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 did not 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.