NAME

DdInqPickCallback − Return the pick callback object of a device

SYNOPSIS

C:

DtObject DdInqPickCallback(device)
DtObject device;

FORTRAN:

INTEGER∗4 DDQPC(DEVICE)
INTEGER∗4 DEVICE

DESCRIPTION

DdInqPickCallback returns the pick callback object used on the device, device. 

Picking is a method of identifying displayable primitives that fall within a specified volume known as the device pick aperture.  A pick is initiated by a call to DdPickObjs <DDPO>.  The pick callback is a callback object that selects which primitives found within the pick aperture during a pick (known as "hits") will actually be returned.  Doré provides three standard pick callback objects that may be used; however users may also easily provide their own.  The standard callback objects are:

DcPickFirst <DCPKFR>
This callback causes DdPickObjs to accept only the first hit that it finds. 

DcPickClosest <DCPKCL>
This callback causes DdPickObjs to accept only the hit that was frontmost (closest to the viewer) in the pick aperture. 

DcPickAll <DCPKAL>
This callback causes DdPickObjs <DDPO> to add all hits found to the hit list. 

Users may include functions that accept or exclude only hits on certain types of objects or ones that only accept up to a maximum number of hits before terminating a search.  See DdSetPickCallback for information on creating pick callbacks. 

ERRORS

DdInqPickCallback will fail if passed an invalid device handle; the value DcNullObject <DCNULL> is returned. 

[WARNING - invalid device handle]

SEE ALSO

DdSetPickCallback(3D), DdPickObjs(3D), DdSetPickAperture(3D), DdInqPickAperture(3D), DdSetPickPathOrder(3D), DdInqPickPathOrder(3D), DoPickID(3D)

September 02, 1992