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Tidy up the terminal detection and feature code and add named sets of
terminal features, each of which are defined in one place and map to a
builtin set of terminfo(5) capabilities. Features can be specified based
on TERM with a new terminal-features option or with the -T flag when
running tmux. tmux will also detect a few common terminals from the DA
and DSR responses.

This is intended to make it easier to configure tmux's use of
terminfo(5) even in the presence of outdated ncurses(3) or terminfo(5)
databases or for features which do not yet have a terminfo(5) entry.
Instead of having to grok terminfo(5) capability names and what they
should be set to in the terminal-overrides option, the user can
hopefully just give tmux a feature name and let it do the right thing.

The terminal-overrides option remains both for backwards compatibility
and to allow tweaks of individual capabilities.

tmux already did much of this already, this makes it tidier and simpler
to configure.

/* $OpenBSD: tty-acs.c,v 1.9 2020/04/20 13:25:36 nicm Exp $ */

/*
 * Copyright (c) 2010 Nicholas Marriott <nicholas.marriott@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

#include <stdlib.h>

#include "tmux.h"

static int	tty_acs_cmp(const void *, const void *);

/* Table mapping ACS entries to UTF-8. */
struct tty_acs_entry {
	u_char	 	 key;
	const char	*string;
};
static const struct tty_acs_entry tty_acs_table[] = {
	{ '+', "\342\206\222" },	/* arrow pointing right */
	{ ',', "\342\206\220" },	/* arrow pointing left */
	{ '-', "\342\206\221" },	/* arrow pointing up */
	{ '.', "\342\206\223" },	/* arrow pointing down */
	{ '0', "\342\226\256" },	/* solid square block */
	{ '`', "\342\227\206" },	/* diamond */
	{ 'a', "\342\226\222" },	/* checker board (stipple) */
	{ 'b', "\342\220\211" },
	{ 'c', "\342\220\214" },
	{ 'd', "\342\220\215" },
	{ 'e', "\342\220\212" },
	{ 'f', "\302\260" },		/* degree symbol */
	{ 'g', "\302\261" },		/* plus/minus */
	{ 'h', "\342\220\244" },
	{ 'i', "\342\220\213" },
	{ 'j', "\342\224\230" },	/* lower right corner */
	{ 'k', "\342\224\220" },	/* upper right corner */
	{ 'l', "\342\224\214" },	/* upper left corner */
	{ 'm', "\342\224\224" },	/* lower left corner */
	{ 'n', "\342\224\274" },	/* large plus or crossover */
	{ 'o', "\342\216\272" },	/* scan line 1 */
	{ 'p', "\342\216\273" },	/* scan line 3 */
	{ 'q', "\342\224\200" },	/* horizontal line */
	{ 'r', "\342\216\274" },	/* scan line 7 */
	{ 's', "\342\216\275" },	/* scan line 9 */
	{ 't', "\342\224\234" },	/* tee pointing right */
	{ 'u', "\342\224\244" },	/* tee pointing left */
	{ 'v', "\342\224\264" },	/* tee pointing up */
	{ 'w', "\342\224\254" },	/* tee pointing down */
	{ 'x', "\342\224\202" },	/* vertical line */
	{ 'y', "\342\211\244" },	/* less-than-or-equal-to */
	{ 'z', "\342\211\245" },	/* greater-than-or-equal-to */
	{ '{', "\317\200" },   		/* greek pi */
	{ '|', "\342\211\240" },	/* not-equal */
	{ '}', "\302\243" },		/* UK pound sign */
	{ '~', "\302\267" }		/* bullet */
};

static int
tty_acs_cmp(const void *key, const void *value)
{
	const struct tty_acs_entry	*entry = value;
	u_char				 ch;

	ch = *(u_char *) key;
	return (ch - entry->key);
}

/* Should this terminal use ACS instead of UTF-8 line drawing? */
int
tty_acs_needed(struct tty *tty)
{
	if (tty == NULL)
		return (0);

	/*
	 * If the U8 flag is present, it marks whether a terminal supports
	 * UTF-8 and ACS together.
	 *
	 * If it is present and zero, we force ACS - this gives users a way to
	 * turn off UTF-8 line drawing.
	 *
	 * If it is nonzero, we can fall through to the default and use UTF-8
	 * line drawing on UTF-8 terminals.
	 */
	if (tty_term_has(tty->term, TTYC_U8) &&
	    tty_term_number(tty->term, TTYC_U8) == 0)
		return (1);

	if (tty->client->flags & CLIENT_UTF8)
		return (0);
	return (1);
}

/* Retrieve ACS to output as a string. */
const char *
tty_acs_get(struct tty *tty, u_char ch)
{
	struct tty_acs_entry	*entry;

	/* Use the ACS set instead of UTF-8 if needed. */
	if (tty_acs_needed(tty)) {
		if (tty->term->acs[ch][0] == '\0')
			return (NULL);
		return (&tty->term->acs[ch][0]);
	}

	/* Otherwise look up the UTF-8 translation. */
	entry = bsearch(&ch, tty_acs_table, nitems(tty_acs_table),
	    sizeof tty_acs_table[0], tty_acs_cmp);
	if (entry == NULL)
		return (NULL);
	return (entry->string);
}