The ANNSMARTDISTANCE contains information about the unit to be used for a ruler.
A "smart unit" is a unit that can be automatically promoted to the next higher unit. For example, suppose you have a ruler that is 13 inches long. If the units of the ruler are ANNUNIT_INCHES, then the length is 13. However, if the units of the ruler are ANNUNIT_SMART_ENGLISH, then the length of the ruler is automatically promoted to feet. The length in this case would be 1.0833 feet.
For more information, see the documentation for L_AnnGetDistance2.
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