/*
 * Copyright (C) 1984-2012  Mark Nudelman
 * Modified for use with illumos by Garrett D'Amore.
 * Copyright 2014 Garrett D'Amore <garrett@damore.org>
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information, see the README file.
 */

/*
 * Routines to manipulate the "line buffer".
 * The line buffer holds a line of output as it is being built
 * in preparation for output to the screen.
 */

#include <wchar.h>
#include <wctype.h>

#include "charset.h"
#include "less.h"

static char *linebuf = NULL;    /* Buffer which holds the current output line */
static char *attr = NULL;       /* Extension of linebuf to hold attributes */
int size_linebuf = 0;           /* Size of line buffer (and attr buffer) */

static int cshift;              /* Current left-shift of output line buffer */
int hshift;                     /* Desired left-shift of output line buffer */
int tabstops[TABSTOP_MAX] = { 0 }; /* Custom tabstops */
int ntabstops = 1;              /* Number of tabstops */
int tabdefault = 8;             /* Default repeated tabstops */
off_t highest_hilite;           /* Pos of last hilite in file found so far */

static int curr;                /* Total number of bytes in linebuf */
static int column;              /* Display columns needed to show linebuf */
static int overstrike;          /* Next char should overstrike previous char */
static int is_null_line;        /* There is no current line */
static int lmargin;             /* Index in linebuf of start of content */
static char pendc;
static off_t pendpos;
static char *end_ansi_chars;
static char *mid_ansi_chars;

static int attr_swidth(int);
static int attr_ewidth(int);
static int do_append(LWCHAR, char *, off_t);

extern int bs_mode;
extern int linenums;
extern int ctldisp;
extern int twiddle;
extern int binattr;
extern int status_col;
extern int auto_wrap, ignaw;
extern int bo_s_width, bo_e_width;
extern int ul_s_width, ul_e_width;
extern int bl_s_width, bl_e_width;
extern int so_s_width, so_e_width;
extern int sc_width, sc_height;
extern int utf_mode;
extern off_t start_attnpos;
extern off_t end_attnpos;

static char mbc_buf[MAX_UTF_CHAR_LEN];
static int mbc_buf_index = 0;
static off_t mbc_pos;

/*
 * Initialize from environment variables.
 */
void
init_line(void)
{
        end_ansi_chars = lgetenv("LESSANSIENDCHARS");
        if (end_ansi_chars == NULL || *end_ansi_chars == '\0')
                end_ansi_chars = "m";

        mid_ansi_chars = lgetenv("LESSANSIMIDCHARS");
        if (mid_ansi_chars == NULL || *mid_ansi_chars == '\0')
                mid_ansi_chars = "0123456789;[?!\"'#%()*+ ";

        linebuf = ecalloc(LINEBUF_SIZE, sizeof (char));
        attr = ecalloc(LINEBUF_SIZE, sizeof (char));
        size_linebuf = LINEBUF_SIZE;
}

/*
 * Expand the line buffer.
 */
static int
expand_linebuf(void)
{
        /* Double the size of the line buffer. */
        int new_size = size_linebuf * 2;

        /* Just realloc to expand the buffer, if we can. */
        char *new_buf = recallocarray(linebuf, size_linebuf, new_size, 1);
        if (new_buf != NULL) {
                char *new_attr = recallocarray(attr, size_linebuf, new_size, 1);
                linebuf = new_buf;
                if (new_attr != NULL) {
                        attr = new_attr;
                        size_linebuf = new_size;
                        return (0);
                }
        }
        return (1);
}

/*
 * Is a character ASCII?
 */
static int
is_ascii_char(LWCHAR ch)
{
        return (ch <= 0x7F);
}

/*
 * Rewind the line buffer.
 */
void
prewind(void)
{
        curr = 0;
        column = 0;
        cshift = 0;
        overstrike = 0;
        is_null_line = 0;
        pendc = '\0';
        lmargin = 0;
        if (status_col)
                lmargin += 1;
}

