FIX: enable install_repl_displayhook when switching backends

tacaswell · tacaswell · commit 27969d64cec6 · 2022-05-17T17:39:36.000-04:00
closes #23042 In #22005 we change `pyplot` so that at import time we do not force a switch of the backend and install the repl displayhook. However, this meant that in some cases (primarily through `ipython --pylab`) to end up with a session where `install_repl_displayhook` had never been called.
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -206,12 +206,6 @@ 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
 
 
@@ -302,6 +296,10 @@ 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())
