Qt中 QCustomPlot 库中的一段【文件保存代码】（save files）

void MainWindow::on_actionSave_Document_triggered()
{
  QString fileName = QFileDialog::getSaveFileName(this, "Save document...", qApp->applicationDirPath(), "*.pdf");
  if (!fileName.isEmpty())
  {
    QPrinter printer;
    printer.setOutputFormat(QPrinter::PdfFormat);
    printer.setOutputFileName(fileName);
    QMargins pageMargins(20, 20, 20, 20);
#if QT_VERSION < QT_VERSION_CHECK(5, 3, 0)
    printer.setFullPage(false);
    printer.setPaperSize(QPrinter::A4);
    printer.setOrientation(QPrinter::Portrait);
    printer.setPageMargins(pageMargins.left(), pageMargins.top(), pageMargins.right(), pageMargins.bottom(), QPrinter::Millimeter);
#else
    QPageLayout pageLayout;
    pageLayout.setMode(QPageLayout::StandardMode);
    pageLayout.setOrientation(QPageLayout::Portrait);
    pageLayout.setPageSize(QPageSize(QPageSize::A4));
    pageLayout.setUnits(QPageLayout::Millimeter);
    pageLayout.setMargins(QMarginsF(pageMargins));
    printer.setPageLayout(pageLayout);
#endif

#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    ui->textEdit->document()->setPageSize(printer.pageRect().size());
#else
    ui->textEdit->document()->setPageSize(printer.pageLayout().paintRectPixels(printer.resolution()).size());
#endif
    ui->textEdit->document()->print(&printer);
  }
}