Backport PR #13085: ENH: add support for Qt6 input hooks

IPython/core/pylabtools.py

@@ -1,388 +1,389 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
 import warnings
 
 from IPython.core.display import _pngxy
 from IPython.utils.decorators import flag_calls
 
 # If user specifies a GUI, that dictates the backend, otherwise we read the
 # user's mpl default from the mpl rc structure
 backends = {
     "tk": "TkAgg",
     "gtk": "GTKAgg",
     "gtk3": "GTK3Agg",
     "wx": "WXAgg",
     "qt4": "Qt4Agg",
     "qt5": "Qt5Agg",
+    "qt6": "QtAgg",
     "qt": "Qt5Agg",
     "osx": "MacOSX",
     "nbagg": "nbAgg",
     "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:
 backend2gui = dict(zip(backends.values(), backends.keys()))
 # Our tests expect backend2gui to just return 'qt'
 backend2gui['Qt4Agg'] = 'qt'
 # In the reverse mapping, there are a few extra valid matplotlib backends that
 # map to the same GUI support
 backend2gui['GTK'] = backend2gui['GTKCairo'] = 'gtk'
 backend2gui['GTK3Cairo'] = 'gtk3'
 backend2gui['WX'] = 'wx'
 backend2gui['CocoaAgg'] = 'osx'
 # And some backends that don't need GUI integration
 del backend2gui["nbAgg"]
 del backend2gui["agg"]
 del backend2gui["svg"]
 del backend2gui["pdf"]
 del backend2gui["ps"]
 del backend2gui["module://matplotlib_inline.backend_inline"]
 
 #-----------------------------------------------------------------------------
 # 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', **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``.
     """
     # 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')
     return data
 
 def retina_figure(fig, **kwargs):
     """format a figure as a pixel-doubled (retina) PNG"""
     pngdata = print_figure(fig, fmt='retina', **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}
     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
         is_interactive = matplotlib.rcParams['interactive']
         matplotlib.interactive(False)
         safe_execfile(fname,*where,**kw)
         matplotlib.interactive(is_interactive)
         # 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:
         raise NotImplementedError()
     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 == 'nbagg' or mplbackend == '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, lambda fig: print_figure(fig, 'png', **kwargs))
     if 'retina' in formats or 'png2x' in formats:
         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))
     if 'jpg' in formats or 'jpeg' in formats:
         jpg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'jpg', **kwargs))
     if 'svg' in formats:
         svg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'svg', **kwargs))
     if 'pdf' in formats:
         pdf_formatter.for_type(Figure, lambda fig: print_figure(fig, 'pdf', **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 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
         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]
 
     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.core.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)

IPython/external/qt_for_kernel.py

@@ -1,95 +1,129 b''
 """ Import Qt in a manner suitable for an IPython kernel.
 
 This is the import used for the `gui=qt` or `matplotlib=qt` initialization.
 
 Import Priority:
 
 if Qt has been imported anywhere else:
    use that
 
 if matplotlib has been imported and doesn't support v2 (<= 1.0.1):
     use PyQt4 @v1
 
 Next, ask QT_API env variable
 
 if QT_API not set:
     ask matplotlib what it's using. If Qt4Agg or Qt5Agg, then use the
         version matplotlib is configured with
 
     else: (matplotlib said nothing)
         # this is the default path - nobody told us anything
         try in this order:
             PyQt default version, PySide, PyQt5
 else:
     use what QT_API says
 
 """
 # NOTE: This is no longer an external, third-party module, and should be
 # considered part of IPython. For compatibility however, it is being kept in
 # IPython/external.
 
 import os
 import sys
 
 from IPython.utils.version import check_version
-from IPython.external.qt_loaders import (load_qt, loaded_api, QT_API_PYSIDE,
-                                         QT_API_PYSIDE2, QT_API_PYQT, QT_API_PYQT5,
-                                         QT_API_PYQTv1, QT_API_PYQT_DEFAULT)
+from IPython.external.qt_loaders import (
+    load_qt,
+    loaded_api,
+    enum_factory,
+    # QT6
+    QT_API_PYQT6,
+    QT_API_PYSIDE6,
+    # QT5
+    QT_API_PYQT5,
+    QT_API_PYSIDE2,
+    # QT4
+    QT_API_PYQTv1,
+    QT_API_PYQT,
+    QT_API_PYSIDE,
+    # default
+    QT_API_PYQT_DEFAULT,
+)
+
+_qt_apis = (
+    # QT6
+    QT_API_PYQT6,
+    QT_API_PYSIDE6,
+    # QT5
+    QT_API_PYQT5,
+    QT_API_PYSIDE2,
+    # QT4
+    QT_API_PYQTv1,
+    QT_API_PYQT,
+    QT_API_PYSIDE,
+    # default
+    QT_API_PYQT_DEFAULT,
+)
 