/*
 * Insert the line number (of the given position) into the line buffer.
 */
void
plinenum(off_t pos)
{
        off_t linenum = 0;
        int i;

        if (linenums == OPT_ONPLUS) {
                /*
                 * Get the line number and put it in the current line.
                 * {{ Note: since find_linenum calls forw_raw_line,
                 *    it may seek in the input file, requiring the caller
                 *    of plinenum to re-seek if necessary. }}
                 * {{ Since forw_raw_line modifies linebuf, we must
                 *    do this first, before storing anything in linebuf. }}
                 */
                linenum = find_linenum(pos);
        }

        /*
         * Display a status column if the -J option is set.
         */
        if (status_col) {
                linebuf[curr] = ' ';
                if (start_attnpos != -1 &&
                    pos >= start_attnpos && pos < end_attnpos)
                        attr[curr] = AT_NORMAL|AT_HILITE;
                else
                        attr[curr] = AT_NORMAL;
                curr++;
                column++;
        }
        /*
         * Display the line number at the start of each line
         * if the -N option is set.
         */
        if (linenums == OPT_ONPLUS) {
                char buf[23];
                int n;

                postoa(linenum, buf, sizeof(buf));
                n = strlen(buf);
                if (n < MIN_LINENUM_WIDTH)
                        n = MIN_LINENUM_WIDTH;
                snprintf(linebuf+curr, size_linebuf-curr, "%*s ", n, buf);
                n++;    /* One space after the line number. */
                for (i = 0; i < n; i++)
                        attr[curr+i] = AT_NORMAL;
                curr += n;
                column += n;
                lmargin += n;
        }

        /*
         * Append enough spaces to bring us to the lmargin.
         */
        while (column < lmargin) {
                linebuf[curr] = ' ';
                attr[curr++] = AT_NORMAL;
                column++;
        }
}

/*
 * Shift the input line left.
 * Starting at lmargin, some bytes are discarded from the linebuf,
 * until the number of display columns needed to show these bytes
 * would exceed the argument.
 */
static void
pshift(int shift)
{
        int shifted = 0;  /* Number of display columns already discarded. */
        int from;         /* Index in linebuf of the current character. */
        int to;           /* Index in linebuf to move this character to. */
        int len;          /* Number of bytes in this character. */
        int width = 0;    /* Display columns needed for this character. */
        int prev_attr;    /* Attributes of the preceding character. */
        int next_attr;    /* Attributes of the following character. */
        unsigned char c;  /* First byte of current character. */

        if (shift > column - lmargin)
                shift = column - lmargin;
        if (shift > curr - lmargin)
                shift = curr - lmargin;

        to = from = lmargin;
        /*
         * We keep on going when shifted == shift
         * to get all combining chars.
         */
        while (shifted <= shift && from < curr) {
                c = linebuf[from];
                if (ctldisp == OPT_ONPLUS && c == ESC) {
                        /* Keep cumulative effect.  */
                        linebuf[to] = c;
                        attr[to++] = attr[from++];
                        while (from < curr && linebuf[from]) {
                                linebuf[to] = linebuf[from];
                                attr[to++] = attr[from];
                                if (!is_ansi_middle(linebuf[from++]))
                                        break;
                        }
                        continue;
                }
                if (utf_mode && !isascii(c)) {
                        wchar_t ch;
                        /*
                         * Before this point, UTF-8 validity was already
                         * checked, but for additional safety, treat
                         * invalid bytes as single-width characters
                         * if they ever make it here.  Similarly, treat
                         * non-printable characters as width 1.
                         */
                        len = mbtowc(&ch, linebuf + from, curr - from);
                        if (len == -1)
                                len = width = 1;
                        else if ((width = wcwidth(ch)) == -1)
                                width = 1;
                } else {
                        len = 1;
                        if (c == '\b')
                                /* XXX - Incorrect if several '\b' in a row.  */
                                width = width > 0 ? -width : -1;
                        else
                                width = iscntrl(c) ? 0 : 1;
                }

                if (width == 2 && shift - shifted == 1) {
                        /*
                         * Move the first half of a double-width character
                         * off screen.  Print a space instead of the second
                         * half.  This should never happen when called
                         * by pshift_all().
                         */
                        attr[to] = attr[from];
                        linebuf[to++] = ' ';
                        from += len;
                        shifted++;
                        break;
                }

