Unless a quantity is dimensionless or uses a specified unit of measure, ICAP_UNITS determines the unit of measure for all quantities.
Applications should be able to handle TWUN_PIXELS if they want to support data transfers from "dimensionless" devices such as digital cameras.
Integer
TWUN_INCHES(0)
TWUN_INCHES(0), TWUN_CENTIMETERS(1), TWUN_PICAS(2), TWUN_POINTS(3), TWUN_TWIPS(4), TWUN_PIXELS(5)
TW_ENUMERATION, TW_ONEVALUE
ICAP_FRAMES