DdInqPickCallback(3D)

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. Dore 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)