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Subject: Re: [PyQt] Multithreaded Update of the QStandardItemModel Data
From: Christian Schulze <c.schulze () tlk-thermo ! com>
Date: 2018-03-12 22:35:44
Message-ID: FRXPR01MB0072796866C25A51FEBACA61D1D30 () FRXPR01MB0072 ! DEUPRD01 ! PROD ! OUTLOOK ! DE
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Great! The issues are fixed! Thanks!
The updated example is attached. I'll try implement it in my code.
Christian
Von: Barry [mailto:barry@barrys-emacs.org]
Gesendet: Montag, 12. März 2018 23:03
An: Christian Schulze <c.schulze@tlk-thermo.com>
Cc: Florian Bruhin <me@the-compiler.org>; pyqt@riverbankcomputing.com
Betreff: Re: [PyQt] Multithreaded Update of the QStandardItemModel Data
The trick you need is that you can send a signal from a non-main thread to the gui main-thread.
In response to the signal you update the model. Put all the information that you need as the \
signal arg or args.
I use this idea in scm-workbench to sync the ui to background changes.
Barry
On 12 Mar 2018, at 21:52, Christian Schulze \
<c.schulze@tlk-thermo.com<mailto:c.schulze@tlk-thermo.com>> wrote: Hi Florian,
I need to update many items continuously. Several rows are updated at least once per second. \
For some use cases I have 20000 rows in total. I prepared all the data (new/modified/removed \
items), so that hardly any calculation is done in the main thread.
However, the main thead seems to be blocked for too long. The GUI seems to freeze for a short \
moment when I update the data. This is really annoying when you're working with the application \
and I'd like to fix that.
I had expected that I'm allowed to modify the item model, since the GUI thread only reads data. \
I don't care if an intermediate state is displayed.
So I need to implement my own threadsafe item model? Is any python based item model \
implementation threadsafe due to the GIL? Is the interaction of python and C++ fast enough to \
do this?
Thanks,
Christian
Von: Florian Bruhin [mailto:me@the-compiler.org]
Gesendet: Montag, 12. März 2018 22:13
An: Christian Schulze <c.schulze@tlk-thermo.com<mailto:c.schulze@tlk-thermo.com>>
Cc: pyqt@riverbankcomputing.com<mailto:pyqt@riverbankcomputing.com>
Betreff: Re: [PyQt] Multithreaded Update of the QStandardItemModel Data
Hi,
On Mon, Mar 12, 2018 at 08:59:11PM +0000, Christian Schulze wrote:
> I'm trying to update the QStandardItemModel data from another thread. This causes several \
> issues:
> [...]
QStandardItemModel is part of QtGui, and stuff in QtGui is not
threadsafe and must be used from the main (GUI) thread only.
> It would be great if someone could tell me how to fix this!
Your only option is pretty much "don't do this". Why do you need to
modify a QStandardItemModel from a non-main thread?
Florian
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<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Great! \
The issues are fixed! Thanks!<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">The \
updated example is attached. I'll try implement it in my code.<o:p></o:p></span></p> <p \
class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Christian<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif">Von:</span></b><span \
lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Barry \
[mailto:barry@barrys-emacs.org] <br>
<b>Gesendet:</b> Montag, 12. März 2018 23:03<br>
<b>An:</b> Christian Schulze <c.schulze@tlk-therm</span><span \
style="font-size:11.0pt;font-family:"Calibri",sans-serif">o.com><br> <b>Cc:</b> \
Florian Bruhin <me@the-compiler.org>; pyqt@riverbankcomputing.com<br> <b>Betreff:</b> Re: \
[PyQt] Multithreaded Update of the QStandardItemModel Data<o:p></o:p></span></p> </div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">The trick you need is that you can send a signal from a non-main thread to \
the gui main-thread.<o:p></o:p></p> </div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">In response to the signal you update the model. Put all the information \
that you need as the signal arg or args.<o:p></o:p></p> </div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">I use this idea in scm-workbench to sync the ui to background \
changes.<o:p></o:p></p> </div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Barry<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
On 12 Mar 2018, at 21:52, Christian Schulze <<a \
href="mailto:c.schulze@tlk-thermo.com">c.schulze@tlk-thermo.com</a>> wrote:<o:p></o:p></p> \
</div> <blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Hi \
Florian,</span><o:p></o:p></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">I \
