[Qt-interest] boost::signals2 with Q_SLOTS - QPixmap not safe outside GUI thread?

[Malyushytsky, Alex]

What is inside connectOnDeviceParameterChanged?

You should use Qt::QueuedConnection ( or sometimes Qt::BlockingQueuedConnection ) ( in connect call) to communicate with gui thread,
but default Qt::AutoConnection flag should do the job , cause

"If the signal is emitted from the thread in which the receiving object lives, the slot is invoked directly, as with Qt::DirectConnection; otherwise the signal is queued, as with Qt::QueuedConnection."

So  you should check if object emitting signal ids in other thread and/or type of connection you specified.

Alex



-----Original Message-----
From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of Ed Sutton
Sent: Wednesday, September 23, 2009 11:19 AM
To: qt-interest at trolltech.com
Subject: [Qt-interest] boost::signals2 with Q_SLOTS - QPixmap not safe outside GUI thread?

I understand the concept of single-threaded GUI and realize this
message is bad.

Here is what I am doing:

1 - My worker thread lib implements a boost::signal2.
2 - In my QT GUI project I have CONFIG += no_keywords and I replaced
the related keywords with the equivalent Q_ macros.
2 - My QMainWindow slot connects to the signal and receives the data
as demonstrated when I output the data to cout.
3 - Attempts to update statusBar()->showMessage() result in:
"QPixmap: It is not safe to use pixmaps outside the GUI thread"

How can I properly connect my worker thread using boost::signals2 to
the QT GUI thread?

Thanks in advance for any tips or direction,

-Ed

// Binding the worker thread signal to the MainWindow GUI handler
m_pMyWorkerThreadLib->connectOnDeviceParameterChanged(boost::bind(&MainWindow::onDeviceParameterChangedHandler,
this, _1));

class MainWindow : public QMainWindow
{

public Q_SLOTS:

// The GUI slot signalled   from the worker
void onDeviceParameterChangedHandler( Device* pDevice)
{
   // Beware: QPixmap: It is not safe to use pixmaps outside the GUI thread
   statusBar()->showMessage(tr("onDeviceParameterChangedHandler"));
}


}
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