Usage:
focus [ atom-spec ]

Focus adjusts the view and center of rotation based on atoms, bonds, and/or ribbon segments that are displayed (possibly including items that are invisible). If atoms are specified, only those both specified and displayed are considered in making the adjustments. Focusing consists of:

1. adjusting the view to include the item(s) (similar to window)
2. setting the center of rotation to the center of view (like cofr view)

See also: center, cofr, window