def start_event_loop(self, timeout=0):
if hasattr(self, "_event_loop") and self._event_loop.isRunning():
raise RuntimeError("Event loop already running")
self._event_loop = event_loop = QtCore.QEventLoop()
if timeout:
timer = QtCore.QTimer.singleShot(timeout * 1000, event_loop.quit)
event_loop.exec_()
def default_during_task(blocking_event):
"""
The default setting for the RunEngine's during_task parameter.
This makes it possible for plots that use matplotlib's Qt backend to update
live during data acquisition.
It solves the problem that Qt must be run from the main thread.
If matplotlib and a known Qt binding are already imported, run the
matplotlib qApp until the task completes. If not, there is no need to
handle qApp: just wait on the task.
"""
global _qapp
if 'matplotlib' not in sys.modules:
# We are not using matplotlib + Qt. Just wait on the Event.
blocking_event.wait()
# Figure out if we are using matplotlib with which backend
# without importing anything that is not already imported.
else:
import matplotlib
backend = matplotlib.get_backend().lower()
# if with a Qt backend, do the scary thing
if 'qt' in backend:
from matplotlib.backends.qt_compat import QtCore, QtWidgets
app = QtWidgets.QApplication.instance()
if app is None:
_qapp = app = QtWidgets.QApplication([b'bluesky'])
assert app is not None
event_loop = QtCore.QEventLoop()
def start_killer_thread():
def exit_loop():
blocking_event.wait()
# If the above wait ends quickly, we need to avoid the race
# condition where this thread might try to exit the qApp
# before it even starts. Therefore, we use QTimer, below,
# which will not start running until the qApp event loop is
# running.
event_loop.exit()
threading.Thread(target=exit_loop).start()
# https://www.riverbankcomputing.com/pipermail/pyqt/2015-March/035674.html
# adapted from code at
# https://bitbucket.org/tortoisehg/thg/commits/550e1df5fbad
if os.name == 'posix' and hasattr(signal, 'set_wakeup_fd'):
# Wake up Python interpreter via pipe so that SIGINT
# can be handled immediately.
# (http://qt-project.org/doc/qt-4.8/unix-signals.html)
# Updated docs:
# https://doc.qt.io/qt-5/unix-signals.html
import fcntl
rfd, wfd = os.pipe()
for fd in (rfd, wfd):
flags = fcntl.fcntl(fd, fcntl.F_GETFL)
fcntl.fcntl(fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)
wakeupsn = QtCore.QSocketNotifier(rfd,
QtCore.QSocketNotifier.Read)
origwakeupfd = signal.set_wakeup_fd(wfd)
def cleanup():
wakeupsn.setEnabled(False)
rfd = wakeupsn.socket()
wfd = signal.set_wakeup_fd(origwakeupfd)
os.close(int(rfd))
os.close(wfd)
def handleWakeup(inp):
# here Python signal handler will be invoked
# this book-keeping is to drain the pipe
wakeupsn.setEnabled(False)
rfd = wakeupsn.socket()
try:
os.read(int(rfd), 4096)
except OSError as inst:
print('failed to read wakeup fd: %s\n' % inst)
wakeupsn.setEnabled(True)
wakeupsn.activated.connect(handleWakeup)
else:
# On Windows, non-blocking anonymous pipe or socket is
# not available.
def null():
...
# we need to 'kick' the python interpreter so it sees
# system signals
# https://stackoverflow.com/a/4939113/380231
kick_timer = QtCore.QTimer()
kick_timer.timeout.connect(null)
kick_timer.start(50)
cleanup = kick_timer.stop
# we also need to make sure that the qApp never sees
# exceptions raised by python inside of a c++ callback (as
# it will segfault its self because due to the way the
# code is called there is no clear way to propgate that
# back to the python code.
vals = (None, None, None)
old_sys_handler = sys.excepthook
def my_exception_hook(exctype, value, traceback):
nonlocal vals
vals = (exctype, value, traceback)
event_loop.exit()
old_sys_handler(exctype, value, traceback)
# this kill the Qt event loop when the plan is finished
killer_timer = QtCore.QTimer()
killer_timer.setSingleShot(True)
killer_timer.timeout.connect(start_killer_thread)
killer_timer.start(0)
try:
sys.excepthook = my_exception_hook
event_loop.exec_()
# make sure any pending signals are processed
event_loop.processEvents()
if vals[1] is not None:
raise vals[1]
finally:
try:
cleanup()
finally:
sys.excepthook = old_sys_handler
elif 'ipympl' in backend or 'nbagg' in backend:
Gcf = matplotlib._pylab_helpers.Gcf
while True:
done = blocking_event.wait(.1)
for f_mgr in Gcf.get_all_fig_managers():
if f_mgr.canvas.figure.stale:
f_mgr.canvas.draw()
if done:
return
else:
# We are not using matplotlib + Qt. Just wait on the Event.
blocking_event.wait()
