Re: scrolling regions and ncurses demo program rain

[Roumen Petrov]

Hi,

Thomas Dickey wrote:
> On Thu, Aug 20, 2020 at 09:28:49PM +0300, Roumen Petrov wrote:
> > Hi,
> >
> > Thomas Dickey wrote:
> > > On Wed, Aug 19, 2020 at 10:59:24PM +0300, Roumen Petrov wrote:
> > > > Hello,
> > > >
> > > > I read code of rain program and library code but some things are not clear to
> > > > me.
> > > >
> > > > Why demo program uses escape sequence to set margins on screen?
> > >
> > > Which particular escape sequence are you talking about?
> >
> > Esc [ Pn ; Pn r - set top and bottom margins
>
> DEC used "margin" for left/right and top/bottom, but in most
> other contexts (e.g., termcap, terminfo and curses),
> that's a "scroll region".
>   
> > Attached picture shows a dump of program output.
>
> In terminfo, you'd see "csr".
>
> man 5 terminfo:
>
>         change_scroll_region          csr        cs        change region to
>                                                            line #1 to line #2
>                                                            (P)
>
> curses (not just ncurses) does this when updating the screen.
>
> In ncurses, that's used when the library decides that it would
> be more efficient to shift the existing text up or down and paint
> just a few lines rather than several lines.

Ok. So scroll region is due to output optimisation supported by some curses 
implementations.

[SNIP]


Thanks for details,
Roumen Petrov