Printing with QCustomPlot

[BrianE]

OK, so I thought I'd managed to grasp what to do but sadly it seems not. The following code gives me a preview dialogue (thankfully) but the area where I expect to see the plot is blank (plot is just ui->customplot). Please just point me in the right direction! I need a clue.

void MainWindow::on_actionPreview_triggered()
{
    // display print preview dialog
    QPrinter             myprinter( QPrinter::HighResolution );
    QPrintPreviewDialog  mypreview( &myprinter, this );
    connect( &mypreview, SIGNAL(paintRequested(QPrinter*)), SLOT(printfunction(QPrinter*)) );
    mypreview.exec();
}

void MainWindow::printfunction(QPrinter *aprinter)
{
    // this is the actual put it on the page bit
    // create a PAINTER do the job
    QCPPainter mypainter(aprinter);

    // use the painter to create the page
    int      w = aprinter->pageRect().width();
    int      h = aprinter->pageRect().height();
//    mypainter.begin(aprinter);
    plot->toPainter(&mypainter, w, h);
    mypainter.end();
}