MNT: remove pyside2 support

pyside2 does not support python 3.12+

Author: rcomer

.github/workflows/cygwin.yml

@@ -186,10 +186,6 @@ jobs:
              python -c 'import PyQt5.QtCore' &&
              echo 'PyQt5 is available' ||
              echo 'PyQt5 is not available'
-          python -mpip install --upgrade pyside2 &&
-              python -c 'import PySide2.QtCore' &&
-              echo 'PySide2 is available' ||
-              echo 'PySide2 is not available'
           python -m pip uninstall --yes wxpython || echo 'wxPython already uninstalled'
 
       - name: Install Matplotlib

doc/api/backend_qt_api.rst

@@ -22,10 +22,9 @@ a dependency to building the docs.
 Qt Bindings
 -----------
 
-There are currently 2 actively supported Qt versions, Qt5 and Qt6, and two
-supported Python bindings per version -- `PyQt5
-<https://www.riverbankcomputing.com/static/Docs/PyQt5/>`_ and `PySide2
-<https://doc.qt.io/qtforpython-5/contents.html>`_ for Qt5 and `PyQt6
+There are currently 2 actively supported Qt versions, Qt5 and Qt6. `PyQt5
+<https://www.riverbankcomputing.com/static/Docs/PyQt5/>`_ is the supported
+Python binding for Qt5 and there are both `PyQt6
 <https://www.riverbankcomputing.com/static/Docs/PyQt6/>`_ and `PySide6
 <https://doc.qt.io/qtforpython/contents.html>`_ for Qt6 [#]_.  Matplotlib's
 qtagg and qtcairo backends (``matplotlib.backends.backend_qtagg`` and
@@ -35,13 +34,12 @@ parts factored out in the ``matplotlib.backends.backend_qt`` module.
 At runtime, these backends select the actual binding used as follows:
 
 1. If a binding's ``QtCore`` subpackage is already imported, that binding is
-   selected (the order for the check is ``PyQt6``, ``PySide6``, ``PyQt5``,
-   ``PySide2``).
+   selected (the order for the check is ``PyQt6``, ``PySide6``, ``PyQt5``).
 2. If the :envvar:`QT_API` environment variable is set to one of "PyQt6",
-   "PySide6", "PyQt5", "PySide2" (case-insensitive), that binding is selected.
+   "PySide6", "PyQt5" (case-insensitive), that binding is selected.
    (See also the documentation on :ref:`environment-variables`.)
 3. Otherwise, the first available backend in the order ``PyQt6``, ``PySide6``,
-   ``PyQt5``, ``PySide2`` is selected.
+   ``PyQt5`` is selected.
 
 In the past, Matplotlib used to have separate backends for each version of Qt
 (e.g. qt4agg/``matplotlib.backends.backend_qt4agg`` and
@@ -62,8 +60,9 @@ change without warning [#]_.
 
 .. [#] There is also `PyQt4
        <https://www.riverbankcomputing.com/static/Docs/PyQt4/>`_ and `PySide
-       <https://srinikom.github.io/pyside-docs/>`_ for Qt4 but these are no
-       longer supported by Matplotlib and upstream support for Qt4 ended
+       <https://srinikom.github.io/pyside-docs/>`_ for Qt4 and `PySide2
+       <https://doc.qt.io/qtforpython-5/contents.html>`_ for Qt5 but these are
+       no longer supported by Matplotlib. Upstream support for Qt4 ended
        in 2015.
 .. [#] Despite the slight API differences, the more important distinction
        between the PyQt and Qt for Python series of bindings is licensing.

doc/install/dependencies.rst

@@ -62,8 +62,7 @@ and the capabilities they provide.
 * Tk_ (>= 8.5, != 8.6.0 or 8.6.1): for the Tk-based backends. Tk is part of
   most standard Python installations, but it's not part of Python itself and
   thus may not be present in rare cases.
-* PyQt6_ (>= 6.1), PySide6_, PyQt5_ (>= 5.12), or PySide2_: for the Qt-based
-  backends.
+* PyQt6_ (>= 6.1), PySide6_, or PyQt5_ (>= 5.12): for the Qt-based backends.
 * PyGObject_ and pycairo_ (>= 1.14.0): for the GTK-based backends. If using pip
   (but not conda or system package manager) PyGObject must be built from
   source; see `pygobject documentation
@@ -78,7 +77,6 @@ and the capabilities they provide.
 
