it's even worse, document another horrible case

[nvi.git] / vi / v_txt.c

/*-
 * Copyright (c) 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "$Id: v_txt.c,v 8.75 1993/12/27 17:09:26 bostic Exp $ (Berkeley) $Date: 1993/12/27 17:09:26 $";
#endif /* not lint */

#include <sys/types.h>
#include <sys/time.h>

#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "vi.h"
#include "seq.h"
#include "vcmd.h"
#include "excmd.h"

static int       txt_abbrev __P((SCR *, TEXT *, ARG_CHAR_T, int, int *, int *));
static void      txt_ai_resolve __P((SCR *, TEXT *));
static TEXT     *txt_backup __P((SCR *, EXF *, TEXTH *, TEXT *, u_int));
static void      txt_err __P((SCR *, EXF *, TEXTH *));
static int       txt_hex __P((SCR *, TEXT *, int *, ARG_CHAR_T));
static int       txt_indent __P((SCR *, TEXT *));
static int       txt_margin __P((SCR *, TEXT *, int *, ARG_CHAR_T));
static int       txt_outdent __P((SCR *, TEXT *));
static void      txt_showmatch __P((SCR *, EXF *));
static int       txt_resolve __P((SCR *, EXF *, TEXTH *));

/* Cursor character (space is hard to track on the screen). */
#if defined(DEBUG) && 0
#undef  CURSOR_CH
#define CURSOR_CH       '+'
#endif

/* Local version of BINC. */
#define TBINC(sp, lp, llen, nlen) {                                     \
        if ((nlen) > llen && binc(sp, &(lp), &(llen), nlen))            \
                goto err;                                               \
}

/*
 * newtext --
 *      Read in text from the user.
 *
 * !!!
 * Historic vi always used:
 *
 *      ^D: autoindent deletion
 *      ^H: last character deletion
 *      ^W: last word deletion
 *      ^V: quote the next character
 *
 * regardless of the user's choices for these characters.  The user's erase
 * and kill characters worked in addition to these characters.  Ex was not
 * completely consistent with this, as it did map the scroll command to the
 * user's EOF character.
 *
 * This implementation does not use fixed characters, but uses whatever the
 * user specified as described by the termios structure.  I'm getting away
 * with something here, but I think I'm unlikely to get caught.
 *
 * !!!
 * Historic vi did a special screen optimization for tab characters.  For
 * the keystrokes "iabcd<esc>0C<tab>", the tab would overwrite the rest of
 * the string when it was displayed.  Because this implementation redisplays
 * the entire line on each keystroke, the "bcd" gets pushed to the right as
 * we ignore that the user has "promised" to change the rest of the characters.
 * Users have noticed, but this isn't worth fixing, and, the way that the
 * historic vi did it results in an even worse bug.  Given the keystrokes
 * "iabcd<esc>0R<tab><esc>", the "bcd" disappears, and magically reappears
 * on the second <esc> key.
 */
int
v_ntext(sp, ep, tiqh, tm, lp, len, rp, prompt, ai_line, flags)
        SCR *sp;
        EXF *ep;
        TEXTH *tiqh;
        MARK *tm;               /* To MARK. */
        const char *lp;         /* Input line. */
        const size_t len;       /* Input line length. */
        MARK *rp;               /* Return MARK. */
        int prompt;             /* Prompt to display. */
        recno_t ai_line;        /* Line number to use for autoindent count. */
        u_int flags;            /* TXT_ flags. */
{
                                /* State of abbreviation checks. */
        enum { A_NOTSET, A_SPACE, A_NOTSPACE } abb;
                                /* State of the "[^0]^D" sequences. */
        enum { C_NOTSET, C_CARATSET, C_NOCHANGE, C_ZEROSET } carat_st;
                                /* State of the hex input character. */
        enum { H_NOTSET, H_NEXTCHAR, H_INHEX } hex;
                                /* State of quotation. */
        enum { Q_NOTSET, Q_NEXTCHAR, Q_THISCHAR } quoted;
        CH ikey;                /* Input character structure. */
        CHAR_T ch;              /* Input character. */
        GS *gp;                 /* Global pointer. */
        TEXT *tp, *ntp, ait;    /* Input and autoindent text structures. */
        size_t rcol;            /* 0-N: insert offset in the replay buffer. */
        size_t col;             /* Current column. */
        u_long margin;          /* Wrapmargin value. */
        u_int iflags;           /* Input flags. */
        int ab_cnt, ab_turnoff; /* Abbreviation count, if turned off. */
        int eval;               /* Routine return value. */
        int replay;             /* If replaying a set of input. */
        int showmatch;          /* Showmatch set on this character. */
        int testnr;             /* Test first character for nul replay. */
        int max, tmp;
        char *p;

        /*
         * Set the input flag, so tabs get displayed correctly
         * and everyone knows that the text buffer is in use.
         */
        F_SET(sp, S_INPUT);

        /* Local initialization. */
        eval = 0;
        gp = sp->gp;

        /*
         * Get one TEXT structure with some initial buffer space, reusing
         * the last one if it's big enough.  (All TEXT bookkeeping fields
         * default to 0 -- text_init() handles this.)  If changing a line,
         * copy it into the TEXT buffer.
         */
        if (tiqh->cqh_first != (void *)tiqh) {
                tp = tiqh->cqh_first;
                if (tp->q.cqe_next != (void *)tiqh || tp->lb_len < len + 32) {
                        text_lfree(tiqh);
                        goto newtp;
                }
                tp->ai = tp->insert = tp->offset = tp->owrite = 0;
                if (lp != NULL) {
                        tp->len = len;
                        memmove(tp->lb, lp, len);
                } else
                        tp->len = 0;
        } else {
newtp:          if ((tp = text_init(sp, lp, len, len + 32)) == NULL)
                        return (1);
                CIRCLEQ_INSERT_HEAD(tiqh, tp, q);
        }

        /* Set the starting line number. */
        tp->lno = sp->lno;

        /*
         * Set the insert and overwrite counts.  If overwriting characters,
         * do insertion afterward.  If not overwriting characters, assume
         * doing insertion.  If change is to a mark, emphasize it with an
         * END_CH.
         */
        if (len) {
                if (LF_ISSET(TXT_OVERWRITE)) {
                        tp->owrite = tm->cno - sp->cno;
                        tp->insert = len - tm->cno;
                } else
                        tp->insert = len - sp->cno;

                if (LF_ISSET(TXT_EMARK))
                        tp->lb[tm->cno - 1] = END_CH;
        }

