path: root/vt.c

/*
 * Copyright © 2004 Bruno T. C. de Oliveira
 * Copyright © 2006 Pierre Habouzit
 * Copyright © 2008-2016 Marc André Tanner
 *
 * 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 <stdlib.h>
#include <stdint.h>
#include <signal.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <langinfo.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <termios.h>
#include <signal.h>
#include <wchar.h>
#if defined(__linux__) || defined(__CYGWIN__)
# include <pty.h>
#elif defined(__FreeBSD__) || defined(__DragonFly__)
# include <libutil.h>
#elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__APPLE__)
# include <util.h>
#endif

#include "vt.h"

#ifdef _AIX
# include "forkpty-aix.c"
#elif defined __sun
# include "forkpty-sunos.c"
#endif

#ifndef NCURSES_ATTR_SHIFT
# define NCURSES_ATTR_SHIFT 8
#endif

#ifndef NCURSES_ACS
# ifdef PDCURSES
#  define NCURSES_ACS(c) (acs_map[(unsigned char)(c)])
# else /* BSD curses */
#  define NCURSES_ACS(c) (_acs_map[(unsigned char)(c)])
# endif
#endif

#ifdef NCURSES_VERSION
# ifndef NCURSES_EXT_COLORS
#  define NCURSES_EXT_COLORS 0
# endif
# if !NCURSES_EXT_COLORS
#  define MAX_COLOR_PAIRS MIN(COLOR_PAIRS, 256)
# endif
#endif
#ifndef MAX_COLOR_PAIRS
# define MAX_COLOR_PAIRS COLOR_PAIRS
#endif

#if defined _AIX && defined CTRL
# undef CTRL
#endif
#ifndef CTRL
# define CTRL(k)   ((k) & 0x1F)
#endif

#define IS_CONTROL(ch) !((ch) & 0xffffff60UL)
#define MIN(x, y) ((x) < (y) ? (x) : (y))
#define LENGTH(arr) (sizeof(arr) / sizeof((arr)[0]))

static bool is_utf8, has_default_colors;
static short color_pairs_reserved, color_pairs_max, color_pair_current;
static short *color2palette, default_fg, default_bg;
static char vt_term[32];

typedef struct {
	wchar_t text;
	attr_t attr;
	short fg;
	short bg;
} Cell;

typedef struct {
	Cell *cells;
	unsigned dirty:1;
} Row;

/* Buffer holding the current terminal window content (as an array) as well
 * as the scroll back buffer content (as a circular/ring buffer).
 *
 * If new content is added to terminal the view port slides down and the
 * previously top most line is moved into the scroll back buffer at postion
 * scroll_index. This index will eventually wrap around and thus overwrite
 * the oldest lines.
 *
 * In the scenerio below a scroll up has been performed. That is 'scroll_above'
 * lines still lie above the current view port. Further scrolling up will show
 * them. Similarly 'scroll_below' is the amount of lines below the current
 * viewport.
 *
 * The function buffer_boundary sets the row pointers to the start/end range
 * of the section delimiting the region before/after the viewport. The functions
 * buffer_row_{first,last} return the first/last logical row. And
 * buffer_row_{next,prev} allows to iterate over the logical lines in either
 * direction.
 *
 *                                     scroll back buffer
 *
 *                      scroll_buf->+----------------+-----+
 *                                  |                |     | ^  \
 *                                  |     before     |     | |  |
 *    current terminal content      |    viewport    |     | |  |
 *                                  |                |     |    |
 *    +----------------+-----+\     |                |     | s   > scroll_above
 *  ^ |                |  i  | \    |                |  i  | c  |
 *  | |                |  n  |  \   |                |  n  | r  |
 *    |                |  v  |   \  |                |  v  | o  |
 *  r |                |  i  |    \ |                |  i  | l  /
 *  o |    viewport    |  s  |     >|<- scroll_index |  s  | l  \
 *  w |                |  i  |    / |                |  i  |    |
 *  s |                |  b  |   /  |     after      |  b  | s   > scroll_below
 *    |                |  l  |  /   |    viewport    |  l  | i  |
 *  v |                |  e  | /    |                |  e  | z  /
 *    +----------------+-----+/     |     unused     |     | e
 *     <-    maxcols      ->        |   scroll back  |     |
 *     <-    cols    ->             |     buffer     |     | |
 *                                  |                |     | |
 *                                  |                |     | v
 *          roll_buf + scroll_size->+----------------+-----+
 *                                   <-    maxcols       ->
 *                                   <-    cols    ->
 */
typedef struct {
	Row *lines;            /* array of Row pointers of size 'rows' */
	Row *curs_row;         /* row on which the cursor currently resides */
	Row *scroll_buf;       /* a ring buffer holding the scroll back content */
	Row *scroll_top;       /* row in lines where scrolling region starts */
	Row *scroll_bot;       /* row in lines where scrolling region ends */
	bool *tabs;            /* a boolean flag for each column whether it is a tab */
	int scroll_size;       /* maximal capacity of scroll back buffer (in lines) */
	int scroll_index;      /* current index into the ring buffer */
	int scroll_above;      /* number of lines above current viewport */
	int scroll_below;      /* number of lines below current viewport */
	int rows, cols;        /* current dimension of buffer */
	int maxcols;           /* allocated cells (maximal cols over time) */
	attr_t curattrs, savattrs; /* current and saved attributes for cells */
	int curs_col;          /* current cursor column (zero based) */
	int curs_srow, curs_scol; /* saved cursor row/colmn (zero based) */
	short curfg, curbg;    /* current fore and background colors */
	short savfg, savbg;    /* saved colors */
} Buffer;

