Neither QPixmap nor QwtPlot: you can't grab something that is not already there.

1) The geometry of the plot is triggered by resize events. I haven't checked it myself, but I expect that a plot, that is on a hidden tab, that has never been shown, never got one.

2) The content of the plot is rendered by QwtPlot::replot. If you don't call it manually and autoReplot is off, the first replot is done in QwtPlot::polish, what is also not called, if the tab has not been shown once.

So I recommend to call QwtPlot::replot manually (after construction) and again, use QwtPlot::print, that doesn't need resizeEvents and is the better solution anyway.

HTH,
Uwe