xref: /freebsd/contrib/nvi/common/key.c (revision 0fcececbac9880b092aeb56a41a16f1ec8ac1ae6)

/*-
 * Copyright (c) 1991, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 * Copyright (c) 1991, 1993, 1994, 1995, 1996
 *	Keith Bostic.  All rights reserved.
 *
 * See the LICENSE file for redistribution information.
 */

#include "config.h"

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

#include <bitstring.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#include "common.h"
#include "../vi/vi.h"

static int	v_event_append(SCR *, EVENT *);
static int	v_event_grow(SCR *, int);
static int	v_key_cmp(const void *, const void *);
static void	v_keyval(SCR *, int, scr_keyval_t);
static void	v_sync(SCR *, int);
static const char *alt_key_notation(int ch);

/*
 * !!!
 * Historic vi always used:
 *
 *	^D: autoindent deletion
 *	^H: last character deletion
 *	^W: last word deletion
 *	^Q: quote the next character (if not used in flow control).
 *	^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.  Nvi wires
 * down the above characters, but in addition permits the VEOF, VERASE, VKILL
 * and VWERASE characters described by the user's termios structure.
 *
 * Ex was not consistent with this scheme, as it historically ran in tty
 * cooked mode.  This meant that the scroll command and autoindent erase
 * characters were mapped to the user's EOF character, and the character
 * and word deletion characters were the user's tty character and word
 * deletion characters.  This implementation makes it all consistent, as
 * described above for vi.
 *
 * !!!
 * This means that all screens share a special key set.
 */
KEYLIST keylist[] = {
	{K_BACKSLASH,	  '\\'},	/*  \ */
	{K_CARAT,	   '^'},	/*  ^ */
	{K_CNTRLD,	'\004'},	/* ^D */
	{K_CNTRLR,	'\022'},	/* ^R */
	{K_CNTRLT,	'\024'},	/* ^T */
	{K_CNTRLZ,	'\032'},	/* ^Z */
	{K_COLON,	   ':'},	/*  : */
	{K_CR,		  '\r'},	/* \r */
	{K_ESCAPE,	'\033'},	/* ^[ */
	{K_FORMFEED,	  '\f'},	/* \f */
	{K_HEXCHAR,	'\030'},	/* ^X */
	{K_NL,		  '\n'},	/* \n */
	{K_RIGHTBRACE,	   '}'},	/*  } */
	{K_RIGHTPAREN,	   ')'},	/*  ) */
	{K_TAB,		  '\t'},	/* \t */
	{K_VERASE,	  '\b'},	/* \b */
	{K_VKILL,	'\025'},	/* ^U */
	{K_VLNEXT,	'\021'},	/* ^Q */
	{K_VLNEXT,	'\026'},	/* ^V */
	{K_VWERASE,	'\027'},	/* ^W */
	{K_ZERO,	   '0'},	/*  0 */

#define	ADDITIONAL_CHARACTERS	4
	{K_NOTUSED, 0},			/* VEOF, VERASE, VKILL, VWERASE */
	{K_NOTUSED, 0},
	{K_NOTUSED, 0},
	{K_NOTUSED, 0},
};
static int nkeylist =
    (sizeof(keylist) / sizeof(keylist[0])) - ADDITIONAL_CHARACTERS;

/*
 * v_key_init --
 *	Initialize the special key lookup table.
 *
 * PUBLIC: int v_key_init(SCR *);
 */
int
v_key_init(SCR *sp)
{
	int ch;
	GS *gp;
	KEYLIST *kp;
	int cnt;

	gp = sp->gp;

	v_key_ilookup(sp);

	v_keyval(sp, K_CNTRLD, KEY_VEOF);
	v_keyval(sp, K_VERASE, KEY_VERASE);
	v_keyval(sp, K_VKILL, KEY_VKILL);
	v_keyval(sp, K_VWERASE, KEY_VWERASE);

	/* Sort the special key list. */
	qsort(keylist, nkeylist, sizeof(keylist[0]), v_key_cmp);

