matplotlib · QuLogic · Aug 5, 2021 · Jan 3, 2021 · Jan 18, 2021 · Jan 28, 2021
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -95,6 +95,9 @@ jobs:
               texlive-luatex \
               texlive-xetex \
               ttf-wqy-zenhei
+            if [[ "${{ matrix.os }}" = ubuntu-20.04 ]]; then
+              sudo apt install -yy libopengl0
+            fi
             ;;
           macOS)
             brew install ccache
@@ -106,25 +109,25 @@ jobs:
         if: startsWith(runner.os, 'Linux')
         with:
           path: ~/.cache/pip
-          key: ${{ runner.os }}-py${{ matrix.python-version }}-pip-${{ hashFiles('requirements/*/*.txt') }}
+          key: ${{ matrix.os }}-py${{ matrix.python-version }}-pip-${{ hashFiles('requirements/*/*.txt') }}
           restore-keys: |
-            ${{ runner.os }}-py${{ matrix.python-version }}-pip-
+            ${{ matrix.os }}-py${{ matrix.python-version }}-pip-
       - name: Cache pip
         uses: actions/cache@v2
         if: startsWith(runner.os, 'macOS')
         with:
           path: ~/Library/Caches/pip
-          key: ${{ runner.os }}-py${{ matrix.python-version }}-pip-${{ hashFiles('requirements/*/*.txt') }}
+          key: ${{ matrix.os }}-py${{ matrix.python-version }}-pip-${{ hashFiles('requirements/*/*.txt') }}
           restore-keys: |
-            ${{ runner.os }}-py${{ matrix.python-version }}-pip-
+            ${{ matrix.os }}-py${{ matrix.python-version }}-pip-
       - name: Cache ccache
         uses: actions/cache@v2
         with:
           path: |
             ~/.ccache
-          key: ${{ runner.os }}-py${{ matrix.python-version }}-ccache-${{ hashFiles('src/*') }}
+          key: ${{ matrix.os }}-py${{ matrix.python-version }}-ccache-${{ hashFiles('src/*') }}
           restore-keys: |
-            ${{ runner.os }}-py${{ matrix.python-version }}-ccache-
+            ${{ matrix.os }}-py${{ matrix.python-version }}-ccache-
       - name: Cache Matplotlib
         uses: actions/cache@v2
         with:
@@ -171,17 +174,28 @@ jobs:
             # Sept 2020) for either pyqt5 (there are only wheels for 10.13+) or
             # pyside2 (the latest version (5.13.2) with 10.12 wheels has a
             # fatal to us bug, it was fixed in 5.14.0 which has 10.13 wheels)
-             python -m pip install --upgrade pyqt5${{ matrix.pyqt5-ver }} &&
-               python -c 'import PyQt5.QtCore' &&
-               echo 'PyQt5 is available' ||
-               echo 'PyQt5 is not available'
-             python -m pip install --upgrade pyside2 &&
-               python -c 'import PySide2.QtCore' &&
-               echo 'PySide2 is available' ||
-               echo 'PySide2 is not available'
+            python -mpip install --upgrade pyqt5${{ matrix.pyqt5-ver }} &&
+              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'
+            # Qt6 crashes on Github's ubuntu 18.04 runner.
+            if [[ "${{ matrix.os }}" = ubuntu-20.04 ]]; then
+              python -mpip install --upgrade pyqt6 &&
+                python -c 'import PyQt6.QtCore' &&
+                echo 'PyQt6 is available' ||
+                echo 'PyQt6 is not available'
+              python -mpip install --upgrade pyside6 &&
+                python -c 'import PySide6.QtCore' &&
+                echo 'PySide6 is available' ||
+                echo 'PySide6 is not available'
+            fi
           fi
-          python -m pip install --upgrade \
-            -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-$(lsb_release -r -s) \
+          python -mpip install --upgrade \
+            -f "https://extras.wxpython.org/wxPython4/extras/linux/gtk3/${{ matrix.os }}" \
             wxPython &&
             python -c 'import wx' &&
             echo 'wxPython is available' ||

diff --git a/doc/devel/dependencies.rst b/doc/devel/dependencies.rst
@@ -41,7 +41,7 @@ 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.
-* PyQt5_ or PySide2_: for the Qt5-based backends.
+* PyQt6_ (>= 6.1), PySide6_, PyQt5_, or PySide2_: for the Qt-based backends.
 * PyGObject_: for the GTK3-based backends [#]_.
 * wxPython_ (>= 4) [#]_: for the wx-based backends.
 * pycairo_ (>= 1.11.0) or cairocffi_ (>= 0.8): for the GTK3 and/or cairo-based
@@ -51,6 +51,8 @@ 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/
 .. _wxPython: https://www.wxpython.org/
 .. _pycairo: https://pycairo.readthedocs.io/en/latest/

diff --git a/doc/users/interactive.rst b/doc/users/interactive.rst
@@ -63,7 +63,7 @@ it also ensures that the GUI toolkit event loop is properly integrated
 with the command line (see :ref:`cp_integration`).
 
