ren: do not output completed lines unnecessarily in render_rec()

[neatroff.git] / ren.c

/* rendering lines and managing traps */
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "roff.h"

#define cfmt            env_fmt()       /* current formatter */
#define cwb             env_wb()        /* current word buffer */

/* diversions */
struct div {
        struct sbuf sbuf;       /* diversion output */
        int reg;                /* diversion register */
        int tpos;               /* diversion trap position */
        int treg;               /* diversion trap register */
        int dl;                 /* diversion width */
        int prev_d;             /* previous \n(.d value */
        int prev_h;             /* previous \n(.h value */
        int prev_mk;            /* previous .mk internal register */
        int prev_ns;            /* previous .ns value */
};
static struct div divs[NPREV];  /* diversion stack */
static struct div *cdiv;        /* current diversion */
static int ren_div;             /* rendering a diversion */
static int trap_em = -1;        /* end macro */

static int ren_nl;              /* just after a newline */
static int ren_partial;         /* reading an input line in render_rec() */
static int ren_unbuf[8];        /* ren_back() buffer */
static int ren_un;
static int ren_aborted;         /* .ab executed */

static int bp_first = 1;        /* prior to the first page */
static int bp_next = 1;         /* next page number */
static int bp_count;            /* number of pages so far */
static int bp_ejected;          /* current ejected page */
static int bp_final;            /* 1: executing em, 2: the final page, 3: the 2nd final page */
static int ren_level;           /* the depth of render_rec() calls */

static char c_fa[GNLEN];        /* field delimiter */
static char c_fb[GNLEN];        /* field padding */

static int ren_next(void)
{
        return ren_un > 0 ? ren_unbuf[--ren_un] : tr_next();
}

static void ren_back(int c)
{
        ren_unbuf[ren_un++] = c;
}

void tr_di(char **args)
{
        if (args[1]) {
                cdiv = cdiv ? cdiv + 1 : divs;
                memset(cdiv, 0, sizeof(*cdiv));
                sbuf_init(&cdiv->sbuf);
                cdiv->reg = map(args[1]);
                cdiv->treg = -1;
                if (args[0][2] == 'a' && str_get(cdiv->reg))    /* .da */
                        sbuf_append(&cdiv->sbuf, str_get(cdiv->reg));
                sbuf_printf(&cdiv->sbuf, "%c%s\n", c_cc, TR_DIVBEG);
                cdiv->prev_d = n_d;
                cdiv->prev_h = n_h;
                cdiv->prev_mk = n_mk;
                cdiv->prev_ns = n_ns;
                n_d = 0;
                n_h = 0;
                n_mk = 0;
                n_ns = 0;
        } else if (cdiv) {
                sbuf_putnl(&cdiv->sbuf);
                sbuf_printf(&cdiv->sbuf, "%c%s\n", c_cc, TR_DIVEND);
                str_set(cdiv->reg, sbuf_buf(&cdiv->sbuf));
                sbuf_done(&cdiv->sbuf);
                n_dl = cdiv->dl;
                n_dn = n_d;
                n_d = cdiv->prev_d;
                n_h = cdiv->prev_h;
                n_mk = cdiv->prev_mk;
                n_ns = cdiv->prev_ns;
                cdiv = cdiv > divs ? cdiv - 1 : NULL;
        }
}

int charwid(int fn, int sz, int wid)
{
        if (dev_getcs(fn))
                return dev_getcs(n_f) * SC_EM / 36;
        return DEVWID(sz, wid) + (dev_getbd(fn) ? dev_getbd(fn) - 1 : 0);
}

int f_divreg(void)
{
        return cdiv ? cdiv->reg : -1;
}

int f_hpos(void)
{
        return fmt_wid(cfmt) + wb_wid(cwb);
}

void tr_divbeg(char **args)
{
        odiv_beg();
        ren_div++;
}

void tr_divend(char **args)
{
        if (ren_div <= 0)
                errdie("neatroff: diversion stack empty\n");
        odiv_end();
        ren_div--;
}

