matplotlib
diff --git a/‎doc/api/backend_qt_api.rst
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diff --git a/‎doc/api/next_api_changes/removals/19894-ES.rst
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diff --git a/‎doc/api/prev_api_changes/api_changes_3.3.0/deprecations.rst
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diff --git a/‎doc/devel/dependencies.rst
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diff --git a/‎examples/user_interfaces/embedding_in_qt_sgskip.py
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diff --git a/‎lib/matplotlib/__init__.py
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diff --git a/‎lib/matplotlib/backend_bases.py
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diff --git a/‎lib/matplotlib/backends/backend_qt4.py
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diff --git a/‎lib/matplotlib/backends/backend_qt4agg.py
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diff --git a/‎lib/matplotlib/backends/backend_qt4cairo.py
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diff --git a/‎lib/matplotlib/backends/backend_qt5.py
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diff --git a/‎lib/matplotlib/backends/qt_compat.py
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@@ -6,16 +6,6 @@ to building the docs.
 .. redirect-from:: /api/backend_qt5agg_api
 .. redirect-from:: /api/backend_qt5cairo_api
 
-:mod:`matplotlib.backends.backend_qt4agg`
-=========================================
-
-.. module:: matplotlib.backends.backend_qt4agg
-
-:mod:`matplotlib.backends.backend_qt4cairo`
-===========================================
-
-.. module:: matplotlib.backends.backend_qt4cairo
-
 :mod:`matplotlib.backends.backend_qt5agg`
 =========================================
 
 
@@ -0,0 +1,5 @@
+Qt4-based backends
+~~~~~~~~~~~~~~~~~~
+The qt4agg and qt4cairo backends have been removed. Qt4 has reached its
+end-of-life in 2015 and there are no releases of either PyQt4 or PySide for
+recent versions of Python. Please use one of the Qt5 or Qt6 backends.
@@ -609,8 +609,8 @@ accepted.
 Qt modifier keys
 ~~~~~~~~~~~~~~~~
 The ``MODIFIER_KEYS``, ``SUPER``, ``ALT``, ``CTRL``, and ``SHIFT``
-global variables of the :mod:`matplotlib.backends.backend_qt4agg`,
-:mod:`matplotlib.backends.backend_qt4cairo`,
+global variables of the ``matplotlib.backends.backend_qt4agg``,
+``matplotlib.backends.backend_qt4cairo``,
 :mod:`matplotlib.backends.backend_qt5agg` and
 :mod:`matplotlib.backends.backend_qt5cairo` modules are deprecated.
 
 
@@ -40,7 +40,6 @@ Matplotlib figures can be rendered to various user interfaces. See
 and the capabilities they provide.
 
 * Tk_ (>= 8.3, != 8.6.0 or 8.6.1) [#]_: for the Tk-based backends.
-* PyQt4_ (>= 4.6) or PySide_ (>= 1.0.3) [#]_: for the Qt4-based backends.
 * PyQt5_ or PySide2_: for the Qt5-based backends.
 * PyGObject_: for the GTK3-based backends [#]_.
 * wxPython_ (>= 4) [#]_: for the wx-based backends.
@@ -49,8 +48,6 @@ and the capabilities they provide.
 * Tornado_: for the WebAgg backend.
 
 .. _Tk: https://docs.python.org/3/library/tk.html
-.. _PyQt4: https://pypi.org/project/PyQt4
-.. _PySide: https://pypi.org/project/PySide
 .. _PyQt5: https://pypi.org/project/PyQt5
 .. _PySide2: https://pypi.org/project/PySide2
 .. _PyGObject: https://pygobject.readthedocs.io/en/latest/
 
@@ -15,12 +15,8 @@
 import numpy as np
 
 from matplotlib.backends.qt_compat import QtCore, QtWidgets
-if QtCore.qVersion() >= "5.":
-    from matplotlib.backends.backend_qt5agg import (
-        FigureCanvas, NavigationToolbar2QT as NavigationToolbar)
-else:
-    from matplotlib.backends.backend_qt4agg import (
-        FigureCanvas, NavigationToolbar2QT as NavigationToolbar)
+from matplotlib.backends.backend_qt5agg import (
+    FigureCanvas, NavigationToolbar2QT as NavigationToolbar)
 from matplotlib.figure import Figure
 
 
 
@@ -1066,7 +1066,7 @@ def use(backend, *, force=True):
 
         - interactive backends:
           GTK3Agg, GTK3Cairo, MacOSX, nbAgg,
-          Qt4Agg, Qt4Cairo, Qt5Agg, Qt5Cairo,
+          Qt5Agg, Qt5Cairo,
           TkAgg, TkCairo, WebAgg, WX, WXAgg, WXCairo
 
         - non-interactive backends:
 
@@ -99,7 +99,6 @@ def _safe_pyplot_import():
         if current_framework is None:
             raise  # No, something else went wrong, likely with the install...
