/*
 * $Id: zle_refresh.c,v 3.1.0.9 1996/12/10 02:26:53 hzoli Exp $
 *
 * zle_refresh.c - screen update
 *
 * This file is part of zsh, the Z shell.
 *
 * Copyright (c) 1992-1996 Paul Falstad
 * All rights reserved.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and to distribute modified versions of this software for any
 * purpose, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 *
 * In no event shall Paul Falstad or the Zsh Development Group be liable
 * to any party for direct, indirect, special, incidental, or consequential
 * damages arising out of the use of this software and its documentation,
 * even if Paul Falstad and the Zsh Development Group have been advised of
 * the possibility of such damage.
 *
 * Paul Falstad and the Zsh Development Group specifically disclaim any
 * warranties, including, but not limited to, the implied warranties of
 * merchantability and fitness for a particular purpose.  The software
 * provided hereunder is on an "as is" basis, and Paul Falstad and the
 * Zsh Development Group have no obligation to provide maintenance,
 * support, updates, enhancements, or modifications.
 *
 */

#include "zle.h"

#ifdef HAVE_SELECT
#define SELECT_ADD_COST(X)	cost += X
#define zputc(a, b)		putc(a, b), cost++
#define zwrite(a, b, c, d)	fwrite(a, b, c, d), cost += (b * c)
#else
#define SELECT_ADD_COST(X)
#define zputc(a, b)		putc(a, b)
#define zwrite(a, b, c, d)	fwrite(a, b, c, d)
#endif

/* Oct/Nov 94: <mason> some code savagely redesigned to fix several bugs -
   refreshline() & tc_rightcurs() majorly rewritten; refresh() fixed -
   I've put my fingers into just about every routine in here -
   any queries about updates to mason@werple.net.au */

char **nbuf = NULL,		/* new video buffer line-by-line char array */
    **obuf = NULL;		/* old video buffer line-by-line char array */
static char *lpptbuf, *rpptbuf; /* prompt buffers			    */
static int more_start,		/* more text before start of screen?	    */
    more_end,			/* more stuff after end of screen?	    */
    olnct,			/* previous number of lines		    */
    ovln,			/* previous video cursor position line	    */
    lpptlen, rpptlen,           /* length of prompt buffers                 */
    pptw, rpw,                  /* prompt widths on screen                  */
    vcs, vln,			/* video cursor position column & line	    */
    vmaxln,			/* video maximum number of lines	    */
    winw, winh, rwinh,		/* window width & height		    */
    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 */

/**/
void
resetvideo(void)
{
    int ln;
    static int lwinw = -1, lwinh = -1;	/* last window width & height */
 
    genprompts();
    winw = columns;  /* terminal width */
    if (isset(SINGLELINEZLE) || termok != TERM_OK)
	winh = 1;
    else
	winh = (lines < 2) ? 24 : lines;
    rwinh = lines;		/* keep the real number of lines */
    winpos = vln = vmaxln = 0;
    if (lwinw != winw || lwinh != winh) {
	if (nbuf) {
	    for (ln = 0; ln != lwinh; ln++) {
		zfree(nbuf[ln], lwinw + 1);
		zfree(obuf[ln], lwinw + 1);
	    }
	    free(nbuf);
	    free(obuf);
	}
	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);

	lwinw = winw;
	lwinh = winh;
    }
    for (ln = 0; ln != winh + 1; ln++) {
	if (nbuf[ln])
	    *nbuf[ln] = '\0';
	if (obuf[ln])
	    *obuf[ln] = '\0';
    }

    if (pptw) {
    	memset(nbuf[0], ' ', pptw);
	memset(obuf[0], ' ', pptw);
	nbuf[0][pptw] = obuf[0][pptw] = '\0';
    }

    vcs = pptw;
    olnct = nlnct = 0;
    if (showinglist > 0)
	showinglist = -2;
}

/*
 * Nov 96: <mason> changed to single line scroll
 */

/**/
void
scrollwindow(int tline)
{
    int t0;
    char *s;

    s = nbuf[tline];
    for (t0 = tline; t0 < winh - 1; t0++)
	nbuf[t0] = nbuf[t0 + 1];
    nbuf[winh - 1] = s;
    if (!tline)
	more_start = 1;
    return;
}