 .. _Tk: https://docs.python.org/3/library/tk.html
 .. _PyQt5: https://pypi.org/project/PyQt5/
-.. _PySide2: https://pypi.org/project/PySide2/
 .. _PyQt6: https://pypi.org/project/PyQt6/
 .. _PySide6: https://pypi.org/project/PySide6/
 .. _PyGObject: https://pygobject.readthedocs.io/en/latest/

galleries/examples/user_interfaces/embedding_in_qt_sgskip.py

@@ -4,7 +4,7 @@
 ===========
 
 Simple Qt application embedding Matplotlib canvases.  This program will work
-equally well using any Qt binding (PyQt6, PySide6, PyQt5, PySide2).  The
+equally well using any Qt binding (PyQt6, PySide6, PyQt5).  The
 binding can be selected by setting the :envvar:`QT_API` environment variable to
 the binding name, or by first importing it.
 """

galleries/examples/user_interfaces/mplcvd.py

@@ -104,7 +104,7 @@ def setup(figure):
             break
     if pkg == "gi":
         _setup_gtk(tb)
-    elif pkg in ("PyQt5", "PySide2", "PyQt6", "PySide6"):
+    elif pkg in ("PyQt5", "PyQt6", "PySide6"):
         _setup_qt(tb)
     elif pkg == "tkinter":
         _setup_tk(tb)

galleries/users_explain/figure/backends.rst

@@ -321,7 +321,7 @@ program that can be run to test basic functionality.  If this test fails, try re
 QtAgg, QtCairo, Qt5Agg, and Qt5Cairo
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Test ``PyQt6`` (if you have ``PyQt5``, ``PySide2`` or ``PySide6`` installed
+Test ``PyQt6`` (if you have ``PyQt5`` or ``PySide6`` installed
 rather than ``PyQt6``, just change the import accordingly):
 
 .. code-block:: bash

lib/matplotlib/backends/backend_qt.py

@@ -104,9 +104,9 @@ def _create_qApp():
         # Check to make sure a QApplication from a different major version
         # of Qt is not instantiated in the process
         if QT_API in {'PyQt6', 'PySide6'}:
-            other_bindings = ('PyQt5', 'PySide2')
+            other_bindings = ('PyQt5',)
             qt_version = 6
-        elif QT_API in {'PyQt5', 'PySide2'}:
+        elif QT_API == 'PyQt5':
             other_bindings = ('PyQt6', 'PySide6')
             qt_version = 5
         else:
@@ -195,10 +195,7 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
     def __del__(self):
-        # The check for deletedness is needed to avoid an error at animation
-        # shutdown with PySide2.
-        if not _isdeleted(self._timer):
-            self._timer_stop()
+        self._timer_stop()
 
     def _timer_set_single_shot(self):
         self._timer.setSingleShot(self._single)

lib/matplotlib/backends/backend_qtagg.py

@@ -2,7 +2,6 @@
 Render to qt from agg.
 """
 
-import ctypes
 
 from matplotlib.transforms import Bbox
 
@@ -62,11 +61,6 @@ def paintEvent(self, event):
             # set origin using original QT coordinates
             origin = QtCore.QPoint(rect.left(), rect.top())
             painter.drawImage(origin, qimage)
-            # Adjust the buf reference count to work around a memory
-            # leak bug in QImage under PySide.
-            if QT_API == "PySide2" and QtCore.__version_info__ < (5, 12):
-                ctypes.c_long.from_address(id(buf)).value = 1
-
             self._draw_rect_callback(painter)
         finally:
             painter.end()

lib/matplotlib/backends/backend_qtcairo.py

@@ -1,8 +1,7 @@
-import ctypes
 
 from .backend_cairo import cairo, FigureCanvasCairo
 from .backend_qt import _BackendQT, FigureCanvasQT
-from .qt_compat import QT_API, QtCore, QtGui
+from .qt_compat import QT_API, QtGui
 