        /*
         * Many of the special cases in this routine are to handle autoindent
         * support.  Somebody decided that it would be a good idea if "^^D"
         * and "0^D" deleted all of the autoindented characters.  In an editor
         * that takes single character input from the user, this wasn't a very
         * good idea.  Note also that "^^D" resets the next lines' autoindent,
         * but "0^D" doesn't.
         *
         * We assume that autoindent only happens on empty lines, so insert
         * and overwrite will be zero.  If doing autoindent, figure out how
         * much indentation we need and fill it in.  Update input column and
         * screen cursor as necessary.
         */
        if (LF_ISSET(TXT_AUTOINDENT) && ai_line != OOBLNO) {
                if (txt_auto(sp, ep, ai_line, NULL, 0, tp))
                        return (1);
                sp->cno = tp->ai;
        } else {
                /*
                 * The cc and S commands have a special feature -- leading
                 * <blank> characters are handled as autoindent characters.
                 * Beauty!
                 */
                if (LF_ISSET(TXT_AICHARS)) {
                        tp->offset = 0;
                        tp->ai = sp->cno;
                } else
                        tp->offset = sp->cno;
        }

        /* If getting a command buffer from the user, there may be a prompt. */
        if (LF_ISSET(TXT_PROMPT)) {
                tp->lb[sp->cno++] = prompt;
                ++tp->len;
                ++tp->offset;
        }

        /*
         * If appending after the end-of-line, add a space into the buffer
         * and move the cursor right.  This space is inserted, i.e. pushed
         * along, and then deleted when the line is resolved.  Assumes that
         * the cursor is already positioned at the end of the line.  This
         * avoids the nastiness of having the cursor reside on a magical
         * column, i.e. a column that doesn't really exist.  The only down
         * side is that we may wrap lines or scroll the screen before it's
         * strictly necessary.  Not a big deal.
         */
        if (LF_ISSET(TXT_APPENDEOL)) {
                tp->lb[sp->cno] = CURSOR_CH;
                ++tp->len;
                ++tp->insert;
        }

        /*
         * Historic practice is that the wrapmargin value was a distance
         * from the RIGHT-HAND column, not the left.  It's more useful to
         * us as a distance from the left-hand column.
         *
         * !!!
         * Replay commands are not affected by wrapmargin values.  What
         * I found surprising was that people actually depend on it, as
         * in this gem of a macro which centers lines:
         *
         *      map #c $mq81a ^V^[81^V|D`qld0:s/  / /g^V^M$p
         *
         * XXX
         * Setting margin causes a significant performance hit.  Normally
         * we don't update the screen if there are keys waiting, but we
         * have to if margin is set, otherwise the screen routines don't
         * know where the cursor is.
         */
        if (LF_ISSET(TXT_REPLAY) || !LF_ISSET(TXT_WRAPMARGIN))
                margin = 0;
        else if ((margin = O_VAL(sp, O_WRAPMARGIN)) != 0)
                margin = sp->cols - margin;

        /* Initialize abbreviations checks. */
        if (F_ISSET(gp, G_ABBREV) && LF_ISSET(TXT_MAPINPUT)) {
                abb = A_NOTSPACE;
                ab_cnt = ab_turnoff = 0;
        } else
                abb = A_NOTSET;

        /*
         * Set up the dot command.  Dot commands are done by saving the
         * actual characters and replaying the input.  We have to push
         * the characters onto the key stack and then handle them normally,
         * otherwise things like wrapmargin will fail.
         *
         * XXX
         * It would be nice if we could swallow backspaces and such, but
         * it's not all that easy to do.  Another possibility would be to
         * recognize full line insertions, which could be performed quickly,
         * without replay.
         */
nullreplay:
        rcol = 0;
        if (replay = LF_ISSET(TXT_REPLAY)) {
                /*
                 * !!!
                 * Historically, it wasn't an error to replay non-existent
                 * input.  This test is necessary, we get here by the user
                 * doing an input command followed by a nul.
                 *
                 * !!!
                 * Historically, vi did not remap or reabbreviate replayed
                 * input.  It did, however, beep at you if you changed an
                 * abbreviation and then replayed the input.  We're not that
                 * compatible.
                 */
                if (VIP(sp)->rep == NULL)
                        return (0);
                if (term_push(sp, VIP(sp)->rep, VIP(sp)->rep_cnt, 0, CH_NOMAP))
                        return (1);
                testnr = 0;
                abb = A_NOTSET;
                LF_CLR(TXT_RECORD);
        } else
                testnr = 1;

        iflags = LF_ISSET(TXT_MAPCOMMAND | TXT_MAPINPUT);
        for (gp, showmatch = 0,
            carat_st = C_NOTSET, hex = H_NOTSET, quoted = Q_NOTSET;;) {
                /*
                 * Reset the line and update the screen.  (The txt_showmatch()
                 * code refreshes the screen for us.)  Don't refresh unless
                 * we're about to wait on a character or we need to know where
                 * the cursor really is.
                 */
                if (showmatch || margin || !KEYS_WAITING(sp)) {
                        if (sp->s_change(sp, ep, tp->lno, LINE_RESET))
                                goto err;
                        if (showmatch) {
                                showmatch = 0;
                                txt_showmatch(sp, ep);
                        } else if (sp->s_refresh(sp, ep))
                                goto err;
                }

                /* Get the next character. */
next_ch:        if (term_key(sp, &ikey, iflags) != INP_OK)
                        goto err;
                ch = ikey.ch;

                /* Abbreviation check.  See comment in txt_abbrev(). */
#define MAX_ABBREVIATION_EXPANSION      256
                if (ikey.flags & CH_ABBREVIATED) {
                        if (++ab_cnt > MAX_ABBREVIATION_EXPANSION) {
                                term_ab_flush(sp,
                        "Abbreviation exceeded maximum number of characters");
                                ab_cnt = 0;
                                continue;
                        }
                } else
                        ab_cnt = 0;
                        
                /*
                 * !!!
                 * Historic feature.  If the first character of the input is
                 * a nul, replay the previous input.  This isn't documented
                 * anywhere, and is a great test of vi clones.
                 */
                if (ch == '\0' && testnr) {
                        LF_SET(TXT_REPLAY);
                        goto nullreplay;
                }
                testnr = 0;

                /*
                 * Check to see if the character fits into the input (and
                 * replay, if necessary) buffers.  It isn't necessary to
                 * have tp->len bytes, since it doesn't consider overwrite
                 * characters, but not worth fixing.
                 */
                if (LF_ISSET(TXT_RECORD)) {
                        TBINC(sp, VIP(sp)->rep, VIP(sp)->rep_len, rcol + 1);
                        VIP(sp)->rep[rcol++] = ch;
                }
                TBINC(sp, tp->lb, tp->lb_len, tp->len + 1);

                /*
                 * If the character was quoted, replace the last character
                 * (the literal mark) with the new character.  If quoted
                 * by someone else, simply insert the character.
                 *
                 * !!!
                 * Extension -- if the quoted character is HEX_CH, enter hex
                 * mode.  If the user enters "<HEX_CH>[isxdigit()]*" we will
                 * try to use the value as a character.  Anything else resets
                 * hex mode.
                 */
                if (ikey.flags & CH_QUOTED)
                        goto ins_ch;
                if (quoted == Q_THISCHAR) {
                        --sp->cno;
                        ++tp->owrite;
                        quoted = Q_NOTSET;

