with "attach" i mean the function QwtPlotCurve->attach(QwtPlot*) to have a curve attached to the qwtPlot. Other threads then simply update the curve's data and replots the qwtPlot. As it's always the same curve that has to be updated, I want it to be initialized in either the ui_mainwindow (in the setupUI function) or in the inherited class (mainwindow.cpp/h). Because the ui file is created new whenever the GUI changes, it's a bad solution to put it in there. But putting it into the mainwindow file doesn't work.