QPrintDialog can not set custom paper size

[hooanghiep]

i am using QPrintDialog for specifying the printer's configuration.
This is how i tried:

QTextDocument *document = new QTextDocument();

QPrinter printer;

printer.setPageSize(QPrinter::A4);//default
printer.setOutputFormat(QPrinter::PdfFormat);

document->setPageSize(printer.pageRect().size()); 
document->setHtml(report::mReportContent);
QPrintDialog *dlg = new QPrintDialog(&printer,0);

dlg->setOption( QAbstractPrintDialog::PrintToFile,        false );
dlg->setOption( QAbstractPrintDialog::PrintSelection,     true );
dlg->setOption( QAbstractPrintDialog::PrintPageRange,     false );
dlg->setOption( QAbstractPrintDialog::PrintShowPageSize,  true );
dlg->setOption( QAbstractPrintDialog::PrintCollateCopies, false );
dlg->setOption( QAbstractPrintDialog::PrintCurrentPage, false );
if(dlg->exec() == QDialog::Accepted)
{
    //pre set paper size to A5
    document->print(&printer);
}
delete dlg;
delete document;

======================================
By default i set paper size to A4, everything is ok
But when dialog open and i set any different paper size(like A5) then it is back to A4.
My question is that how can i set custom paper size to the printer?

p/s My OS is ubuntu 16.04

Thanks,
Hiep

[JonB]

@hooanghiep
It may not help you, but under Ubuntu/Mint/etc. I believe yours is same as reported recently in https://forum.qt.io/topic/100529/qprintdialog ?

[hooanghiep]

@JonB thanks for your inform :)

[Pl45m4]

@hooanghiep

Do you really need a custom size or is your paper just not standard A4 / A5 / A3?
Here are all default paper size options.

Is

printer.pageRect().size()

a valid format?

What happens, if you comment this "printer.setPageSize(QPrinter::A4);//default" line? I think your selection gets overwritten by your default value (A4).
Have you tried to debug output the actual paper size while the dialog is running?

From https://doc.qt.io/qt-5/qpagedpaintdevice.html#setPageSize:

To get the current QPageSize use pageLayout().pageSize().

You should call this before calling QPainter::begin(), or immediately before calling newPage() to apply the new page size to a new page. You should not call any painting methods between a call to setPageSize() and newPage() as the wrong paint metrics may be used.

Returns true if the page size was successfully set to pageSize.

EDIT: Maybe you have to set the PageSize to EnumVal "30" (= ::Custom) first, to make the printer accept your own values?