                        if (ch == HEX_CH)
                                hex = H_NEXTCHAR;
                        goto ins_ch;
                }

                switch (ikey.value) {
                case K_CR:
                case K_NL:                              /* New line. */
#define LINE_RESOLVE {                                                  \
                        /*                                              \
                         * Handle abbreviations.  If there was one,     \
                         * discard the replay characters.               \
                         */                                             \
                        if (abb == A_NOTSPACE && !replay) {             \
                                if (txt_abbrev(sp, tp, ch,              \
                                    LF_ISSET(TXT_INFOLINE), &tmp,       \
                                    &ab_turnoff))                       \
                                        goto err;                       \
                                if (tmp) {                              \
                                        if (LF_ISSET(TXT_RECORD))       \
                                                rcol -= tmp;            \
                                        goto next_ch;                   \
                                }                                       \
                        }                                               \
                        if (abb != A_NOTSET)                            \
                                abb = A_SPACE;                          \
                        /* Handle hex numbers. */                       \
                        if (hex == H_INHEX) {                           \
                                if (txt_hex(sp, tp, &tmp, ch))          \
                                        goto err;                       \
                                if (tmp) {                              \
                                        hex = H_NOTSET;                 \
                                        goto next_ch;                   \
                                }                                       \
                        }                                               \
                        /*                                              \
                         * The 'R' command returns any overwriteable    \
                         * characters in the first line to the original \
                         * characters.
                         */                                             \
                        if (LF_ISSET(TXT_REPLACE) && tp->owrite &&      \
                            tp == tiqh->cqh_first) {                    \
                                memmove(tp->lb + sp->cno,               \
                                    lp + sp->cno, tp->owrite);          \
                                tp->insert += tp->owrite;               \
                                tp->owrite = 0;                         \
                        }                                               \
                        /* Delete any appended cursor. */               \
                        if (LF_ISSET(TXT_APPENDEOL)) {                  \
                                --tp->len;                              \
                                --tp->insert;                           \
                        }                                               \
}
                        LINE_RESOLVE;

                        /* CR returns from the vi command line. */
                        if (LF_ISSET(TXT_CR)) {
                                /*
                                 * If a script window and not the colon
                                 * line, push a <cr> so it gets executed.
                                 */
                                if (F_ISSET(sp, S_SCRIPT) &&
                                    !LF_ISSET(TXT_INFOLINE))
                                        (void)term_push(sp,
                                            "\r", 1, 0, CH_NOMAP);
                                goto k_escape;
                        }

                        /*
                         * Historic practice was to delete any <blank>
                         * characters following the inserted newline.
                         * This affects the 'R', 'c', and 's' commands.
                         */
                        for (p = tp->lb + sp->cno + tp->owrite;
                            tp->insert && isblank(*p);
                            ++p, ++tp->owrite, --tp->insert);

                        /*
                         * Move any remaining insert characters into
                         * a new TEXT structure.
                         */
                        if ((ntp = text_init(sp,
                            tp->lb + sp->cno + tp->owrite,
                            tp->insert, tp->insert + 32)) == NULL)
                                goto err;
                        CIRCLEQ_INSERT_TAIL(tiqh, ntp, q);

                        /* Set bookkeeping for the new line. */
                        ntp->lno = tp->lno + 1;
                        ntp->insert = tp->insert;

                        /*
                         * Note if the user inserted any characters on this
                         * line.  Done before calling txt_ai_resolve() because
                         * it changes the value of sp->cno without making the
                         * corresponding changes to tp->ai.
                         */
                        tmp = sp->cno <= tp->ai;

                        /*
                         * Resolve autoindented characters for the old line.
                         * Reset the autoindent line value.  0^D keeps the ai
                         * line from changing, ^D changes the level, even if
                         * there are no characters in the old line.  Note,
                         * if using the current tp structure, use the cursor
                         * as the length, the user may have erased autoindent
                         * characters.
                         */
                        if (LF_ISSET(TXT_AUTOINDENT)) {
                                txt_ai_resolve(sp, tp);

                                if (carat_st == C_NOCHANGE) {
                                        if (txt_auto(sp, ep,
                                            OOBLNO, &ait, ait.ai, ntp))
                                                goto err;
                                        FREE_SPACE(sp, ait.lb, ait.lb_len);
                                } else
                                        if (txt_auto(sp, ep,
                                            OOBLNO, tp, sp->cno, ntp))
                                                goto err;
                                carat_st = C_NOTSET;
                        }

                        /*
                         * If the user hasn't entered any characters, delete
                         * any autoindent characters.
                         *
                         * !!!
                         * Historic vi didn't get the insert test right, if
                         * there were characters after the cursor, entering
                         * a <cr> left the autoindent characters on the line.
                         */
                        if (tmp)
                                sp->cno = 0;

                        /* Reset bookkeeping for the old line. */
                        tp->len = sp->cno;
                        tp->ai = tp->insert = tp->owrite = 0;

                        /* New cursor position. */
                        sp->cno = ntp->ai;

                        /* New lines are TXT_APPENDEOL if nothing to insert. */
                        if (ntp->insert == 0) {
                                TBINC(sp, tp->lb, tp->lb_len, tp->len + 1);
                                LF_SET(TXT_APPENDEOL);
                                ntp->lb[sp->cno] = CURSOR_CH;
                                ++ntp->insert;
                                ++ntp->len;
                        }

                        /* Update the old line. */
                        if (sp->s_change(sp, ep, tp->lno, LINE_RESET))
                                goto err;

                        /* Swap old and new TEXT's. */
                        tp = ntp;

                        /* Reset the cursor. */
                        sp->lno = tp->lno;

                        /* Update the new line. */
                        if (sp->s_change(sp, ep, tp->lno, LINE_INSERT))
                                goto err;

                        /* Set the renumber bit. */
                        F_SET(sp, S_RENUMBER);

                        /* Refresh if nothing waiting. */
                        if ((margin || !KEYS_WAITING(sp)) &&
                            sp->s_refresh(sp, ep))
                                goto err;
                        goto next_ch;
                case K_ESCAPE:                          /* Escape. */
                        if (!LF_ISSET(TXT_ESCAPE))
                                goto ins_ch;

                        LINE_RESOLVE;

                        /*
                         * If there aren't any trailing characters in the line
                         * and the user hasn't entered any characters, delete
                         * the autoindent characters.
                         */
                        if (!tp->insert && sp->cno <= tp->ai) {
                                tp->len = tp->owrite = 0;
                                sp->cno = 0;
                        } else if (LF_ISSET(TXT_AUTOINDENT))
                                txt_ai_resolve(sp, tp);

                        /* If there are insert characters, copy them down. */
k_escape:               if (tp->insert && tp->owrite)
                                memmove(tp->lb + sp->cno,
                                    tp->lb + sp->cno + tp->owrite, tp->insert);
                        tp->len -= tp->owrite;

                        /*
                         * Delete any lines that were inserted into the text
                         * structure and then erased.
                         */
                        while (tp->q.cqe_next != (void *)tiqh) {
                                ntp = tp->q.cqe_next;
                                CIRCLEQ_REMOVE(tiqh, ntp, q);
                                text_free(ntp);
                        }

