use signal&slot between two tabs

[stella1016]

I hope I did something wrong. Maybe you can help me solve my old problem. I post my code here. My app is to display the camera output images in QGLWidget.

MyThread: in its run method, it does the while-loop

run()
{
   while(flag)
   {
	IplImage *lp_color = t_camera.get_image();
	myQLWidget->setCurrentImageIpl(lp_color);
 	cvReleaseImage(&lp_color);
    }
}

run()
{
   while(flag)
   {
	IplImage *lp_color = t_camera.get_image();
	myQLWidget->setCurrentImageIpl(lp_color);
 	cvReleaseImage(&lp_color);
    }
}

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MyQLWidget: in charge of updating the texture when it receives any image.
I am using SIGNAL & SLOT in MyQLWidget, because in method setCurrentImageIpl(), I cannot directly call updateGL(). This is because OpenGl & Thread issue... So in setCurrentImageIpl() I emit a SIGNAL to a SLOT, the SLOT will do updateGL() for me.

MyQLWidget::setCurrentImageIpl()
{
 
    ...(set image)
    imageData = ...;
    update = true;
    emit newData();
 
}

MyQLWidget::setCurrentImageIpl()
{
     
    ...(set image)
    imageData = ...;
    update = true;
    emit newData();

}

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newData is connect to SLOT updateImage()

MyQLWidget::updateImage()
{
  this->updateGL();
}
 
MyQLWidget::paintGL()
{
  if(update)
       glTexSubImage2D = (.....imageData);
}

MyQLWidget::updateImage()
{
  this->updateGL();
}

MyQLWidget::paintGL()
{
  if(update)
       glTexSubImage2D = (.....imageData);
}

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During displaying the first few frames that grasped by camera, my program crashes. Not every time. I don't know where is the problem. When it crashes, the reason is that the imageData is not set jet, so when update texture it crashes.

I set breakpoint, and found that in the first few steps, ...emit... executes twice, but updateImage() only once. Maybe this causes the crash, I am not sure.

Hard to explain what I did in my code here.