/* this is the messy part. */
/* this define belongs where it's used!!! */

#define nextline					\
{							\
    *s = '\0';						\
    if (ln != winh - 1)					\
	ln++;						\
    else {						\
	if (!canscroll)	{				\
	    if (nvln != -1 && nvln != winh - 1		\
		&& (numscrolls != onumscrolls - 1	\
		    || nvln <= winh / 2))		\
	        break;					\
	    numscrolls++;				\
	    canscroll = winh / 2;			\
	}						\
	canscroll--;					\
	scrollwindow(0);				\
	if (nvln != -1)					\
	    nvln--;					\
    }							\
    if (!nbuf[ln])					\
	nbuf[ln] = (char *)zalloc(winw + 1);		\
    s = (unsigned char *)nbuf[ln];			\
    sen = s + winw;					\
}

#define snextline					\
{							\
    *s = '\0';						\
    if (ln != winh - 1)					\
	ln++;						\
    else						\
	if (tosln < 3) {				\
	    more_status = 1;				\
	    scrollwindow(tosln + 1);			\
	} else if (tosln - 1 <= nvln) {			\
	    scrollwindow(0);				\
	    if (nvln)					\
		nvln--, tosln--;			\
	} else {					\
	    tosln--;					\
	    scrollwindow(tosln);			\
	}						\
    if (!nbuf[ln])					\
	nbuf[ln] = (char *)zalloc(winw + 1);		\
    s = (unsigned char *)nbuf[ln];			\
    sen = s + winw;					\
}

int cleareol,			/* clear to end-of-line (if can't cleareod) */
    clearf = 0;			/* alwayslastprompt used immediately before */
static int put_rpmpt,		/* whether we should display right-prompt   */
    oput_rpmpt,			/* whether displayed right-prompt last time */
    oxtabs,			/* oxtabs - tabs expand to spaces if set    */
    numscrolls, onumscrolls;
extern int clearflag;		/* set to non-zero if alwayslastprompt used */

/**/
void
refresh(void)
{
    static int inlist;		/* avoiding recursion                        */
    int canscroll = 0,		/* number of lines we are allowed to scroll  */
	ln = 0,			/* current line we're working on	     */
	more_status = 0,	/* more stuff in status line		     */
	nvcs = 0, nvln = -1,	/* video cursor column and line		     */
	t0 = -1,		/* tmp					     */
	tosln = 0;		/* tmp in statusline stuff		     */
    unsigned char *s,		/* pointer into the video buffer	     */
	*t,			/* pointer into the real buffer		     */
	*sen,			/* pointer to end of the video buffer (eol)  */
	*scs;			/* pointer to cursor position in real buffer */
    char **qbuf;		/* tmp					     */

    /* If this is called from listmatches() (indirectly via trashzle()), and *
     * that was called from the end of refresh(), then we don't need to do   *
     * anything.  All this `inlist' code is actually unnecessary, but it     *
     * improves speed a little in a common case.                             */
    if (inlist)
	return;

#ifdef HAVE_SELECT
    cost = 0;			/* reset */
#endif

/* Nov 96: <mason>  This looks ugly and I haven't checked how complete it is.
   sgtty stuff may or may not work */
#if defined(HAVE_TERMIOS_H) || defined(HAVE_TERMIO_H)
    oxtabs = (shttyinfo.tio.c_oflag &
#else	/* we're using sgtty */
    oxtabs = (shttyinfo.sgttyb.sg_flags &
#endif
#ifdef __EMX__
#ifndef TAB3
#define TAB3 0x1800
#endif
#endif
# ifdef TAB3
				 	TAB3) == TAB3;
# else
#  ifdef OXTABS
					OXTABS) == OXTABS;
#  else
#ifndef __EMX__
					XTABS) == XTABS;
#endif

#  endif
# endif

    cleareol = 0;		/* unset */
    more_start = more_end = 0;	/* unset */
    if (resetneeded) {
	onumscrolls = 0;
	setterm();
#ifdef TIOCGWINSZ
	if (winchanged) {
	    moveto(0, 0);
	    t0 = olnct;		/* this is to clear extra lines even when */
	    winchanged = 0;	/* the terminal cannot TCCLEAREOD	  */
	}
#endif
	resetvideo();
	resetneeded = 0;	/* unset */
	oput_rpmpt = 0;		/* no right-prompt currently on screen */
        if (!clearflag)
            if (tccan(TCCLEAREOD))
                tcout(TCCLEAREOD);
            else
                cleareol = 1;   /* request: clear to end of line */
        if (t0 > -1)
            olnct = t0;
        if (isset(SINGLELINEZLE) || termok != TERM_OK)
            vcs = 0;
        else if (!clearflag && lpptlen)
            zwrite(lpptbuf, lpptlen, 1, shout);
	if (clearflag) {
	    zputc('\r', shout);
	    vcs = 0;
	    moveto(0, pptw);
	}
	fflush(shout);
	clearf = clearflag;
    } else if (winw != columns || rwinh != lines)
	resetvideo();