 In this example, we create and modify a figure via an IPython prompt.
-The figure displays in a Qt5Agg GUI window. To configure the integration
+The figure displays in a QtAgg GUI window. To configure the integration
 and enable :ref:`interactive mode <controlling-interactive>` use the
 ``%matplotlib`` magic:
 
@@ -72,7 +72,7 @@ and enable :ref:`interactive mode <controlling-interactive>` use the
 ::
 
    In [1]: %matplotlib
-   Using matplotlib backend: Qt5Agg
+   Using matplotlib backend: QtAgg
 
    In [2]: import matplotlib.pyplot as plt
 

diff --git a/examples/user_interfaces/embedding_in_qt_sgskip.py b/examples/user_interfaces/embedding_in_qt_sgskip.py
@@ -4,18 +4,18 @@
 ===============
 
 Simple Qt application embedding Matplotlib canvases.  This program will work
-equally well using Qt4 and Qt5.  Either version of Qt can be selected (for
-example) by setting the ``MPLBACKEND`` environment variable to "Qt4Agg" or
-"Qt5Agg", or by first importing the desired version of PyQt.
+equally well using any Qt binding (PyQt6, PySide6, PyQt5, PySide2).  The
+binding can be selected by setting the ``QT_API`` environment variable to the
+binding name, or by first importing it.
 """
 
 import sys
 import time
 
 import numpy as np
 
-from matplotlib.backends.qt_compat import QtCore, QtWidgets
-from matplotlib.backends.backend_qt5agg import (
+from matplotlib.backends.qt_compat import QtWidgets
+from matplotlib.backends.backend_qtagg import (
     FigureCanvas, NavigationToolbar2QT as NavigationToolbar)
 from matplotlib.figure import Figure
 
@@ -28,13 +28,15 @@ def __init__(self):
         layout = QtWidgets.QVBoxLayout(self._main)
 
         static_canvas = FigureCanvas(Figure(figsize=(5, 3)))
+        # Ideally one would use self.addToolBar here, but it is slightly
+        # incompatible between PyQt6 and other bindings, so we just add the
+        # toolbar as a plain widget instead.
+        layout.addWidget(NavigationToolbar(static_canvas, self))
         layout.addWidget(static_canvas)
-        self.addToolBar(NavigationToolbar(static_canvas, self))
 
         dynamic_canvas = FigureCanvas(Figure(figsize=(5, 3)))
         layout.addWidget(dynamic_canvas)
-        self.addToolBar(QtCore.Qt.BottomToolBarArea,
-                        NavigationToolbar(dynamic_canvas, self))
+        layout.addWidget(NavigationToolbar(dynamic_canvas, self))
 
         self._static_ax = static_canvas.figure.subplots()
         t = np.linspace(0, 10, 501)
@@ -66,4 +68,4 @@ def _update_canvas(self):
     app.show()
     app.activateWindow()
     app.raise_()
-    qapp.exec_()
+    qapp.exec()
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -1100,9 +1100,8 @@ def use(backend, *, force=True):
         backend names, which are case-insensitive:
 
         - interactive backends:
-          GTK3Agg, GTK3Cairo, MacOSX, nbAgg,
-          Qt5Agg, Qt5Cairo,
-          TkAgg, TkCairo, WebAgg, WX, WXAgg, WXCairo
+          GTK3Agg, GTK3Cairo, MacOSX, nbAgg, QtAgg, QtCairo,
+          TkAgg, TkCairo, WebAgg, WX, WXAgg, WXCairo, Qt5Agg, Qt5Cairo
 
         - non-interactive backends:
           agg, cairo, pdf, pgf, ps, svg, template

diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -98,12 +98,14 @@ def _safe_pyplot_import():
         current_framework = cbook._get_running_interactive_framework()
         if current_framework is None:
             raise  # No, something else went wrong, likely with the install...
-        backend_mapping = {'qt5': 'qt5agg',
-                           'gtk3': 'gtk3agg',
-                           'wx': 'wxagg',
-                           'tk': 'tkagg',
-                           'macosx': 'macosx',
-                           'headless': 'agg'}
+        backend_mapping = {
+            'qt': 'qtagg',
+            'gtk3': 'gtk3agg',
+            'wx': 'wxagg',
+            'tk': 'tkagg',
+            'macosx': 'macosx',
+            'headless': 'agg',
+        }
         backend = backend_mapping[current_framework]
         rcParams["backend"] = mpl.rcParamsOrig["backend"] = backend
         import matplotlib.pyplot as plt  # Now this should succeed.
@@ -1662,7 +1664,7 @@ class FigureCanvasBase:
         A high-level figure instance.
     """
 
-    # Set to one of {"qt5", "gtk3", "wx", "tk", "macosx"} if an
+    # Set to one of {"qt", "gtk3", "wx", "tk", "macosx"} if an
     # interactive framework is required, or None otherwise.
     required_interactive_framework = None
 
@@ -1738,7 +1740,7 @@ def _fix_ipython_backend2gui(cls):
             # don't break on our side.
             return
         rif = getattr(cls, "required_interactive_framework", None)
-        backend2gui_rif = {"qt5": "qt", "gtk3": "gtk3",
+        backend2gui_rif = {"qt": "qt", "gtk3": "gtk3",
                            "wx": "wx", "macosx": "osx"}.get(rif)
         if backend2gui_rif:
             if _is_non_interactive_terminal_ipython(ip):