Convert "osx" gui framework to/from "macosx" in Matplotlib (#14420)

This is a correction to the code that moves backend handling to
Matplotlib, which came to light during the review of
matplotlib/matplotlib#27948. The GUI framework of macOSX is called `osx`
in IPython but `macosx` in Matplotlib.

It would be possible to allow passing a GUI framework of `osx` to
Matplotlib and internally converting it to `macosx`, but the reverse
direction is problematic as we would like the answer to be `osx` if we
are using IPython and `macosx` if using pure Matplotlib. Therefore the
simplest solution is to do the translation in IPython. It is not ideal
as we want to minimise such Matplotlib-related implementation details in
IPython, but the changes here are small and simple and hence I think
they are acceptable.

There are two new private functions `_convert_gui_to_matplotlib` and
`_convert_gui_from_matplotlib` to do the required checking and
conversion, and these are called whenever a GUI framework name is passed
to or from Matplotlib. There are only 3 places in the code where this is
currently required.

Inevitably this comes to light just after the release of IPython 8.24.0!
But it is not a problem for end users until the next Matplotlib release
which contains matplotlib/matplotlib#27948. If that occurs really
quickly (sometime in May?) perhaps we could release an IPython 8.24.1
just beforehand, otherwise the usual planned release at the end of next
month would be fine.

IPython/core/pylabtools.py

@@ -1,518 +1,538 b''
 # -*- coding: utf-8 -*-
 """Pylab (matplotlib) support utilities."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from io import BytesIO
 from binascii import b2a_base64
 from functools import partial
 import warnings
 
 from IPython.core.display import _pngxy
 from IPython.utils.decorators import flag_calls
 
 
 # Matplotlib backend resolution functionality moved from IPython to Matplotlib
 # in IPython 8.24 and Matplotlib 3.9.1. Need to keep `backends` and `backend2gui`
 # here for earlier Matplotlib and for external backend libraries such as
 # mplcairo that might rely upon it.
 _deprecated_backends = {
     "tk": "TkAgg",
     "gtk": "GTKAgg",
     "gtk3": "GTK3Agg",
     "gtk4": "GTK4Agg",
     "wx": "WXAgg",
     "qt4": "Qt4Agg",
     "qt5": "Qt5Agg",
     "qt6": "QtAgg",
     "qt": "QtAgg",
     "osx": "MacOSX",
     "nbagg": "nbAgg",
     "webagg": "WebAgg",
     "notebook": "nbAgg",
     "agg": "agg",
     "svg": "svg",
     "pdf": "pdf",
     "ps": "ps",
     "inline": "module://matplotlib_inline.backend_inline",
     "ipympl": "module://ipympl.backend_nbagg",
     "widget": "module://ipympl.backend_nbagg",
 }
 
 # We also need a reverse backends2guis mapping that will properly choose which
 # GUI support to activate based on the desired matplotlib backend.  For the
 # most part it's just a reverse of the above dict, but we also need to add a
 # few others that map to the same GUI manually:
 _deprecated_backend2gui = dict(
     zip(_deprecated_backends.values(), _deprecated_backends.keys())
 )
 # In the reverse mapping, there are a few extra valid matplotlib backends that
 # map to the same GUI support
 _deprecated_backend2gui["GTK"] = _deprecated_backend2gui["GTKCairo"] = "gtk"
 _deprecated_backend2gui["GTK3Cairo"] = "gtk3"
 _deprecated_backend2gui["GTK4Cairo"] = "gtk4"
 _deprecated_backend2gui["WX"] = "wx"
 _deprecated_backend2gui["CocoaAgg"] = "osx"
 # There needs to be a hysteresis here as the new QtAgg Matplotlib backend
 # supports either Qt5 or Qt6 and the IPython qt event loop support Qt4, Qt5,
 # and Qt6.
 _deprecated_backend2gui["QtAgg"] = "qt"
 _deprecated_backend2gui["Qt4Agg"] = "qt4"
 _deprecated_backend2gui["Qt5Agg"] = "qt5"
 
 # And some backends that don't need GUI integration
 del _deprecated_backend2gui["nbAgg"]
 del _deprecated_backend2gui["agg"]
 del _deprecated_backend2gui["svg"]
 del _deprecated_backend2gui["pdf"]
 del _deprecated_backend2gui["ps"]
 del _deprecated_backend2gui["module://matplotlib_inline.backend_inline"]
 del _deprecated_backend2gui["module://ipympl.backend_nbagg"]
 
 
 # Deprecated attributes backends and backend2gui mostly following PEP 562.
 def __getattr__(name):
     if name in ("backends", "backend2gui"):
         warnings.warn(
             f"{name} is deprecated since IPython 8.24, backends are managed "
             "in matplotlib and can be externally registered.",
             DeprecationWarning,
         )
         return globals()[f"_deprecated_{name}"]
     raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
 
 
 #-----------------------------------------------------------------------------
 # Matplotlib utilities
 #-----------------------------------------------------------------------------
 
 
 def getfigs(*fig_nums):
     """Get a list of matplotlib figures by figure numbers.
 
     If no arguments are given, all available figures are returned.  If the
     argument list contains references to invalid figures, a warning is printed
     but the function continues pasting further figures.
 
     Parameters
     ----------
     figs : tuple
         A tuple of ints giving the figure numbers of the figures to return.
     """
     from matplotlib._pylab_helpers import Gcf
     if not fig_nums:
         fig_managers = Gcf.get_all_fig_managers()
         return [fm.canvas.figure for fm in fig_managers]
     else:
         figs = []
         for num in fig_nums:
             f = Gcf.figs.get(num)
             if f is None:
                 print('Warning: figure %s not available.' % num)
             else:
                 figs.append(f.canvas.figure)
         return figs
 
 
 def figsize(sizex, sizey):
     """Set the default figure size to be [sizex, sizey].
 
     This is just an easy to remember, convenience wrapper that sets::
 
       matplotlib.rcParams['figure.figsize'] = [sizex, sizey]
     """
     import matplotlib
     matplotlib.rcParams['figure.figsize'] = [sizex, sizey]
 
 
 def print_figure(fig, fmt="png", bbox_inches="tight", base64=False, **kwargs):
     """Print a figure to an image, and return the resulting file data
 
     Returned data will be bytes unless ``fmt='svg'``,
     in which case it will be unicode.
 
     Any keyword args are passed to fig.canvas.print_figure,
     such as ``quality`` or ``bbox_inches``.
 
     If `base64` is True, return base64-encoded str instead of raw bytes
     for binary-encoded image formats
 
     .. versionadded:: 7.29
         base64 argument
     """
     # When there's an empty figure, we shouldn't return anything, otherwise we
     # get big blank areas in the qt console.
     if not fig.axes and not fig.lines:
         return
 
     dpi = fig.dpi
     if fmt == 'retina':
         dpi = dpi * 2
         fmt = 'png'
 
     # build keyword args
     kw = {
         "format":fmt,
         "facecolor":fig.get_facecolor(),
         "edgecolor":fig.get_edgecolor(),
         "dpi":dpi,
         "bbox_inches":bbox_inches,
     }
     # **kwargs get higher priority
     kw.update(kwargs)
 
     bytes_io = BytesIO()
     if fig.canvas is None:
         from matplotlib.backend_bases import FigureCanvasBase
         FigureCanvasBase(fig)
 
     fig.canvas.print_figure(bytes_io, **kw)
     data = bytes_io.getvalue()
     if fmt == 'svg':
         data = data.decode('utf-8')
     elif base64:
         data = b2a_base64(data, newline=False).decode("ascii")
     return data
 
 def retina_figure(fig, base64=False, **kwargs):
     """format a figure as a pixel-doubled (retina) PNG
 
     If `base64` is True, return base64-encoded str instead of raw bytes
     for binary-encoded image formats
 
     .. versionadded:: 7.29
         base64 argument
     """
     pngdata = print_figure(fig, fmt="retina", base64=False, **kwargs)
     # Make sure that retina_figure acts just like print_figure and returns
     # None when the figure is empty.
     if pngdata is None:
         return
     w, h = _pngxy(pngdata)
     metadata = {"width": w//2, "height":h//2}
     if base64:
         pngdata = b2a_base64(pngdata, newline=False).decode("ascii")
     return pngdata, metadata
 
 
 # We need a little factory function here to create the closure where
 # safe_execfile can live.
 def mpl_runner(safe_execfile):
     """Factory to return a matplotlib-enabled runner for %run.
 
     Parameters
     ----------
     safe_execfile : function
         This must be a function with the same interface as the
         :meth:`safe_execfile` method of IPython.
 