 
 class FigureCanvasQTCairo(FigureCanvasCairo, FigureCanvasQT):
@@ -29,10 +28,6 @@ def paintEvent(self, event):
         qimage = QtGui.QImage(
             ptr, width, height,
             QtGui.QImage.Format.Format_ARGB32_Premultiplied)
-        # Adjust the buf reference count to work around a memory leak bug in
-        # QImage under PySide.
-        if QT_API == "PySide2" and QtCore.__version_info__ < (5, 12):
-            ctypes.c_long.from_address(id(buf)).value = 1
         qimage.setDevicePixelRatio(self.device_pixel_ratio)
         painter = QtGui.QPainter(self)
         painter.eraseRect(event.rect())

lib/matplotlib/backends/qt_compat.py

@@ -2,7 +2,7 @@
 Qt binding and backend selector.
 
 The selection logic is as follows:
-- if any of PyQt6, PySide6, PyQt5, or PySide2 have already been
+- if any of PyQt6, PySide6, or PyQt5 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;
@@ -23,13 +23,12 @@
 QT_API_PYQT6 = "PyQt6"
 QT_API_PYSIDE6 = "PySide6"
 QT_API_PYQT5 = "PyQt5"
-QT_API_PYSIDE2 = "PySide2"
 QT_API_ENV = os.environ.get("QT_API")
 if QT_API_ENV is not None:
     QT_API_ENV = QT_API_ENV.lower()
 _ETS = {  # Mapping of QT_API_ENV to requested binding.
     "pyqt6": QT_API_PYQT6, "pyside6": QT_API_PYSIDE6,
-    "pyqt5": QT_API_PYQT5, "pyside2": QT_API_PYSIDE2,
+    "pyqt5": QT_API_PYQT5,
 }
 # First, check if anything is already imported.
 if sys.modules.get("PyQt6.QtCore"):
@@ -38,15 +37,13 @@
     QT_API = QT_API_PYSIDE6
 elif sys.modules.get("PyQt5.QtCore"):
     QT_API = QT_API_PYQT5
-elif sys.modules.get("PySide2.QtCore"):
-    QT_API = QT_API_PYSIDE2
 # 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 _get_backend_or_none to avoid
 # triggering backend resolution (which can result in a partially but
 # incompletely imported backend_qt5).
 elif (mpl.rcParams._get_backend_or_none() or "").lower().startswith("qt5"):
-    if QT_API_ENV in ["pyqt5", "pyside2"]:
+    if QT_API_ENV == "pyqt5":
         QT_API = _ETS[QT_API_ENV]
     else:
         _QT_FORCE_QT5_BINDING = True  # noqa: F811
@@ -92,33 +89,22 @@ def _isdeleted(obj): return not shiboken6.isValid(obj)
         QtCore.Property = QtCore.pyqtProperty
         _isdeleted = sip.isdeleted
         _to_int = int
-    elif QT_API == QT_API_PYSIDE2:
-        from PySide2 import QtCore, QtGui, QtWidgets, QtSvg, __version__
-        try:
-            from PySide2 import shiboken2
-        except ImportError:
-            import shiboken2
-        def _isdeleted(obj):
-            return not shiboken2.isValid(obj)
-        _to_int = int
     else:
         raise AssertionError(f"Unexpected QT_API: {QT_API}")
 
 
-if QT_API in [QT_API_PYQT6, QT_API_PYQT5, QT_API_PYSIDE6, QT_API_PYSIDE2]:
+if QT_API in [QT_API_PYQT6, QT_API_PYQT5, QT_API_PYSIDE6]:
     _setup_pyqt5plus()
 elif QT_API is None:  # See above re: dict.__getitem__.
     if _QT_FORCE_QT5_BINDING:
         _candidates = [
             (_setup_pyqt5plus, QT_API_PYQT5),
-            (_setup_pyqt5plus, QT_API_PYSIDE2),
         ]
     else:
         _candidates = [
             (_setup_pyqt5plus, QT_API_PYQT6),
             (_setup_pyqt5plus, QT_API_PYSIDE6),
             (_setup_pyqt5plus, QT_API_PYQT5),
-            (_setup_pyqt5plus, QT_API_PYSIDE2),
         ]
     for _setup, QT_API in _candidates:
         try: