Generic function
Returns the default units for the specified display.
display-units display => value
<display>.
one-of(#"device", #"pixels", #"mm").
duim-sheets
duim-sheets
Returns the default units for display. These are the units in which height and width measurements are made, both for the display, and for any children of the display. Unless otherwise specified, the value returned is #"default", so as to maintain a device-independent measurement as far as possible.