     Returns
     -------
     A function suitable for use as the ``runner`` argument of the %run magic
     function.
     """
 
     def mpl_execfile(fname,*where,**kw):
         """matplotlib-aware wrapper around safe_execfile.
 
         Its interface is identical to that of the :func:`execfile` builtin.
 
         This is ultimately a call to execfile(), but wrapped in safeties to
         properly handle interactive rendering."""
 
         import matplotlib
         import matplotlib.pyplot as plt
 
         #print '*** Matplotlib runner ***' # dbg
         # turn off rendering until end of script
         with matplotlib.rc_context({"interactive": False}):
             safe_execfile(fname, *where, **kw)
 
         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()
             plt.draw_if_interactive.called = False
 
         # re-draw everything that is stale
         try:
             da = plt.draw_all
         except AttributeError:
             pass
         else:
             da()
 
     return mpl_execfile
 
 
 def _reshow_nbagg_figure(fig):
     """reshow an nbagg figure"""
     try:
         reshow = fig.canvas.manager.reshow
     except AttributeError as e:
         raise NotImplementedError() from e
     else:
         reshow()
 
 
 def select_figure_formats(shell, formats, **kwargs):
     """Select figure formats for the inline backend.
 
     Parameters
     ----------
     shell : InteractiveShell
         The main IPython instance.
     formats : str or set
         One or a set of figure formats to enable: 'png', 'retina', 'jpeg', 'svg', 'pdf'.
     **kwargs : any
         Extra keyword arguments to be passed to fig.canvas.print_figure.
     """
     import matplotlib
     from matplotlib.figure import Figure
 
     svg_formatter = shell.display_formatter.formatters['image/svg+xml']
     png_formatter = shell.display_formatter.formatters['image/png']
     jpg_formatter = shell.display_formatter.formatters['image/jpeg']
     pdf_formatter = shell.display_formatter.formatters['application/pdf']
 
     if isinstance(formats, str):
         formats = {formats}
     # cast in case of list / tuple
     formats = set(formats)
 
     [ f.pop(Figure, None) for f in shell.display_formatter.formatters.values() ]
     mplbackend = matplotlib.get_backend().lower()
     if mplbackend in ("nbagg", "ipympl", "widget", "module://ipympl.backend_nbagg"):
         formatter = shell.display_formatter.ipython_display_formatter
         formatter.for_type(Figure, _reshow_nbagg_figure)
 
     supported = {'png', 'png2x', 'retina', 'jpg', 'jpeg', 'svg', 'pdf'}
     bad = formats.difference(supported)
     if bad:
         bs = "%s" % ','.join([repr(f) for f in bad])
         gs = "%s" % ','.join([repr(f) for f in supported])
         raise ValueError("supported formats are: %s not %s" % (gs, bs))
 
     if "png" in formats:
         png_formatter.for_type(
             Figure, partial(print_figure, fmt="png", base64=True, **kwargs)
         )
     if "retina" in formats or "png2x" in formats:
         png_formatter.for_type(Figure, partial(retina_figure, base64=True, **kwargs))
     if "jpg" in formats or "jpeg" in formats:
         jpg_formatter.for_type(
             Figure, partial(print_figure, fmt="jpg", base64=True, **kwargs)
         )
     if "svg" in formats:
         svg_formatter.for_type(Figure, partial(print_figure, fmt="svg", **kwargs))
     if "pdf" in formats:
         pdf_formatter.for_type(
             Figure, partial(print_figure, fmt="pdf", base64=True, **kwargs)
         )
 
 #-----------------------------------------------------------------------------
 # Code for initializing matplotlib and importing pylab
 #-----------------------------------------------------------------------------
 
 
 def find_gui_and_backend(gui=None, gui_select=None):
     """Given a gui string return the gui and mpl backend.
 
     Parameters
     ----------
     gui : str
         Can be one of ('tk','gtk','wx','qt','qt4','inline','agg').
     gui_select : str
         Can be one of ('tk','gtk','wx','qt','qt4','inline').
         This is any gui already selected by the shell.
 