                        /*
                         * If not resolving the lines into the file, end
                         * it with a nul.
                         *
                         * XXX
                         * This is wrong, should pass back a length.
                         */
                        if (LF_ISSET(TXT_RESOLVE)) {
                                if (txt_resolve(sp, ep, tiqh))
                                        goto err;
                                /*
                                 * Clear input flag -- input buffer no longer
                                 * valid.
                                 */
                                F_CLR(sp, S_INPUT);
                        } else {
                                TBINC(sp, tp->lb, tp->lb_len, tp->len + 1);
                                tp->lb[tp->len] = '\0';
                        }

                        /*
                         * Set the return cursor position to rest on the last
                         * inserted character.
                         */
                        if (rp != NULL) {
                                rp->lno = tp->lno;
                                rp->cno = sp->cno ? sp->cno - 1 : 0;
                                if (sp->s_change(sp, ep, rp->lno, LINE_RESET))
                                        goto err;
                        }
                        goto ret;
                case K_CARAT:                   /* Delete autoindent chars. */
                        if (LF_ISSET(TXT_AUTOINDENT) && sp->cno <= tp->ai)
                                carat_st = C_CARATSET;
                        goto ins_ch;
                case K_ZERO:                    /* Delete autoindent chars. */
                        if (LF_ISSET(TXT_AUTOINDENT) && sp->cno <= tp->ai)
                                carat_st = C_ZEROSET;
                        goto ins_ch;
                case K_VEOF:                    /* Delete autoindent char. */
                        /*
                         * If in the first column or no characters to erase,
                         * ignore the ^D (this matches historic practice).  If
                         * not doing autoindent or already inserted non-ai
                         * characters, it's a literal.  The latter test is done
                         * in the switch, as the CARAT forms are N + 1, not N.
                         */
                        if (!LF_ISSET(TXT_AUTOINDENT))
                                goto ins_ch;
                        if (sp->cno == 0 || tp->ai == 0)
                                break;
                        switch (carat_st) {
                        case C_CARATSET:        /* ^^D */
                                if (sp->cno > tp->ai + tp->offset + 1)
                                        goto ins_ch;

                                /* Save the ai string for later. */
                                ait.lb = NULL;
                                ait.lb_len = 0;
                                TBINC(sp, ait.lb, ait.lb_len, tp->ai);
                                memmove(ait.lb, tp->lb, tp->ai);
                                ait.ai = ait.len = tp->ai;

                                carat_st = C_NOCHANGE;
                                goto leftmargin;
                        case C_ZEROSET:         /* 0^D */
                                if (sp->cno > tp->ai + tp->offset + 1)
                                        goto ins_ch;
                                carat_st = C_NOTSET;
leftmargin:                     tp->lb[sp->cno - 1] = ' ';
                                tp->owrite += sp->cno - tp->offset;
                                tp->ai = 0;
                                sp->cno = tp->offset;
                                break;
                        case C_NOTSET:          /* ^D */
                                if (sp->cno > tp->ai + tp->offset)
                                        goto ins_ch;
                                (void)txt_outdent(sp, tp);
                                break;
                        default:
                                abort();
                        }
                        break;
                case K_VERASE:                  /* Erase the last character. */
                        /*
                         * If can erase over the prompt, return.  Len is 0
                         * if backspaced over the prompt, 1 if only CR entered.
                         */
                        if (LF_ISSET(TXT_BS) && sp->cno <= tp->offset) {
                                tp->len = 0;
                                goto ret;
                        }

                        /*
                         * If at the beginning of the line, try and drop back
                         * to a previously inserted line.
                         */
                        if (sp->cno == 0) {
                                if ((ntp = txt_backup(sp,
                                    ep, tiqh, tp, flags)) == NULL)
                                        goto err;
                                tp = ntp;
                                break;
                        }

                        /* If nothing to erase, bell the user. */
                        if (sp->cno <= tp->offset) {
                                msgq(sp, M_BERR,
                                    "No more characters to erase.");
                                break;
                        }

                        /* Drop back one character. */
                        --sp->cno;

                        /*
                         * Increment overwrite, decrement ai if deleted.
                         *
                         * !!!
                         * Historic vi did not permit users to use erase
                         * characters to delete autoindent characters.
                         */
                        ++tp->owrite;
                        if (sp->cno < tp->ai)
                                --tp->ai;
                        break;
                case K_VWERASE:                 /* Skip back one word. */
                        /*
                         * If at the beginning of the line, try and drop back
                         * to a previously inserted line.
                         */
                        if (sp->cno == 0) {
                                if ((ntp = txt_backup(sp,
                                    ep, tiqh, tp, flags)) == NULL)
                                        goto err;
                                tp = ntp;
                        }

                        /*
                         * If at offset, nothing to erase so bell the user.
                         */
                        if (sp->cno <= tp->offset) {
                                msgq(sp, M_BERR,
                                    "No more characters to erase.");
                                break;
                        }

                        /*
                         * First werase goes back to any autoindent
                         * and second werase goes back to the offset.
                         *
                         * !!!
                         * Historic vi did not permit users to use erase
                         * characters to delete autoindent characters.
                         */
                        if (tp->ai && sp->cno > tp->ai)
                                max = tp->ai;
                        else {
                                tp->ai = 0;
                                max = tp->offset;
                        }

                        /* Skip over trailing space characters. */
                        while (sp->cno > max && isblank(tp->lb[sp->cno - 1])) {
                                --sp->cno;
                                ++tp->owrite;
                        }
                        if (sp->cno == max)
                                break;
                        /*
                         * There are three types of word erase found on UNIX
                         * systems.  They can be identified by how the string
                         * /a/b/c is treated -- as 1, 3, or 6 words.  Historic
                         * vi had two classes of characters, and strings were
                         * delimited by them and <blank>'s, so, 6 words.  The
                         * historic tty interface used <blank>'s to delimit
                         * strings, so, 1 word.  The algorithm offered in the
                         * 4.4BSD tty interface (as stty altwerase) treats it
                         * as 3 words -- there are two classes of characters,
                         * and strings are delimited by them and <blank>'s.
                         * The difference is that the type of the first erased
                         * character erased is ignored, which is exactly right
                         * when erasing pathname components.  Here, the options
                         * TXT_ALTWERASE and TXT_TTYWERASE specify the 4.4BSD
                         * tty interface and the historic tty driver behavior,
                         * respectively, and the default is the same as the
                         * historic vi behavior.
                         */ 
                        if (LF_ISSET(TXT_TTYWERASE))
                                while (sp->cno > max) {
                                        --sp->cno;
                                        ++tp->owrite;
                                        if (isblank(tp->lb[sp->cno - 1]))
                                                break;
                                }
                        else {
                                if (LF_ISSET(TXT_ALTWERASE)) {
                                        --sp->cno;
                                        ++tp->owrite;
                                        if (isblank(tp->lb[sp->cno - 1]))
                                                break;
                                }
                                if (sp->cno > max)
                                        tmp = inword(tp->lb[sp->cno - 1]);
                                while (sp->cno > max) {
                                        --sp->cno;
                                        ++tp->owrite;
                                        if (tmp != inword(tp->lb[sp->cno - 1])
                                            || isblank(tp->lb[sp->cno - 1]))
                                                break;
                                }
                        }
                        break;
                case K_VKILL:                   /* Restart this line. */
                        /*
                         * If at the beginning of the line, try and drop back
                         * to a previously inserted line.
                         */
                        if (sp->cno == 0) {
                                if ((ntp = txt_backup(sp,
                                    ep, tiqh, tp, flags)) == NULL)
                                        goto err;
                                tp = ntp;
                        }