/* now winw equals columns and winh equals lines 
   width comparisons can be made with winw, height comparisons with winh */

    if (isset(SINGLELINEZLE) || termok != TERM_OK) {
	singlerefresh();
	return;
    }

    if (cs < 0) {
#ifdef DEBUG
	fprintf(stderr, "BUG: negative cursor position\n");
	fflush(stderr); 
#endif
	cs = 0;
    }
    scs = line + cs;
    numscrolls = 0;

/* first, we generate the video line buffers so we know what to put on
   the screen - also determine final cursor position (nvln, nvcs) */

    /* Deemed necessary by PWS 1995/05/15 due to kill-line problems */
    if (!*nbuf)
	*nbuf = (char *)zalloc(winw + 1);

    s = (unsigned char *)(nbuf[ln = 0] + pptw);
    t = line;
    sen = (unsigned char *)(*nbuf + winw);
    for (; t < line+ll; t++) {
	if (t == scs)			/* if cursor is here, remember it */
	    nvcs = s - (unsigned char *)(nbuf[nvln = ln]);

	if (*t == '\n')			/* newline */
	    nextline
	else if (*t == '\t') {		/* tab */
	    t0 = (char *)s - nbuf[ln];
	    if ((t0 | 7) + 1 >= winw)
		nextline
	    else
		do
		    *s++ = ' ';
		while ((++t0) & 7);
	} else if (icntrl(*t)) {	/* other control character */
	    *s++ = '^';
	    if (s == sen)
		nextline
	    *s++ = (*t == 127) ? '?' : (*t | '@');
	} else				/* normal character */
	    *s++ = *t;
	if (s == sen)
	    nextline
    }

/* if we're really on the next line, don't fake it; do everything properly */
    if (t == scs && (nvcs = s - (unsigned char *)(nbuf[nvln = ln])) == winw) {
	*s = '\0';
	switch (*s) { 		/* a sad hack to make the break */
	case '\0':		/* in nextline work */
	    nextline
	}
	*s = '\0';
	nvcs = 0;
	nvln++;
    }

    if (t != line + ll)
	more_end = 1;

    if (statusline) {
	tosln = ln + 1;
	snextline
	t = (unsigned char *)statusline;
	for (; t < (unsigned char *)statusline + statusll; t++) {
	    if (icntrl(*t)) {	/* simplified processing in the status line */
		*s++ = '^';
		if (s == sen)
		    snextline
		*s++ = (*t == 127) ? '?' : (*t | '@');
	    } else
		*s++ = *t;
	    if (s == sen)
		snextline
	}
    }

/* insert <.... at end of last line if there is more text past end of screen */
    if (more_end) {
	if (!statusline)
	    tosln = winh;
	strncpy(nbuf[tosln - 1] + winw - 7, " <.... ", 7);
	nbuf[tosln - 1][winw] = '\0';
    }

/* insert <....> at end of first status line if status is too big */
    if (more_status) {
	strncpy(nbuf[tosln] + winw - 8, " <....> ", 8);
	nbuf[tosln][winw] = '\0';
    }

    *s = '\0';
    nlnct = ln + 1;
    for (ln = nlnct; ln < winh; ln++)
	zfree(nbuf[ln], winw + 1), nbuf[ln] = NULL;

/* determine whether the right-prompt exists and can fit on the screen */
    if (!more_start)
	put_rpmpt = rpptlen && (int)strlen(nbuf[0]) + rpw < winw - 1;
    else {
/* insert >.... on first line if there is more text before start of screen */
	memset(nbuf[0], ' ', pptw);
	t0 = winw - pptw;
	t0 = t0 > 5 ? 5 : t0;
	strncpy(nbuf[0] + pptw, ">....", t0);
	memset(nbuf[0] + pptw + t0, ' ', winw - t0 - pptw);
	nbuf[0][winw] = '\0';
    }

    for (ln = 0; !clearf && (ln < nlnct); ln++) {
	/* if we have more lines than last time, clear the newly-used lines */
	if (ln >= olnct)
	    cleareol = 1;

