Re: What, exactly, _is_ "line-breakout optimization"?

[Bill Gray]

Hi Thomas,  all,

   (much snipped)

> > At 2024-05-19T08:59:47-0500, G. Branden Robinson wrote:
> > "If fildes is a valid file descriptor, typeahead is enabled during
> > refresh; Curses periodically checks fildes for input and aborts the
> > refresh if any character is available."

   Just out of curiosity : I gather that the idea is that this helps on 
devices where a full refresh might take appreciable time,  and a key hit 
might come in while that refresh was taking place that would force yet 
another update and refresh.  (Say,  scrolling through a file in a text 
editor,  with the cursor key held down;  if the time to redraw the 
screen was close to the key repeat rate,  you'd do better to stop the 
moment you knew a key had been hit.)

   You'd presumably want to check for a key hit after refreshing N 
characters or N lines,  with N smaller for slower refreshes and/or 
cheaper key hit detection.

   I see PDCurses had this capability,  but it was removed because "the 
line-breakout optimization system... simply didn't work,  and never 
has"[1].  At this point,  screen refreshes are fast enough that I don't 
see how the capability could be useful.

-- Bill

[1] https://github.com/Bill-Gray/PDCursesMod/blob/master/docs/HISTORY.md

> > If I had to guess, I'd say the language of which I complain came from
> > the same source as the breezy flogging of "a modified Heckel algorithm
> > on line hashes to fill in scramble-vector information" in a May 1996
> > change.
>
> yes - some of that's amusing (actually I looked up the Heckel paper a long
> time ago, and didn't see the resemblance versus the algorithm - chalked it
> up to hyperbole).
>   
> > Thomas Dickey noted[1] that "when [he] measured it, rather than
> > improving performance, the result was often slower, typically 5-20%".
> >
> > Presumably the objective of the feature was not to improve the
> > performance of ncurses, but to astound the credulous reader with
> > impressive-sounding buzzwords.
> >
> > Regards,
> > Branden
> >
> > [1] https://invisible-island.net/ncurses/ncurses-license.html