     Returns
     -------
     A tuple of (gui, backend) where backend is one of ('TkAgg','GTKAgg',
     'WXAgg','Qt4Agg','module://matplotlib_inline.backend_inline','agg').
     """
 
     import matplotlib
 
     if _matplotlib_manages_backends():
         backend_registry = matplotlib.backends.registry.backend_registry
 
         # gui argument may be a gui event loop or may be a backend name.
         if gui in ("auto", None):
             backend = matplotlib.rcParamsOrig["backend"]
             backend, gui = backend_registry.resolve_backend(backend)
         else:
+            gui = _convert_gui_to_matplotlib(gui)
             backend, gui = backend_registry.resolve_gui_or_backend(gui)
 
+        gui = _convert_gui_from_matplotlib(gui)
         return gui, backend
 
     # Fallback to previous behaviour (Matplotlib < 3.9)
     mpl_version_info = getattr(matplotlib, "__version_info__", (0, 0))
     has_unified_qt_backend = mpl_version_info >= (3, 5)
 
     from IPython.core.pylabtools import backends
 
     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]
         if gui == 'agg':
             gui = None
     else:
         # We need to read the backend from the original data structure, *not*
         # from mpl.rcParams, since a prior invocation of %matplotlib may have
         # overwritten that.
         # WARNING: this assumes matplotlib 1.1 or newer!!
         backend = matplotlib.rcParamsOrig['backend']
         # In this case, we need to find what the appropriate gui selection call
         # should be for IPython, so we can activate inputhook accordingly
         from IPython.core.pylabtools import backend2gui
         gui = backend2gui.get(backend, None)
 
         # If we have already had a gui active, we need it and inline are the
         # ones allowed.
         if gui_select and gui != gui_select:
             gui = gui_select
             backend = backends_[gui]
 
     # Matplotlib before _matplotlib_manages_backends() can return "inline" for
     # no gui event loop rather than the None that IPython >= 8.24.0 expects.
     if gui == "inline":
         gui = None
 
     return gui, backend
 
 
 def activate_matplotlib(backend):
     """Activate the given backend and set interactive to True."""
 
     import matplotlib
     matplotlib.interactive(True)
 
     # Matplotlib had a bug where even switch_backend could not force
     # the rcParam to update. This needs to be set *before* the module
     # magic of switch_backend().
     matplotlib.rcParams['backend'] = backend
 
     # Due to circular imports, pyplot may be only partially initialised
     # when this function runs.
     # So avoid needing matplotlib attribute-lookup to access pyplot.
     from matplotlib import pyplot as plt
 
     plt.switch_backend(backend)
 
     plt.show._needmain = False
     # We need to detect at runtime whether show() is called by the user.
     # For this, we wrap it into a decorator which adds a 'called' flag.
     plt.draw_if_interactive = flag_calls(plt.draw_if_interactive)
 
 
 def import_pylab(user_ns, import_all=True):
     """Populate the namespace with pylab-related values.
 
     Imports matplotlib, pylab, numpy, and everything from pylab and numpy.
 
     Also imports a few names from IPython (figsize, display, getfigs)
 
     """
 
     # Import numpy as np/pyplot as plt are conventions we're trying to
     # somewhat standardize on.  Making them available to users by default
     # will greatly help this.
     s = ("import numpy\n"
           "import matplotlib\n"
           "from matplotlib import pylab, mlab, pyplot\n"
           "np = numpy\n"
           "plt = pyplot\n"
           )
     exec(s, user_ns)
 
     if import_all:
         s = ("from matplotlib.pylab import *\n"
              "from numpy import *\n")
         exec(s, user_ns)
 
     # IPython symbols to add
     user_ns['figsize'] = figsize
     from IPython.display import display
     # Add display and getfigs to the user's namespace
     user_ns['display'] = display
     user_ns['getfigs'] = getfigs
 
 
 def configure_inline_support(shell, backend):
     """
     .. deprecated:: 7.23
 
         use `matplotlib_inline.backend_inline.configure_inline_support()`
 
     Configure an IPython shell object for matplotlib use.
 
     Parameters
     ----------
     shell : InteractiveShell instance
     backend : matplotlib backend
     """
     warnings.warn(
         "`configure_inline_support` is deprecated since IPython 7.23, directly "
         "use `matplotlib_inline.backend_inline.configure_inline_support()`",
         DeprecationWarning,
         stacklevel=2,
     )
 
     from matplotlib_inline.backend_inline import (
         configure_inline_support as configure_inline_support_orig,
     )
 
     configure_inline_support_orig(shell, backend)
 
 
 # Determine if Matplotlib manages backends only if needed, and cache result.
 # Do not read this directly, instead use _matplotlib_manages_backends().
 _matplotlib_manages_backends_value: bool | None = None
 
 
 def _matplotlib_manages_backends() -> bool:
     """Return True if Matplotlib manages backends, False otherwise.
 
