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import sys
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import os
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from IPython.external.qt_for_kernel import QtCore, QtGui
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# If we create a QApplication, keep a reference to it so that it doesn't get
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# garbage collected.
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_appref = None
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_already_warned = False
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def inputhook(context):
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global _appref
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app = QtCore.QCoreApplication.instance()
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if not app:
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if sys.platform == 'linux':
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if not os.environ.get('DISPLAY') \
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and not os.environ.get('WAYLAND_DISPLAY'):
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import warnings
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global _already_warned
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if not _already_warned:
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_already_warned = True
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warnings.warn(
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'The DISPLAY or WAYLAND_DISPLAY environment variable is '
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'not set or empty and Qt5 requires this environment '
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'variable. Deactivate Qt5 code.'
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)
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return
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_appref = app = QtGui.QApplication([" "])
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event_loop = QtCore.QEventLoop(app)
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if sys.platform == 'win32':
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# The QSocketNotifier method doesn't appear to work on Windows.
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# Use polling instead.
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timer = QtCore.QTimer()
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timer.timeout.connect(event_loop.quit)
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while not context.input_is_ready():
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timer.start(50) # 50 ms
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event_loop.exec_()
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timer.stop()
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else:
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# On POSIX platforms, we can use a file descriptor to quit the event
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# loop when there is input ready to read.
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notifier = QtCore.QSocketNotifier(context.fileno(),
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QtCore.QSocketNotifier.Read)
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# connect the callback we care about before we turn it on
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notifier.activated.connect(event_loop.exit)
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notifier.setEnabled(True)
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# only start the event loop we are not already flipped
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if not context.input_is_ready():
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event_loop.exec_()
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