[Oberon] SystemV - Viewer Scroll
andreas_pirklbauer at yahoo.com
Tue Mar 19 16:34:48 CET 2019
> This discussion is interesting for a physicist. Time in physics theories
> can equally well flow in either direction. The motion as a function of T
> is equally good as the motion as a function of (-T). I would think that
> the situation is the same with Text display. Scrolling up or down should
> be equivalent. Why is the beginning of the Text any different from the end?
> If you can count from the beginning, you can equally well count from the end.
> If not then why not?
In principle scrolling of text should of course be "direction-symmetric", just like
the classical laws of physics are time-symmetric (replace T by -T).
However, the underlying access operations (Texts.Read and Files.Read) are not
direction-symmetric, and that is what complicates things a little bit (but not much).
(ps: as a fun exercise, you can in fact make Files.Read and Texts.Read totally direction-
symmetric by modifying the underlying modules Files and Texts - in such a world text
scrolling would indeed be completely direction-symmetric as well, taking either dY
or -dY. But this is quite involved, as it would require meddling with both the file
buffer mechanism in Files and the piece list in Texts.. it’s just not worth it).
More information about the Oberon