     If it returns True, the caller can be sure that
     matplotlib.backends.registry.backend_registry is available along with
     member functions resolve_gui_or_backend, resolve_backend, list_all, and
     list_gui_frameworks.
     """
     global _matplotlib_manages_backends_value
     if _matplotlib_manages_backends_value is None:
         try:
             from matplotlib.backends.registry import backend_registry
 
             _matplotlib_manages_backends_value = hasattr(
                 backend_registry, "resolve_gui_or_backend"
             )
         except ImportError:
             _matplotlib_manages_backends_value = False
 
     return _matplotlib_manages_backends_value
 
 
 def _list_matplotlib_backends_and_gui_loops() -> list[str]:
     """Return list of all Matplotlib backends and GUI event loops.
 
     This is the list returned by
         %matplotlib --list
     """
     if _matplotlib_manages_backends():
         from matplotlib.backends.registry import backend_registry
 
-        ret = backend_registry.list_all() + backend_registry.list_gui_frameworks()
+        ret = backend_registry.list_all() + [
+            _convert_gui_from_matplotlib(gui)
+            for gui in backend_registry.list_gui_frameworks()
+        ]
     else:
         from IPython.core import pylabtools
 
         ret = list(pylabtools.backends.keys())
 
     return sorted(["auto"] + ret)
+
+
+# Matplotlib and IPython do not always use the same gui framework name.
+# Always use the approprate one of these conversion functions when passing a
+# gui framework name to/from Matplotlib.
+def _convert_gui_to_matplotlib(gui: str | None) -> str | None:
+    if gui and gui.lower() == "osx":
+        return "macosx"
+    return gui
+
+
+def _convert_gui_from_matplotlib(gui: str | None) -> str | None:
+    if gui and gui.lower() == "macosx":
+        return "osx"
+    return gui

IPython/core/tests/test_pylabtools.py

@@ -1,354 +1,352 b''
 """Tests for pylab tools module.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 
 from binascii import a2b_base64
 from io import BytesIO
 
 import pytest
 
 matplotlib = pytest.importorskip("matplotlib")
 matplotlib.use('Agg')
 from matplotlib.figure import Figure
 
 from matplotlib import pyplot as plt
 from matplotlib_inline import backend_inline
 import numpy as np
 
 from IPython.core.getipython import get_ipython
 from IPython.core.interactiveshell import InteractiveShell
 from IPython.core.display import _PNG, _JPEG
 from .. import pylabtools as pt
 
 from IPython.testing import decorators as dec
 
 
 def test_figure_to_svg():
     # simple empty-figure test
     fig = plt.figure()
     assert pt.print_figure(fig, "svg") is None
 
     plt.close('all')
 
     # simple check for at least svg-looking output
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     svg = pt.print_figure(fig, "svg")[:100].lower()
     assert "doctype svg" in svg
 
 
 def _check_pil_jpeg_bytes():
     """Skip if PIL can't write JPEGs to BytesIO objects"""
     # PIL's JPEG plugin can't write to BytesIO objects
     # Pillow fixes this
     from PIL import Image
     buf = BytesIO()
     img = Image.new("RGB", (4,4))
     try:
         img.save(buf, 'jpeg')
     except Exception as e:
         ename = e.__class__.__name__
         raise pytest.skip("PIL can't write JPEG to BytesIO: %s: %s" % (ename, e)) from e
 
 @dec.skip_without("PIL.Image")
 def test_figure_to_jpeg():
     _check_pil_jpeg_bytes()
     # simple check for at least jpeg-looking output
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     jpeg = pt.print_figure(fig, 'jpeg', pil_kwargs={'optimize': 50})[:100].lower()
     assert jpeg.startswith(_JPEG)
 
 def test_retina_figure():
     # simple empty-figure test
     fig = plt.figure()
     assert pt.retina_figure(fig) == None
     plt.close('all')
 
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     png, md = pt.retina_figure(fig)
     assert png.startswith(_PNG)
     assert "width" in md
     assert "height" in md
 
