Available in LEADTOOLS Document and Medical Imaging toolkits.
Selecting all objects in a rectangle:
L_AnnGetSelectCount
L_AnnGetSelectItems
L_AnnSelectRect
Selecting an object at a particular point:
L_AnnSelectPoint
Getting the bounding rectangle of selected objects:
L_AnnGetSelectRect
Identifying an object at a particular point:
L_AnnHitTest
L_AnnSendToBack