    /* if old line and new line are different,
       see if we can insert/delete a line to speed up update */

	if (ln < olnct - 1 && !(hasam && vcs == winw) &&
	    nbuf[ln] && obuf[ln] &&
	    strncmp(nbuf[ln], obuf[ln], 16)) {
	    if (tccan(TCDELLINE) && obuf[ln + 1] && obuf[ln + 1][0] &&
		nbuf[ln] && !strncmp(nbuf[ln], obuf[ln + 1], 16)) {
		moveto(ln, 0);
		tcout(TCDELLINE);
		zfree(obuf[ln], winw + 1);
		for (t0 = ln; t0 != olnct; t0++)
		    obuf[t0] = obuf[t0 + 1];
		obuf[--olnct] = NULL;
	    }
	/* don't try to insert a line if olnct = vmaxln (vmaxln is the number
	   of lines that have been displayed by this routine) so that we don't
	   go off the end of the screen. */

	    else if (tccan(TCINSLINE) && olnct < vmaxln && nbuf[ln + 1] &&
		     obuf[ln] && !strncmp(nbuf[ln + 1], obuf[ln], 16)) {
		moveto(ln, 0);
		tcout(TCINSLINE);
		for (t0 = olnct; t0 != ln; t0--)
		    obuf[t0] = obuf[t0 - 1];
		obuf[ln] = NULL;
		olnct++;
	    }
	}

    /* update the single line */
	refreshline(ln);

    /* output the right-prompt if appropriate */
	if (put_rpmpt && !ln && !oput_rpmpt) {
	    moveto(0, winw - 1 - rpw);
	    zwrite(rpptbuf, rpptlen, 1, shout);
	    vcs = winw - 1;
	/* reset character attributes to that set by the main prompt */
	    txtchange = pmpt_attr;
	    if (txtchangeisset(TXTNOBOLDFACE) && (rpmpt_attr & TXTBOLDFACE))
		tsetcap(TCALLATTRSOFF, 0);
	    if (txtchangeisset(TXTNOSTANDOUT) && (rpmpt_attr & TXTSTANDOUT))
		tsetcap(TCSTANDOUTEND, 0);
	    if (txtchangeisset(TXTNOUNDERLINE) && (rpmpt_attr & TXTUNDERLINE))
		tsetcap(TCUNDERLINEEND, 0);
	    if (txtchangeisset(TXTBOLDFACE) && (rpmpt_attr & TXTNOBOLDFACE))
		tsetcap(TCBOLDFACEBEG, 0);
	    if (txtchangeisset(TXTSTANDOUT) && (rpmpt_attr & TXTNOSTANDOUT))
		tsetcap(TCSTANDOUTBEG, 0);
	    if (txtchangeisset(TXTUNDERLINE) && (rpmpt_attr & TXTNOUNDERLINE))
		tsetcap(TCUNDERLINEBEG, 0);
	}
    }

/* if old buffer had extra lines, set them to be cleared and refresh them
individually */

    if (olnct > nlnct) {
	cleareol = 1;
	for (ln = nlnct; ln < olnct; ln++)
	    refreshline(ln);
    }

/* reset character attributes */
    if (clearf && postedit) {
	if ((txtchange = pmpt_attr ? pmpt_attr : rpmpt_attr)) {
	    if (txtchangeisset(TXTNOBOLDFACE))
		tsetcap(TCALLATTRSOFF, 0);
	    if (txtchangeisset(TXTNOSTANDOUT))
		tsetcap(TCSTANDOUTEND, 0);
	    if (txtchangeisset(TXTNOUNDERLINE))
		tsetcap(TCUNDERLINEEND, 0);
	    if (txtchangeisset(TXTBOLDFACE))
		tsetcap(TCBOLDFACEBEG, 0);
	    if (txtchangeisset(TXTSTANDOUT))
		tsetcap(TCSTANDOUTBEG, 0);
	    if (txtchangeisset(TXTUNDERLINE))
		tsetcap(TCUNDERLINEBEG, 0);
	}
    }
    clearf = 0;

/* move to the new cursor position */
    moveto(nvln, nvcs);

/* swap old and new buffers - better than freeing/allocating every time */
    qbuf = nbuf;
    nbuf = obuf;
    obuf = qbuf;
/* store current values so we can use them next time */
    ovln = nvln;
    olnct = nlnct;
    oput_rpmpt = put_rpmpt;
    onumscrolls = numscrolls;
    if (nlnct > vmaxln)
	vmaxln = nlnct;
    fflush(shout);		/* make sure everything is written out */