                /* Adjust width for magic cookies. */
                prev_attr = (to > 0) ? attr[to-1] : AT_NORMAL;
                next_attr = (from + len < curr) ? attr[from + len] : prev_attr;
                if (!is_at_equiv(attr[from], prev_attr) &&
                    !is_at_equiv(attr[from], next_attr)) {
                        width += attr_swidth(attr[from]);
                        if (from + len < curr)
                                width += attr_ewidth(attr[from]);
                        if (is_at_equiv(prev_attr, next_attr)) {
                                width += attr_ewidth(prev_attr);
                                if (from + len < curr)
                                        width += attr_swidth(next_attr);
                        }
                }

                if (shift - shifted < width)
                        break;
                from += len;
                shifted += width;
                if (shifted < 0)
                        shifted = 0;
        }
        while (from < curr) {
                linebuf[to] = linebuf[from];
                attr[to++] = attr[from++];
        }
        curr = to;
        column -= shifted;
        cshift += shifted;
}

/*
 *
 */
void
pshift_all(void)
{
        pshift(column);
}

/*
 * Return the printing width of the start (enter) sequence
 * for a given character attribute.
 */
static int
attr_swidth(int a)
{
        int w = 0;

        a = apply_at_specials(a);

        if (a & AT_UNDERLINE)
                w += ul_s_width;
        if (a & AT_BOLD)
                w += bo_s_width;
        if (a & AT_BLINK)
                w += bl_s_width;
        if (a & AT_STANDOUT)
                w += so_s_width;

        return (w);
}

/*
 * Return the printing width of the end (exit) sequence
 * for a given character attribute.
 */
static int
attr_ewidth(int a)
{
        int w = 0;

        a = apply_at_specials(a);

        if (a & AT_UNDERLINE)
                w += ul_e_width;
        if (a & AT_BOLD)
                w += bo_e_width;
        if (a & AT_BLINK)
                w += bl_e_width;
        if (a & AT_STANDOUT)
                w += so_e_width;

        return (w);
}

/*
 * Return the printing width of a given character and attribute,
 * if the character were added to the current position in the line buffer.
 * Adding a character with a given attribute may cause an enter or exit
 * attribute sequence to be inserted, so this must be taken into account.
 */
static int
pwidth(wchar_t ch, int a, wchar_t prev_ch)
{
        int w;

        /*
         * In case of a backspace, back up by the width of the previous
         * character.  If that is non-printable (for example another
         * backspace) or zero width (for example a combining accent),
         * the terminal may actually back up to a character even further
         * back, but we no longer know how wide that may have been.
         * The best guess possible at this point is that it was
         * hopefully width one.
         */
        if (ch == L'\b') {
                w = wcwidth(prev_ch);
                if (w <= 0)
                        w = 1;
                return (-w);
        }

        w = wcwidth(ch);

        /*
         * Non-printable characters can get here if the -r flag is in
         * effect, and possibly in some other situations (XXX check that!).
         * Treat them as zero width.
         * That may not always match their actual behaviour,
         * but there is no reasonable way to be more exact.
         */
        if (w == -1)
                w = 0;

        /*
         * Combining accents take up no space.
         * Some terminals, upon failure to compose them with the
         * characters that precede them, will actually take up one column
         * for the combining accent; there isn't much we could do short
         * of testing the (complex) composition process ourselves and
         * printing a binary representation when it fails.
         */
        if (w == 0)
                return (0);

