display vs video sync vs ^L

[Kenneth Brody]

Quoting Fairlight (Wed, 17 Jan 2007 10:38:32 -0500):

> Y'all catch dis heeyah?  Kenneth Brody been jivin' 'bout like:
> >
> > The O/S has no concept of what is on the screen.  Some screen
> managers,
> > like "screen", _may_ keep track of this to enable multiple screens on
> > one physical display.
>
> "Screen manager" is really an inadequate way to describe screen(1).  At
> any rate, it isn't just "may", it flat-out MUST keep that information.
> Switching between multiplexed screens, copy for copy&paste from not only
> the current screen but a scrollback line history, the presence of the
> more modern doublevision/ttysnoop-like multiuser mode, etc., all
> necessitate that it track this information.
>
> Each screen has a buffer associated with it, and any time you switch
> between screens the parts of the buffers that differ are redrawn via
> curses for optimal redraw speed.
[...]

When I first came across it, or something similarly-named, many years
ago, it did not auto-draw the screens.  When running filePro within
it, a screen switch necessitated a Ctrl-L to refresh the screen.  Now,
if the terminal itself supported multiple screens, and the termcap
was written correctly, it would use the terminal's screen memory to
handle this.  (I forget which termcap entries define this.)

It may be that today's versions do handle this (or at least attempt to
handle it as best they can), but this has not always been the case.

--
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