                        /* If at offset, nothing to erase so bell the user. */
                        if (sp->cno <= tp->offset) {
                                msgq(sp, M_BERR,
                                    "No more characters to erase.");
                                break;
                        }

                        /*
                         * First kill goes back to any autoindent
                         * and second kill goes back to the offset.
                         *
                         * !!!
                         * Historic vi did not permit users to use erase
                         * characters to delete autoindent characters.
                         */
                        if (tp->ai && sp->cno > tp->ai)
                                max = tp->ai;
                        else {
                                tp->ai = 0;
                                max = tp->offset;
                        }
                        tp->owrite += sp->cno - max;
                        sp->cno = max;
                        break;
                case K_CNTRLT:                  /* Add autoindent char. */
                        if (!LF_ISSET(TXT_CNTRLT))
                                goto ins_ch;
                        if (txt_indent(sp, tp))
                                goto err;
                        goto ebuf_chk;
                case K_CNTRLZ:
                        (void)sp->s_suspend(sp);
                        break;
#ifdef  HISTORIC_PRACTICE_IS_TO_INSERT_NOT_REPAINT
                case K_FORMFEED:
                        F_SET(sp, S_REFRESH);
                        break;
#endif
                case K_RIGHTBRACE:
                case K_RIGHTPAREN:
                        showmatch = LF_ISSET(TXT_SHOWMATCH);
                        goto ins_ch;
                case K_VLNEXT:                  /* Quote the next character. */
                        /* If in hex mode, see if we've entered a hex value. */
                        if (hex == H_INHEX) {
                                if (txt_hex(sp, tp, &tmp, ch))
                                        goto err;
                                if (tmp) {
                                        hex = H_NOTSET;
                                        goto next_ch;
                                }
                        }
                        ch = '^';
                        quoted = Q_NEXTCHAR;
                        /* FALLTHROUGH */
                default:                        /* Insert the character. */
ins_ch:                 /*
                         * If entering a space character after a word, check
                         * for abbreviations.  If there was one, discard the
                         * replay characters.
                         */
                        if (isblank(ch) && abb == A_NOTSPACE && !replay) {
                                if (txt_abbrev(sp, tp, ch,
                                    LF_ISSET(TXT_INFOLINE), &tmp, &ab_turnoff))
                                        goto err;
                                if (tmp) {
                                        if (LF_ISSET(TXT_RECORD))
                                                rcol -= tmp;
                                        goto next_ch;
                                }
                        }
                        /* If in hex mode, see if we've entered a hex value. */
                        if (hex == H_INHEX && !isxdigit(ch)) {
                                if (txt_hex(sp, tp, &tmp, ch))
                                        goto err;
                                if (tmp) {
                                        hex = H_NOTSET;
                                        goto next_ch;
                                }
                        }
                        /* Check to see if we've crossed the margin. */
                        if (margin) {
                                if (sp->s_column(sp, ep, &col))
                                        goto err;
                                if (col >= margin) {
                                        if (txt_margin(sp, tp, &tmp, ch))
                                                goto err;
                                        if (tmp)
                                                goto next_ch;
                                }
                        }
                        if (abb != A_NOTSET)
                                abb = isblank(ch) ? A_SPACE : A_NOTSPACE;

                        if (tp->owrite)         /* Overwrite a character. */
                                --tp->owrite;
                        else if (tp->insert) {  /* Insert a character. */
                                ++tp->len;
                                if (tp->insert == 1)
                                        tp->lb[sp->cno + 1] = tp->lb[sp->cno];
                                else
                                        memmove(tp->lb + sp->cno + 1,
                                            tp->lb + sp->cno, tp->insert);
                        }

                        tp->lb[sp->cno++] = ch;

                        /*
                         * If we've reached the end of the buffer, then we
                         * need to switch into insert mode.  This happens
                         * when there's a change to a mark and the user puts
                         * in more characters than the length of the motion.
                         */
ebuf_chk:               if (sp->cno >= tp->len) {
                                TBINC(sp, tp->lb, tp->lb_len, tp->len + 1);
                                LF_SET(TXT_APPENDEOL);
                                tp->lb[sp->cno] = CURSOR_CH;
                                ++tp->insert;
                                ++tp->len;
                        }

                        if (hex == H_NEXTCHAR)
                                hex = H_INHEX;
                        if (quoted == Q_NEXTCHAR)
                                quoted = Q_THISCHAR;
                        break;
                }
#if defined(DEBUG) && 1
                if (sp->cno + tp->insert + tp->owrite != tp->len)
                        msgq(sp, M_ERR,
                            "len %u != cno: %u ai: %u insert %u overwrite %u",
                            tp->len, sp->cno, tp->ai, tp->insert, tp->owrite);
                tp->len = sp->cno + tp->insert + tp->owrite;
#endif
        }

        /* Clear input flag. */
ret:    F_CLR(sp, S_INPUT);

        if (LF_ISSET(TXT_RECORD))
                VIP(sp)->rep_cnt = rcol;
        return (eval);

        /* Error jump. */
err:    eval = 1;
        txt_err(sp, ep, tiqh);
        goto ret;
}

/*
 * txt_abbrev --
 *      Handle abbreviations.
 */
static int
txt_abbrev(sp, tp, pushc, isinfoline, didsubp, turnoffp)
        SCR *sp;
        TEXT *tp;
        ARG_CHAR_T pushc;
        int isinfoline, *didsubp, *turnoffp;
{
        CHAR_T ch;
        SEQ *qp;
        size_t len, off;
        char *p;

        /* Find the beginning of this "word". */
        for (off = sp->cno - 1, p = tp->lb + off, len = 0;; --p, --off) {
                if (isblank(*p)) {
                        ++p;
                        break;
                }
                ++len;
                if (off == tp->ai || off == tp->offset)
                        break;
        }

