Re: Two bugs

[Peter Stephenson <pws@ifh.de>]

a.main@dcs.warwick.ac.uk wrote:
> >% Src/zsh -f
> >bolyai% bindkey '^j' self-insert
> >bolyai%
> >
> >Now press ^J twice type anything and press ^J again.  The first character yo
> u
> >typed will disappear from the screen.  If there are more lines the first
> >character after each blank lines will disappear.  It is very bad in zed.
> 
> Actually, the symtom, more precisely, is that the last line preceded by
> a blank line gets as its first character the first character on the
> last line, and the first character of every other line preceded by a
> blank line disappears.  I'm 99% certain that this is related to
> am_char, as the characters that disappear are the ones that are output
> by the code that outputs am_char.  (Change it to output, say, 'X'
> instead of am_char, and you'll see what I mean.)

Yes, my changes seem to have brought this on.  I don't feel morally
responsible, however... The problem was that the character for
automatic margin stored was always the one for the line being changed,
which is not necessarily where the cursor currently is.  Consequently,
if the cursor is at the end of some other line the wrong am_char is
printed.  I've fixed this by turning this into an array.  (However, it
still shouldn't actually be happening because you don't need to print
out all those 80 spaces...)

> Actually, I find that the recent refresh changes, outputting spaces to
> the end of lines instead of merely moving onto the next line, results
> in an unacceptable performance penalty.  I'm working at 19200 baud
> here, and multi-line command editing is now painfully slow.  Would it
> work to merely clear with spaces the *first* time a line needs it, and
> go back to the old behaviour thereafter?

This shouldn't all be necessary:  we only need to go to the lengths of
printing out all the spaces if they're `really' there, which is only
likely to be a couple of spaces at the end of a line with a
continuation, so that the difference in efficiency should be
unnoticeable.

What is confusing me is the condition for using delete-eol or not,
which is in the following chunk of code:

/* 2: see if we can clear to end-of-line, and if it's faster, work out where
   to do it from - we can normally only do so if there's no right-prompt.
   With automatic margins, we shouldn't do it if there is another line, in
   case it messes up cut and paste. */

    col_cleareol = -1;
    if (tccan(TCCLEAREOL) && (!hasam || ln == nlnct - 1) && 
	(nllen == winw ||	/* new buffer goes to the end of the line */
	put_rpmpt != oput_rpmpt)) {


I just added the (!hasam || ln == nlnct - 1); it should really be
(!hasam || nllen != winw || ln == nlnct -1), but the last part of the
condition suggests this was only arising anyway if the line would fill
to the end of the line, either by being long or by having an altered
rpmpt.  It should be possible to alter it so that only *really* long
lines have this !hasam test applied.  I'll think about it myself if I
get another chance, but at the moment I've got several other things to
do.  Perhaps some else understands the logic here.

Here's the patch to fix the first problem (except may be in
pathological cases).

*** Src/zle_refresh.c.orig	Thu Dec 21 23:44:43 1995
--- Src/zle_refresh.c	Wed Jan 10 16:51:38 1996
***************
*** 56,62 ****
      winpos;			/* singlelinezle: line's position in window */
  static unsigned pmpt_attr = 0,	/* text attributes after displaying prompt  */
      rpmpt_attr = 0;		/* text attributes after displaying rprompt */
! static char am_char = ' ';	/* first col char if needed for automargin  */
  
  /**/
  void
--- 56,62 ----
      winpos;			/* singlelinezle: line's position in window */
  static unsigned pmpt_attr = 0,	/* text attributes after displaying prompt  */
      rpmpt_attr = 0;		/* text attributes after displaying rprompt */
! static char *am_chars;		/* first col chars if needed for automargin  */
  
  /**/
  void
***************
*** 79,89 ****
--- 79,92 ----
  	    }
  	    free(nbuf);
  	    free(obuf);
+ 	    free(am_chars);
  	}
  	nbuf = (char **)zcalloc((winh + 1) * sizeof(char *));
  	obuf = (char **)zcalloc((winh + 1) * sizeof(char *));
  	nbuf[0] = (char *)zalloc(winw + 1);
  	obuf[0] = (char *)zalloc(winw + 1);
+ 	am_chars = (char *)zcalloc(winh * sizeof(char *));
+ 	memset(am_chars, ' ', winh);
  
  	lwinw = winw;
  	lwinh = winh;
***************
*** 482,488 ****
  
  /* 3: set character for first column, in case automargin stuff needs doing:
     to begin with, this is the first char of the old screen line, if any. */
!     am_char = *ol ? *ol : *nl;
  
  /* 4: main display loop - write out the buffer using whatever tricks we can */
  
--- 485,492 ----
  
  /* 3: set character for first column, in case automargin stuff needs doing:
     to begin with, this is the first char of the old screen line, if any. */
!     if (ln)
!       am_chars[ln-1] = *ol ? *ol : *nl;
  
  /* 4: main display loop - write out the buffer using whatever tricks we can */
  
***************
*** 597,614 ****
  	return;
  
      if (vcs == winw) {
! 	if (!hasam) {
  	    putc('\r', shout);
  	    putc('\n', shout);
  	    SELECT_ADD_COST(2);
  	} else {
! 	    putc(am_char, shout);
  	    tcout(TCLEFT);
  	    SELECT_ADD_COST(1 + tclen[TCLEFT]);
  	}
  	vln++, vcs = 0;
      }
-     am_char = ' ';
  
  /* move up */
      if (ln < vln) {
--- 601,617 ----
  	return;
  
      if (vcs == winw) {
! 	if (!hasam || vln >= nlnct) {
  	    putc('\r', shout);
  	    putc('\n', shout);
  	    SELECT_ADD_COST(2);
  	} else {
! 	    putc(am_chars[vln], shout);
  	    tcout(TCLEFT);
  	    SELECT_ADD_COST(1 + tclen[TCLEFT]);
  	}
  	vln++, vcs = 0;
      }
  
  /* move up */
      if (ln < vln) {

-- 
Peter Stephenson <pws@ifh.de>       Tel: +49 33762 77366
WWW:  http://www.ifh.de/~pws/       Fax: +49 33762 77330
Deutches Electronen-Synchrotron --- Institut fuer Hochenergiephysik Zeuthen
DESY-IfH, 15735 Zeuthen, Germany.