	/* Initialize the fast lookup table. */
	for (kp = keylist, cnt = nkeylist; cnt--; ++kp)
		gp->special_key[kp->ch] = kp->value;

	/* Find a non-printable character to use as a message separator. */
	for (ch = 1; ch <= UCHAR_MAX; ++ch)
		if (!isprint(ch)) {
			gp->noprint = ch;
			break;
		}
	if (ch != gp->noprint) {
		msgq(sp, M_ERR, "079|No non-printable character found");
		return (1);
	}
	return (0);
}

/*
 * v_keyval --
 *	Set key values.
 *
 * We've left some open slots in the keylist table, and if these values exist,
 * we put them into place.  Note, they may reset (or duplicate) values already
 * in the table, so we check for that first.
 */
static void
v_keyval(SCR *sp, int val, scr_keyval_t name)
{
	KEYLIST *kp;
	CHAR_T ch;
	int dne;

	/* Get the key's value from the screen. */
	if (sp->gp->scr_keyval(sp, name, &ch, &dne))
		return;
	if (dne)
		return;

	/* Check for duplication. */
	for (kp = keylist; kp->value != K_NOTUSED; ++kp)
		if (kp->ch == ch) {
			kp->value = val;
			return;
		}

	/* Add a new entry. */
	if (kp->value == K_NOTUSED) {
		keylist[nkeylist].ch = ch;
		keylist[nkeylist].value = val;
		++nkeylist;
	}
}

/*
 * v_key_ilookup --
 *	Build the fast-lookup key display array.
 *
 * PUBLIC: void v_key_ilookup(SCR *);
 */
void
v_key_ilookup(SCR *sp)
{
	UCHAR_T ch;
	char *p, *t;
	GS *gp;
	size_t len;

	for (gp = sp->gp, ch = 0;; ++ch) {
		for (p = gp->cname[ch].name, t = v_key_name(sp, ch),
		    len = gp->cname[ch].len = sp->clen; len--;)
			*p++ = *t++;
		if (ch == MAX_FAST_KEY)
			break;
	}
}

/*
 * v_key_len --
 *	Return the length of the string that will display the key.
 *	This routine is the backup for the KEY_LEN() macro.
 *
 * PUBLIC: size_t v_key_len(SCR *, ARG_CHAR_T);
 */
size_t
v_key_len(SCR *sp, ARG_CHAR_T ch)
{
	(void)v_key_name(sp, ch);
	return (sp->clen);
}

/*
 * v_key_name --
 *	Return the string that will display the key.  This routine
 *	is the backup for the KEY_NAME() macro.
 *
 * PUBLIC: char *v_key_name(SCR *, ARG_CHAR_T);
 */
char *
v_key_name(SCR *sp, ARG_CHAR_T ach)
{
	static const char hexdigit[] = "0123456789abcdef";
	static const char octdigit[] = "01234567";
	int ch;
	size_t len;
	char *chp;

	/*
	 * Cache the last checked character.  It won't be a problem
	 * since nvi will rescan the mapping when settings changed.
	 */
	if (ach && sp->lastc == ach)
		return (sp->cname);
	sp->lastc = ach;

#ifdef USE_WIDECHAR
	len = wctomb(sp->cname, ach);
	if (len > MB_CUR_MAX)
#endif
		sp->cname[(len = 1)-1] = (u_char)ach;

	ch = (u_char)sp->cname[0];
	sp->cname[len] = '\0';

	/* See if the character was explicitly declared printable or not. */
	if ((chp = O_STR(sp, O_PRINT)) != NULL)
		if (strstr(chp, sp->cname) != NULL)
			goto done;
	if ((chp = O_STR(sp, O_NOPRINT)) != NULL)
		if (strstr(chp, sp->cname) != NULL)
			goto nopr;

