Parameters
Returns a constant representing what action was taken.
Description
This function attempts to interpret a selection from a popup menu item as one for changing axis parameters. If it finds a valid menu item, it changes the property of the axis accordingly, and returns kPopupUpdate.
The value of which should be 0 for the first element in the axis popup menu. Thus, the calling function needs to determine for which axis popup menu the selection was made, and ensure a zero-based start for the present axis.