        /*
         * Other characters take one or two columns,
         * plus the width of any attribute enter/exit sequence.
         */
        if (curr > 0 && !is_at_equiv(attr[curr-1], a))
                w += attr_ewidth(attr[curr-1]);
        if ((apply_at_specials(a) != AT_NORMAL) &&
            (curr == 0 || !is_at_equiv(attr[curr-1], a)))
                w += attr_swidth(a);
        return (w);
}

/*
 * Delete to the previous base character in the line buffer.
 * Return 1 if one is found.
 */
static int
backc(void)
{
        wchar_t  ch, prev_ch;
        int      len, width;

        if ((len = mbtowc_left(&ch, linebuf + curr, curr)) <= 0)
                return (0);
        curr -= len;

        /* This assumes that there is no '\b' in linebuf.  */
        while (curr >= lmargin && column > lmargin &&
            !(attr[curr] & (AT_ANSI|AT_BINARY))) {
                if ((len = mbtowc_left(&prev_ch, linebuf + curr, curr)) <= 0)
                        prev_ch = L'\0';
                width = pwidth(ch, attr[curr], prev_ch);
                column -= width;
                if (width > 0)
                        return (1);
                curr -= len;
                if (prev_ch == L'\0')
                        return (0);
                ch = prev_ch;
        }
        return (0);
}

/*
 * Is a character the end of an ANSI escape sequence?
 */
static int
is_ansi_end(LWCHAR ch)
{
        if (!is_ascii_char(ch))
                return (0);
        return (strchr(end_ansi_chars, (char)ch) != NULL);
}

/*
 *
 */
int
is_ansi_middle(LWCHAR ch)
{
        if (!is_ascii_char(ch))
                return (0);
        if (is_ansi_end(ch))
                return (0);
        return (strchr(mid_ansi_chars, (char)ch) != NULL);
}

/*
 * Append a character and attribute to the line buffer.
 */
static int
store_char(LWCHAR ch, char a, char *rep, off_t pos)
{
        int i;
        int w;
        int replen;
        char cs;
        int matches;

        if (is_hilited(pos, pos+1, 0, &matches)) {
                /*
                 * This character should be highlighted.
                 * Override the attribute passed in.
                 */
                if (a != AT_ANSI) {
                        if (highest_hilite != -1 && pos > highest_hilite)
                                highest_hilite = pos;
                        a |= AT_HILITE;
                }
        }

        w = -1;
        if (ctldisp == OPT_ONPLUS) {
                /*
                 * Set i to the beginning of an ANSI escape sequence
                 * that was begun and not yet ended, or to -1 otherwise.
                 */
                for (i = curr - 1; i >= 0; i--) {
                        if (linebuf[i] == ESC)
                                break;
                        if (!is_ansi_middle(linebuf[i]))
                                i = 0;
                }
                if (i >= 0 && !is_ansi_end(ch) && !is_ansi_middle(ch)) {
                        /* Remove whole unrecognized sequence.  */
                        curr = i;
                        return (0);
                }
                if (i >= 0 || ch == ESC) {
                        a = AT_ANSI;  /* Will force re-AT_'ing around it. */
                        w = 0;
                }
        }
        if (w == -1) {
                wchar_t prev_ch;
                if (mbtowc_left(&prev_ch, linebuf + curr, curr) <= 0)
                        prev_ch = L' ';
                w = pwidth(ch, a, prev_ch);
        }

        if (ctldisp != OPT_ON && column + w + attr_ewidth(a) > sc_width)
                /*
                 * Won't fit on screen.
                 */
                return (1);

        if (rep == NULL) {
                cs = (char)ch;
                rep = &cs;
                replen = 1;
        } else {
                replen = utf_len(rep[0]);
        }
        if (curr + replen >= size_linebuf-6) {
                /*
                 * Won't fit in line buffer.
                 * Try to expand it.
                 */
                if (expand_linebuf())
                        return (1);
        }

        while (replen-- > 0) {
                linebuf[curr] = *rep++;
                attr[curr] = a;
                curr++;
        }
        column += w;
        return (0);
}

