Use the example
Qt4: qt/demos/textedit/
Qt5: qt5/qtbase/examples/widgets/richtext/textedit

Alter the function,

void TextEdit::filePrintPreview()
{
#ifndef QT_NO_PRINTER
    QPrinter printer(QPrinter::HighResolution);
// Try 1
    printer.setPageMargins(0,0,0,0,QPrinter::Inch);
// Try 2
    printer.setFullPage(true);
....
}

Issue 1:
Run the example, Click on File > Print Preview
See that the behaviour is same for both Try 1 and 2 in Qt5
wheras different in Qt4.

Expected as in Qt4.

Issue 2:
Also Run the example, print native and check the outputs.
Expected as in Qt4