    /* if we have a new list showing, note it; if part of the list has been
    overwritten, redisplay it. */
    if (showinglist == -2 || (showinglist > 0 && showinglist < nlnct)) {
	inlist = 1;
	listmatches();
	inlist = 0;
	refresh();
    }
    if (showinglist == -1)
	showinglist = nlnct;
}

#define tcinscost(X)   (tccan(TCMULTINS) ? tclen[TCMULTINS] : (X)*tclen[TCINS])
#define tcdelcost(X)   (tccan(TCMULTDEL) ? tclen[TCMULTDEL] : (X)*tclen[TCDEL])
#define tc_delchars(X)	(void) tcmultout(TCDEL, TCMULTDEL, (X))
#define tc_inschars(X)	(void) tcmultout(TCINS, TCMULTINS, (X))
#define tc_upcurs(X)	(void) tcmultout(TCUP, TCMULTUP, (X))
#define tc_leftcurs(X)	(void) tcmultout(TCLEFT, TCMULTLEFT, (X))

/* refresh one line, using whatever speed-up tricks are provided by the tty */

/**/
void
refreshline(int ln)
{
    char *nl, *ol, *p1;		/* line buffer pointers			 */
    int ccs = 0,		/* temporary count for cursor position	 */
	char_ins = 0,		/* number of characters inserted/deleted */
	col_cleareol,		/* clear to end-of-line from this column */
	i, j,			/* tmp					 */
	nllen, ollen,		/* new and old line buffer lengths	 */
	rnllen;			/* real new line buffer length		 */

/* 0: setup */
    nl = nbuf[ln];
    rnllen = nllen = nl ? strlen(nl) : 0;
    ol = obuf[ln] ? obuf[ln] : "";
    ollen = strlen(ol);

/* optimisation: can easily happen for clearing old lines.  If the terminal has
   the capability, then this is the easiest way to skip unnecessary stuff */
    if (cleareol && !nllen && !(hasam && ln < nlnct - 1)
	&& tccan(TCCLEAREOL)) {
	moveto(ln, 0);
	tcout(TCCLEAREOL);
	return;	
    }

/* 1: pad out the new buffer with spaces to contain _all_ of the characters
      which need to be written. do this now to allow some pre-processing */

    if (cleareol 		/* request to clear to end of line */
	|| !nllen 		/* no line buffer given */
	|| (ln == 0 && (put_rpmpt != oput_rpmpt))) {	/* prompt changed */
	p1 = halloc(winw + 1);
	if (nllen)
	    strncpy(p1, nl, nllen);
	memset(p1 + nllen, ' ', winw - nllen);
	p1[winw] = '\0';
	if (ln && nbuf[ln])
	    strncpy(nl, p1, winw + 1);	/* next time obuf will be up-to-date */
	else
	    nl = p1;		/* don't keep the padding for prompt line */
	nllen = winw;
    } else if (ollen > nllen) { /* make new line at least as long as old */
	p1 = halloc(ollen + 1);
	strncpy(p1, nl, nllen);
	memset(p1 + nllen, ' ', ollen - nllen);
	p1[ollen] = '\0';
	nl = p1;
	nllen = ollen;
    }

/* 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. */

    if (hasam && ln < nlnct - 1 && rnllen == winw)
	col_cleareol = -2;	/* clearing eol would be evil so don't */
    else {
	col_cleareol = -1;
	if (tccan(TCCLEAREOL) && (nllen == winw || put_rpmpt != oput_rpmpt)) {
	    for (i = nllen; i && nl[i - 1] == ' '; i--);
	    for (j = ollen; j && ol[j - 1] == ' '; j--);
	    if ((j > i + tclen[TCCLEAREOL])	/* new buf has enough spaces */
		|| (nllen == winw && nl[winw - 1] == ' '))
		col_cleareol = i;
	}
    }

/* 2b: first a new trick for automargin niceness - good for cut and paste */

    if (hasam && vcs == winw) {
	vln++, vcs = 1;
        if (nbuf[vln]  && *nbuf[vln])
	    zputc(*nbuf[vln], shout);
	else
	    zputc(' ', shout);  /* I don't think this should happen */
	if (ln == vln) {	/* better safe than sorry */
	    nl++;
	    if (*ol)
		ol++;
	    ccs = 1;
	}			/* else  hmmm... I wonder what happened */
    }

