gtk:selection-owner-set-for-display (display widget selection time)

display -- a gdk:display object where the selection is set
widget -- a new selection owner, a gtk:widget object, or nil
selection -- a gdk:atom-as-string as a string representing the selection to claim
time -- an unsigned integer with the timestamp with which to claim the selection

True if the operation succeeded.

Claim ownership of a given selection for a particular widget, or, if the widget argument is nil, release ownership of the selection.