XtGetSelectionValueIncremental, XtGetSelectionValuesIncremental - obtain
  selection values
#include <X11/Intrinsic.h>
void XtGetSelectionValueIncremental(Widget w, Atom
    selection, Atom target, XtSelectionCallbackProc
    callback, XtPointer client_data, Time time);
void XtGetSelectionValuesIncremental(Widget w, Atom
    selection, Atom *targets, int count,
    XtSelectionCallbackProc callback, XtPointer *client_data, Time
    time);
  - callback
- Specifies the callback procedure that is to be called when the selection
      value has been obtained.
- client_data
- Specifies the argument that is to be passed to the specified procedure
      when it is called.
- client_data
- Specifies the client data (one for each target type) that is passed to the
      callback procedure when it is called for that target.
- count
- Specifies the length of the targets and client_data lists.
- selection
- Specifies the particular selection desired (that is, primary or
      secondary).
- target
- Specifies the type of the information that is needed about the
    selection.
- targets
- Specifies the types of information that is needed about the
    selection.
- time
- Specifies the timestamp that indicates when the selection value is
      desired.
- w
- Specifies the widget that is making the request.
The XtGetSelectionValueIncremental function is similar to
  XtGetSelectionValue except that the selection_callback procedure
  will be called repeatedly upon delivery of multiple segments of the selection
  value. The end of the selection value is indicated when
  selection_callback is called with a non-NULL value of length zero,
  which must still be freed by the client. If the transfer of the selection is
  aborted in the middle of a transfer (for example, because to timeout), the
  selection_callback procedure is called with a type value equal to the
  symbolic constant XT_CONVERT_FAIL so that the requestor can dispose of
  the partial selection value it has collected up until that point. Upon
  receiving XT_CONVERT_FAIL, the requesting client must determine for
  itself whether or not a partially completed transfer is meaningful.The XtGetSelectionValuesIncremental function is similar to
    XtGetSelectionValueIncremental except that it takes a list of target
    types and a list of client data and obtains the current value of the
    selection converted to each of the targets. The effect is as if each target
    were specified in a separate call to XtGetSelectionValueIncremental.
    The callback is called once with the corresponding client data for each
    target. XtGetSelectionValuesIncremental does guarantee that all the
    conversions will use the same selection value because the ownership of the
    selection cannot change in the middle of the list, as would be when calling
    XtGetSelectionValueIncremental repeatedly.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface