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#------------------------------------------------------------------------------
# Copyright (c) 2010, Enthought Inc
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD license.
#
# Author: Enthought Inc
# Description: Qt API selector. Can be used to switch between pyQt and PySide
#------------------------------------------------------------------------------
import importlib
import os
import sys
QtAPIs = [
('pyside', 'PySide'),
('pyside2', 'PySide2'),
('pyqt5', 'PyQt5'),
('pyqt', 'PyQt4'),
]
def prepare_pyqt4():
""" Set PySide compatible APIs. """
# This is not needed for Python 3 and can be removed when we no longer
# support Python 2.
import sip
try:
sip.setapi('QDate', 2)
sip.setapi('QDateTime', 2)
sip.setapi('QString', 2)
sip.setapi('QTextStream', 2)
sip.setapi('QTime', 2)
sip.setapi('QUrl', 2)
sip.setapi('QVariant', 2)
except ValueError as exc:
if sys.version_info[0] <= 2:
# most likely caused by something else setting the API version
# before us: try to give a better error message to direct the user
# how to fix.
msg = exc.args[0]
msg += (". Pyface expects PyQt API 2 under Python 2. "
"Either import Pyface before any other Qt-using packages, "
"or explicitly set the API before importing any other "
"Qt-using packages.")
raise ValueError(msg)
else:
# don't expect the above on Python 3, so just re-raise
raise
qt_api = None
# have we already imported a Qt API?
for api_name, module in QtAPIs:
if module in sys.modules:
qt_api = api_name
if qt_api == 'pyqt':
# set the PyQt4 APIs
# this is a likely place for failure - pyface really wants to be
# imported first, before eg. matplotlib
prepare_pyqt4()
break
else:
# does our environment give us a preferred API?
qt_api = os.environ.get('QT_API')
if qt_api == 'pyqt':
# set the PyQt4 APIs
prepare_pyqt4()
# if we have no preference, is a Qt API available? Or fail with ImportError.
if qt_api is None:
for api_name, module in QtAPIs:
try:
if api_name == 'pyqt':
# set the PyQt4 APIs
prepare_pyqt4()
importlib.import_module(module)
importlib.import_module('.QtCore', module)
qt_api = api_name
break
except ImportError:
continue
else:
raise ImportError('Cannot import PySide, PySide2, PyQt5 or PyQt4')
# otherwise check QT_API value is valid
elif qt_api not in {api_name for api_name, module in QtAPIs}:
msg = ("Invalid Qt API %r, valid values are: " +
"'pyside, 'pyside2', 'pyqt' or 'pyqt5'") % qt_api
raise RuntimeError(msg)
# useful constants
is_qt4 = (qt_api in {'pyqt', 'pyside'})
is_qt5 = (qt_api in {'pyqt5', 'pyside2'})
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