/* 2c: if we're on the first line, start checking at the end of the prompt;
   we shouldn't be doing anything within the prompt */

    if (ln == 0 && pptw) {
	i = pptw - ccs;
	j = strlen(ol);
	nl += i;
	ol += (i > j ? j : i);	/* if ol is too short, point it to '\0' */
	ccs = pptw;
    }

/* 3: main display loop - write out the buffer using whatever tricks we can */

    for (;;) {
	if (*nl && *ol && nl[1] == ol[1]) /* skip only if second chars match */
	/* skip past all matching characters */
	    for (; *nl && (*nl == *ol); nl++, ol++, ccs++) ;

	if (!*nl) {
	    if ((char_ins <= 0)	|| (ccs >= winw))    /* written everything */
		return;
	    else		/* we've got junk on the right yet to clear */
		if (tccan(TCCLEAREOL) && (char_ins >= tclen[TCCLEAREOL])
	    	    && col_cleareol != -2)
		    col_cleareol = 0;	/* force a clear to end of line */
	}

	moveto(ln, ccs);	/* move to where we do all output from */

    /* if we can finish quickly, do so */
	if ((col_cleareol >= 0) && (ccs >= col_cleareol)) {
	    tcout(TCCLEAREOL);
	    return;
	}

    /* we've written out the new but yet to clear rubbish due to inserts */
	if (!*nl) {
	    i = (winw - ccs < char_ins) ? (winw - ccs) : char_ins;
	    if (tccan(TCDEL) && (tcdelcost(i) <= i + 1))
		tc_delchars(i);
	    else {
		vcs += i;
		while (i-- > 0)
		    zputc(' ', shout);
	    }
	    return;
	}

    /* if we've reached the end of the old buffer, then there are few tricks
       we can do, so we just dump out what we must and clear if we can */
	if (!*ol) {
	    i = (col_cleareol >= 0) ? col_cleareol : nllen;
	    i -= vcs;
	    zwrite(nl, i, 1, shout);
	    vcs += i;
	    if (col_cleareol >= 0)
		tcout(TCCLEAREOL);
	    return;
	}

    /* inserting & deleting chars: we can if there's no right-prompt */
	if ((ln || !put_rpmpt || !oput_rpmpt) 
	    && (nl[1] && ol[1] && nl[1] != ol[1])) { 

	/* deleting characters - see if we can find a match series that
	   makes it cheaper to delete intermediate characters
	   eg. oldline: hifoobar \ hopefully cheaper here to delete two
	       newline: foobar	 / characters, then we have six matches */
	    if (tccan(TCDEL)) {
		for (i = 1; *(ol + i); i++)
		    if (tcdelcost(i) < pfxlen(ol + i, nl)) {
			tc_delchars(i);
			ol += i;
			char_ins -= i;
			i = 0;
			break;
		    }
		if (!i)
		    continue;
	    }
	/* inserting characters - characters pushed off the right should be
	   annihilated, but we don't do this if we're on the last line lest
	   undesired scrolling occurs due to `illegal' characters on screen */

	    if (tccan(TCINS) && (vln != lines - 1)) {	/* not on last line */
		for (i = 1; *(nl + i); i++)
		    if (tcinscost(i) < pfxlen(nl + i, ol)) {
			tc_inschars(i);
			zwrite(nl, i, 1, shout);
			nl += i;
			char_ins += i;
			ccs = (vcs += i);
		    /* if we've pushed off the right, truncate oldline */
			for (i = 0; *(ol + i) && i < winw - ccs; i++);
			if (i == winw - ccs)
			    *(ol + i) = '\0';
			i = 0;
			break;
		    }
		if (!i)
		    continue;
	    }
	}
    /* we can't do any fancy tricks, so just dump the single character
       and keep on trying */
	zputc(*nl, shout);
	nl++, ol++;
	ccs++, vcs++;
    }
}

/* move the cursor to line ln (relative to the prompt line),
   absolute column cl; update vln, vcs - video line and column */

/**/
void
moveto(int ln, int cl)
{
    if (vcs == winw) {
	vln++, vcs = 0;
	if (!hasam) {
	    zputc('\r', shout);
	    zputc('\n', shout);
	} else {
	    if ((vln < nlnct) && nbuf[vln] && *nbuf[vln])
		zputc(*nbuf[vln], shout);
	    else
		zputc(' ', shout);
	    zputc('\r', shout);
	    if ((vln < olnct) && obuf[vln] && *obuf[vln])
		*obuf[vln] = *nbuf[vln];
	}
    }

    if (ln == vln && cl == vcs)
	return;

