I've come in touch with tkoutline through tkgamepack.kit.
On unix platforms, scrolling with wheel-mice is done by
acting on <4> and <5> button events.
If I scroll down in an outline-window, the mouse
sometimes happens to be on a hyperlink, and if
that happens, the next <4>-event will both scroll
down further *and* open whatever it happened to
There should be no reason to open hyperlinks on
any other button than <1>, anyway.