        /*
         * !!!
         * Historic vi exploded abbreviations on the command line.  This has
         * obvious problems in that unabbreviating the string can be extremely
         * tricky, particularly if the string has, say, an embedded escape
         * character.  Personally, I think it's a stunningly bad idea.  Other
         * examples of problems this caused in historic vi are:
         *      :ab foo bar
         *      :ab foo baz
         * results in "bar" being abbreviated to "baz", which wasn't what the
         * user had in mind at all.  Also, the commands:
         *      :ab foo bar
         *      :unab foo<space>
         * resulted in an error message that "bar" wasn't mapped.  Finally,
         * since the string was already exploded by the time the unabbreviate
         * command got it, all it knew was that an abbreviation had occurred.
         * Cleverly, it checked the replacement string for its unabbreviation
         * match, which meant that the commands:
         *      :ab foo1 bar
         *      :ab foo2 bar
         *      :unab foo2
         * unabbreviates "foo1", and the commands:
         *      :ab foo bar
         *      :ab bar baz
         * unabbreviates "foo"!
         *
         * Anyway, people neglected to first ask my opinion before they wrote
         * macros that depend on this stuff, so, we make this work as follows.
         * When checking for an abbreviation on the command line, if we get a
         * string which is <blank> terminated and which starts at the beginning
         * of the line, we check to see it is the abbreviate or unabbreviate
         * commands.  If it is, turn abbreviations off and return as if no
         * abbreviation was found.  Note also, minor trickiness, so that if the
         * user erases the line and starts another command, we go ahead an turn
         * abbreviations back on.
         *
         * This makes the layering look like a Nachos Supreme.
         */
        *didsubp = 0;
        if (isinfoline)
                if (off == tp->ai || off == tp->offset)
                        if (ex_is_abbrev(p, len)) {
                                *turnoffp = 1;
                                return (0);
                        } else
                                *turnoffp = 0;
                else
                        if (*turnoffp)
                                return (0);

        /* Check for any abbreviations. */
        if ((qp = seq_find(sp, NULL, p, len, SEQ_ABBREV, NULL)) == NULL)
                return (0);

        /*
         * Push the abbreviation onto the tty stack.  Historically, characters
         * resulting from an abbreviation expansion were themselves subject to
         * map expansions, O_SHOWMATCH matching etc.  This means the expanded
         * characters will be re-tested for abbreviations.  It's difficult to
         * know what historic practice in this case was, since abbreviations
         * were applied to :colon command lines, so entering abbreviations that
         * looped was tricky, although possible.  In addition, obvious loops
         * didn't work as expected.  (The command ':ab a b|ab b c|ab c a' will
         * silently only implement and/or display the last abbreviation.)
         *
         * This implementation doesn't recover well from such abbreviations.
         * The main input loop counts abbreviated characters, and, when it
         * reaches a limit, discards any abbreviated characters on the queue.
         * It's difficult to back up to the original position, as the replay
         * queue would have to be adjusted, and the line state when an initial
         * abbreviated character was received would have to be saved.
         */
        ch = pushc;
        if (term_push(sp, &ch, 1, 0, CH_ABBREVIATED))
                return (1);
        if (term_push(sp, qp->output, qp->olen, 0, CH_ABBREVIATED))
                return (1);

        /*
         * Move the cursor to the start of the abbreviation,
         * adjust the length.
         */
        sp->cno -= len;
        tp->len -= len;

        /* Copy any insert characters back. */
        if (tp->insert)
                memmove(tp->lb + sp->cno + tp->owrite,
                    tp->lb + sp->cno + tp->owrite + len, tp->insert);

        /*
         * We return the length of the abbreviated characters.  This is so
         * the calling routine can replace the replay characters with the
         * abbreviation.  This means that subsequent '.' commands will produce
         * the same text, regardless of intervening :[un]abbreviate commands.
         * This is historic practice.
         */
        *didsubp = len;
        return (0);
}

/* Offset to next column of stop size. */
#define STOP_OFF(c, stop)       (stop - (c) % stop)

/*
 * txt_ai_resolve --
 *      When a line is resolved by <esc> or <cr>, review autoindent
 *      characters.
 */
static void
txt_ai_resolve(sp, tp)
        SCR *sp;
        TEXT *tp;
{
        u_long ts;
        int del;
        size_t cno, len, new, old, scno, spaces, tab_after_sp, tabs;
        char *p;

        /*
         * If the line is empty, has an offset, or no autoindent
         * characters, we're done.
         */
        if (!tp->len || tp->offset || !tp->ai)
                return;

        /*
         * The autoindent characters plus any leading <blank> characters
         * in the line are resolved into the minimum number of characters.
         * Historic practice.
         */
        ts = O_VAL(sp, O_TABSTOP);

        /* Figure out the last <blank> screen column. */
        for (p = tp->lb, scno = 0, len = tp->len,
            spaces = tab_after_sp = 0; len-- && isblank(*p); ++p)
                if (*p == '\t') {
                        if (spaces)
                                tab_after_sp = 1;
                        scno += STOP_OFF(scno, ts);
                } else {
                        ++spaces;
                        ++scno;
                }

        /*
         * If there are no spaces, or no tabs after spaces and less than
         * ts spaces, it's already minimal.
         */
        if (!spaces || !tab_after_sp && spaces < ts)
                return;

        /* Count up spaces/tabs needed to get to the target. */
        for (cno = 0, tabs = 0; cno + STOP_OFF(cno, ts) <= scno; ++tabs)
                cno += STOP_OFF(cno, ts);
        spaces = scno - cno;

        /*
         * Figure out how many characters we're dropping -- if we're not
         * dropping any, it's already minimal, we're done.
         */
        old = p - tp->lb;
        new = spaces + tabs;
        if (old == new)
                return;

        /* Shift the rest of the characters down, adjust the counts. */
        del = old - new;
        memmove(p - del, p, tp->len - old);
        sp->cno -= del;
        tp->len -= del;

        /* Fill in space/tab characters. */
        for (p = tp->lb; tabs--;)
                *p++ = '\t';
        while (spaces--)
                *p++ = ' ';
}

/*
 * txt_auto --
 *      Handle autoindent.  If aitp isn't NULL, use it, otherwise,
 *      retrieve the line.
 */
int
txt_auto(sp, ep, lno, aitp, len, tp)
        SCR *sp;
        EXF *ep;
        recno_t lno;
        size_t len;
        TEXT *aitp, *tp;
{
        size_t nlen;
        char *p, *t;
        
        if (aitp == NULL) {
                if ((p = t = file_gline(sp, ep, lno, &len)) == NULL)
                        return (0);
        } else
                p = t = aitp->lb;
        for (nlen = 0; len; ++p) {
                if (!isblank(*p))
                        break;
                /* If last character is a space, it counts. */
                if (--len == 0) {
                        ++p;
                        break;
                }
        }

        /* No indentation. */
        if (p == t)
                return (0);

        /* Set count. */
        nlen = p - t;

        /* Make sure the buffer's big enough. */
        BINC_RET(sp, tp->lb, tp->lb_len, tp->len + nlen);

        /* Copy the indentation into the new buffer. */
        memmove(tp->lb + nlen, tp->lb, tp->len);
        memmove(tp->lb, t, nlen);
        tp->len += nlen;

        /* Return the additional length. */
        tp->ai = nlen;
        return (0);
}

/*
 * txt_backup --
 *      Back up to the previously edited line.
 */
static TEXT *
txt_backup(sp, ep, tiqh, tp, flags)
        SCR *sp;
        EXF *ep;
        TEXTH *tiqh;
        TEXT *tp;
        u_int flags;
{
        TEXT *ntp;
        size_t col;

        if (tp->q.cqe_prev == (void *)tiqh) {
                msgq(sp, M_BERR, "Already at the beginning of the insert");
                return (tp);
        }

