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import sys
import os
from IPython.external.qt_for_kernel import QtCore, QtGui
# If we create a QApplication, keep a reference to it so that it doesn't get
# garbage collected.
_appref = None
_already_warned = False
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 enviroment variable is '
'not set or empty and Qt5 requires this enviroment '
'variable. Deactivate Qt5 code.'
)
return
_appref = app = QtGui.QApplication([" "])
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)
# connect the callback we care about before we turn it on
notifier.activated.connect(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_()
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