/*
 * Append a tab to the line buffer.
 * Store spaces to represent the tab.
 */
static int
store_tab(int attr, off_t pos)
{
        int to_tab = column + cshift - lmargin;
        int i;

        if (ntabstops < 2 || to_tab >= tabstops[ntabstops-1])
                to_tab = tabdefault -
                    ((to_tab - tabstops[ntabstops-1]) % tabdefault);
        else {
                for (i = ntabstops - 2; i >= 0; i--)
                        if (to_tab >= tabstops[i])
                                break;
                to_tab = tabstops[i+1] - to_tab;
        }

        if (column + to_tab - 1 + pwidth(' ', attr, 0) +
            attr_ewidth(attr) > sc_width)
                return (1);

        do {
                if (store_char(' ', attr, " ", pos))
                        return (1);
        } while (--to_tab > 0);
        return (0);
}

static int
store_prchar(char c, off_t pos)
{
        char *s;

        /*
         * Convert to printable representation.
         */
        s = prchar(c);

        /*
         * Make sure we can get the entire representation
         * of the character on this line.
         */
        if (column + (int)strlen(s) - 1 +
            pwidth(' ', binattr, 0) + attr_ewidth(binattr) > sc_width)
                return (1);

        for (; *s != 0; s++) {
                if (store_char(*s, AT_BINARY, NULL, pos))
                        return (1);
        }
        return (0);
}

static int
flush_mbc_buf(off_t pos)
{
        int i;

        for (i = 0; i < mbc_buf_index; i++) {
                if (store_prchar(mbc_buf[i], pos))
                        return (mbc_buf_index - i);
        }
        return (0);
}

/*
 * Append a character to the line buffer.
 * Expand tabs into spaces, handle underlining, boldfacing, etc.
 * Returns 0 if ok, 1 if couldn't fit in buffer.
 */
int
pappend(char c, off_t pos)
{
        mbstate_t mbs;
        size_t sz;
        wchar_t ch;
        int r;

        if (pendc) {
                if (do_append(pendc, NULL, pendpos))
                        /*
                         * Oops.  We've probably lost the char which
                         * was in pendc, since caller won't back up.
                         */
                        return (1);
                pendc = '\0';
        }

        if (c == '\r' && bs_mode == BS_SPECIAL) {
                if (mbc_buf_index > 0)  /* utf_mode must be on. */ {
                        /* Flush incomplete (truncated) sequence. */
                        r = flush_mbc_buf(mbc_pos);
                        mbc_buf_index = 0;
                        if (r)
                                return (r + 1);
                }

                /*
                 * Don't put the CR into the buffer until we see
                 * the next char.  If the next char is a newline,
                 * discard the CR.
                 */
                pendc = c;
                pendpos = pos;
                return (0);
        }

        if (!utf_mode) {
                r = do_append((LWCHAR) c, NULL, pos);
        } else {
                for (;;) {
                        if (mbc_buf_index == 0)
                                mbc_pos = pos;
                        mbc_buf[mbc_buf_index++] = c;
                        memset(&mbs, 0, sizeof(mbs));
                        sz = mbrtowc(&ch, mbc_buf, mbc_buf_index, &mbs);

                        /* Incomplete UTF-8: wait for more bytes. */
                        if (sz == (size_t)-2)
                                return (0);

                        /* Valid UTF-8: use the character. */
                        if (sz != (size_t)-1) {
                                r = do_append(ch, mbc_buf, mbc_pos) ?
                                    mbc_buf_index : 0;
                                break;
                        }

                        /* Invalid start byte: encode it. */
                        if (mbc_buf_index == 1) {
                                r = store_prchar(c, pos);
                                break;
                        }

                        /*
                         * Invalid continuation.
                         * Encode the preceding bytes.
                         * If they fit, handle the interrupting byte.
                         * Otherwise, tell the caller to back up
                         * by the  number of bytes that do not fit,
                         * plus one for the new byte.
                         */
                        mbc_buf_index--;
                        if ((r = flush_mbc_buf(mbc_pos) + 1) == 1)
                                mbc_buf_index = 0;
                        else
                                break;
                }
        }

