Fix/mpl integration (#14128)

- Closes https://github.com/matplotlib/matplotlib/issues/17454
- fixes qt5/qt6 confusion

IPython/core/pylabtools.py

@@ -23,7 +23,7 b' backends = {'
     "qt4": "Qt4Agg",
     "qt5": "Qt5Agg",
     "qt6": "QtAgg",
-    "qt": "Qt5Agg",
+    "qt": "QtAgg",
     "osx": "MacOSX",
     "nbagg": "nbAgg",
     "webagg": "WebAgg",
@@ -53,8 +53,8 b' backend2gui["CocoaAgg"] = "osx"'
 # supports either Qt5 or Qt6 and the IPython qt event loop support Qt4, Qt5,
 # and Qt6.
 backend2gui["QtAgg"] = "qt"
-backend2gui["Qt4Agg"] = "qt"
-backend2gui["Qt5Agg"] = "qt"
+backend2gui["Qt4Agg"] = "qt4"
+backend2gui["Qt5Agg"] = "qt5"
 
 # And some backends that don't need GUI integration
 del backend2gui["nbAgg"]
@@ -208,10 +208,12 b' def mpl_runner(safe_execfile):'
 
         #print '*** Matplotlib runner ***' # dbg
         # turn off rendering until end of script
-        is_interactive = matplotlib.rcParams['interactive']
-        matplotlib.interactive(False)
+        with matplotlib.rc_context({"interactive": False}):
         safe_execfile(fname,*where,**kw)
-        matplotlib.interactive(is_interactive)
+
+        if matplotlib.is_interactive():
+            plt.show()
+
         # make rendering call now, if the user tried to do it
         if plt.draw_if_interactive.called:
             plt.draw()
@@ -317,9 +319,15 b' def find_gui_and_backend(gui=None, gui_select=None):'
 
     import matplotlib
 
+    has_unified_qt_backend = getattr(matplotlib, "__version_info__", (0, 0)) >= (3, 5)
+
+    backends_ = dict(backends)
+    if not has_unified_qt_backend:
+        backends_["qt"] = "qt5agg"
+
     if gui and gui != 'auto':
         # select backend based on requested gui
-        backend = backends[gui]
+        backend = backends_[gui]
         if gui == 'agg':
             gui = None
     else:
@@ -336,7 +344,7 b' def find_gui_and_backend(gui=None, gui_select=None):'
         # ones allowed.
         if gui_select and gui != gui_select:
             gui = gui_select
-            backend = backends[gui]
+            backend = backends_[gui]
 
     return gui, backend
 

IPython/core/tests/test_pylabtools.py

@@ -173,8 +173,8 b' class TestPylabSwitch(object):'
         # Save rcParams since they get modified
         self._saved_rcParams = matplotlib.rcParams
         self._saved_rcParamsOrig = matplotlib.rcParamsOrig
-        matplotlib.rcParams = dict(backend='Qt4Agg')
-        matplotlib.rcParamsOrig = dict(backend='Qt4Agg')
+        matplotlib.rcParams = dict(backend="QtAgg")
+        matplotlib.rcParamsOrig = dict(backend="QtAgg")
 
         # Mock out functions
         self._save_am = pt.activate_matplotlib