QPrinterInfo - is it possible to recognize a plotter?

my application is printing to plotters & "regular" printers, and i must know if the selected printer is a plotter or not. i tried to use QPrinterInfo::supportedPaperSizes on the only plotter i have (HP designjet 800ps 42 tried it on windows7), i'm getting no indication for the option to support a large paper. (i'm getting: Letter, Legal & custom). is this the expected behaviour for plotter? is there any way to know the printer is a plotter? is there a way to know if paper source is a roll?

Roll paper is custom sized.

What paper sources are returned in the QPrinter object?