         backend_mapping = {'qt5': 'qt5agg',
-                           'qt4': 'qt4agg',
                            'gtk3': 'gtk3agg',
                            'wx': 'wxagg',
                            'tk': 'tkagg',
@@ -1680,7 +1679,7 @@ class FigureCanvasBase:
         A high-level figure instance.
     """
 
-    # Set to one of {"qt5", "qt4", "gtk3", "wx", "tk", "macosx"} if an
+    # Set to one of {"qt5", "gtk3", "wx", "tk", "macosx"} if an
     # interactive framework is required, or None otherwise.
     required_interactive_framework = None
 
@@ -1756,7 +1755,7 @@ def _fix_ipython_backend2gui(cls):
             # don't break on our side.
             return
         rif = getattr(cls, "required_interactive_framework", None)
-        backend2gui_rif = {"qt5": "qt", "qt4": "qt", "gtk3": "gtk3",
+        backend2gui_rif = {"qt5": "qt", "gtk3": "gtk3",
                            "wx": "wx", "macosx": "osx"}.get(rif)
         if backend2gui_rif:
             if _is_non_interactive_terminal_ipython(ip):
 
@@ -124,22 +124,22 @@ def _create_qApp():
 
 def _allow_super_init(__init__):
     """
-    Decorator for ``__init__`` to allow ``super().__init__`` on PyQt4/PySide2.
+    Decorator for ``__init__`` to allow ``super().__init__`` on PySide2.
     """
 
     if QT_API == "PyQt5":
 
         return __init__
 
     else:
-        # To work around lack of cooperative inheritance in PyQt4, PySide,
-        # and PySide2, when calling FigureCanvasQT.__init__, we temporarily
-        # patch QWidget.__init__ by a cooperative version, that first calls
+        # To work around lack of cooperative inheritance in PySide2, when
+        # calling FigureCanvasQT.__init__, we temporarily patch
+        # QWidget.__init__ by a cooperative version, that first calls
         # QWidget.__init__ with no additional arguments, and then finds the
         # next class in the MRO with an __init__ that does support cooperative
-        # inheritance (i.e., not defined by the PyQt4, PySide, PySide2, sip
-        # or Shiboken packages), and manually call its `__init__`, once again
-        # passing the additional arguments.
+        # inheritance (i.e., not defined by the PySide2, sip or Shiboken
+        # packages), and manually call its `__init__`, once again passing the
+        # additional arguments.
 
         qwidget_init = QtWidgets.QWidget.__init__
 
@@ -149,7 +149,7 @@ def cooperative_qwidget_init(self, *args, **kwargs):
             next_coop_init = next(
                 cls for cls in mro[mro.index(QtWidgets.QWidget) + 1:]
                 if cls.__module__.split(".")[0] not in [
-                    "PyQt4", "sip", "PySide", "PySide2", "Shiboken"])
+                    "sip", "PySide2", "Shiboken"])
             next_coop_init.__init__(self, *args, **kwargs)
 
         @functools.wraps(__init__)
@@ -293,27 +293,16 @@ def mouseReleaseEvent(self, event):
             FigureCanvasBase.button_release_event(self, x, y, button,
                                                   guiEvent=event)
 
-    if QtCore.qVersion() >= "5.":
-        def wheelEvent(self, event):
-            x, y = self.mouseEventCoords(event)
-            # from QWheelEvent::delta doc
-            if event.pixelDelta().x() == 0 and event.pixelDelta().y() == 0:
-                steps = event.angleDelta().y() / 120
-            else:
-                steps = event.pixelDelta().y()
-            if steps:
-                FigureCanvasBase.scroll_event(
-                    self, x, y, steps, guiEvent=event)
-    else:
-        def wheelEvent(self, event):
-            x = event.x()
-            # flipy so y=0 is bottom of canvas
-            y = self.figure.bbox.height - event.y()
-            # from QWheelEvent::delta doc
-            steps = event.delta() / 120
-            if event.orientation() == QtCore.Qt.Vertical:
-                FigureCanvasBase.scroll_event(
-                    self, x, y, steps, guiEvent=event)
+    def wheelEvent(self, event):
+        x, y = self.mouseEventCoords(event)
+        # from QWheelEvent::delta doc
+        if event.pixelDelta().x() == 0 and event.pixelDelta().y() == 0:
+            steps = event.angleDelta().y() / 120
+        else:
+            steps = event.pixelDelta().y()
+        if steps:
+            FigureCanvasBase.scroll_event(
+                self, x, y, steps, guiEvent=event)
 
     def keyPressEvent(self, event):
         key = self._get_key(event)
@@ -650,8 +639,7 @@ def _icon(self, name):
         Construct a `.QIcon` from an image file *name*, including the extension
         and relative to Matplotlib's "images" data directory.
