Returns the width of the printable page in the internal units used by the printer driver or printing subsystem.
The printer-metrics-device-width function takes a printer-metrics object as its argument and returns the width of the printable page in the internal units used by the printer driver or printing subsystem of the printer. This function and printer-metrics-device-height should not be used to determine the aspect ratio of the printable page as some printers have size units that differ in the x and y directions.