/* move up */
    if (ln < vln) {
	tc_upcurs(vln - ln);
	vln = ln;
    }
/* move down; if we might go off the end of the screen, use newlines
   instead of TCDOWN */

    while (ln > vln) {
	if (vln < vmaxln - 1)
	    if (ln > vmaxln - 1) {
		if (tc_downcurs(vmaxln - 1 - vln))
		    vcs = 0;
		vln = vmaxln - 1;
	    } else {
		if (tc_downcurs(ln - vln))
		    vcs = 0;
		vln = ln;
		continue;
	    }
	zputc('\r', shout), vcs = 0; /* safety precaution */
	while (ln > vln) {
	    zputc('\n', shout);
	    vln++;
	}
    }

    if (cl == vcs)
	return;

/* choose cheapest movements for ttys without multiple movement capabilities -
   do this now because it's easier (to code) */
    if (cl <= vcs / 2) {
	zputc('\r', shout);
	vcs = 0;
    }
    if (vcs < cl)
	tc_rightcurs(cl);
    else if (vcs > cl)
	tc_leftcurs(vcs - cl);
    vcs = cl;
}

/**/
int
tcmultout(int cap, int multcap, int ct)
{
    if (tccan(multcap) && (!tccan(cap) || tclen[multcap] <= tclen[cap] * ct)) {
	tcoutarg(multcap, ct);
	return 1;
    } else if (tccan(cap)) {
	while (ct--)
	    tcout(cap);
	return 1;
    }
    return 0;
}

/**/
void
tc_rightcurs(int cl)
{
    int ct,			/* number of characters to move across	    */
	i = vcs,		/* cursor position after initial movements  */
	j;
    char *t;

    ct = cl - vcs;

/* do a multright if we can - it's the most reliable */
    if (tccan(TCMULTRIGHT)) {
	tcoutarg(TCMULTRIGHT, ct);
	return;
    }

/* try tabs if tabs are non destructive and multright is not possible */
    if (!oxtabs && tccan(TCNEXTTAB) && ((vcs | 7) < cl)) {
	i = (vcs | 7) + 1;
	tcout(TCNEXTTAB);
	for ( ; i + 8 <= cl; i += 8)
	    tcout(TCNEXTTAB);
	if ((ct = cl - i) == 0) /* number of chars still to move across */
	    return;
    }

/* otherwise _carefully_ write the contents of the video buffer.
   if we're anywhere in the prompt, goto the left column and write the whole
   prompt out unless lpptlen == pptw : we can cheat then */
    if (vln == 0 && i < pptw) {
	if (lpptlen == pptw)
	    zwrite(lpptbuf + i, lpptlen - i, 1, shout);
	else if (tccan(TCRIGHT) && (tclen[TCRIGHT] * ct <= lpptlen))
	    /* it is cheaper to send TCRIGHT than reprint the whole prompt */
	    for (ct = pptw - i; ct--; )
		tcout(TCRIGHT);
        else {
	    if (i != 0)
		zputc('\r', shout);
	    zwrite(lpptbuf, lpptlen, 1, shout);
	}
	i = pptw;
	ct = cl - i;
    }

    if (nbuf[vln]) {
	for (j = 0, t = nbuf[vln]; *t && (j < i); j++, t++);
	if (j == i)
	    for ( ; *t && ct; ct--, t++)
		zputc(*t, shout);
    }
    while (ct--)
	zputc(' ', shout);	/* not my fault your terminal can't go right */
}

/**/
int
tc_downcurs(int ct)
{
    int ret = 0;

    if (ct && !tcmultout(TCDOWN, TCMULTDOWN, ct)) {
	while (ct--)
	    zputc('\n', shout);
	zputc('\r', shout), ret = -1;
    }
    return ret;
}

/**/
void
tcout(int cap)
{
    tputs(tcstr[cap], 1, putshout);
    SELECT_ADD_COST(tclen[cap]);
}

/**/
void
tcoutarg(int cap, int arg)
{
    char *result;

    result = tgoto(tcstr[cap], arg, arg);
    tputs(result, 1, putshout);
    SELECT_ADD_COST(strlen(result));
}

/**/
void
clearscreen(void)
{
    tcout(TCCLEARSCREEN);
    resetneeded = 1;
    clearflag = 0;
}

/**/
void
redisplay(void)
{
    moveto(0, pptw);
    zputc('\r', shout);
    resetneeded = 1;
    clearflag = 0;
}