-_qt_apis = (QT_API_PYSIDE, QT_API_PYSIDE2, QT_API_PYQT, QT_API_PYQT5, QT_API_PYQTv1,
-            QT_API_PYQT_DEFAULT)
 
-#Constraints placed on an imported matplotlib
 def matplotlib_options(mpl):
+    """Constraints placed on an imported matplotlib."""
     if mpl is None:
         return
     backend = mpl.rcParams.get('backend', None)
     if backend == 'Qt4Agg':
         mpqt = mpl.rcParams.get('backend.qt4', None)
         if mpqt is None:
             return None
         if mpqt.lower() == 'pyside':
             return [QT_API_PYSIDE]
         elif mpqt.lower() == 'pyqt4':
             return [QT_API_PYQT_DEFAULT]
         elif mpqt.lower() == 'pyqt4v2':
             return [QT_API_PYQT]
         raise ImportError("unhandled value for backend.qt4 from matplotlib: %r" %
                           mpqt)
     elif backend == 'Qt5Agg':
         mpqt = mpl.rcParams.get('backend.qt5', None)
         if mpqt is None:
             return None
         if mpqt.lower() == 'pyqt5':
             return [QT_API_PYQT5]
         raise ImportError("unhandled value for backend.qt5 from matplotlib: %r" %
                           mpqt)
 
 def get_options():
-    """Return a list of acceptable QT APIs, in decreasing order of
-    preference
-    """
+    """Return a list of acceptable QT APIs, in decreasing order of preference."""
     #already imported Qt somewhere. Use that
     loaded = loaded_api()
     if loaded is not None:
         return [loaded]
 
     mpl = sys.modules.get('matplotlib', None)
 
     if mpl is not None and not check_version(mpl.__version__, '1.0.2'):
         #1.0.1 only supports PyQt4 v1
         return [QT_API_PYQT_DEFAULT]
 
     qt_api = os.environ.get('QT_API', None)
     if qt_api is None:
         #no ETS variable. Ask mpl, then use default fallback path
-        return matplotlib_options(mpl) or [QT_API_PYQT_DEFAULT, QT_API_PYSIDE,
-                                           QT_API_PYQT5, QT_API_PYSIDE2]
+        return matplotlib_options(mpl) or [
+            QT_API_PYQT_DEFAULT,
+            QT_API_PYQT6,
+            QT_API_PYSIDE6,
+            QT_API_PYQT5,
+            QT_API_PYSIDE2,
+            QT_API_PYQT,
+            QT_API_PYSIDE,
+        ]
     elif qt_api not in _qt_apis:
         raise RuntimeError("Invalid Qt API %r, valid values are: %r" %
                            (qt_api, ', '.join(_qt_apis)))
     else:
         return [qt_api]
 
+
 api_opts = get_options()
 QtCore, QtGui, QtSvg, QT_API = load_qt(api_opts)
+enum_helper = enum_factory(QT_API, QtCore)

IPython/external/qt_loaders.py

@@ -1,334 +1,401 b''
 """
 This module contains factory functions that attempt
 to return Qt submodules from the various python Qt bindings.
 
 It also protects against double-importing Qt with different
 bindings, which is unstable and likely to crash
 
 This is used primarily by qt and qt_for_kernel, and shouldn't
 be accessed directly from the outside
 """
 import sys
 import types
-from functools import partial
-from importlib import import_module
+from functools import partial, lru_cache
+import operator
 
 from IPython.utils.version import check_version
 
-# Available APIs.
-QT_API_PYQT = 'pyqt' # Force version 2
+# ### Available APIs.
+# Qt6
+QT_API_PYQT6 = "pyqt6"
+QT_API_PYSIDE6 = "pyside6"
+
+# Qt5
 QT_API_PYQT5 = 'pyqt5'
-QT_API_PYQTv1 = 'pyqtv1' # Force version 2
-QT_API_PYQT_DEFAULT = 'pyqtdefault' # use system default for version 1 vs. 2
-QT_API_PYSIDE = 'pyside'
 QT_API_PYSIDE2 = 'pyside2'
 