        /* Update the old line on the screen. */
        if (sp->s_change(sp, ep, tp->lno, LINE_DELETE))
                return (NULL);

        /* Get a handle on the previous TEXT structure. */
        ntp = tp->q.cqe_prev;

        /* Make sure that we can get enough space. */
        if (LF_ISSET(TXT_APPENDEOL) && ntp->len + 1 > ntp->lb_len &&
            binc(sp, &ntp->lb, &ntp->lb_len, ntp->len + 1))
                return (NULL);

        /*
         * Release current TEXT; now committed to the swap, nothing
         * better fail.
         */
        CIRCLEQ_REMOVE(tiqh, tp, q);
        text_free(tp);

        /* Swap TEXT's. */
        tp = ntp;

        /* Set bookkeeping information. */
        col = tp->len;
        if (LF_ISSET(TXT_APPENDEOL)) {
                tp->lb[col] = CURSOR_CH;
                ++tp->insert;
                ++tp->len;
        }
        sp->lno = tp->lno;
        sp->cno = col;
        return (tp);
}

/*
 * txt_err --
 *      Handle an error during input processing.
 */
static void
txt_err(sp, ep, tiqh)
        SCR *sp;
        EXF *ep;
        TEXTH *tiqh;
{
        recno_t lno;
        size_t len;

        /*
         * The problem with input processing is that the cursor is at an
         * indeterminate position since some input may have been lost due
         * to a malloc error.  So, try to go back to the place from which
         * the cursor started, knowing that it may no longer be available.
         *
         * We depend on at least one line number being set in the text
         * chain.
         */
        for (lno = tiqh->cqh_first->lno;
            file_gline(sp, ep, lno, &len) == NULL && lno > 0; --lno);

        sp->lno = lno == 0 ? 1 : lno;
        sp->cno = 0;

        /* Redraw the screen, just in case. */
        F_SET(sp, S_REDRAW);
}

/*
 * txt_hex --
 *      Let the user insert any character value they want.
 *
 * !!!
 * This is an extension.  The pattern "^Vx[0-9a-fA-F]*" is a way
 * for the user to specify a character value which their keyboard
 * may not be able to enter.
 */
static int
txt_hex(sp, tp, was_hex, pushc)
        SCR *sp;
        TEXT *tp;
        int *was_hex;
        ARG_CHAR_T pushc;
{
        CHAR_T ch, savec;
        size_t len, off;
        u_long value;
        char *p, *wp;

        /*
         * Null-terminate the string.  Since nul isn't a legal hex value,
         * this should be okay, and lets us use a local routine, which
         * presumably understands the character set, to convert the value.
         */
        savec = tp->lb[sp->cno];
        tp->lb[sp->cno] = 0;

        /* Find the previous HEX_CH. */
        for (off = sp->cno - 1, p = tp->lb + off, len = 0;; --p, --off) {
                if (*p == HEX_CH) {
                        wp = p + 1;
                        break;
                }
                ++len;
                /* If not on this line, there's nothing to do. */
                if (off == tp->ai || off == tp->offset)
                        goto nothex;
        }

        /* If no length, then it wasn't a hex value. */
        if (len == 0)
                goto nothex;

        /* Get the value. */
        value = strtol(wp, NULL, 16);
        if (value == LONG_MIN || value == LONG_MAX || value > MAX_CHAR_T) {
nothex:         tp->lb[sp->cno] = savec;
                *was_hex = 0;
                return (0);
        }
                
        ch = pushc;
        if (term_push(sp, &ch, 1, 0, CH_NOMAP | CH_QUOTED))
                return (1);
        ch = value;
        if (term_push(sp, &ch, 1, 0, CH_NOMAP | CH_QUOTED))
                return (1);

        tp->lb[sp->cno] = savec;

        /* Move the cursor to the start of the hex value, adjust the length. */
        sp->cno -= len + 1;
        tp->len -= len + 1;

        /* Copy any insert characters back. */
        if (tp->insert)
                memmove(tp->lb + sp->cno + tp->owrite,
                    tp->lb + sp->cno + tp->owrite + len + 1, tp->insert);

        *was_hex = 1;
        return (0);
}

/*
 * Txt_indent and txt_outdent are truly strange.  ^T and ^D do movements
 * to the next or previous shiftwidth value, i.e. for a 1-based numbering,
 * with shiftwidth=3, ^T moves a cursor on the 7th, 8th or 9th column to
 * the 10th column, and ^D moves it back.
 *
 * !!!
 * The ^T and ^D characters in historical vi only had special meaning when
 * they were the first characters typed after entering text input mode.
 * Since normal erase characters couldn't erase autoindent (in this case
 * ^T) characters, this meant that inserting text into previously existing
 * text was quite strange, ^T only worked if it was the first keystroke,
 * and then it could only be erased by using ^D.  This implementation treats
 * ^T specially anywhere it occurs in the input, and permits the standard
 * erase characters to erase characters inserted using it.
 *
 * XXX
 * Technically, txt_indent, txt_outdent should part of the screen interface,
 * as they require knowledge of the size of a space character on the screen.
 * (Not the size of tabs, because tabs are logically composed of spaces.)
 * They're left in the text code  because they're complicated, not to mention
 * the gruesome awareness that if spaces aren't a single column on the screen
 * for any language, we're into some serious, ah, for lack of a better word,
 * "issues".
 */

/*
 * txt_indent --
 *      Handle ^T indents.
 */
static int
txt_indent(sp, tp)
        SCR *sp;
        TEXT *tp;
{
        u_long sw, ts;
        size_t cno, off, scno, spaces, tabs;

        ts = O_VAL(sp, O_TABSTOP);
        sw = O_VAL(sp, O_SHIFTWIDTH);

        /* Get the current screen column. */
        for (off = scno = 0; off < sp->cno; ++off)
                if (tp->lb[off] == '\t')
                        scno += STOP_OFF(scno, ts);
                else
                        ++scno;

        /* Count up spaces/tabs needed to get to the target. */
        for (cno = scno, scno += STOP_OFF(scno, sw), tabs = 0;
            cno + STOP_OFF(cno, ts) <= scno; ++tabs)
                cno += STOP_OFF(cno, ts);
        spaces = scno - cno;

        /* Put space/tab characters in place of any overwrite characters. */
        for (; tp->owrite && tabs; --tp->owrite, --tabs, ++tp->ai)
                tp->lb[sp->cno++] = '\t';
        for (; tp->owrite && spaces; --tp->owrite, --spaces, ++tp->ai)
                tp->lb[sp->cno++] = ' ';

        if (!tabs && !spaces)
                return (0);

        /* Make sure there's enough room. */
        BINC_RET(sp, tp->lb, tp->lb_len, tp->len + spaces + tabs);