        /*
         * If we need to shift the line, do it.
         * But wait until we get to at least the middle of the screen,
         * so shifting it doesn't affect the chars we're currently
         * pappending.  (Bold & underline can get messed up otherwise.)
         */
        if (cshift < hshift && column > sc_width / 2) {
                linebuf[curr] = '\0';
                pshift(hshift - cshift);
        }
        mbc_buf_index = 0;
        return (r);
}

static int
do_append(LWCHAR ch, char *rep, off_t pos)
{
        wchar_t prev_ch;
        int a;

        a = AT_NORMAL;

        if (ch == '\b') {
                if (bs_mode == BS_CONTROL)
                        goto do_control_char;

                /*
                 * A better test is needed here so we don't
                 * backspace over part of the printed
                 * representation of a binary character.
                 */
                if (curr <= lmargin ||
                    column <= lmargin ||
                    (attr[curr - 1] & (AT_ANSI|AT_BINARY))) {
                        if (store_prchar('\b', pos))
                                return (1);
                } else if (bs_mode == BS_NORMAL) {
                        if (store_char(ch, AT_NORMAL, NULL, pos))
                                return (1);
                } else if (bs_mode == BS_SPECIAL) {
                        overstrike = backc();
                }

                return (0);
        }

        if (overstrike > 0) {
                /*
                 * Overstrike the character at the current position
                 * in the line buffer.  This will cause either
                 * underline (if a "_" is overstruck),
                 * bold (if an identical character is overstruck),
                 * or just deletion of the character in the buffer.
                 */
                overstrike = utf_mode ? -1 : 0;
                /* To be correct, this must be a base character.  */
                if (mbtowc(&prev_ch, linebuf + curr, MB_CUR_MAX) == -1) {
                        (void)mbtowc(NULL, NULL, MB_CUR_MAX);
                        prev_ch = L'\0';
                }
                a = attr[curr];
                if (ch == prev_ch) {
                        /*
                         * Overstriking a char with itself means make it bold.
                         * But overstriking an underscore with itself is
                         * ambiguous.  It could mean make it bold, or
                         * it could mean make it underlined.
                         * Use the previous overstrike to resolve it.
                         */
                        if (ch == '_') {
                                if ((a & (AT_BOLD|AT_UNDERLINE)) != AT_NORMAL)
                                        a |= (AT_BOLD|AT_UNDERLINE);
                                else if (curr > 0 && attr[curr - 1] & AT_UNDERLINE)
                                        a |= AT_UNDERLINE;
                                else if (curr > 0 && attr[curr - 1] & AT_BOLD)
                                        a |= AT_BOLD;
                                else
                                        a |= AT_INDET;
                        } else {
                                a |= AT_BOLD;
                        }
                } else if (ch == '_' && prev_ch != L'\0') {
                        a |= AT_UNDERLINE;
                        ch = prev_ch;
                        rep = linebuf + curr;
                } else if (prev_ch == '_') {
                        a |= AT_UNDERLINE;
                }
                /* Else we replace prev_ch, but we keep its attributes.  */
        } else if (overstrike < 0) {
                if (wcwidth(ch) == 0) {
                        /* Continuation of the same overstrike.  */
                        if (curr > 0)
                                a = attr[curr - 1] & (AT_UNDERLINE | AT_BOLD);
                        else
                                a = AT_NORMAL;
                } else
                        overstrike = 0;
        }

