From d2da83f2d0851dd6a855f7f43564c9fbab6e3fe0 Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Mon, 23 May 2022 15:46:47 +0200
Subject: [PATCH 1/3] Backport PR #23057: FIX: ensure switching the backend
 installs repl hook

Merge pull request #23057 from tacaswell/fix_pylab

(cherry picked from commit b31c5ae782876386006a544a5cc833ddddb4b877)
---
 lib/matplotlib/pyplot.py            | 10 ++++------
 lib/matplotlib/tests/test_pyplot.py | 24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
index 2120a0120749..31719b458807 100644
--- a/lib/matplotlib/pyplot.py
+++ b/lib/matplotlib/pyplot.py
@@ -215,12 +215,6 @@ def _get_backend_mod():
         # will (re)import pyplot and then call switch_backend if we need to
         # resolve the auto sentinel)
         switch_backend(dict.__getitem__(rcParams, "backend"))
-        # Just to be safe.  Interactive mode can be turned on without calling
-        # `plt.ion()` so register it again here.  This is safe because multiple
-        # calls to `install_repl_displayhook` are no-ops and the registered
-        # function respects `mpl.is_interactive()` to determine if it should
-        # trigger a draw.
-        install_repl_displayhook()
     return _backend_mod
 
 
@@ -311,6 +305,10 @@ class backend_mod(matplotlib.backend_bases._Backend):
     # See https://github.com/matplotlib/matplotlib/issues/6092
     matplotlib.backends.backend = newbackend
 
+    # make sure the repl display hook is installed in case we become
+    # interactive
+    install_repl_displayhook()
+
 
 def _warn_if_gui_out_of_main_thread():
     if (_get_required_interactive_framework(_get_backend_mod())
diff --git a/lib/matplotlib/tests/test_pyplot.py b/lib/matplotlib/tests/test_pyplot.py
index 0105c6f22d47..d6069944d7e3 100644
--- a/lib/matplotlib/tests/test_pyplot.py
+++ b/lib/matplotlib/tests/test_pyplot.py
@@ -1,5 +1,6 @@
 import difflib
 import numpy as np
+import os
 import subprocess
 import sys
 from pathlib import Path
@@ -335,3 +336,26 @@ def test_fallback_position():
     axtest = plt.axes([0.2, 0.2, 0.5, 0.5], position=[0.1, 0.1, 0.8, 0.8])
     np.testing.assert_allclose(axtest.bbox.get_points(),
                                axref.bbox.get_points())
+
+
+def test_pylab_integration():
+    pytest.importorskip("IPython")
+    subprocess.run(
+        [
+            sys.executable,
+            "-m",
+            "IPython",
+            "--pylab",
+            "-c",
+            ";".join((
+                "import matplotlib.pyplot as plt",
+                "assert plt._REPL_DISPLAYHOOK == plt._ReplDisplayHook.IPYTHON",
+            )),
+        ],
+        env={**os.environ, "SOURCE_DATE_EPOCH": "0"},
+        timeout=60,
+        check=True,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        universal_newlines=True,
+    )

From 829b699858c8a25016e23701d4600b193a6ae378 Mon Sep 17 00:00:00 2001
From: Thomas A Caswell <tcaswell@gmail.com>
Date: Mon, 23 May 2022 18:06:17 -0400
Subject: [PATCH 2/3] Merge pull request #23106 from anntzer/tpi

MNT: Reuse subprocess_run_helper in test_pylab_integration.
(cherry picked from commit 51624b6e7d5df970a19e5eac5ff6928ffc035654)
---
 lib/matplotlib/tests/test_pyplot.py | 28 +++++++++-------------------
 1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/lib/matplotlib/tests/test_pyplot.py b/lib/matplotlib/tests/test_pyplot.py
index d6069944d7e3..a6d16ff065be 100644
--- a/lib/matplotlib/tests/test_pyplot.py
+++ b/lib/matplotlib/tests/test_pyplot.py
@@ -1,6 +1,5 @@
 import difflib
 import numpy as np
-import os
 import subprocess
 import sys
 from pathlib import Path
@@ -339,23 +338,14 @@ def test_fallback_position():
 
 
 def test_pylab_integration():
-    pytest.importorskip("IPython")
-    subprocess.run(
-        [
-            sys.executable,
-            "-m",
-            "IPython",
-            "--pylab",
-            "-c",
-            ";".join((
-                "import matplotlib.pyplot as plt",
-                "assert plt._REPL_DISPLAYHOOK == plt._ReplDisplayHook.IPYTHON",
-            )),
-        ],
-        env={**os.environ, "SOURCE_DATE_EPOCH": "0"},
+    IPython = pytest.importorskip("IPython")
+    mpl.testing.subprocess_run_helper(
+        IPython.start_ipython,
+        "--pylab",
+        "-c",
+        ";".join((
+            "import matplotlib.pyplot as plt",
+            "assert plt._REPL_DISPLAYHOOK == plt._ReplDisplayHook.IPYTHON",
+        )),
         timeout=60,
-        check=True,
-        stdout=subprocess.PIPE,
-        stderr=subprocess.PIPE,
-        universal_newlines=True,
     )

From d4879e57e24f9021898aab7e52705c9d7f12c8cc Mon Sep 17 00:00:00 2001
From: Thomas A Caswell <tcaswell@gmail.com>
Date: Thu, 26 May 2022 19:52:09 -0400
Subject: [PATCH 3/3] TST: Adjust to state tracking on 3.5.x branch

The implementation of tracking if the repl displayhook is installed changed on
main.  Adjust the backported test to work with the old way.
---
 lib/matplotlib/tests/test_pyplot.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/matplotlib/tests/test_pyplot.py b/lib/matplotlib/tests/test_pyplot.py
index a6d16ff065be..b376c1b54af3 100644
--- a/lib/matplotlib/tests/test_pyplot.py
+++ b/lib/matplotlib/tests/test_pyplot.py
@@ -345,7 +345,7 @@ def test_pylab_integration():
         "-c",
         ";".join((
             "import matplotlib.pyplot as plt",
-            "assert plt._REPL_DISPLAYHOOK == plt._ReplDisplayHook.IPYTHON",
+            "assert plt._IP_REGISTERED is not None",
         )),
         timeout=60,
     )