Now I debug the realtime_plot examples and find a problems:
This example show that how to draw points whit growing data; but i want to play a curve . so delete the sentence
d_curve->setStyle(QwtPlotCurve::NoCurve);
and add a sentence:
d_curve->setPen(QPen(Qt::red));

but when i run , it just show the points but not curve; and when i left-clicked the mouse, the curve is showed. if i don't nothing, the curve can't show, just show points. Anybody know why? How i edit the code to let it show curve?