        /* Move the insert characters out of the way. */
        if (tp->insert)
                memmove(tp->lb + sp->cno + spaces + tabs,
                    tp->lb + sp->cno, tp->insert);

        /* Add new space/tab characters. */
        for (; tabs--; ++tp->len, ++tp->ai)
                tp->lb[sp->cno++] = '\t';
        for (; spaces--; ++tp->len, ++tp->ai)
                tp->lb[sp->cno++] = ' ';
        return (0);
}

/*
 * txt_outdent --
 *      Handle ^D outdents.
 *
 */
static int
txt_outdent(sp, tp)
        SCR *sp;
        TEXT *tp;
{
        u_long sw, ts;
        size_t cno, off, scno, spaces;

        ts = O_VAL(sp, O_TABSTOP);
        sw = O_VAL(sp, O_SHIFTWIDTH);

        /* Get the current screen column. */
        for (off = scno = 0; off < sp->cno; ++off)
                if (tp->lb[off] == '\t')
                        scno += STOP_OFF(scno, ts);
                else
                        ++scno;

        /* Get the previous shiftwidth column. */
        for (cno = scno; --scno % sw != 0;);

        /* Decrement characters until less than or equal to that slot. */
        for (; cno > scno; --sp->cno, --tp->ai, ++tp->owrite)
                if (tp->lb[--off] == '\t')
                        cno -= STOP_OFF(cno, ts);
                else
                        --cno;

        /* Spaces needed to get to the target. */
        spaces = scno - cno;

        /* Maybe just a delete. */
        if (spaces == 0)
                return (0);

        /* Make sure there's enough room. */
        BINC_RET(sp, tp->lb, tp->lb_len, tp->len + spaces);

        /* Use up any overwrite characters. */
        for (; tp->owrite && spaces; --spaces, ++tp->ai, --tp->owrite)
                tp->lb[sp->cno++] = ' ';

        /* Maybe that was enough. */
        if (spaces == 0)
                return (0);

        /* Move the insert characters out of the way. */
        if (tp->insert)
                memmove(tp->lb + sp->cno + spaces,
                    tp->lb + sp->cno, tp->insert);

        /* Add new space characters. */
        for (; spaces--; ++tp->len, ++tp->ai)
                tp->lb[sp->cno++] = ' ';
        return (0);
}

/*
 * txt_resolve --
 *      Resolve the input text chain into the file.
 */
static int
txt_resolve(sp, ep, tiqh)
        SCR *sp;
        EXF *ep;
        TEXTH *tiqh;
{
        TEXT *tp;
        recno_t lno;

        /* The first line replaces a current line. */
        tp = tiqh->cqh_first;
        if (file_sline(sp, ep, tp->lno, tp->lb, tp->len))
                return (1);

        /* All subsequent lines are appended into the file. */
        for (lno = tp->lno; (tp = tp->q.cqe_next) != (void *)&sp->tiq; ++lno)
                if (file_aline(sp, ep, 0, lno, tp->lb, tp->len))
                        return (1);
        return (0);
}

/*
 * txt_showmatch --
 *      Show a character match.
 *
 * !!!
 * Historic vi tried to display matches even in the :colon command line.
 * I think not.
 */
static void
txt_showmatch(sp, ep)
        SCR *sp;
        EXF *ep;
{
        struct timeval second;
        VCS cs;
        MARK m;
        fd_set zero;
        int cnt, endc, startc;

        /*
         * Do a refresh first, in case the v_ntext() code hasn't done
         * one in awhile, so the user can see what we're complaining
         * about.
         */
        if (sp->s_refresh(sp, ep))
                return;
        /*
         * We don't display the match if it's not on the screen.  Find
         * out what the first character on the screen is.
         */
        if (sp->s_position(sp, ep, &m, 0, P_TOP))
                return;

        /* Initialize the getc() interface. */
        cs.cs_lno = sp->lno;
        cs.cs_cno = sp->cno - 1;
        if (cs_init(sp, ep, &cs))
                return;
        startc = (endc = cs.cs_ch)  == ')' ? '(' : '{';

        /* Search for the match. */
        for (cnt = 1;;) {
                if (cs_prev(sp, ep, &cs))
                        return;
                if (cs.cs_lno < m.lno ||
                    cs.cs_lno == m.lno && cs.cs_cno < m.cno)
                        return;
                if (cs.cs_flags != 0) {
                        if (cs.cs_flags == CS_EOF || cs.cs_flags == CS_SOF) {
                                (void)sp->s_bell(sp);
                                return;
                        }
                        continue;
                }
                if (cs.cs_ch == endc)
                        ++cnt;
                else if (cs.cs_ch == startc && --cnt == 0)
                        break;
        }

        /* Move to the match. */
        m.lno = sp->lno;
        m.cno = sp->cno;
        sp->lno = cs.cs_lno;
        sp->cno = cs.cs_cno;
        (void)sp->s_refresh(sp, ep);

        /*
         * Sleep(3) is eight system calls.  Do it fast -- besides,
         * I don't want to wait an entire second.
         */
        FD_ZERO(&zero);
        second.tv_sec = O_VAL(sp, O_MATCHTIME) / 10;
        second.tv_usec = (O_VAL(sp, O_MATCHTIME) % 10) * 100000L;
        (void)select(0, &zero, &zero, &zero, &second);

        /* Return to the current location. */
        sp->lno = m.lno;
        sp->cno = m.cno;
        (void)sp->s_refresh(sp, ep);
}

/*
 * txt_margin --
 *      Handle margin wrap.
 *
 * !!!
 * Historic vi belled the user each time a character was entered after
 * crossing the margin until a space was entered which could be used to
 * break the line.  I don't, it tends to wake the cats.
 */
static int
txt_margin(sp, tp, didbreak, pushc)
        SCR *sp;
        TEXT *tp;
        int *didbreak;
        ARG_CHAR_T pushc;
{
        CHAR_T ch;
        size_t len, off, tlen;
        char *p, *wp;

        /* Find the closest previous blank. */
        for (off = sp->cno - 1, p = tp->lb + off, len = 0;; --p, --off) {
                if (isblank(*p)) {
                        wp = p + 1;
                        break;
                }
                ++len;
                /* If it's the beginning of the line, there's nothing to do. */
                if (off == tp->ai || off == tp->offset) {
                        *didbreak = 0;
                        return (0);
                }
        }

        /*
         * Historic practice is to delete any trailing whitespace
         * from the previous line.
         */
        for (tlen = len;; --p, --off) {
                if (!isblank(*p))
                        break;
                ++tlen;
                if (off == tp->ai || off == tp->offset)
                        break;
        }

        ch = pushc;
        if (term_push(sp, &ch, 1, 0, CH_NOMAP | CH_QUOTED))
                return (1);
        if (len && term_push(sp, wp, len, 0, CH_NOMAP | CH_QUOTED))
                return (1);
        ch = '\n';
        if (term_push(sp, &ch, 1, 0, CH_NOMAP))
                return (1);

        sp->cno -= tlen;
        tp->owrite += tlen;
        *didbreak = 1;
        return (0);
}