	/*
	 * Historical (ARPA standard) mappings.  Printable characters are left
	 * alone.  Control characters less than 0x20 are represented as '^'
	 * followed by the character offset from the '@' character in the ASCII
	 * character set.  Del (0x7f) is represented as '^' followed by '?'.
	 *
	 * If set O_ALTNOTATION, control characters less than 0x20 are
	 * represented in <C-char> notations.  Carriage feed, escape, and
	 * delete are marked as <Enter>, <Esc>, and <Del>, respectively.
	 *
	 * XXX
	 * The following code depends on the current locale being identical to
	 * the ASCII map from 0x40 to 0x5f (since 0x1f + 0x40 == 0x5f).  I'm
	 * told that this is a reasonable assumption...
	 *
	 * XXX
	 * The code prints non-printable wide characters in 4 or 5 digits
	 * Unicode escape sequences, so only supports plane 0 to 15.
	 */
	if (CAN_PRINT(sp, ach))
		goto done;
nopr:	if (iscntrl(ch) && (ch < 0x20 || ch == 0x7f)) {
		if (O_ISSET(sp, O_ALTNOTATION)) {
			const char *notation = alt_key_notation(ch);
			len = strlcpy(sp->cname, notation, sizeof(sp->cname));
		} else {
			sp->cname[0] = '^';
			sp->cname[1] = ch == 0x7f ? '?' : '@' + ch;
			len = 2;
		}
		goto done;
	}
#ifdef USE_WIDECHAR
	if (INTISWIDE(ach)) {
		int uc = -1;

		if (!strcmp(codeset(), "UTF-8"))
			uc = decode_utf8(sp->cname);
#ifdef USE_ICONV
		else {
			char buf[sizeof(sp->cname)] = "";
			size_t left = sizeof(sp->cname);
			char *in = sp->cname;
			char *out = buf;
			iconv(sp->conv.id[IC_IE_TO_UTF16],
			    (iconv_src_t)&in, &len, &out, &left);
			iconv(sp->conv.id[IC_IE_TO_UTF16],
			    NULL, NULL, NULL, NULL);
			uc = decode_utf16(buf, 1);
		}
#endif
		if (uc >= 0) {
			len = snprintf(sp->cname, sizeof(sp->cname),
			    uc < 0x10000 ? "\\u%04x" : "\\U%05X", uc);
			goto done;
		}
	}
#endif
	if (O_ISSET(sp, O_OCTAL)) {
		sp->cname[0] = '\\';
		sp->cname[1] = octdigit[(ch & 0300) >> 6];
		sp->cname[2] = octdigit[(ch &  070) >> 3];
		sp->cname[3] = octdigit[ ch &   07      ];
	} else {
		sp->cname[0] = '\\';
		sp->cname[1] = 'x';
		sp->cname[2] = hexdigit[(ch & 0xf0) >> 4];
		sp->cname[3] = hexdigit[ ch & 0x0f      ];
	}
	len = 4;
done:	sp->cname[sp->clen = len] = '\0';
	return (sp->cname);
}

/*
 * v_key_val --
 *	Fill in the value for a key.  This routine is the backup
 *	for the KEY_VAL() macro.
 *
 * PUBLIC: e_key_t v_key_val(SCR *, ARG_CHAR_T);
 */
e_key_t
v_key_val(SCR *sp, ARG_CHAR_T ch)
{
	KEYLIST k, *kp;

	k.ch = ch;
	kp = bsearch(&k, keylist, nkeylist, sizeof(keylist[0]), v_key_cmp);
	return (kp == NULL ? K_NOTUSED : kp->value);
}

/*
 * v_event_push --
 *	Push events/keys onto the front of the buffer.
 *
 * There is a single input buffer in ex/vi.  Characters are put onto the
 * end of the buffer by the terminal input routines, and pushed onto the
 * front of the buffer by various other functions in ex/vi.  Each key has
 * an associated flag value, which indicates if it has already been quoted,
 * and if it is the result of a mapping or an abbreviation.
 *
 * PUBLIC: int v_event_push(SCR *, EVENT *, CHAR_T *, size_t, u_int);
 */
int
v_event_push(SCR *sp,
	EVENT *p_evp,			/* Push event. */
	CHAR_T *p_s,			/* Push characters. */
	size_t nitems,			/* Number of items to push. */
	u_int flags)			/* CH_* flags. */
{
	EVENT *evp;
	GS *gp;
	size_t total;

