Long-running tasks and updating dialogs

hakan42 · 06-13-2013, 01:09 PM

I am in the process of writing an OPDS Client plugin for Beam Ebooks. The source is at github.

Following the examples in the development manual, I created a dialog (in gui.py), in which I launch my OPDS client.

Code:

class DownloadDialog(QDialog):

    def __init__(self, gui, icon, do_user_config):
        QDialog.__init__(self, gui)
        self.gui = gui
        self.do_user_config = do_user_config
...
        self.download_button = QPushButton('Download books', self)
        self.download_button.clicked.connect(self.download)
        self.layout.addWidget(self.download_button)
...
    def download(self):
        # My OPDS stuff is called here...
...

What I am observing is that the GUI of calibre hangs until I return from the download task. Is there something I should do, perhaps somehow periodically yield control back to a GUI thread or something? I must admit that I am not really clueful concerning PyQT

kovidgoyal · 06-13-2013, 10:00 PM

1) Show your dialog with show() not exec_() if you want the dialog to be non-modal

2) Run your download code in a separate thread, but be sure never to interact with the GUI from the separate thread as Qt is not thread safe.

3) Generally, in calibre, long running background tasks are managed witht he jobs system and you only popup a dialog when the task completes to show the results.

hakan42 · 06-15-2013, 01:29 AM

Thank you, I will read through one of the existing plugins to learn how to use the jobs framework.

06-13-2013, 01:09 PM	#1
hakan42 Zealot Posts: 136 Karma: 60 Join Date: Jul 2009 Location: Munich, Germany Device: Nook Classic rooted; Galaxy S IV with Aldiko, other older devices	Long-running tasks and updating dialogs I am in the process of writing an OPDS Client plugin for Beam Ebooks. The source is at github. Following the examples in the development manual, I created a dialog (in gui.py), in which I launch my OPDS client. Code: class DownloadDialog(QDialog): def __init__(self, gui, icon, do_user_config): QDialog.__init__(self, gui) self.gui = gui self.do_user_config = do_user_config ... self.download_button = QPushButton('Download books', self) self.download_button.clicked.connect(self.download) self.layout.addWidget(self.download_button) ... def download(self): # My OPDS stuff is called here... ... What I am observing is that the GUI of calibre hangs until I return from the download task. Is there something I should do, perhaps somehow periodically yield control back to a GUI thread or something? I must admit that I am not really clueful concerning PyQT

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06-13-2013, 10:00 PM	#2
kovidgoyal creator of calibre Posts: 43,864 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	1) Show your dialog with show() not exec_() if you want the dialog to be non-modal 2) Run your download code in a separate thread, but be sure never to interact with the GUI from the separate thread as Qt is not thread safe. 3) Generally, in calibre, long running background tasks are managed witht he jobs system and you only popup a dialog when the task completes to show the results.

06-15-2013, 01:29 AM	#3
hakan42 Zealot Posts: 136 Karma: 60 Join Date: Jul 2009 Location: Munich, Germany Device: Nook Classic rooted; Galaxy S IV with Aldiko, other older devices	Thank you, I will read through one of the existing plugins to learn how to use the jobs framework.