need to update many items continuously. Several rows are updated at least once per second. For \
some use cases I have 20000 rows in total. I prepared all the data (new/modified/removed \
items), so that hardly any calculation is done in the main thread.</span><o:p></o:p></p> <p \
class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">However, \
the main thead seems to be blocked for too long. The GUI seems to freeze for a short moment \
when I update the data. This is really annoying when you're working with the application and \
I'd like to fix that.</span><o:p></o:p></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">I \
had expected that I'm allowed to modify the item model, since the GUI thread only reads data. I \
don't care if an intermediate state is displayed.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">So \
I need to implement my own threadsafe item model? Is any python based item model implementation \
threadsafe due to the GIL? Is the interaction of python and C++ fast enough to do \
this?</span><o:p></o:p></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Thanks,</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Christian</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif">Von:</span></b><span \
lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Florian \
Bruhin [<a href="mailto:me@the-compiler.org">mailto:me@the-compiler.org</a>] <br>
<b>Gesendet:</b> Montag, 12. März 2018 22:13<br>
<b>An:</b> Christian Schulze <<a \
href="mailto:c.schulze@tlk-thermo.com">c.schulze@tlk-thermo.com</a>><br> <b>Cc:</b> <a \
href="mailto:pyqt@riverbankcomputing.com">pyqt@riverbankcomputing.com</a><br> <b>Betreff:</b> \
Re: [PyQt] Multithreaded Update of the QStandardItemModel Data</span><o:p></o:p></p> </div>
</div>
<p class="MsoNormal"><span lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">Hi,</span><span \
lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">On Mon, Mar 12, 2018 \
at 08:59:11PM +0000, Christian Schulze wrote:</span><span lang="EN-US"> <br>
</span><span lang="EN-US" style="font-family:"Calibri",sans-serif">> I'm trying to \
update the QStandardItemModel data from another thread. This causes several issues:</span><span \
lang="EN-US"> <br>
</span><span lang="EN-US" style="font-family:"Calibri",sans-serif">></span><span \
lang="EN-US"> <br>
</span><span lang="EN-US" style="font-family:"Calibri",sans-serif">> \
[...]</span><span lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">QStandardItemModel is \
part of QtGui, and stuff in QtGui is not</span><span lang="EN-US"> <br>
</span><span lang="EN-US" style="font-family:"Calibri",sans-serif">threadsafe and \
must be used from the main (GUI) thread only.</span><span lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">> It would be great \
if someone could tell me how to fix this!</span><span lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">Your only option is \
pretty much "don't do this". Why do you need to</span><span lang="EN-US"> <br>
</span><span lang="EN-US" style="font-family:"Calibri",sans-serif">modify a \
QStandardItemModel from a non-main thread?</span><span lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">Florian</span><span \
lang="EN-US"> </span><o:p></o:p></p>
<p><span lang="EN-US" style="font-family:"Calibri",sans-serif">-- </span><span \
lang="EN-US"><br> </span><span style="font-family:"Calibri",sans-serif"><a \
href="https://www.qutebrowser.org"><span \
lang="EN-US">https://www.qutebrowser.org</span></a></span><span lang="EN-US" \
style="font-family:"Calibri",sans-serif"> | </span><span \
style="font-family:"Calibri",sans-serif"><a href="mailto:me@the-compiler.org"><span \
lang="EN-US">me@the-compiler.org</span></a></span><span lang="EN-US" \
style="font-family:"Calibri",sans-serif"> (Mail/XMPP)</span><span lang="EN-US"> <br>
</span><span lang="EN-US" style="font-family:"Calibri",sans-serif"> GPG: \
916E B0C8 FD55 A072 | </span><span style="font-family:"Calibri",sans-serif"><a \
href="https://the-compiler.org/pubkey.asc"><span \
lang="EN-US">https://the-compiler.org/pubkey.asc</span></a></span><span lang="EN-US"> <br>
</span><span lang="EN-US" \
style="font-family:"Calibri",sans-serif"> \
I love long mails! </span><span style="font-family:"Calibri",sans-serif">| <a \
href="https://email.is-not-s.ms/"> https://email.is-not-s.ms/</a></span> <o:p></o:p></p>
</div>
</blockquote>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal">_______________________________________________<br>
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