	/* If we have room, stuff the items into the buffer. */
	gp = sp->gp;
	if (nitems <= gp->i_next ||
	    (gp->i_event != NULL && gp->i_cnt == 0 && nitems <= gp->i_nelem)) {
		if (gp->i_cnt != 0)
			gp->i_next -= nitems;
		goto copy;
	}

	/*
	 * If there are currently items in the queue, shift them up,
	 * leaving some extra room.  Get enough space plus a little
	 * extra.
	 */
#define	TERM_PUSH_SHIFT	30
	total = gp->i_cnt + gp->i_next + nitems + TERM_PUSH_SHIFT;
	if (total >= gp->i_nelem && v_event_grow(sp, MAX(total, 64)))
		return (1);
	if (gp->i_cnt)
		memmove(gp->i_event + TERM_PUSH_SHIFT + nitems,
		    gp->i_event + gp->i_next, gp->i_cnt * sizeof(EVENT));
	gp->i_next = TERM_PUSH_SHIFT;

	/* Put the new items into the queue. */
copy:	gp->i_cnt += nitems;
	for (evp = gp->i_event + gp->i_next; nitems--; ++evp) {
		if (p_evp != NULL)
			*evp = *p_evp++;
		else {
			evp->e_event = E_CHARACTER;
			evp->e_c = *p_s++;
			evp->e_value = KEY_VAL(sp, evp->e_c);
			F_INIT(&evp->e_ch, flags);
		}
	}
	return (0);
}

/*
 * v_event_append --
 *	Append events onto the tail of the buffer.
 */
static int
v_event_append(SCR *sp, EVENT *argp)
{
	CHAR_T *s;			/* Characters. */
	EVENT *evp;
	GS *gp;
	size_t nevents;			/* Number of events. */

	/* Grow the buffer as necessary. */
	nevents = argp->e_event == E_STRING ? argp->e_len : 1;
	gp = sp->gp;
	if (gp->i_event == NULL ||
	    nevents > gp->i_nelem - (gp->i_next + gp->i_cnt))
		v_event_grow(sp, MAX(nevents, 64));
	evp = gp->i_event + gp->i_next + gp->i_cnt;
	gp->i_cnt += nevents;

	/* Transform strings of characters into single events. */
	if (argp->e_event == E_STRING)
		for (s = argp->e_csp; nevents--; ++evp) {
			evp->e_event = E_CHARACTER;
			evp->e_c = *s++;
			evp->e_value = KEY_VAL(sp, evp->e_c);
			evp->e_flags = 0;
		}
	else
		*evp = *argp;
	return (0);
}

/* Remove events from the queue. */
#define	QREM(len) do {							\
	if ((gp->i_cnt -= len) == 0)					\
		gp->i_next = 0;						\
	else								\
		gp->i_next += len;					\
} while (0)

