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Re: Problem with scroll in curses

From: Thomas Dickey
Subject: Re: Problem with scroll in curses
Date: Tue, 27 Apr 2004 18:08:18 -0400 (EDT)

On Tue, 27 Apr 2004, Daniel Weaver wrote:

> At 12:46 PM 4/27/2004 -0400, Thomas Dickey wrote:
> >On Sat, 24 Apr 2004, shivangi desai wrote:
> >
> > > I found documentation stating that my screen will physically scroll on
> > > calling idlok but this does not happen.
> >
> >Not exactly (perhaps the wording could be improved).  idlok() is used to
> >tell curses whether it can use the escape sequences for inserting or
> >deleting lines as part of the optimization.  Old terminals were sometimes
> >very slow when performing these operations.
> >
> >scrollok() is closer to what you are saying, but the rest of the problem
> >report gives me the impression that you are misunderstanding what happens
> >when a terminal scrolls.  It shifts the text on the screen - but the text
> >that is shifted off the screen is lost.
> How does this interact with the Data_above (da) and Data_below (db)
> attributes?  I would think that when these attributes were set the user
> could have some expectation that the data should be retained.

I suppose so.  But (aside, say, from simulating it with xterm), I don't
know to test if other implementations of curses might do something special
for this.  The various HP terminals seem to be the only ones that provide
this feature.

> Does ncurses use this information to permit data to be scrolled off the
> screen or just to guarantee garbage is not scrolled onto the screen?

Only the latter.

Thomas E. Dickey

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