Can CURSES do a simple scroll?

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2 total messages Started by Nikos B. Troullinos Wed, 12 Sep 1990 05:16

#847

Author: Nikos B. Troullinos
Date: Wed, 12 Sep 1990 05:16

49 lines
1823 bytes

Can anyone shed some light in the following perplexing problem?

I am trying to use CURSES in a program where decent scrolling off the 
screen is required when the cursor is in the last line and a newline
is echoed (how unusual!)

Compiling with cc under SUN OS 4.1 I get scrolling but also repainting
of the whole screen for each and every scroll! (whether idlok() is there or
not)

Compiling with /usr/5bin/cc (and the corresponding library) things
improve but instead of a simple echoing of a nl/cr, the insert/delete
capabilities of the terminal (vt100) are used and the cursor is sent for
a brief time on the upper left 'home' position. This is very noticeable
at a low baud rate.

Is it too much to ask for curses to behave reasonably and just send a nl/cr?

Or am I missing something really obvious? My little test program follows:

Nikos Troullinos, CIS
Syracuse University
---------------------------------------------------------------------------
#include <curses.h>
#define EOT 0x4

/* 
   Minimum curses program to make curses do A SIMPLE SCROLLING 
   under SUN OS 4.1 and with a vt100 terminal setting.
*/

void main()
{
int c;

   initscr();
   cbreak();
   noecho();
   nl(); 
   idlok(stdscr, TRUE);
   scrollok(stdscr, TRUE);  
   refresh();

   while ((c=getch()) != EOT) 
     {addch(c);refresh();}

   refresh();
   endwin();
}

Re: Can CURSES do a simple scroll?

#850

Author: Adam Bryant
Date: Wed, 12 Sep 1990 16:18

69 lines
2518 bytes

In article <1990Sep12.051641.11113@rodan.acs.syr.edu> nicktrou@rodan.acs.syr.edu (Nikos B. Troullinos) writes:
+
+  Path: bu.edu!rpi!uupsi!rodan.acs.syr.edu!nicktrou
+  From: nicktrou@rodan.acs.syr.edu (Nikos B. Troullinos)
+  Newsgroups: comp.unix.programmer
+  Keywords: curses
+  Date: 12 Sep 90 05:16:41 GMT
+  Organization: Syracuse University, Syracuse, NY
+  Lines: 49
+
+  I am trying to use CURSES in a program where decent scrolling off the 
+  screen is required when the cursor is in the last line and a newline
+  is echoed (how unusual!)
+
+   void main()
+   {
+   int c;
+
+     initscr();
+     cbreak();
+     noecho();
+     nl(); 
+     idlok(stdscr, TRUE);
+     scrollok(stdscr, TRUE);  
+     refresh();
+
+     while ((c=getch()) != EOT) 
+     {addch(c);refresh();}
+      refresh();
+     endwin();
+  }

Try changing the line:

      {addch(c); refresh(); }

to
      {
        if ((c == '\n') || (c == '\r'))
          scroll(stdscr);
        else
          addch(c);
        refresh();
      }

I have only made a little use of the scrolling functionality of curses
myself, and have found that it often makes mistakes, such as when you
scroll up a line that has the same characters on the line about, it
forgets to redraw those characters during the scroll.

[I get around that by redrawing the entire screen all over again in
 memory and then issuing a refresh().  The way to do that is to use:

   move(0, 0);
   clrtobot();

in place of 'clear()'.  Only use 'clear()' when you absolutely know
that the screen will be greatly changed, since this tremendously
increased display speed]

Hope this correctly answers your question.

adam
ps.  Now, if only curses would implement backward scrolling, my built
in pager would be really efficient.
--
Adam Bryant                               INTERNET: adb@cs.bu.edu
Conquer Hack'n'Slasher                    BITNET:   adb@buenga
list: conquer-news-request@cs.bu.edu      UUCP:  ...!harvard!bu-cs!adb

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