16.5.1 Information about the picked atom

As a simple example, the following procedure calls the ``mol_weight'' command (in the previous section).

proc mol_weight_trace_fctn {args} {
      mol_weight
}

(This function is needed because the functions registered with trace take three arguments, but ``mol_weight'' only takes one.)

The trace function is registered as:

trace variable vmd_pick_atom w mol_weight_trace_fctn

And now the residue masses will be printed automatically when an atom is picked. To turn this off,

trace vdelete vmd_pick_atom w mol_weight_trace_fctn