        if (ch == '\t') {
                /*
                 * Expand a tab into spaces.
                 */
                switch (bs_mode) {
                case BS_CONTROL:
                        goto do_control_char;
                case BS_NORMAL:
                case BS_SPECIAL:
                        if (store_tab(a, pos))
                                return (1);
                        break;
                }
        } else if ((!utf_mode || is_ascii_char(ch)) &&
            !isprint((unsigned char)ch)) {
do_control_char:
                if (ctldisp == OPT_ON ||
                    (ctldisp == OPT_ONPLUS && ch == ESC)) {
                        /*
                         * Output as a normal character.
                         */
                        if (store_char(ch, AT_NORMAL, rep, pos))
                                return (1);
                } else {
                        if (store_prchar(ch, pos))
                                return (1);
                }
        } else if (utf_mode && ctldisp != OPT_ON && !iswprint(ch)) {
                char *s;

                s = prutfchar(ch);

                if (column + (int)strlen(s) - 1 +
                    pwidth(' ', binattr, 0) + attr_ewidth(binattr) > sc_width)
                        return (1);

                for (; *s != 0; s++) {
                        if (store_char(*s, AT_BINARY, NULL, pos))
                                return (1);
                }
        } else {
                if (store_char(ch, a, rep, pos))
                        return (1);
        }
        return (0);
}

/*
 *
 */
int
pflushmbc(void)
{
        int r = 0;

        if (mbc_buf_index > 0) {
                /* Flush incomplete (truncated) sequence.  */
                r = flush_mbc_buf(mbc_pos);
                mbc_buf_index = 0;
        }
        return (r);
}

/*
 * Terminate the line in the line buffer.
 */
void
pdone(int endline, int forw)
{
        int i;

        (void) pflushmbc();

        if (pendc && (pendc != '\r' || !endline))
                /*
                 * If we had a pending character, put it in the buffer.
                 * But discard a pending CR if we are at end of line
                 * (that is, discard the CR in a CR/LF sequence).
                 */
                (void) do_append(pendc, NULL, pendpos);

        for (i = curr - 1; i >= 0; i--) {
                if (attr[i] & AT_INDET) {
                        attr[i] &= ~AT_INDET;
                        if (i < curr - 1 && attr[i + 1] & AT_BOLD)
                                attr[i] |= AT_BOLD;
                        else
                                attr[i] |= AT_UNDERLINE;
                }
        }

        /*
         * Make sure we've shifted the line, if we need to.
         */
        if (cshift < hshift)
                pshift(hshift - cshift);

        if (ctldisp == OPT_ONPLUS && is_ansi_end('m')) {
                /* Switch to normal attribute at end of line. */
                char *p = "\033[m";
                for (; *p != '\0'; p++) {
                        linebuf[curr] = *p;
                        attr[curr++] = AT_ANSI;
                }
        }

        /*
         * Add a newline if necessary,
         * and append a '\0' to the end of the line.
         * We output a newline if we're not at the right edge of the screen,
         * or if the terminal doesn't auto wrap,
         * or if this is really the end of the line AND the terminal ignores
         * a newline at the right edge.
         * (In the last case we don't want to output a newline if the terminal
         * doesn't ignore it since that would produce an extra blank line.
         * But we do want to output a newline if the terminal ignores it in case
         * the next line is blank.  In that case the single newline output for
         * that blank line would be ignored!)
         */
        if (column < sc_width || !auto_wrap || (endline && ignaw) ||
            ctldisp == OPT_ON) {
                linebuf[curr] = '\n';
                attr[curr] = AT_NORMAL;
                curr++;
        } else if (ignaw && column >= sc_width && forw) {
                /*
                 * Terminals with "ignaw" don't wrap until they *really* need
                 * to, i.e. when the character *after* the last one to fit on a
                 * line is output. But they are too hard to deal with when they
                 * get in the state where a full screen width of characters
                 * have been output but the cursor is sitting on the right edge
                 * instead of at the start of the next line.
                 * So we nudge them into wrapping by outputting a space
                 * character plus a backspace.  But do this only if moving
                 * forward; if we're moving backward and drawing this line at
                 * the top of the screen, the space would overwrite the first
                 * char on the next line.  We don't need to do this "nudge"
                 * at the top of the screen anyway.
                 */
                linebuf[curr] = ' ';
                attr[curr++] = AT_NORMAL;
                linebuf[curr] = '\b';
                attr[curr++] = AT_NORMAL;
        }
        linebuf[curr] = '\0';
        attr[curr] = AT_NORMAL;
}