-api_to_module = {QT_API_PYSIDE2: 'PySide2',
-                 QT_API_PYSIDE: 'PySide',
-                 QT_API_PYQT: 'PyQt4',
-                 QT_API_PYQTv1: 'PyQt4',
-                 QT_API_PYQT5: 'PyQt5',
-                 QT_API_PYQT_DEFAULT: 'PyQt4',
-                }
+# Qt4
+QT_API_PYQT = "pyqt"  # Force version 2
+QT_API_PYQTv1 = "pyqtv1"  # Force version 2
+QT_API_PYSIDE = "pyside"
+
+QT_API_PYQT_DEFAULT = "pyqtdefault"  # use system default for version 1 vs. 2
+
+api_to_module = {
+    # Qt6
+    QT_API_PYQT6: "PyQt6",
+    QT_API_PYSIDE6: "PySide6",
+    # Qt5
+    QT_API_PYQT5: "PyQt5",
+    QT_API_PYSIDE2: "PySide2",
+    # Qt4
+    QT_API_PYSIDE: "PySide",
+    QT_API_PYQT: "PyQt4",
+    QT_API_PYQTv1: "PyQt4",
+    # default
+    QT_API_PYQT_DEFAULT: "PyQt6",
+}
 
 
 class ImportDenier(object):
     """Import Hook that will guard against bad Qt imports
     once IPython commits to a specific binding
     """
 
     def __init__(self):
         self.__forbidden = set()
 
     def forbid(self, module_name):
         sys.modules.pop(module_name, None)
         self.__forbidden.add(module_name)
 
     def find_module(self, fullname, path=None):
         if path:
             return
         if fullname in self.__forbidden:
             return self
 
     def load_module(self, fullname):
         raise ImportError("""
     Importing %s disabled by IPython, which has
     already imported an Incompatible QT Binding: %s
     """ % (fullname, loaded_api()))
 
+
 ID = ImportDenier()
 sys.meta_path.insert(0, ID)
 
 
 def commit_api(api):
     """Commit to a particular API, and trigger ImportErrors on subsequent
        dangerous imports"""
+    modules = set(api_to_module.values())
 
-    if api == QT_API_PYSIDE2:
-        ID.forbid('PySide')
-        ID.forbid('PyQt4')
-        ID.forbid('PyQt5')
-    elif api == QT_API_PYSIDE:
-        ID.forbid('PySide2')
-        ID.forbid('PyQt4')
-        ID.forbid('PyQt5')
-    elif api == QT_API_PYQT5:
-        ID.forbid('PySide2')
-        ID.forbid('PySide')
-        ID.forbid('PyQt4')
-    else:   # There are three other possibilities, all representing PyQt4
-        ID.forbid('PyQt5')
-        ID.forbid('PySide2')
-        ID.forbid('PySide')
+    modules.remove(api_to_module[api])
+    for mod in modules:
+        ID.forbid(mod)
 
 
 def loaded_api():
     """Return which API is loaded, if any
 
     If this returns anything besides None,
     importing any other Qt binding is unsafe.
 
     Returns
     -------
-    None, 'pyside2', 'pyside', 'pyqt', 'pyqt5', or 'pyqtv1'
+    None, 'pyside6', 'pyqt6', 'pyside2', 'pyside', 'pyqt', 'pyqt5', 'pyqtv1'
     """
-    if 'PyQt4.QtCore' in sys.modules:
+    if sys.modules.get("PyQt6.QtCore"):
+        return QT_API_PYQT6
+    elif sys.modules.get("PySide6.QtCore"):
+        return QT_API_PYSIDE6
+    elif sys.modules.get("PyQt5.QtCore"):
+        return QT_API_PYQT5
+    elif sys.modules.get("PySide2.QtCore"):
+        return QT_API_PYSIDE2
+    elif sys.modules.get("PyQt4.QtCore"):
         if qtapi_version() == 2:
             return QT_API_PYQT
         else:
             return QT_API_PYQTv1
-    elif 'PySide.QtCore' in sys.modules:
+    elif sys.modules.get("PySide.QtCore"):
         return QT_API_PYSIDE
-    elif 'PySide2.QtCore' in sys.modules:
-        return QT_API_PYSIDE2
-    elif 'PyQt5.QtCore' in sys.modules:
-        return QT_API_PYQT5
+
     return None
 
 
 def has_binding(api):
     """Safely check for PyQt4/5, PySide or PySide2, without importing submodules
 
         Parameters
         ----------
         api : str [ 'pyqtv1' | 'pyqt' | 'pyqt5' | 'pyside' | 'pyside2' | 'pyqtdefault']
              Which module to check for
 
