printer-metrics object is returned by get-printer-metrics. The readers for the slots of a
printer-metrics object are described below.
printer-metrics-device-width respectively return the height and width of the printable page in the internal units used by the printer driver or printing subsystem of the printer. These functions 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.
printer-metrics-dpi-y return the number of printer device units per inch in the x and y directions respectively. This typically corresponds to the printer resolution, although in some cases this may not be known. For example, a generic PostScript language compatible driver might always return 300dpi, even though it cannot know the resolution of the printer the PostScript file will actually be printed on.
CAPI User Guide and Reference Manual (Unix version) - 3 Aug 2017