/**/
void
singlerefresh(void)
{
    char *vbuf, *vp,		/* video buffer and pointer    */
	**qbuf,			/* tmp			       */
	*refreshop = *obuf;	/* pointer to old video buffer */
    int t0,			/* tmp			       */
	vsiz,			/* size of new video buffer    */
	nvcs = 0;		/* new video cursor column     */

    nlnct = 1;
/* generate the new line buffer completely */
    for (vsiz = 1 + pptw, t0 = 0; t0 != ll; t0++, vsiz++)
	if (line[t0] == '\t')
	    vsiz = (vsiz | 7) + 1;
	else if (icntrl(line[t0]))
	    vsiz++;
    vbuf = (char *)zalloc(vsiz);

    if (cs < 0) {
#ifdef DEBUG
	fprintf(stderr, "BUG: negative cursor position\n");
	fflush(stderr); 
#endif
	cs = 0;
    }

    memcpy(vbuf, lpptbuf + lpptlen - pptw, pptw); /* only use last part of prompt */
    vbuf[pptw] = '\0';
    vp = vbuf + pptw;

    for (t0 = 0; t0 != ll; t0++) {
	if (line[t0] == '\t')
	    for (*vp++ = ' '; (vp - vbuf) & 7; )
		*vp++ = ' ';
	else if (line[t0] == '\n') {
	    *vp++ = '\\';
	    *vp++ = 'n';
	} else if (line[t0] == 0x7f) {
	    *vp++ = '^';
	    *vp++ = '?';
	} else if (icntrl(line[t0])) {
	    *vp++ = '^';
	    *vp++ = line[t0] | '@';
	} else
	    *vp++ = line[t0];
	if (t0 == cs)
	    nvcs = vp - vbuf - 1;
    }
    if (t0 == cs)
	nvcs = vp - vbuf;
    *vp = '\0';

/* determine which part of the new line buffer we want for the display */
    if ((winpos && nvcs < winpos + 1) || (nvcs > winpos + winw - 2)) {
	if ((winpos = nvcs - ((winw - hasam) / 2)) < 0)
	    winpos = 0;
    }
    if (winpos)
	vbuf[winpos] = '<';	/* line continues to the left */
    if ((int)strlen(vbuf + winpos) > (winw - hasam)) {
	vbuf[winpos + winw - hasam - 1] = '>';	/* line continues to right */
	vbuf[winpos + winw - hasam] = '\0';
    }
    strcpy(nbuf[0], vbuf + winpos);
    zfree(vbuf, vsiz);
    nvcs -= winpos;

/* display the `visable' portion of the line buffer */
    for (t0 = 0, vp = *nbuf;;) {
    /* skip past all matching characters */
	for (; *vp && *vp == *refreshop; t0++, vp++, refreshop++) ;

	if (!*vp && !*refreshop)
	    break;

	singmoveto(t0);		/* move to where we do all output from */

	if (!*refreshop) {
	    if ((t0 = strlen(vp)))
		zwrite(vp, t0, 1, shout);
	    vcs += t0;
	    break;
	}
	if (!*vp) {
	    if (tccan(TCCLEAREOL))
		tcout(TCCLEAREOL);
	    else
		for (; *refreshop++; vcs++)
		    zputc(' ', shout);
	    break;
	}
	zputc(*vp, shout);
	vcs++, t0++;
	vp++, refreshop++;
    }
/* move to the new cursor position */
    singmoveto(nvcs);

    qbuf = nbuf;
    nbuf = obuf;
    obuf = qbuf;
    fflush(shout);		/* make sure everything is written out */
}

/**/
void
singmoveto(int pos)
{
    if (pos == vcs)
	return;
    if (pos <= vcs / 2) {
	zputc('\r', shout);
	vcs = 0;
    }
    if (pos < vcs) {
	tc_leftcurs(vcs - pos);
	vcs = pos;
    }
    if (pos > vcs) {
	if (tcmultout(TCRIGHT, TCMULTRIGHT, pos - vcs))
	    vcs = pos;
	else
	    while (pos > vcs) {
		zputc(nbuf[0][vcs], shout);
		vcs++;
	    }
    }
}

/* generate left and right prompts */

/**/
void
genprompts(void)
{
    zfree(lpptbuf, lpptlen);
    zfree(rpptbuf, rpptlen);
    lpptbuf = putprompt(lpmpt, &lpptlen, &pptw, 1);
    pmpt_attr = txtchange;
    rpptbuf = putprompt(rpmpt, &rpptlen, &rpw, 1);
    rpmpt_attr = txtchange;
}
