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Implement blocking Qt event loop. #8185
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Avoids raising a deprecation warning (due to use of the default busy waiting loop) when running e.g. ``` plt.gca(); plt.gcf().ginput(4) ``` or ``` plt.gca(); plt.gcf().ginput(4, timeout=2) ``` The implementation is similar to the one for the Wx backend.
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Users report that this has worked out so 👍 from me.
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Why do we need an event loop separate from the one provided in the 'qApp?
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This entire machinery is only used by blocking_input.py (ginput), in order to not block event handling while waiting for the user to select points on the plot. See https://wiki.qt.io/Threads_Events_QObjects#Forcing_event_dispatching for the pattern.
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Do you need to check if it's running, too (i.e., if the timer has already expired and called quit)?
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No, you can re-quit an already exited loop:
In [1]: plt.gca(); plt.gcf().ginput(4, timeout=2)
Out[1]:
[(0.70564516129032262, 0.42803030303030309),
(0.38911290322580649, 0.26298701298701299)]
In [2]: el = plt.gcf().canvas._event_loop; print(el.isRunning()); el.quit()
False
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Seems to work for me.
Avoids raising a deprecation warning (due to use of the default busy
waiting loop) when running e.g.
or
The implementation is similar to the one for the Wx backend.