 
 _fmt_mime_map = {
     'png': 'image/png',
     'jpeg': 'image/jpeg',
     'pdf': 'application/pdf',
     'retina': 'image/png',
     'svg': 'image/svg+xml',
 }
 
 def test_select_figure_formats_str():
     ip = get_ipython()
     for fmt, active_mime in _fmt_mime_map.items():
         pt.select_figure_formats(ip, fmt)
         for mime, f in ip.display_formatter.formatters.items():
             if mime == active_mime:
                 assert Figure in f
             else:
                 assert Figure not in f
 
 def test_select_figure_formats_kwargs():
     ip = get_ipython()
     kwargs = dict(bbox_inches="tight")
     pt.select_figure_formats(ip, "png", **kwargs)
     formatter = ip.display_formatter.formatters["image/png"]
     f = formatter.lookup_by_type(Figure)
     cell = f.keywords
     expected = kwargs
     expected["base64"] = True
     expected["fmt"] = "png"
     assert cell == expected
 
     # check that the formatter doesn't raise
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     formatter.enabled = True
     png = formatter(fig)
     assert isinstance(png, str)
     png_bytes = a2b_base64(png)
     assert png_bytes.startswith(_PNG)
 
 def test_select_figure_formats_set():
     ip = get_ipython()
     for fmts in [
         {'png', 'svg'},
         ['png'],
         ('jpeg', 'pdf', 'retina'),
         {'svg'},
     ]:
         active_mimes = {_fmt_mime_map[fmt] for fmt in fmts}
         pt.select_figure_formats(ip, fmts)
         for mime, f in ip.display_formatter.formatters.items():
             if mime in active_mimes:
                 assert Figure in f
             else:
                 assert Figure not in f
 
 def test_select_figure_formats_bad():
     ip = get_ipython()
     with pytest.raises(ValueError):
         pt.select_figure_formats(ip, 'foo')
     with pytest.raises(ValueError):
         pt.select_figure_formats(ip, {'png', 'foo'})
     with pytest.raises(ValueError):
         pt.select_figure_formats(ip, ['retina', 'pdf', 'bar', 'bad'])
 
 def test_import_pylab():
     ns = {}
     pt.import_pylab(ns, import_all=False)
     assert "plt" in ns
     assert ns["np"] == np
 
 
 class TestPylabSwitch(object):
     class Shell(InteractiveShell):
         def init_history(self):
             """Sets up the command history, and starts regular autosaves."""
             self.config.HistoryManager.hist_file = ":memory:"
             super().init_history()
 
         def enable_gui(self, gui):
             pass
 
     def setup_method(self):
         import matplotlib
         def act_mpl(backend):
             matplotlib.rcParams['backend'] = backend
 
         # Save rcParams since they get modified
         self._saved_rcParams = matplotlib.rcParams
         self._saved_rcParamsOrig = matplotlib.rcParamsOrig
         matplotlib.rcParams = dict(backend="QtAgg")
         matplotlib.rcParamsOrig = dict(backend="QtAgg")
 
         # Mock out functions
         self._save_am = pt.activate_matplotlib
         pt.activate_matplotlib = act_mpl
         self._save_ip = pt.import_pylab
         pt.import_pylab = lambda *a,**kw:None
         self._save_cis = backend_inline.configure_inline_support
         backend_inline.configure_inline_support = lambda *a, **kw: None
 
     def teardown_method(self):
         pt.activate_matplotlib = self._save_am
         pt.import_pylab = self._save_ip
         backend_inline.configure_inline_support = self._save_cis
         import matplotlib
         matplotlib.rcParams = self._saved_rcParams
         matplotlib.rcParamsOrig = self._saved_rcParamsOrig
 
     def test_qt(self):
         s = self.Shell()
         gui, backend = s.enable_matplotlib(None)
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
         gui, backend = s.enable_matplotlib("inline")
         assert gui is None
         assert s.pylab_gui_select == "qt"
 
         gui, backend = s.enable_matplotlib("qt")
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
         gui, backend = s.enable_matplotlib("inline")
         assert gui is None
         assert s.pylab_gui_select == "qt"
 
         gui, backend = s.enable_matplotlib()
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
     def test_inline(self):
         s = self.Shell()
         gui, backend = s.enable_matplotlib("inline")
         assert gui is None
         assert s.pylab_gui_select == None
 
         gui, backend = s.enable_matplotlib("inline")
         assert gui is None
         assert s.pylab_gui_select == None
 
         gui, backend = s.enable_matplotlib("qt")
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
     def test_inline_twice(self):
         "Using '%matplotlib inline' twice should not reset formatters"
 