         Returns
         -------
         True if the relevant module appears to be importable
      """
     module_name = api_to_module[api]
     from importlib.util import find_spec
 
     required = ['QtCore', 'QtGui', 'QtSvg']
-    if api in (QT_API_PYQT5, QT_API_PYSIDE2):
+    if api in (QT_API_PYQT5, QT_API_PYSIDE2, QT_API_PYQT6, QT_API_PYSIDE6):
         # QT5 requires QtWidgets too
         required.append('QtWidgets')
 
     for submod in required:
         try:
             spec = find_spec('%s.%s' % (module_name, submod))
         except ImportError:
             # Package (e.g. PyQt5) not found
             return False
         else:
             if spec is None:
                 # Submodule (e.g. PyQt5.QtCore) not found
                 return False
 
     if api == QT_API_PYSIDE:
         # We can also safely check PySide version
         import PySide
         return check_version(PySide.__version__, '1.0.3')
 
     return True
 
 
 def qtapi_version():
     """Return which QString API has been set, if any
 
     Returns
     -------
     The QString API version (1 or 2), or None if not set
     """
     try:
         import sip
     except ImportError:
         # as of PyQt5 5.11, sip is no longer available as a top-level
         # module and needs to be imported from the PyQt5 namespace
         try:
             from PyQt5 import sip
         except ImportError:
             return
     try:
         return sip.getapi('QString')
     except ValueError:
         return
 
 
 def can_import(api):
     """Safely query whether an API is importable, without importing it"""
     if not has_binding(api):
         return False
 
     current = loaded_api()
     if api == QT_API_PYQT_DEFAULT:
-        return current in [QT_API_PYQT, QT_API_PYQTv1, None]
+        return current in [QT_API_PYQT6, None]
     else:
         return current in [api, None]
 
 
 def import_pyqt4(version=2):
     """
     Import PyQt4
 
     Parameters
     ----------
     version : 1, 2, or None
       Which QString/QVariant API to use. Set to None to use the system
       default
 
     ImportErrors rasied within this function are non-recoverable
     """
     # The new-style string API (version=2) automatically
     # converts QStrings to Unicode Python strings. Also, automatically unpacks
     # QVariants to their underlying objects.
     import sip
 
     if version is not None:
         sip.setapi('QString', version)
         sip.setapi('QVariant', version)
 
     from PyQt4 import QtGui, QtCore, QtSvg
 
     if not check_version(QtCore.PYQT_VERSION_STR, '4.7'):
         raise ImportError("IPython requires PyQt4 >= 4.7, found %s" %
                           QtCore.PYQT_VERSION_STR)
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # query for the API version (in case version == None)
     version = sip.getapi('QString')
     api = QT_API_PYQTv1 if version == 1 else QT_API_PYQT
     return QtCore, QtGui, QtSvg, api
 
 
 def import_pyqt5():
     """
     Import PyQt5
 
     ImportErrors rasied within this function are non-recoverable
     """
 
     from PyQt5 import QtCore, QtSvg, QtWidgets, QtGui
-    
+
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType('QtGuiCompat')
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
 
     api = QT_API_PYQT5
     return QtCore, QtGuiCompat, QtSvg, api
 
 
+def import_pyqt6():
+    """
+    Import PyQt6
+
+    ImportErrors rasied within this function are non-recoverable
+    """
+
+    from PyQt6 import QtCore, QtSvg, QtWidgets, QtGui
+
+    # Alias PyQt-specific functions for PySide compatibility.
+    QtCore.Signal = QtCore.pyqtSignal
+    QtCore.Slot = QtCore.pyqtSlot
+
+    # Join QtGui and QtWidgets for Qt4 compatibility.
+    QtGuiCompat = types.ModuleType("QtGuiCompat")
+    QtGuiCompat.__dict__.update(QtGui.__dict__)
+    QtGuiCompat.__dict__.update(QtWidgets.__dict__)
+
+    api = QT_API_PYQT6
+    return QtCore, QtGuiCompat, QtSvg, api
+
+
 def import_pyside():
     """
     Import PySide
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide import QtGui, QtCore, QtSvg
     return QtCore, QtGui, QtSvg, QT_API_PYSIDE
 
 def import_pyside2():
     """
     Import PySide2
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide2 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType('QtGuiCompat')
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
     QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
 
     return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE2
 
 
+def import_pyside6():
+    """
+    Import PySide6
+
+    ImportErrors raised within this function are non-recoverable
+    """
+    from PySide6 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
+
+    # Join QtGui and QtWidgets for Qt4 compatibility.
+    QtGuiCompat = types.ModuleType("QtGuiCompat")
+    QtGuiCompat.__dict__.update(QtGui.__dict__)
+    QtGuiCompat.__dict__.update(QtWidgets.__dict__)
+    QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
+
+    return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE6
+
+
 def load_qt(api_options):
     """
     Attempt to import Qt, given a preference list
     of permissible bindings
 
     It is safe to call this function multiple times.
 