/*
 *
 */
void
set_status_col(char c)
{
        linebuf[0] = c;
        attr[0] = AT_NORMAL|AT_HILITE;
}

/*
 * Get a character from the current line.
 * Return the character as the function return value,
 * and the character attribute in *ap.
 */
int
gline(int i, int *ap)
{
        if (is_null_line) {
                /*
                 * If there is no current line, we pretend the line is
                 * either "~" or "", depending on the "twiddle" flag.
                 */
                if (twiddle) {
                        if (i == 0) {
                                *ap = AT_BOLD;
                                return ('~');
                        }
                        --i;
                }
                /* Make sure we're back to AT_NORMAL before the '\n'.  */
                *ap = AT_NORMAL;
                return (i ? '\0' : '\n');
        }

        *ap = attr[i];
        return (linebuf[i] & 0xFF);
}

/*
 * Indicate that there is no current line.
 */
void
null_line(void)
{
        is_null_line = 1;
        cshift = 0;
}

/*
 * Analogous to forw_line(), but deals with "raw lines":
 * lines which are not split for screen width.
 * {{ This is supposed to be more efficient than forw_line(). }}
 */
off_t
forw_raw_line(off_t curr_pos, char **linep, int *line_lenp)
{
        int n;
        int c;
        off_t new_pos;

        if (curr_pos == -1 || ch_seek(curr_pos) ||
            (c = ch_forw_get()) == EOI)
                return (-1);

        n = 0;
        for (;;) {
                if (c == '\n' || c == EOI || abort_sigs()) {
                        new_pos = ch_tell();
                        break;
                }
                if (n >= size_linebuf-1) {
                        if (expand_linebuf()) {
                                /*
                                 * Overflowed the input buffer.
                                 * Pretend the line ended here.
                                 */
                                new_pos = ch_tell() - 1;
                                break;
                        }
                }
                linebuf[n++] = (char)c;
                c = ch_forw_get();
        }
        linebuf[n] = '\0';
        if (linep != NULL)
                *linep = linebuf;
        if (line_lenp != NULL)
                *line_lenp = n;
        return (new_pos);
}

/*
 * Analogous to back_line(), but deals with "raw lines".
 * {{ This is supposed to be more efficient than back_line(). }}
 */
off_t
back_raw_line(off_t curr_pos, char **linep, int *line_lenp)
{
        int n;
        int c;
        off_t new_pos;

        if (curr_pos == -1 || curr_pos <= ch_zero() || ch_seek(curr_pos - 1))
                return (-1);

        n = size_linebuf;
        linebuf[--n] = '\0';
        for (;;) {
                c = ch_back_get();
                if (c == '\n' || abort_sigs()) {
                        /*
                         * This is the newline ending the previous line.
                         * We have hit the beginning of the line.
                         */
                        new_pos = ch_tell() + 1;
                        break;
                }
                if (c == EOI) {
                        /*
                         * We have hit the beginning of the file.
                         * This must be the first line in the file.
                         * This must, of course, be the beginning of the line.
                         */
                        new_pos = ch_zero();
                        break;
                }
                if (n <= 0) {
                        int old_size_linebuf = size_linebuf;
                        if (expand_linebuf()) {
                                /*
                                 * Overflowed the input buffer.
                                 * Pretend the line ended here.
                                 */
                                new_pos = ch_tell() + 1;
                                break;
                        }
                        /*
                         * Shift the data to the end of the new linebuf.
                         */
                        n = size_linebuf - old_size_linebuf;
                        memmove(linebuf + n, linebuf, old_size_linebuf);
                }
                linebuf[--n] = c;
        }
        if (linep != NULL)
                *linep = &linebuf[n];
        if (line_lenp != NULL)
                *line_lenp = size_linebuf - 1 - n;
        return (new_pos);
}