code: @SuppressWarnings("PMD.UseVarargs")
      /* default */ void collectHandlers(Collection<HandlerReference> hdlrs,
              EventBase<?> event, Channel[] channels) {
          for (HandlerReference hdlr : handlers) {
              if (hdlr.handles(event, channels)) {
                  hdlrs.add(hdlr);
              }
          }
          for (ComponentVertex child : children) {
              child.collectHandlers(hdlrs, event, channels);
          }
      }
docs: Collects all handlers. Iterates over the tree with this object
  as root and for all child components adds the matching handlers to
  the result set recursively.
  
  @param hdlrs the result set
  @param event the event to match
  @param channels the channels to match