     Parameters
     ----------
     api_options: List of strings
         The order of APIs to try. Valid items are 'pyside', 'pyside2',
         'pyqt', 'pyqt5', 'pyqtv1' and 'pyqtdefault'
 
     Returns
     -------
 
     A tuple of QtCore, QtGui, QtSvg, QT_API
     The first three are the Qt modules. The last is the
     string indicating which module was loaded.
 
     Raises
     ------
     ImportError, if it isn't possible to import any requested
     bindings (either because they aren't installed, or because
     an incompatible library has already been installed)
     """
     loaders = {
-               QT_API_PYSIDE2: import_pyside2,
-               QT_API_PYSIDE: import_pyside,
-               QT_API_PYQT: import_pyqt4,
-               QT_API_PYQT5: import_pyqt5,
-               QT_API_PYQTv1: partial(import_pyqt4, version=1),
-               QT_API_PYQT_DEFAULT: partial(import_pyqt4, version=None)
-              }
+        # Qt6
+        QT_API_PYQT6: import_pyqt6,
+        QT_API_PYSIDE6: import_pyside6,
+        # Qt5
+        QT_API_PYQT5: import_pyqt5,
+        QT_API_PYSIDE2: import_pyside2,
+        # Qt4
+        QT_API_PYSIDE: import_pyside,
+        QT_API_PYQT: import_pyqt4,
+        QT_API_PYQTv1: partial(import_pyqt4, version=1),
+        # default
+        QT_API_PYQT_DEFAULT: import_pyqt6,
+    }
 
     for api in api_options:
 
         if api not in loaders:
             raise RuntimeError(
                 "Invalid Qt API %r, valid values are: %s" %
                 (api, ", ".join(["%r" % k for k in loaders.keys()])))
 
         if not can_import(api):
             continue
 
         #cannot safely recover from an ImportError during this
         result = loaders[api]()
         api = result[-1]  # changed if api = QT_API_PYQT_DEFAULT
         commit_api(api)
         return result
     else:
         raise ImportError("""
     Could not load requested Qt binding. Please ensure that
     PyQt4 >= 4.7, PyQt5, PySide >= 1.0.3 or PySide2 is available,
     and only one is imported per session.
 
     Currently-imported Qt library:                              %r
     PyQt4 available (requires QtCore, QtGui, QtSvg):            %s
     PyQt5 available (requires QtCore, QtGui, QtSvg, QtWidgets): %s
     PySide >= 1.0.3 installed:                                  %s
     PySide2 installed:                                          %s
     Tried to load:                                              %r
     """ % (loaded_api(),
            has_binding(QT_API_PYQT),
            has_binding(QT_API_PYQT5),
            has_binding(QT_API_PYSIDE),
            has_binding(QT_API_PYSIDE2),
            api_options))
+
+
+def enum_factory(QT_API, QtCore):
+    """Construct an enum helper to account for PyQt5 <-> PyQt6 changes."""
+
+    @lru_cache(None)
+    def _enum(name):
+        # foo.bar.Enum.Entry (PyQt6) <=> foo.bar.Entry (non-PyQt6).
+        return operator.attrgetter(
+            name if QT_API == QT_API_PYQT6 else name.rpartition(".")[0]
+        )(sys.modules[QtCore.__package__])
+
+    return _enum

IPython/terminal/pt_inputhooks/__init__.py

@@ -1,50 +1,61 b''
 import importlib
 import os
 
 aliases = {
     'qt4': 'qt',
     'gtk2': 'gtk',
 }
 
 backends = [
-    'qt', 'qt4', 'qt5',
-    'gtk', 'gtk2', 'gtk3',
-    'tk',
-    'wx',
-    'pyglet', 'glut',
-    'osx',
-    'asyncio'
+    "qt",
+    "qt4",
+    "qt5",
+    "qt6",
+    "gtk",
+    "gtk2",
+    "gtk3",
+    "tk",
+    "wx",
+    "pyglet",
+    "glut",
+    "osx",
+    "asyncio",
 ]
 
 registered = {}
 
 def register(name, inputhook):
     """Register the function *inputhook* as an event loop integration."""
     registered[name] = inputhook
 