         ip = self.Shell()
         gui, backend = ip.enable_matplotlib("inline")
         assert gui is None
 
         fmts =  {'png'}
         active_mimes = {_fmt_mime_map[fmt] for fmt in fmts}
         pt.select_figure_formats(ip, fmts)
 
         gui, backend = ip.enable_matplotlib("inline")
         assert gui is None
 
         for mime, f in ip.display_formatter.formatters.items():
             if mime in active_mimes:
                 assert Figure in f
             else:
                 assert Figure not in f
 
     def test_qt_gtk(self):
         s = self.Shell()
         gui, backend = s.enable_matplotlib("qt")
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
         gui, backend = s.enable_matplotlib("gtk3")
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
 
 def test_no_gui_backends():
     for k in ['agg', 'svg', 'pdf', 'ps']:
         assert k not in pt.backend2gui
 
 
 def test_figure_no_canvas():
     fig = Figure()
     fig.canvas = None
     pt.print_figure(fig)
 
 
 @pytest.mark.parametrize(
     "name, expected_gui, expected_backend",
     [
         # name is gui
         ("gtk3", "gtk3", "gtk3agg"),
         ("gtk4", "gtk4", "gtk4agg"),
-        ("headless", "headless", "agg"),
+        ("headless", None, "agg"),
         ("osx", "osx", "macosx"),
         ("qt", "qt", "qtagg"),
         ("qt5", "qt5", "qt5agg"),
-        ("qt6", "qt6", "qt6agg"),
+        ("qt6", "qt6", "qtagg"),
         ("tk", "tk", "tkagg"),
         ("wx", "wx", "wxagg"),
         # name is backend
         ("agg", None, "agg"),
         ("cairo", None, "cairo"),
         ("pdf", None, "pdf"),
         ("ps", None, "ps"),
         ("svg", None, "svg"),
         ("template", None, "template"),
         ("gtk3agg", "gtk3", "gtk3agg"),
         ("gtk3cairo", "gtk3", "gtk3cairo"),
         ("gtk4agg", "gtk4", "gtk4agg"),
         ("gtk4cairo", "gtk4", "gtk4cairo"),
         ("macosx", "osx", "macosx"),
         ("nbagg", "nbagg", "nbagg"),
         ("notebook", "nbagg", "notebook"),
         ("qtagg", "qt", "qtagg"),
         ("qtcairo", "qt", "qtcairo"),
         ("qt5agg", "qt5", "qt5agg"),
         ("qt5cairo", "qt5", "qt5cairo"),
-        ("qt6agg", "qt", "qt6agg"),
-        ("qt6cairo", "qt", "qt6cairo"),
         ("tkagg", "tk", "tkagg"),
         ("tkcairo", "tk", "tkcairo"),
         ("webagg", "webagg", "webagg"),
         ("wxagg", "wx", "wxagg"),
         ("wxcairo", "wx", "wxcairo"),
     ],
 )
 def test_backend_builtin(name, expected_gui, expected_backend):
     # Test correct identification of Matplotlib built-in backends without importing and using them,
     # otherwise we would need to ensure all the complex dependencies such as windowing toolkits are
     # installed.
 
     mpl_manages_backends = pt._matplotlib_manages_backends()
     if not mpl_manages_backends:
         # Backends not supported before _matplotlib_manages_backends or supported
         # but with different expected_gui or expected_backend.
         if (
             name.endswith("agg")
             or name.endswith("cairo")
             or name in ("headless", "macosx", "pdf", "ps", "svg", "template")
         ):
             pytest.skip()
         elif name == "qt6":
             expected_backend = "qtagg"
         elif name == "notebook":
             expected_backend, expected_gui = expected_gui, expected_backend
 
     gui, backend = pt.find_gui_and_backend(name)
     if not mpl_manages_backends:
         gui = gui.lower() if gui else None
         backend = backend.lower() if backend else None
     assert gui == expected_gui
     assert backend == expected_backend
 
 
 def test_backend_entry_point():
     gui, backend = pt.find_gui_and_backend("inline")
     assert gui is None
     expected_backend = (
         "inline"
         if pt._matplotlib_manages_backends()
         else "module://matplotlib_inline.backend_inline"
     )
     assert backend == expected_backend
 
 
 def test_backend_unknown():
     with pytest.raises(RuntimeError if pt._matplotlib_manages_backends() else KeyError):
         pt.find_gui_and_backend("name-does-not-exist")