Thanks Nathan. I guess I will have to find some way to run the Python code in the main thread of the application, or use processEvents in the mean time.
best regards Sébastien Sablé Le 8 février 2012 16:10, Nathan Smith <nathanjsm...@gmail.com> a écrit : > This is an expected limitation due to how Qt works. Even your C++ Qt > application is required to have the GUI run in a single thread. You can do > work in other threads and emit signals across thread boundaries, but the > event loop executes single-threaded. > > > Although QObject is reentrant, the GUI classes, notably QWidget and all > its subclasses, are not reentrant. They can only be used from the main > thread. As noted earlier, QCoreApplication::exec() must also be called from > that thread. > http://developer.qt.nokia.com/doc/qt-4.8/threads-qobject.html > > Nathan > > 2012/2/8 Sébastien Sablé Sablé <sa...@users.sourceforge.net> > >> Hi Alberto, >> >> thank you for your answer! >> >> The event loop is actually running in a separate thread. >> I managed to get the example running by adding a call to processEvents: >> >> from PySide import QtGui >> >> from PySide import QtCore >> >> wid = QtGui.QLabel("Whatever") >> >> wid.resize(450, 150) >> >> wid.setWindowTitle('Simple') >> >> wid.show() >> >> while True: >> >> QtCore.QCoreApplication.processEvents() >> >> >> I think I will use this workaround for the moment. >> It is not clear to me however if this is an expected limitation due to >> how Qt works with threads or if this is a bug in PySide. >> >> I would appreciate if someone could come with a cleaner solution or tell >> me if I should fill a bug request. >> >> best regards >> >> -- >> Sébastien Sablé >> >> >> Le 8 février 2012 15:12, Alberto Soto <alberto.s...@lmsintl.com> a écrit >> : >> >> Hi Sébastien, >>> >>> This sounds to me like an event loop problem. >>> >>> The MessageBox::question static method creates its own event loop >>> and then returns. So that's probably the reason it works. >>> >>> Are you creating the QLabel widget in the same thread as the GUI >>> application thread? I seem to remember a limitation, when working >>> on multithread Qt applications with a GUI. >>> From the "Rapid GUI Programming with Python and Qt" book: >>> PyQt applications always have at least one thread of execution, the >>> primary >>> (initial) thread. In addition, they may create as many secondary threads >>> as >>> they need. However, if the application has a GUI, the GUI operations, >>> such >>> as executing the event loop, may only take place in the primary thread. >>> -- chapter 19. Multithreading. >>> >>> Hope this helps! >>> >>> >>> Alberto SOTO >>> >>> >>> _______________________________________________________________________________________________________ >>> From: pyside-boun...@lists.pyside.org [mailto: >>> pyside-boun...@lists.pyside.org] On Behalf Of Sébastien Sablé Sablé >>> Sent: mercredi 8 février 2012 11:35 >>> To: pyside@lists.pyside.org >>> Subject: [PySide] PySide in a C++ application using Qt >>> >>> Hi, >>> >>> I am using PySide 1.1.0. And I would like to use it inside a C++ >>> application that already uses Qt and provides an embedded Python >>> interpreter. >>> >>> I tried something like that: >>> >>> from PySide import QtGui >>> app = QtGui.QApplication.instance() >>> print app >>> wid = QtGui.QLabel("Whatever") >>> wid.resize(450, 150) >>> wid.setWindowTitle('Simple') >>> wid.show() >>> >>> >>> Since there is already a running QApplication, I do not create a new >>> one. There is also a running event loop in another thread since the >>> application interface reacts. >>> >>> This code snippet works partially: >>> a new window is created, with a "simple" title, but the text inside it >>> is never displayed and the windows does not react at all: >>> I can't move it, resize it or anything. >>> >>> If I call "wid.repaint()", the text inside the window is correctly >>> refreshed; however the window still does not react to any event. >>> >>> I also tried to create a message box like that: >>> QtGui.QMessageBox.question(wid, 'Message', "Existing app: %r" % app, >>> QtGui.QMessageBox.Yes | QtGui.QMessageBox.No, QtGui.QMessageBox.No) >>> >>> This time the message box reacts correctly: it is correctly displayed, >>> it shows the existing QApplication object and the buttons react. >>> >>> A screenshot of the result can be seen here: >>> http://dl.free.fr/dey2Tzig3 >>> >>> It seems as if the QLabel I created does not receive any event. >>> Do you have any idea of how I can fix that? Should I open a bug >>> concerning this behavior? >>> >>> Thanks in advance >>> >>> Sébastien Sablé >>> >>> >>> >> >> _______________________________________________ >> PySide mailing list >> PySide@lists.pyside.org >> http://lists.pyside.org/listinfo/pyside >> >> >
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