+
 class UnknownBackend(KeyError):
     def __init__(self, name):
         self.name = name
 
     def __str__(self):
         return ("No event loop integration for {!r}. "
                 "Supported event loops are: {}").format(self.name,
                                     ', '.join(backends + sorted(registered)))
 
+
 def get_inputhook_name_and_func(gui):
     if gui in registered:
         return gui, registered[gui]
 
     if gui not in backends:
         raise UnknownBackend(gui)
 
     if gui in aliases:
         return get_inputhook_name_and_func(aliases[gui])
 
     gui_mod = gui
-    if gui == 'qt5':
-        os.environ['QT_API'] = 'pyqt5'
-        gui_mod = 'qt'
+    if gui == "qt5":
+        os.environ["QT_API"] = "pyqt5"
+        gui_mod = "qt"
+    elif gui == "qt6":
+        os.environ["QT_API"] = "pyqt6"
+        gui_mod = "qt"
 
     mod = importlib.import_module('IPython.terminal.pt_inputhooks.'+gui_mod)
     return gui, mod.inputhook

IPython/terminal/pt_inputhooks/qt.py

@@ -1,68 +1,83 b''
 import sys
 import os
-from IPython.external.qt_for_kernel import QtCore, QtGui
+from IPython.external.qt_for_kernel import QtCore, QtGui, enum_helper
 from IPython import get_ipython
 
 # If we create a QApplication, keep a reference to it so that it doesn't get
 # garbage collected.
 _appref = None
 _already_warned = False
 
 
+def _exec(obj):
+    # exec on PyQt6, exec_ elsewhere.
+    obj.exec() if hasattr(obj, "exec") else obj.exec_()
+
+
 def _reclaim_excepthook():
     shell = get_ipython()
     if shell is not None:
         sys.excepthook = shell.excepthook
 
 
 def inputhook(context):
     global _appref
     app = QtCore.QCoreApplication.instance()
     if not app:
         if sys.platform == 'linux':
             if not os.environ.get('DISPLAY') \
                     and not os.environ.get('WAYLAND_DISPLAY'):
                 import warnings
                 global _already_warned
                 if not _already_warned:
                     _already_warned = True
                     warnings.warn(
                         'The DISPLAY or WAYLAND_DISPLAY environment variable is '
                         'not set or empty and Qt5 requires this environment '
                         'variable. Deactivate Qt5 code.'
                     )
                 return
-        QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
+        try:
+            QtCore.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
+        except AttributeError:  # Only for Qt>=5.6, <6.
+            pass
+        try:
+            QtCore.QApplication.setHighDpiScaleFactorRoundingPolicy(
+                QtCore.Qt.HighDpiScaleFactorRoundingPolicy.PassThrough
+            )
+        except AttributeError:  # Only for Qt>=5.14.
+            pass
         _appref = app = QtGui.QApplication([" "])
 
         # "reclaim" IPython sys.excepthook after event loop starts
         # without this, it defaults back to BaseIPythonApplication.excepthook
         # and exceptions in the Qt event loop are rendered without traceback
         # formatting and look like "bug in IPython".
         QtCore.QTimer.singleShot(0, _reclaim_excepthook)
 
     event_loop = QtCore.QEventLoop(app)
 
     if sys.platform == 'win32':
         # The QSocketNotifier method doesn't appear to work on Windows.
         # Use polling instead.
         timer = QtCore.QTimer()
         timer.timeout.connect(event_loop.quit)
         while not context.input_is_ready():
             timer.start(50)  # 50 ms
             event_loop.exec_()
             timer.stop()
     else:
         # On POSIX platforms, we can use a file descriptor to quit the event
         # loop when there is input ready to read.
-        notifier = QtCore.QSocketNotifier(context.fileno(),
-                                          QtCore.QSocketNotifier.Read)
+        notifier = QtCore.QSocketNotifier(
+            context.fileno(), enum_helper("QtCore.QSocketNotifier.Type").Read
+        )
         try:
             # connect the callback we care about before we turn it on
             notifier.activated.connect(lambda: event_loop.exit())
             notifier.setEnabled(True)
             # only start the event loop we are not already flipped
             if not context.input_is_ready():
-                event_loop.exec_()
+                _exec(event_loop)
         finally:
             notifier.setEnabled(False)