From d791465bbebffbade2f68a0cab1e876bda74dcbb Mon Sep 17 00:00:00 2001
From: Thomas A Caswell <tcaswell@gmail.com>
Date: Thu, 25 Aug 2022 21:01:59 -0400
Subject: [PATCH] FIX: unbreak ipympl

We must not try to make a toolbar for the classes in backend_webaggcore because
ipympl inherits from these classes and requires its own toolbar to be used.

This also fixes the webagg embedding example without breaking ipympl.

closes #23699
---
 examples/user_interfaces/embedding_webagg_sgskip.py | 2 +-
 lib/matplotlib/backends/backend_webagg_core.py      | 4 +++-
 lib/matplotlib/tests/test_backend_webagg.py         | 6 ++++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/examples/user_interfaces/embedding_webagg_sgskip.py b/examples/user_interfaces/embedding_webagg_sgskip.py
index 338303f230bb..dbd6bfb2bcc9 100644
--- a/examples/user_interfaces/embedding_webagg_sgskip.py
+++ b/examples/user_interfaces/embedding_webagg_sgskip.py
@@ -30,7 +30,7 @@
 
 
 import matplotlib as mpl
-from matplotlib.backends.backend_webagg_core import (
+from matplotlib.backends.backend_webagg import (
     FigureManagerWebAgg, new_figure_manager_given_figure)
 from matplotlib.figure import Figure
 
diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
index 141dbdcc2e39..ee2d73d0cf95 100644
--- a/lib/matplotlib/backends/backend_webagg_core.py
+++ b/lib/matplotlib/backends/backend_webagg_core.py
@@ -427,7 +427,9 @@ def set_history_buttons(self):
 
 
 class FigureManagerWebAgg(backend_bases.FigureManagerBase):
-    _toolbar2_class = ToolbarCls = NavigationToolbar2WebAgg
+    # This must be None to not break ipympl
+    _toolbar2_class = None
+    ToolbarCls = NavigationToolbar2WebAgg
 
     def __init__(self, canvas, num):
         self.web_sockets = set()
diff --git a/lib/matplotlib/tests/test_backend_webagg.py b/lib/matplotlib/tests/test_backend_webagg.py
index 5c6ddfa258c0..992827863b01 100644
--- a/lib/matplotlib/tests/test_backend_webagg.py
+++ b/lib/matplotlib/tests/test_backend_webagg.py
@@ -2,6 +2,7 @@
 import os
 import sys
 import pytest
+import matplotlib.backends.backend_webagg_core
 
 
 @pytest.mark.parametrize("backend", ["webagg", "nbagg"])
@@ -25,3 +26,8 @@ def test_webagg_fallback(backend):
     ret = subprocess.call([sys.executable, "-c", test_code], env=env)
 
     assert ret == 0
+
+
+def test_webagg_core_no_toolbar():
+    fm = matplotlib.backends.backend_webagg_core.FigureManagerWebAgg
+    assert fm._toolbar2_class is None