static int trap_reg(int pos);
static int trap_pos(int pos);
static void trap_exec(int reg);

static void ren_page(int pg, int force)
{
        if (!force && bp_final >= 2)
                return;
        n_nl = 0;
        n_d = 0;
        n_h = 0;
        n_pg = pg;
        bp_next = n_pg + 1;
        bp_count++;
        out("p%d\n", pg);
        out("V%d\n", 0);
        if (trap_pos(-1) == 0)
                trap_exec(trap_reg(-1));
}

static int ren_first(void)
{
        if (bp_first && !cdiv) {
                bp_first = 0;
                ren_page(bp_next, 1);
                return 0;
        }
        return 1;
}

/* when nodiv, do not append .sp to diversions */
static void ren_sp(int n, int nodiv)
{
        ren_first();
        /* ignore .sp without arguments when reading diversions */
        if (!n && ren_div && !n_u)
                return;
        n_d += n ? n : n_v;
        if (n_d > n_h)
                n_h = n_d;
        if (cdiv && !nodiv) {
                sbuf_putnl(&cdiv->sbuf);
                sbuf_printf(&cdiv->sbuf, "%csp %du\n", c_cc, n ? n : n_v);
        } else {
                n_nl = n_d;
        }
}

static int render_rec(int level);
static void trap_exec(int reg)
{
        char cmd[16];
        int partial = ren_partial;
        if (str_get(reg)) {
                sprintf(cmd, "%c%s %d\n", c_cc, TR_POPREN, ren_level);
                in_push(cmd, NULL);
                in_push(str_get(reg), NULL);
                if (partial)
                        in_push("\n", NULL);
                render_rec(++ren_level);
                /* executed the trap while in the middle of an input line */
                if (partial)
                        fmt_suppressnl(cfmt);
        }
}

static int detect_traps(int beg, int end)
{
        int pos = trap_pos(beg);
        return pos >= 0 && (cdiv || pos < n_p) && pos <= end;
}

/* return 1 if executed a trap */
static int ren_traps(int beg, int end, int dosp)
{
        int pos = trap_pos(beg);
        if (detect_traps(beg, end)) {
                if (dosp && pos > beg)
                        ren_sp(pos - beg, 0);
                trap_exec(trap_reg(beg));
                return 1;
        }
        return 0;
}

static int detect_pagelimit(int ne)
{
        return !cdiv && n_nl + ne >= n_p;
}

/* start a new page if needed */
static int ren_pagelimit(int ne)
{
        if (detect_pagelimit(ne)) {
                ren_page(bp_next, 0);
                return 1;
        }
        return 0;
}

/* return 1 if triggered a trap */
static int down(int n)
{
        if (ren_traps(n_d, n_d + (n ? n : n_v), 1))
                return 1;
        ren_sp(n, 0);
        return ren_pagelimit(0);
}

/* line adjustment */
static int ren_ljust(struct sbuf *spre, int w, int ad, int li, int ll)
{
        int ljust = li;
        int llen = ll - ljust;
        n_n = w;
        if ((ad & AD_B) == AD_C)
                ljust += llen > w ? (llen - w) / 2 : 0;
        if ((ad & AD_B) == AD_R)
                ljust += llen - w;
        if (ljust)
                sbuf_printf(spre, "%ch'%du'", c_ec, ljust);
        if (cdiv && cdiv->dl < w + ljust)
                cdiv->dl = w + ljust;
        return ljust;
}

/* append the line to the current diversion or send it to out.c */
static void ren_out(char *beg, char *mid, char *end)
{
        if (cdiv) {
                sbuf_append(&cdiv->sbuf, beg);
                sbuf_append(&cdiv->sbuf, mid);
                sbuf_append(&cdiv->sbuf, end);
        } else {
                out("H%d\n", n_o);
                out("V%d\n", n_d);
                out_line(beg);
                out_line(mid);
                out_line(end);
        }
}

static void ren_transparent(char *s)
{
        if (cdiv)
                sbuf_printf(&cdiv->sbuf, "%s\n", s);
        else
                out("%s\n", s);
}

static int zwid(void)
{
        struct glyph *g = dev_glyph("0", n_f);
        return charwid(n_f, n_s, g ? g->wid : 0);
}

/* append the line number to the output line */
static void ren_lnum(struct sbuf *spre)
{
        char num[16] = "";
        char dig[16] = "";
        struct wb wb;
        int i = 0;
        wb_init(&wb);
        if (n_nn <= 0 && (n_ln % n_nM) == 0)
                sprintf(num, "%d", n_ln);
        wb_hmov(&wb, n_nI * zwid());
        if (strlen(num) < 3)
                wb_hmov(&wb, (3 - strlen(num)) * zwid());
        while (num[i]) {
                dig[0] = num[i++];
                wb_put(&wb, dig);
        }
        wb_hmov(&wb, n_nS * zwid());
        sbuf_append(spre, sbuf_buf(&wb.sbuf));
        wb_done(&wb);
        if (n_nn > 0)
                n_nn--;
        else
                n_ln++;
}

/* append margin character */
static void ren_mc(struct sbuf *sbuf, int w, int ljust)
{
        struct wb wb;
        wb_init(&wb);
        if (w + ljust < n_l + n_mcn)
                wb_hmov(&wb, n_l + n_mcn - w - ljust);
        wb_putexpand(&wb, c_mc);
        sbuf_append(sbuf, sbuf_buf(&wb.sbuf));
        wb_done(&wb);
}

/* process a line and print it with ren_out() */
static int ren_line(char *line, int w, int ad, int body,
                int li, int ll, int els_neg, int els_pos)
{
        struct sbuf sbeg, send;
        int prev_d, lspc, ljust;
        ren_first();
        sbuf_init(&sbeg);
        sbuf_init(&send);
        lspc = MAX(1, n_L) * n_v;       /* line space, ignoreing \x */
        prev_d = n_d;
        if (els_neg)
                ren_sp(-els_neg, 1);
        if (!n_ns || line[0] || els_neg || els_pos) {
                ren_sp(0, 0);
                if (line[0] && n_nm && body)
                        ren_lnum(&sbeg);
                ljust = ren_ljust(&sbeg, w, ad, li, ll);
                if (line[0] && body && n_mc)
                        ren_mc(&send, w, ljust);
                ren_out(sbuf_buf(&sbeg), line, sbuf_buf(&send));
                n_ns = 0;
        }
        sbuf_done(&sbeg);
        sbuf_done(&send);
        if (els_pos)
                ren_sp(els_pos, 1);
        n_a = els_pos;
        if (detect_traps(prev_d, n_d) || detect_pagelimit(lspc - n_v)) {
                if (!ren_pagelimit(lspc - n_v))
                        ren_traps(prev_d, n_d, 0);
                return 1;
        }
        if (lspc - n_v && down(lspc - n_v))
                return 1;
        return 0;
}

/* read a line from fmt and send it to ren_line() */
static int ren_passline(struct fmt *fmt)
{
        struct sbuf sbuf;
        int ll, li, els_neg, els_pos, w, ret;
        int ad = n_j;
        ren_first();
        if (!fmt_morewords(fmt))
                return 0;
        sbuf_init(&sbuf);
        fmt_nextline(fmt, &sbuf, &w, &li, &ll, &els_neg, &els_pos);
        if ((n_cp && !n_u) || n_na)
                ad = AD_L;
        if (n_ce)
                ad = AD_C;
        ret = ren_line(sbuf_buf(&sbuf), w, ad, 1, li, ll, els_neg, els_pos);
        sbuf_done(&sbuf);
        return ret;
}

/* output formatted lines in fmt */
static void ren_fmtpop(struct fmt *fmt)
{
        while (fmt_morelines(fmt))
                ren_passline(fmt);
}

/* format and output all lines in fmt */
static void ren_fmtpopall(struct fmt *fmt)
{
        while (fmt_fill(fmt))
                ren_fmtpop(fmt);
        ren_fmtpop(fmt);
}

/* output current line; returns 1 if triggered a trap */
static int ren_br(void)
{
        ren_fmtpopall(cfmt);
        while (fmt_br(cfmt))
                ren_fmtpop(cfmt);
        return ren_passline(cfmt);
}

void tr_br(char **args)
{
        ren_fmtpopall(cfmt);    /* output the completed lines first */
        if (args[0][0] == c_cc)
                ren_br();
}

void tr_sp(char **args)
{
        int traps = 0;
        int n = args[1] ? eval(args[1], 'v') : n_v;
        if (args[0][0] == c_cc)
                traps = ren_br();
        if (n && !n_ns && !traps)
                down(n);
}

void tr_sv(char **args)
{
        int n = eval(args[1], 'v');
        n_sv = 0;
        if (n_d + n < f_nexttrap())
                down(n);
        else
                n_sv = n;
}

void tr_ns(char **args)
{
        n_ns = 1;
}

void tr_rs(char **args)
{
        n_ns = 0;
}

void tr_os(char **args)
{
        if (n_sv)
                down(n_sv);
        n_sv = 0;
}

void tr_mk(char **args)
{
        if (args[1])
                num_set(map(args[1]), n_d);
        else
                n_mk = n_d;
}

void tr_rt(char **args)
{
        int n = args[1] ? eval_re(args[1], n_d, 'v') : n_mk;
        if (n >= 0 && n < n_d)
                ren_sp(n - n_d, 0);
}

void tr_ne(char **args)
{
        int n = args[1] ? eval(args[1], 'v') : n_v;
        if (!ren_first())
                return;
        if (!ren_traps(n_d, n_d + n - 1, 1))
                ren_pagelimit(n);
}

static void ren_ejectpage(int br)
{
        bp_ejected = bp_count;
        if (br)
                ren_br();
        while (bp_count == bp_ejected && !cdiv) {
                if (detect_traps(n_d, n_p)) {
                        ren_traps(n_d, n_p, 1);
                } else {
                        bp_ejected = 0;
                        ren_page(bp_next, 0);
                }
        }
}

void tr_bp(char **args)
{
        if (!cdiv && (args[1] || !n_ns)) {
                if (args[1])
                        bp_next = eval_re(args[1], n_pg, 0);
                ren_ejectpage(args[0][0] == c_cc);
        }
}

void tr_pn(char **args)
{
        if (args[1])
                bp_next = eval_re(args[1], n_pg, 0);
}

static void ren_ps(char *s)
{
        int ps = !s || !*s || !strcmp("0", s) ? n_s0 : eval_re(s, n_s, 0);
        n_s0 = n_s;
        n_s = MAX(1, ps);
}

void tr_ps(char **args)
{
        ren_ps(args[1]);
}

void tr_ll(char **args)
{
        int ll = args[1] ? eval_re(args[1], n_l, 'm') : n_l0;
        n_l0 = n_l;
        n_l = MAX(0, ll);
}

void tr_in(char **args)
{
        int in = args[1] ? eval_re(args[1], n_i, 'm') : n_i0;
        if (args[0][0] == c_cc)
                ren_br();
        n_i0 = n_i;
        n_i = MAX(0, in);
        n_ti = -1;
}

void tr_ti(char **args)
{
        if (args[0][0] == c_cc)
                ren_br();
        if (args[1])
                n_ti = eval_re(args[1], n_i, 'm');
}

static void ren_ft(char *s)
{
        int fn = !s || !*s || !strcmp("P", s) ? n_f0 : dev_pos(s);
        if (fn < 0) {
                errmsg("neatroff: failed to mount <%s>\n", s);
        } else {
                n_f0 = n_f;
                n_f = fn;
        }
}

void tr_ft(char **args)
{
        ren_ft(args[1]);
}

void tr_fp(char **args)
{
        if (!args[2])
                return;
        if (dev_mnt(atoi(args[1]), args[2], args[3] ? args[3] : args[2]) < 0)
                errmsg("neatroff: failed to mount <%s>\n", args[2]);
}

void tr_nf(char **args)
{
        if (args[0][0] == c_cc)
                ren_br();
        n_u = 0;
}

void tr_fi(char **args)
{
        if (args[0][0] == c_cc)
                ren_br();
        n_u = 1;
}

void tr_ce(char **args)
{
        if (args[0][0] == c_cc)
                ren_br();
        n_ce = args[1] ? atoi(args[1]) : 1;
}

void tr_fc(char **args)
{
        char *fa = args[1];
        char *fb = args[2];
        if (fa && charread(&fa, c_fa) >= 0) {
                if (!fb || charread(&fb, c_fb) < 0)
                        strcpy(c_fb, " ");
        } else {
                c_fa[0] = '\0';
                c_fb[0] = '\0';
        }
}

static void ren_cl(char *s)
{
        int m = !s || !*s ? n_m0 : clr_get(s);
        n_m0 = n_m;
        n_m = m;
}

void tr_cl(char **args)
{
        ren_cl(args[1]);
}

void tr_ab(char **args)
{
        fprintf(stderr, "%s\n", args[1]);
        ren_aborted = 1;
}

static void ren_cmd(struct wb *wb, int c, char *arg)
{
        switch (c) {
        case ' ':
                wb_hmov(wb, N_SS(n_f, n_s));
                break;
        case 'b':
                ren_bcmd(wb, arg);
                break;
        case 'c':
                wb_setpart(wb);
                break;
        case 'D':
                ren_dcmd(wb, arg);
                break;
        case 'd':
                wb_vmov(wb, SC_EM / 2);
                break;
        case 'f':
                ren_ft(arg);
                break;
        case 'h':
                wb_hmov(wb, eval(arg, 'm'));
                break;
        case 'k':
                num_set(map(arg), wb == cwb ? f_hpos() - n_lb : wb_wid(wb));
                break;
        case 'L':
                ren_vlcmd(wb, arg);
                break;
        case 'l':
                ren_hlcmd(wb, arg);
                break;
        case 'm':
                ren_cl(arg);
                break;
        case 'o':
                ren_ocmd(wb, arg);
                break;
        case 'p':
                if (wb == cwb)
                        while (fmt_fillreq(cfmt))
                                ren_fmtpop(cfmt);
                break;
        case 'r':
                wb_vmov(wb, -SC_EM);
                break;
        case 's':
                ren_ps(arg);
                break;
        case 'u':
                wb_vmov(wb, -SC_EM / 2);
                break;
        case 'v':
                wb_vmov(wb, eval(arg, 'v'));
                break;
        case 'X':
                wb_etc(wb, arg);
                break;
        case 'x':
                wb_els(wb, eval(arg, 'v'));
                break;
        case '0':
                wb_hmov(wb, zwid());
                break;
        case '|':
                wb_hmov(wb, SC_EM / 6);
                break;
        case '&':
                wb_hmov(wb, 0);
                break;
        case '^':
                wb_hmov(wb, SC_EM / 12);
                break;
        case '/':
                wb_italiccorrection(wb);
                break;
        case ',':
                wb_italiccorrectionleft(wb);
                break;
        case '{':
        case '}':
                break;
        }
}

static void ren_field(struct wb *wb, int (*next)(void), void (*back)(int));
static void ren_tab(struct wb *wb, char *tc, int (*next)(void), void (*back)(int));

/* insert a character, escape sequence, field or etc into wb */
static void ren_put(struct wb *wb, char *c, int (*next)(void), void (*back)(int))
{
        char arg[ILNLEN];
        char *s;
        int w, n;
        if (c[0] == ' ' || c[0] == '\n') {
                wb_put(wb, c);
                return;
        }
        if (c[0] == '\t' || c[0] == '\x01') {
                ren_tab(wb, c[0] == '\t' ? c_tc : c_lc, next, back);
                return;
        }
        if (c_fa[0] && !strcmp(c_fa, c)) {
                ren_field(wb, next, back);
                return;
        }
        if (c[0] == c_ec) {
                if (c[1] == 'z') {
                        w = wb_wid(wb);
                        ren_char(wb, next, back);
                        wb_hmov(wb, w - wb_wid(wb));
                        return;
                }
                if (c[1] == '!') {
                        if (ren_nl && next == ren_next) {
                                s = arg;
                                n = next();
                                while (n >= 0 && n != '\n') {
                                        *s++ = n;
                                        n = next();
                                }
                                *s = '\0';
                                ren_transparent(arg);
                        }
                        return;
                }
                if (strchr(" bCcDdefHhkLlmNoprSsuvXxz0^|{}&/,", c[1])) {
                        argnext(arg, c[1], next, back);
                        if (c[1] == 'e') {
                                snprintf(c, GNLEN, "%c%c", c_ec, c_ec);
                        } else if (c[1] == 'N') {
                                snprintf(c, GNLEN, "GID=%s", arg);
                        } else {
                                ren_cmd(wb, c[1], arg);
                                return;
                        }
                }
        }
        if (!ren_div && cdef_map(c, n_f)) {             /* .char characters */
                wb_putexpand(wb, c);
                return;
        }
        if (!n_lg || ren_div || wb_lig(wb, c)) {
                if (n_kn && !ren_div)
                        wb_kern(wb, c);
                wb_put(wb, c);
        }
}

/* read one character and place it inside wb buffer */
int ren_char(struct wb *wb, int (*next)(void), void (*back)(int))
{
        char c[GNLEN * 4];
        if (charnext(c, next, back) < 0)
                return -1;
        ren_put(wb, c, next, back);
        return 0;
}

/* like ren_char(); return 1 if d1 was read and d2 if d2 was read */
static int ren_chardel(struct wb *wb, int (*next)(void), void (*back)(int),
                        char *d1, char *d2)
{
        char c[GNLEN * 4];
        if (charnext(c, next, back) < 0)
                return -1;
        if (d1 && !strcmp(d1, c))
                return 1;
        if (d2 && !strcmp(d2, c))
                return 2;
        ren_put(wb, c, next, back);
        return 0;
}

/* read the argument of \w and push its width */
int ren_wid(int (*next)(void), void (*back)(int))
{
        char delim[GNLEN];
        int c, n;
        struct wb wb;
        wb_init(&wb);
        charnext(delim, next, back);
        odiv_beg();
        c = next();
        while (c >= 0 && c != '\n') {
                back(c);
                if (ren_chardel(&wb, next, back, delim, NULL))
                        break;
                c = next();
        }
        odiv_end();
        n = wb_wid(&wb);
        wb_wconf(&wb, &n_ct, &n_st, &n_sb, &n_llx, &n_lly, &n_urx, &n_ury);
        wb_done(&wb);
        return n;
}

/* return 1 if d1 was read and 2 if d2 was read */
static int ren_until(struct wb *wb, char *d1, char *d2,
                        int (*next)(void), void (*back)(int))
{
        int c, ret;
        c = next();
        while (c >= 0 && c != '\n') {
                back(c);
                ret = ren_chardel(wb, next, back, d1, d2);
                if (ret)
                        return ret;
                c = next();
        }
        if (c == '\n')
                back(c);
        return 0;
}

static void wb_cpy(struct wb *dst, struct wb *src, int left)
{
        wb_hmov(dst, left - wb_wid(dst));
        wb_cat(dst, src);
}

void ren_tl(int (*next)(void), void (*back)(int))
{
        struct wb wb, wb2;
        char delim[GNLEN];
        wb_init(&wb);
        wb_init(&wb2);
        charnext(delim, next, back);
        /* the left-adjusted string */
        ren_until(&wb2, delim, NULL, next, back);
        wb_cpy(&wb, &wb2, 0);
        /* the centered string */
        ren_until(&wb2, delim, NULL, next, back);
        wb_cpy(&wb, &wb2, (n_lt - wb_wid(&wb2)) / 2);
        /* the right-adjusted string */
        ren_until(&wb2, delim, NULL, next, back);
        wb_cpy(&wb, &wb2, n_lt - wb_wid(&wb2));
        /* flushing the line */
        ren_line(sbuf_buf(&wb.sbuf), wb_wid(&wb), AD_L, 0,
                        0, n_lt, wb.els_neg, wb.els_pos);
        wb_done(&wb2);
        wb_done(&wb);
}

static void ren_field(struct wb *wb, int (*next)(void), void (*back)(int))
{
        struct wb wbs[NFIELDS];
        int i, n = 0;
        int wid = 0;
        int left, right, cur_left;
        int pad, rem;
        while (n < LEN(wbs)) {
                wb_init(&wbs[n]);
                if (ren_until(&wbs[n++], c_fb, c_fa, next, back) != 1)
                        break;
        }
        left = wb == cwb ? f_hpos() : wb_wid(wb);
        right = tab_next(left);
        for (i = 0; i < n; i++)
                wid += wb_wid(&wbs[i]);
        pad = (right - left - wid) / (n > 1 ? n - 1 : 1);
        rem = (right - left - wid) % (n > 1 ? n - 1 : 1);
        for (i = 0; i < n; i++) {
                if (i == 0)
                        cur_left = left;
                else if (i == n - 1)
                        cur_left = right - wb_wid(&wbs[i]);
                else
                        cur_left = wb_wid(wb) + pad + (i + rem >= n);
                wb_cpy(wb, &wbs[i], cur_left);
                wb_done(&wbs[i]);
        }
}

static void ren_tab(struct wb *wb, char *tc, int (*next)(void), void (*back)(int))
{
        struct wb t;
        int pos = wb == cwb ? f_hpos() : wb_wid(wb);
        int ins = tab_next(pos);        /* insertion position */
        int typ = tab_type(pos);        /* tab type */
        int c;
        wb_init(&t);
        if (typ == 'R' || typ == 'C') {
                c = next();
                while (c >= 0 && c != '\n' && c != '\t' && c != '\x01') {
                        back(c);
                        ren_char(&t, next, back);
                        c = next();
                }
                back(c);
        }
        if (typ == 'C')
                ins -= wb_wid(&t) / 2;
        if (typ == 'R')
                ins -= wb_wid(&t);
        if (!tc[0] || ins <= pos)
                wb_hmov(wb, ins - pos);
        else
                ren_hline(wb, ins - pos, tc);
        wb_cat(wb, &t);
        wb_done(&t);
}

/* parse characters and troff requests of s and append them to wb */
int ren_parse(struct wb *wb, char *s)
{
        int c;
        odiv_beg();
        sstr_push(s);
        c = sstr_next();
        while (c >= 0) {
                sstr_back(c);
                if (ren_char(wb, sstr_next, sstr_back))
                        break;
                c = sstr_next();
        }
        sstr_pop();
        odiv_end();
        return 0;
}

/* cause nested render_rec() to exit */
void tr_popren(char **args)
{
        ren_level = args[1] ? atoi(args[1]) : 0;
}

#define FMT_PAR()       (n_u && !n_na && !n_ce && (n_j & AD_P) == AD_P)

/* read characters from tr.c and pass the rendered lines to out.c */
static int render_rec(int level)
{
        int c;
        while (ren_level >= level) {
                while (!tr_nextreq())
                        if (ren_level < level)
                                break;
                if (ren_level < level)
                        break;
                if (ren_aborted)
                        return 1;
                c = ren_next();
                if (c < 0) {
                        if (bp_final >= 2)
                                break;
                        if (bp_final == 0) {
                                bp_final = 1;
                                ren_fmtpopall(cfmt);
                                if (trap_em >= 0)
                                        trap_exec(trap_em);
                        } else {
                                bp_final = 2;
                                ren_ejectpage(1);
                        }
                }
                if (c >= 0)
                        ren_partial = c != '\n';
                /* add cwb (the current word) to cfmt */
                if (c == ' ' || c == '\n') {
                        if (!wb_part(cwb)) {    /* not after a \c */
                                while (fmt_word(cfmt, cwb))
                                        ren_fmtpop(cfmt);
                                wb_reset(cwb);
                                if (c == '\n')
                                        while (fmt_newline(cfmt))
                                                ren_fmtpop(cfmt);
                                if (!FMT_PAR())
                                        ren_fmtpopall(cfmt);
                                if (c == ' ')
                                        fmt_space(cfmt);
                        }
                }
                /* flush the line if necessary */
                if ((!FMT_PAR() && (c == ' ' || c == '\n')) || c < 0)
                        ren_fmtpop(cfmt);
                if (c == '\n' || ren_nl)        /* end or start of input line */
                        n_lb = f_hpos();
                if (c == '\n' && n_it && --n_itn == 0)
                        trap_exec(n_it);
                if (c == '\n' && !wb_part(cwb))
                        n_ce = MAX(0, n_ce - 1);
                if (c != ' ' && c >= 0) {
                        ren_back(c);
                        ren_char(cwb, ren_next, ren_back);
                }
                if (c >= 0)
                        ren_nl = c == '\n';
        }
        return 0;
}

/* render input words */
int render(void)
{
        n_nl = -1;
        while (!tr_nextreq())
                ;
        ren_first();                    /* transition to the first page */
        render_rec(0);
        bp_final = 3;
        if (fmt_morewords(cfmt))
                ren_page(bp_next, 1);
        ren_br();
        return 0;
}

/* trap handling */

#define tposval(i)              (tpos[i] < 0 ? n_p + tpos[i] : tpos[i])

static int tpos[NTRAPS];        /* trap positions */
static int treg[NTRAPS];        /* trap registers */
static int ntraps;

static int trap_first(int pos)
{
        int best = -1;
        int i;
        for (i = 0; i < ntraps; i++)
                if (treg[i] >= 0 && tposval(i) > pos)
                        if (best < 0 || tposval(i) < tposval(best))
                                best = i;
        return best;
}

static int trap_byreg(int reg)
{
        int i;
        for (i = 0; i < ntraps; i++)
                if (treg[i] == reg)
                        return i;
        return -1;
}

static int trap_bypos(int reg, int pos)
{
        int i;
        for (i = 0; i < ntraps; i++)
                if (treg[i] >= 0 && tposval(i) == pos)
                        if (reg == -1 || treg[i] == reg)
                                return i;
        return -1;
}

void tr_wh(char **args)
{
        int reg, pos, id;
        if (!args[1])
                return;
        pos = eval(args[1], 'v');
        id = trap_bypos(-1, pos);
        if (!args[2]) {
                if (id >= 0)
                        treg[id] = -1;
                return;
        }
        reg = map(args[2]);
        if (id < 0)
                id = trap_byreg(-1);
        if (id < 0)
                id = ntraps++;
        tpos[id] = pos;
        treg[id] = reg;
}

void tr_ch(char **args)
{
        int reg;
        int id;
        if (!args[1])
                return;
        reg = map(args[1]);
        id = trap_byreg(reg);
        if (id >= 0)
                tpos[id] = args[2] ? eval(args[2], 'v') : -1;
}

void tr_dt(char **args)
{
        if (!cdiv)
                return;
        if (args[2]) {
                cdiv->tpos = eval(args[1], 'v');
                cdiv->treg = map(args[2]);
        } else {
                cdiv->treg = -1;
        }
}

void tr_em(char **args)
{
        trap_em = args[1] ? map(args[1]) : -1;
}

static int trap_pos(int pos)
{
        int ret = trap_first(pos);
        if (bp_final >= 3)
                return -1;
        if (cdiv)
                return cdiv->treg && cdiv->tpos > pos ? cdiv->tpos : -1;
        return ret >= 0 ? tposval(ret) : -1;
}

static int trap_reg(int pos)
{
        int ret = trap_first(pos);
        if (cdiv)
                return cdiv->treg && cdiv->tpos > pos ? cdiv->treg : -1;
        return ret >= 0 ? treg[ret] : -1;
}

int f_nexttrap(void)
{
        int pos = trap_pos(n_d);
        if (cdiv)
                return pos >= 0 ? pos : 0x7fffffff;
        return (pos >= 0 && pos < n_p ? pos : n_p) - n_d;
}