Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!columbia!rutgers!topaz.rutgers.edu!gaynor From: gaynor@topaz.rutgers.edu (Silver) Newsgroups: comp.emacs Subject: Re: flow control by termcap Message-ID: <13269@topaz.rutgers.edu> Date: Fri, 10-Jul-87 23:13:19 EDT Article-I.D.: topaz.13269 Posted: Fri Jul 10 23:13:19 1987 Date-Received: Mon, 13-Jul-87 03:46:20 EDT References: <493@yetti.UUCP> <13255@topaz.rutgers.edu> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 48 ron@topaz writes: > Changes EMACS makes to the screen are supposed to appear > instantaneous. This depends upon your environment. It is impossible to perform instantaneous screen updates in a "slow" atmosphere, ... > You are not expected to try to read the screen > during updates, so slowing the scroll down or making it smooth so > you can see is not applicable. ... where the user *will* notice updates. These may occur slowly enough that the user may be able to still read the screen, and even detect what updates are being made. To keep from distracting the user, these changes should be as innocuous as possible. For an example, a redraw is disconcerting in a slow environment. The eyes follow the line insertions (just after registering a gap in the material), and the thought "C'mon, c'mon..." registers unbidden in the mind. Almost without fail. With a (relatively) smooth scroll, though, the eyes and grey matter tend to stay focused on the attended material. It is more appropriate to say "The user will hopefully disregard the screen updates, so do them incognito.". > Scroll is only done because it is a > cheap block move on most terminals. Smooth-scroll is only done to maintain continuity in the display during updates for the benefit of the user. Normal scrolls and redraws might be a little faster. And a little uglier. Don't get me wrong, though. I'm NOT saying that everything should be smooth-scrolled, because it can also be distracting - it's almost as if material being smooth-scrolled has attention-glue on it if it's overused and performed *too* slowly. What I AM saying is that there are other considerations to be taken into account besides display- efficiency. What is efficient for the display is not always efficient for the user (although it seems that this is usually the case). Silver. name: Andy Gaynor (Silver) uucp: ...!rutgers!topaz.rutgers.edu!gaynor arpa: gaynor@topaz.rutgers.edu icbm: 40 34 N / 74 45 W