         """
-        if QtCore.qVersion() >= '5.':
-            name = name.replace('.png', '_large.png')
+        name = name.replace('.png', '_large.png')
         pm = QtGui.QPixmap(str(cbook._get_data_path('images', name)))
         _setDevicePixelRatio(pm, _devicePixelRatioF(self))
         if self.palette().color(self.backgroundRole()).value() < 128:
 
@@ -2,15 +2,13 @@
 Qt binding and backend selector.
 
 The selection logic is as follows:
-- if any of PyQt5, PySide2, PyQt4 or PySide have already been imported
-  (checked in that order), use it;
+- if any of PyQt5, or PySide2 have already been imported (checked in that
+  order), use it;
 - otherwise, if the QT_API environment variable (used by Enthought) is set, use
   it to determine which binding to use (but do not change the backend based on
   it; i.e. if the Qt5Agg backend is requested but QT_API is set to "pyqt4",
   then actually use Qt5 with PyQt5 or PySide2 (whichever can be imported);
 - otherwise, use whatever the rcParams indicate.
-
-Support for PyQt4 is deprecated.
 """
 
 from distutils.version import LooseVersion
@@ -33,7 +31,6 @@
 # Mapping of QT_API_ENV to requested binding.  ETS does not support PyQt4v1.
 # (https://github.com/enthought/pyface/blob/master/pyface/qt/__init__.py)
 _ETS = {"pyqt5": QT_API_PYQT5, "pyside2": QT_API_PYSIDE2,
-        "pyqt": QT_API_PYQTv2, "pyside": QT_API_PYSIDE,
         None: None}
 # First, check if anything is already imported.  Use ``sys.modules.get(name)``
 # rather than ``name in sys.modules`` as entries can also have been explicitly
@@ -42,10 +39,6 @@
     QT_API = QT_API_PYQT5
 elif sys.modules.get("PySide2.QtCore"):
     QT_API = QT_API_PYSIDE2
-elif sys.modules.get("PyQt4.QtCore"):
-    QT_API = QT_API_PYQTv2
-elif sys.modules.get("PySide.QtCore"):
-    QT_API = QT_API_PYSIDE
 # Otherwise, check the QT_API environment variable (from Enthought).  This can
 # only override the binding, not the backend (in other words, we check that the
 # requested backend actually matches).  Use dict.__getitem__ to avoid
@@ -56,11 +49,6 @@
         QT_API = _ETS[QT_API_ENV]
     else:
         QT_API = None
-elif dict.__getitem__(mpl.rcParams, "backend") in ["Qt4Agg", "Qt4Cairo"]:
-    if QT_API_ENV in ["pyqt4", "pyside"]:
-        QT_API = _ETS[QT_API_ENV]
-    else:
-        QT_API = None
 # A non-Qt backend was selected but we still got there (possible, e.g., when
 # fully manually embedding Matplotlib in a Qt app without using pyplot).
 else:
@@ -69,8 +57,7 @@
     except KeyError as err:
         raise RuntimeError(
             "The environment variable QT_API has the unrecognized value {!r};"
-            "valid values are 'pyqt5', 'pyside2', 'pyqt', and "
-            "'pyside'") from err
+            "valid values are 'pyqt5', and 'pyside2'") from err
 
 
 def _setup_pyqt5():
@@ -98,79 +85,13 @@ def is_pyqt5():
         return True
 
 
-def _setup_pyqt4():
-    global QtCore, QtGui, QtWidgets, __version__, is_pyqt5, \
-        _isdeleted, _getSaveFileName
-
-    def _setup_pyqt4_internal(api):
-        global QtCore, QtGui, QtWidgets, \
-            __version__, is_pyqt5, _isdeleted, _getSaveFileName
-        # List of incompatible APIs:
-        # http://pyqt.sourceforge.net/Docs/PyQt4/incompatible_apis.html
-        _sip_apis = ["QDate", "QDateTime", "QString", "QTextStream", "QTime",
-                     "QUrl", "QVariant"]
-        try:
-            import sip
-        except ImportError:
-            pass
-        else:
-            for _sip_api in _sip_apis:
-                try:
-                    sip.setapi(_sip_api, api)
-                except (AttributeError, ValueError):
-                    pass
-        from PyQt4 import QtCore, QtGui
-        import sip  # Always succeeds *after* importing PyQt4.
