int Tk_GetSelection(interp, tkwin, selection, target, proc, clientData)
Tcl_Interp *interp
(in) Tk_Window tkwin
(in) Atom selection
(in) Atom target
(in) Tk_GetSelProc *proc
(in) ClientData clientData
(in) 
Tk_GetSelection retrieves the selection specified by the atom
selection in the format specified by target.  The
selection may actually be retrieved in several pieces; as each piece
is retrieved, proc is called to process the piece.  Proc
should have arguments and result that match the type
Tk_GetSelProc:
typedef int Tk_GetSelProc(
ClientData clientData,
Tcl_Interp *interp,
char *portion);
The clientData and interp parameters to proc 
will be copies of the corresponding arguments to
Tk_GetSelection.  Portion will be a pointer to
a string containing part or all of the selection.  For large
selections, proc will be called several times with successive
portions of the selection.  The X Inter-Client Communication
Conventions Manual allows a selection to be returned in formats
other than strings, e.g. as an array of atoms or integers.  If
this happens, Tk converts the selection back into a string
before calling proc.  If a selection is returned as an
array of atoms, Tk converts it to a string containing the atom names
separated by white space.  For any other format besides string,
Tk converts a selection to a string containing hexadecimal
values separated by white space.
Tk_GetSelection returns to its caller when the selection has been completely retrieved and processed by proc, or when a fatal error has occurred (e.g. the selection owner didn't respond promptly). Tk_GetSelection normally returns TCL_OK; if an error occurs, it returns TCL_ERROR and leaves an error message in interp->result. Proc should also return either TCL_OK or TCL_ERROR. If proc encounters an error in dealing with the selection, it should leave an error message in interp->result and return TCL_ERROR; this will abort the selection retrieval.