/*
 * v_event_get --
 *	Return the next event.
 *
 * !!!
 * The flag EC_NODIGIT probably needs some explanation.  First, the idea of
 * mapping keys is that one or more keystrokes act like a function key.
 * What's going on is that vi is reading a number, and the character following
 * the number may or may not be mapped (EC_MAPCOMMAND).  For example, if the
 * user is entering the z command, a valid command is "z40+", and we don't want
 * to map the '+', i.e. if '+' is mapped to "xxx", we don't want to change it
 * into "z40xxx".  However, if the user enters "35x", we want to put all of the
 * characters through the mapping code.
 *
 * Historical practice is a bit muddled here.  (Surprise!)  It always permitted
 * mapping digits as long as they weren't the first character of the map, e.g.
 * ":map ^A1 xxx" was okay.  It also permitted the mapping of the digits 1-9
 * (the digit 0 was a special case as it doesn't indicate the start of a count)
 * as the first character of the map, but then ignored those mappings.  While
 * it's probably stupid to map digits, vi isn't your mother.
 *
 * The way this works is that the EC_MAPNODIGIT causes term_key to return the
 * end-of-digit without "looking" at the next character, i.e. leaving it as the
 * user entered it.  Presumably, the next term_key call will tell us how the
 * user wants it handled.
 *
 * There is one more complication.  Users might map keys to digits, and, as
 * it's described above, the commands:
 *
 *	:map g 1G
 *	d2g
 *
 * would return the keys "d2<end-of-digits>1G", when the user probably wanted
 * "d21<end-of-digits>G".  So, if a map starts off with a digit we continue as
 * before, otherwise, we pretend we haven't mapped the character, and return
 * <end-of-digits>.
 *
 * Now that that's out of the way, let's talk about Energizer Bunny macros.
 * It's easy to create macros that expand to a loop, e.g. map x 3x.  It's
 * fairly easy to detect this example, because it's all internal to term_key.
 * If we're expanding a macro and it gets big enough, at some point we can
 * assume it's looping and kill it.  The examples that are tough are the ones
 * where the parser is involved, e.g. map x "ayyx"byy.  We do an expansion
 * on 'x', and get "ayyx"byy.  We then return the first 4 characters, and then
 * find the looping macro again.  There is no way that we can detect this
 * without doing a full parse of the command, because the character that might
 * cause the loop (in this case 'x') may be a literal character, e.g. the map
 * map x "ayy"xyy"byy is perfectly legal and won't cause a loop.
 *
 * Historic vi tried to detect looping macros by disallowing obvious cases in
 * the map command, maps that that ended with the same letter as they started
 * (which wrongly disallowed "map x 'x"), and detecting macros that expanded
 * too many times before keys were returned to the command parser.  It didn't
 * get many (most?) of the tricky cases right, however, and it was certainly
 * possible to create macros that ran forever.  And, even if it did figure out
 * what was going on, the user was usually tossed into ex mode.  Finally, any
 * changes made before vi realized that the macro was recursing were left in
 * place.  We recover gracefully, but the only recourse the user has in an
 * infinite macro loop is to interrupt.
 *
 * !!!
 * It is historic practice that mapping characters to themselves as the first
 * part of the mapped string was legal, and did not cause infinite loops, i.e.
 * ":map! { {^M^T" and ":map n nz." were known to work.  The initial, matching
 * characters were returned instead of being remapped.
 *
 * !!!
 * It is also historic practice that the macro "map ] ]]^" caused a single ]
 * keypress to behave as the command ]] (the ^ got the map past the vi check
 * for "tail recursion").  Conversely, the mapping "map n nn^" went recursive.
 * What happened was that, in the historic vi, maps were expanded as the keys
 * were retrieved, but not all at once and not centrally.  So, the keypress ]
 * pushed ]]^ on the stack, and then the first ] from the stack was passed to
 * the ]] command code.  The ]] command then retrieved a key without entering
 * the mapping code.  This could bite us anytime a user has a map that depends
 * on secondary keys NOT being mapped.  I can't see any possible way to make
 * this work in here without the complete abandonment of Rationality Itself.
 *
 * XXX
 * The final issue is recovery.  It would be possible to undo all of the work
 * that was done by the macro if we entered a record into the log so that we
 * knew when the macro started, and, in fact, this might be worth doing at some
 * point.  Given that this might make the log grow unacceptably (consider that
 * cursor keys are done with maps), for now we leave any changes made in place.
 *
 * PUBLIC: int v_event_get(SCR *, EVENT *, int, u_int32_t);
 */
int
v_event_get(SCR *sp, EVENT *argp, int timeout, u_int32_t flags)
{
	EVENT *evp, ev;
	GS *gp;
	SEQ *qp;
	int init_nomap, ispartial, istimeout, remap_cnt;

	gp = sp->gp;

	/* If simply checking for interrupts, argp may be NULL. */
	if (argp == NULL)
		argp = &ev;

retry:	istimeout = remap_cnt = 0;

	/*
	 * If the queue isn't empty and we're timing out for characters,
	 * return immediately.
	 */
	if (gp->i_cnt != 0 && LF_ISSET(EC_TIMEOUT))
		return (0);

	/*
	 * If the queue is empty, we're checking for interrupts, or we're
	 * timing out for characters, get more events.
	 */
	if (gp->i_cnt == 0 || LF_ISSET(EC_INTERRUPT | EC_TIMEOUT)) {
		/*
		 * If we're reading new characters, check any scripting
		 * windows for input.
		 */
		if (F_ISSET(gp, G_SCRWIN) && sscr_input(sp))
			return (1);
loop:		if (gp->scr_event(sp, argp,
		    LF_ISSET(EC_INTERRUPT | EC_QUOTED | EC_RAW), timeout))
			return (1);
		switch (argp->e_event) {
		case E_ERR:
		case E_SIGHUP:
		case E_SIGTERM:
			/*
			 * Fatal conditions cause the file to be synced to
			 * disk immediately.
			 */
			v_sync(sp, RCV_ENDSESSION | RCV_PRESERVE |
			    (argp->e_event == E_SIGTERM ? 0: RCV_EMAIL));
			return (1);
		case E_TIMEOUT:
			istimeout = 1;
			break;
		case E_INTERRUPT:
			/* Set the global interrupt flag. */
			F_SET(sp->gp, G_INTERRUPTED);

			/*
			 * If the caller was interested in interrupts, return
			 * immediately.
			 */
			if (LF_ISSET(EC_INTERRUPT))
				return (0);
			goto append;
		default:
append:			if (v_event_append(sp, argp))
				return (1);
			break;
		}
	}

	/*
	 * If the caller was only interested in interrupts or timeouts, return
	 * immediately.  (We may have gotten characters, and that's okay, they
	 * were queued up for later use.)
	 */
	if (LF_ISSET(EC_INTERRUPT | EC_TIMEOUT))
		return (0);

newmap:	evp = &gp->i_event[gp->i_next];

	/*
	 * If the next event in the queue isn't a character event, return
	 * it, we're done.
	 */
	if (evp->e_event != E_CHARACTER) {
		*argp = *evp;
		QREM(1);
		return (0);
	}

	/*
	 * If the key isn't mappable because:
	 *
	 *	+ ... the timeout has expired
	 *	+ ... it's not a mappable key
	 *	+ ... neither the command or input map flags are set
	 *	+ ... there are no maps that can apply to it
	 *
	 * return it forthwith.
	 */
	if (istimeout || F_ISSET(&evp->e_ch, CH_NOMAP) ||
	    !LF_ISSET(EC_MAPCOMMAND | EC_MAPINPUT) ||
	    ((evp->e_c & ~MAX_BIT_SEQ) == 0 &&
	    !bit_test(gp->seqb, evp->e_c)))
		goto nomap;

	/* Search the map. */
	qp = seq_find(sp, NULL, evp, NULL, gp->i_cnt,
	    LF_ISSET(EC_MAPCOMMAND) ? SEQ_COMMAND : SEQ_INPUT, &ispartial);

	/*
	 * If get a partial match, get more characters and retry the map.
	 * If time out without further characters, return the characters
	 * unmapped.
	 *
	 * !!!
	 * <escape> characters are a problem.  Cursor keys start with <escape>
	 * characters, so there's almost always a map in place that begins with
	 * an <escape> character.  If we timeout <escape> keys in the same way
	 * that we timeout other keys, the user will get a noticeable pause as
	 * they enter <escape> to terminate input mode.  If key timeout is set
	 * for a slow link, users will get an even longer pause.  Nvi used to
	 * simply timeout <escape> characters at 1/10th of a second, but this
	 * loses over PPP links where the latency is greater than 100Ms.
	 */
	if (ispartial) {
		if (O_ISSET(sp, O_TIMEOUT))
			timeout = (evp->e_value == K_ESCAPE ?
			    O_VAL(sp, O_ESCAPETIME) :
			    O_VAL(sp, O_KEYTIME)) * 100;
		else
			timeout = 0;
		goto loop;
	}

	/* If no map, return the character. */
	if (qp == NULL) {
nomap:		if (!ISDIGIT(evp->e_c) && LF_ISSET(EC_MAPNODIGIT))
			goto not_digit;
		*argp = *evp;
		QREM(1);
		return (0);
	}

	/*
	 * If looking for the end of a digit string, and the first character
	 * of the map is it, pretend we haven't seen the character.
	 */
	if (LF_ISSET(EC_MAPNODIGIT) &&
	    qp->output != NULL && !ISDIGIT(qp->output[0])) {
not_digit:	argp->e_c = CH_NOT_DIGIT;
		argp->e_value = K_NOTUSED;
		argp->e_event = E_CHARACTER;
		F_INIT(&argp->e_ch, 0);
		return (0);
	}

	/* Find out if the initial segments are identical. */
	init_nomap = !e_memcmp(qp->output, &gp->i_event[gp->i_next], qp->ilen);

	/* Delete the mapped characters from the queue. */
	QREM(qp->ilen);

	/* If keys mapped to nothing, go get more. */
	if (qp->output == NULL)
		goto retry;

	/* If remapping characters... */
	if (O_ISSET(sp, O_REMAP)) {
		/*
		 * Periodically check for interrupts.  Always check the first
		 * time through, because it's possible to set up a map that
		 * will return a character every time, but will expand to more,
		 * e.g. "map! a aaaa" will always return a 'a', but we'll never
		 * get anywhere useful.
		 */
		if ((++remap_cnt == 1 || remap_cnt % 10 == 0) &&
		    (gp->scr_event(sp, &ev,
		    EC_INTERRUPT, 0) || ev.e_event == E_INTERRUPT)) {
			F_SET(sp->gp, G_INTERRUPTED);
			argp->e_event = E_INTERRUPT;
			return (0);
		}

		/*
		 * If an initial part of the characters mapped, they are not
		 * further remapped -- return the first one.  Push the rest
		 * of the characters, or all of the characters if no initial
		 * part mapped, back on the queue.
		 */
		if (init_nomap) {
			if (v_event_push(sp, NULL, qp->output + qp->ilen,
			    qp->olen - qp->ilen, CH_MAPPED))
				return (1);
			if (v_event_push(sp, NULL,
			    qp->output, qp->ilen, CH_NOMAP | CH_MAPPED))
				return (1);
			evp = &gp->i_event[gp->i_next];
			goto nomap;
		}
		if (v_event_push(sp, NULL, qp->output, qp->olen, CH_MAPPED))
			return (1);
		goto newmap;
	}

	/* Else, push the characters on the queue and return one. */
	if (v_event_push(sp, NULL, qp->output, qp->olen, CH_MAPPED | CH_NOMAP))
		return (1);

	goto nomap;
}

/*
 * v_sync --
 *	Walk the screen lists, sync'ing files to their backup copies.
 */
static void
v_sync(SCR *sp, int flags)
{
	GS *gp;

	gp = sp->gp;
	TAILQ_FOREACH(sp, gp->dq, q)
		rcv_sync(sp, flags);
	TAILQ_FOREACH(sp, gp->hq, q)
		rcv_sync(sp, flags);
}

/*
 * alt_key_notation --
 *	Lookup for alternative notations of control characters.
 */
static const char*
alt_key_notation(int ch)
{
	switch (ch) {
	case 0x00:
		return "<C-@>";
	case 0x01:
		return "<C-a>";
	case 0x02:
		return "<C-b>";
	case 0x03:
		return "<C-c>";
	case 0x04:
		return "<C-d>";
	case 0x05:
		return "<C-e>";
	case 0x06:
		return "<C-f>";
	case 0x07:
		return "<C-g>";
	case 0x08:
		return "<C-h>";
	case 0x09:
		return "<Tab>";
	case 0x0A:
		return "<NL>";
	case 0x0B:
		return "<C-k>";
	case 0x0C:
		return "<C-l>";
	case 0x0D:
		return "<Enter>";
	case 0x0E:
		return "<C-n>";
	case 0x0F:
		return "<C-o>";
	case 0x10:
		return "<C-p>";
	case 0x11:
		return "<C-q>";
	case 0x12:
		return "<C-r>";
	case 0x13:
		return "<C-s>";
	case 0x14:
		return "<C-t>";
	case 0x15:
		return "<C-u>";
	case 0x16:
		return "<C-v>";
	case 0x17:
		return "<C-w>";
	case 0x18:
		return "<C-x>";
	case 0x19:
		return "<C-y>";
	case 0x1A:
		return "<C-z>";
	case 0x1B:
		return "<Esc>";
	case 0x1C:
		return "<C-\\>";
	case 0x1D:
		return "<C-]>";
	case 0x1E:
		return "<C-^>";
	case 0x1F:
		return "<C-_>";
	case 0x7f:
		return "<Del>";
	default:
		__builtin_unreachable();
	}
}

/*
 * v_event_err --
 *	Unexpected event.
 *
 * PUBLIC: void v_event_err(SCR *, EVENT *);
 */
void
v_event_err(SCR *sp, EVENT *evp)
{
	switch (evp->e_event) {
	case E_CHARACTER:
		msgq(sp, M_ERR, "276|Unexpected character event");
		break;
	case E_EOF:
		msgq(sp, M_ERR, "277|Unexpected end-of-file event");
		break;
	case E_INTERRUPT:
		msgq(sp, M_ERR, "279|Unexpected interrupt event");
		break;
	case E_REPAINT:
		msgq(sp, M_ERR, "281|Unexpected repaint event");
		break;
	case E_STRING:
		msgq(sp, M_ERR, "285|Unexpected string event");
		break;
	case E_TIMEOUT:
		msgq(sp, M_ERR, "286|Unexpected timeout event");
		break;
	case E_WRESIZE:
		msgq(sp, M_ERR, "316|Unexpected resize event");
		break;

	/*
	 * Theoretically, none of these can occur, as they're handled at the
	 * top editor level.
	 */
	case E_ERR:
	case E_SIGHUP:
	case E_SIGTERM:
	default:
		abort();
	}

	/* Free any allocated memory. */
	free(evp->e_asp);
}

/*
 * v_event_flush --
 *	Flush any flagged keys, returning if any keys were flushed.
 *
 * PUBLIC: int v_event_flush(SCR *, u_int);
 */
int
v_event_flush(SCR *sp, u_int flags)
{
	GS *gp;
	int rval;

	for (rval = 0, gp = sp->gp; gp->i_cnt != 0 &&
	    F_ISSET(&gp->i_event[gp->i_next].e_ch, flags); rval = 1)
		QREM(1);
	return (rval);
}

/*
 * v_event_grow --
 *	Grow the terminal queue.
 */
static int
v_event_grow(SCR *sp, int add)
{
	GS *gp;
	size_t new_nelem, olen;

	gp = sp->gp;
	new_nelem = gp->i_nelem + add;
	olen = gp->i_nelem * sizeof(gp->i_event[0]);
	BINC_RET(sp, EVENT, gp->i_event, olen, new_nelem * sizeof(gp->i_event[0]));
	gp->i_nelem = olen / sizeof(gp->i_event[0]);
	return (0);
}

/*
 * v_key_cmp --
 *	Compare two keys for sorting.
 */
static int
v_key_cmp(const void *ap, const void *bp)
{
	return (((KEYLIST *)ap)->ch - ((KEYLIST *)bp)->ch);
}