[PySide] sending data from urllib2.urlopen().read() via signal corrupts in receiver

[Frank Rueter | OHUfx]

I am just sending a signal from a worker thread to the main thread. But 
since QPixmap can't be passed betwen threads I thought QImage can't either.

Great link, thank you! For my next task I need to turn a loop that 
spawns various QProcesses into a queu to control the max number of 
concurrent processes. I am hoping to just use QRunnable to launch a 
QProcess and control the max number of threads via the global 
QThreadPool(). But will check that link if this approach is the right now.

Cheers,
frank

On 10/23/2017 01:50 PM, Renaud Talon wrote:
>
> If you’re talking about a QRunnable receiving data from another 
> QRunnable you are correct. QRunnable can’t receive data through 
> signals. I learned that the hard way recently.
>
> You have to use QThread or Qt Concurent if you want to do that, see 
> table called “Comparison of Solutions” here :
>
> http://doc.qt.io/qt-5/threads-technologies.html
>
> *From: *Frank Rueter | OHUfx <mailto:frank at ohufx.com>
> *Sent: *Sunday, October 22, 2017 5:40 PM
> *To: *pyside at qt-project.org <mailto:pyside at qt-project.org>
> *Subject: *Re: [PySide] sending data from urllib2.urlopen().read() via 
> signal corrupts in receiver
>
> Interesting. I assumed you can't do that between different threads to 
> I never tried it.
>
> On 10/23/2017 05:36 AM, Erik Johansson wrote:
>
>     Had the same problem.
>
>     Solved it by creating a QImage and emitting that.
>
>     Cheers,
>
>     Erik
>
>     On Sun, Oct 22, 2017 at 11:19 AM, Frank Rueter | OHUfx
>     <frank at ohufx.com <mailto:frank at ohufx.com>> wrote:
>
>         quick follow up:
>         I am now writing the files to a temp directory and only
>         passing the respective path via the signal, but I'm still
>         curious how I would do this without writing anything to disk.
>
>         Cheers,
>         frank
>
>         On 10/22/2017 09:18 PM, Frank Rueter | OHUfx wrote:
>
>             Hi,
>
>             I am downloading a few images in a separate thread using
>             QRunnable.
>             To download I am just using urllib2.urlopen() like this:
>
>             [...]
>                 def run(self):
>                     imageData = urllib2.urlopen(self.url).read()
>                     print 'emitted:', imageData
>             self.signals.receivedData.emit(imageData) # this signal is
>             declared like this: QtCore.Signal(str)
>
>
>             However, the receiving slot is receiving nothing:
>
>                 def setPixmap(self, imageData):
>                     print 'received:', imageData
>                     pixmap = QtGui.QPixmap()
>                     pixmap.loadFromData(imageData)
>                     self.data['pixmap'] = pixmap
>
>
>             I guess this is too naive an approach to download image
>             data in a separate thread?!
>
>             How can I fix this please?
>
>             Cheers,
>             frank
>
>             -- 
>
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>     *
>     **ERIK JOHANSSON*
>     Pipeline TD
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