QPrinter::PrinterMode and QPrinter::setResolution??

[SkripT]

Hi all, I want to know why there are two ways of setting QPrinter's resolution: using PrinterMode and setResolution. Do they work with the same parameter? Moreover, if I change the resolution with setResolution the volume of the final document (printing in a PDF file) is always the same. Is it a bug of Qt or it's just the correct behaviour?.

I need the resolution because I have to set the page margins from their size in centimeters. Could you suggest me which value of resolution should I use, the one from PrinterMode or the returned calling QPrinter::resolution()??

Thanks.