-        __version__ = QtCore.PYQT_VERSION_STR
-        # PyQt 4.6 introduced getSaveFileNameAndFilter:
-        # https://riverbankcomputing.com/news/pyqt-46
-        if __version__ < LooseVersion("4.6"):
-            raise ImportError("PyQt<4.6 is not supported")
-        QtCore.Signal = QtCore.pyqtSignal
-        QtCore.Slot = QtCore.pyqtSlot
-        QtCore.Property = QtCore.pyqtProperty
-        _isdeleted = sip.isdeleted
-        _getSaveFileName = QtGui.QFileDialog.getSaveFileNameAndFilter
-
-    if QT_API == QT_API_PYQTv2:
-        _setup_pyqt4_internal(api=2)
-    elif QT_API == QT_API_PYSIDE:
-        from PySide import QtCore, QtGui, __version__, __version_info__
-        import shiboken
-        # PySide 1.0.3 fixed the following:
-        # https://srinikom.github.io/pyside-bz-archive/809.html
-        if __version_info__ < (1, 0, 3):
-            raise ImportError("PySide<1.0.3 is not supported")
-        def _isdeleted(obj): return not shiboken.isValid(obj)
-        _getSaveFileName = QtGui.QFileDialog.getSaveFileName
-    elif QT_API == QT_API_PYQT:
-        _setup_pyqt4_internal(api=1)
-    else:
-        raise ValueError("Unexpected value for the 'backend.qt4' rcparam")
-    QtWidgets = QtGui
-
-    @_api.deprecated("3.3", alternative="QtCore.qVersion()")
-    def is_pyqt5():
-        return False
-
-
 if QT_API in [QT_API_PYQT5, QT_API_PYSIDE2]:
     _setup_pyqt5()
-elif QT_API in [QT_API_PYQTv2, QT_API_PYSIDE, QT_API_PYQT]:
-    _setup_pyqt4()
 elif QT_API is None:  # See above re: dict.__getitem__.
-    if dict.__getitem__(mpl.rcParams, "backend") == "Qt4Agg":
-        _candidates = [(_setup_pyqt4, QT_API_PYQTv2),
-                       (_setup_pyqt4, QT_API_PYSIDE),
-                       (_setup_pyqt4, QT_API_PYQT),
-                       (_setup_pyqt5, QT_API_PYQT5),
-                       (_setup_pyqt5, QT_API_PYSIDE2)]
-    else:
-        _candidates = [(_setup_pyqt5, QT_API_PYQT5),
-                       (_setup_pyqt5, QT_API_PYSIDE2),
-                       (_setup_pyqt4, QT_API_PYQTv2),
-                       (_setup_pyqt4, QT_API_PYSIDE),
-                       (_setup_pyqt4, QT_API_PYQT)]
+    _candidates = [
+        (_setup_pyqt5, QT_API_PYQT5),
+        (_setup_pyqt5, QT_API_PYSIDE2),
+    ]
     for _setup, QT_API in _candidates:
         try:
             _setup()
@@ -193,14 +114,10 @@ def is_pyqt5():
 
 
 # These globals are only defined for backcompatibility purposes.
-ETS = dict(pyqt=(QT_API_PYQTv2, 4), pyside=(QT_API_PYSIDE, 4),
-           pyqt5=(QT_API_PYQT5, 5), pyside2=(QT_API_PYSIDE2, 5))
+ETS = dict(pyqt5=(QT_API_PYQT5, 5), pyside2=(QT_API_PYSIDE2, 5))
 
 QT_RC_MAJOR_VERSION = int(QtCore.qVersion().split(".")[0])
 
-if QT_RC_MAJOR_VERSION == 4:
-    _api.warn_deprecated("3.3", name="support for Qt4")
-
 
 def _devicePixelRatioF(obj):
     """