@ def check_alt_backend(alt_backend):
 @pytest.mark.parametrize("backend", _get_testable_interactive_backends())
 @pytest.mark.flaky(reruns=3)
 def test_interactive_backend(backend):
-    proc = subprocess.run([sys.executable, "-c", _test_script],
-                          env={**os.environ, "MPLBACKEND": backend},
-                          timeout=_test_timeout)
+    proc = subprocess.run(
+        [sys.executable, "-c", _test_script],
+        env={**os.environ, "MPLBACKEND": backend}, timeout=_test_timeout,
+        stdout=subprocess.PIPE, universal_newlines=True)
     if proc.returncode:
         pytest.fail("The subprocess returned with non-zero exit status "
                     f"{proc.returncode}.")
+    close_events_count = proc.stdout.count("CloseEvent")
+    if backend.startswith("wx") and close_events_count != 1:
+        pytest.xfail(f"{close_events_count} CloseEvent(s) emitted by "
+                     f"{backend}; expected 1")
+    else:
+        assert close_events_count == 1
 
 
 @pytest.mark.skipif('SYSTEM_TEAMFOUNDATIONCOLLECTIONURI' in os.environ,