struct Vt {
	Buffer buffer_normal;    /* normal screen buffer */
	Buffer buffer_alternate; /* alternate screen buffer */
	Buffer *buffer;          /* currently active buffer (one of the above) */
	attr_t defattrs;         /* attributes to use for normal/empty cells */
	short deffg, defbg;      /* colors to use for back normal/empty cells (white/black) */
	int pty;                 /* master side pty file descriptor */
	pid_t pid;               /* process id of the process running in this vt */
	/* flags */
	unsigned seen_input:1;
	unsigned insert:1;
	unsigned escaped:1;
	unsigned curshid:1;
	unsigned curskeymode:1;
	unsigned bell:1;
	unsigned relposmode:1;
	unsigned mousetrack:1;
	unsigned graphmode:1;
	unsigned savgraphmode:1;
	bool charsets[2];
	/* buffers and parsing state */
	char rbuf[BUFSIZ];
	char ebuf[BUFSIZ];
	unsigned int rlen, elen;
	int srow, scol;          /* last known offset to display start row, start column */
	char title[256];         /* xterm style window title */
	vt_title_handler_t title_handler; /* hook which is called when title changes */
	vt_urgent_handler_t urgent_handler; /* hook which is called upon bell */
	void *data;              /* user supplied data */
};

static const char *keytable[KEY_MAX+1] = {
	[KEY_ENTER]     = "\r",
	['\n']          = "\n",
	/* for the arrow keys the CSI / SS3 sequences are not stored here
	 * because they depend on the current cursor terminal mode
	 */
	[KEY_UP]        = "A",
	[KEY_DOWN]      = "B",
	[KEY_RIGHT]     = "C",
	[KEY_LEFT]      = "D",
#ifdef KEY_SUP
	[KEY_SUP]       = "\e[1;2A",
#endif
#ifdef KEY_SDOWN
	[KEY_SDOWN]     = "\e[1;2B",
#endif
	[KEY_SRIGHT]    = "\e[1;2C",
	[KEY_SLEFT]     = "\e[1;2D",
	[KEY_BACKSPACE] = "\177",
	[KEY_IC]        = "\e[2~",
	[KEY_DC]        = "\e[3~",
	[KEY_PPAGE]     = "\e[5~",
	[KEY_NPAGE]     = "\e[6~",
	[KEY_HOME]      = "\e[7~",
	[KEY_END]       = "\e[8~",
	[KEY_BTAB]      = "\e[Z",
	[KEY_SUSPEND]   = "\x1A",  /* Ctrl+Z gets mapped to this */
	[KEY_F(1)]      = "\e[11~",
	[KEY_F(2)]      = "\e[12~",
	[KEY_F(3)]      = "\e[13~",
	[KEY_F(4)]      = "\e[14~",
	[KEY_F(5)]      = "\e[15~",
	[KEY_F(6)]      = "\e[17~",
	[KEY_F(7)]      = "\e[18~",
	[KEY_F(8)]      = "\e[19~",
	[KEY_F(9)]      = "\e[20~",
	[KEY_F(10)]     = "\e[21~",
	[KEY_F(11)]     = "\e[23~",
	[KEY_F(12)]     = "\e[24~",
	[KEY_F(13)]     = "\e[23~",
	[KEY_F(14)]     = "\e[24~",
	[KEY_F(15)]     = "\e[25~",
	[KEY_F(16)]     = "\e[26~",
	[KEY_F(17)]     = "\e[28~",
	[KEY_F(18)]     = "\e[29~",
	[KEY_F(19)]     = "\e[31~",
	[KEY_F(20)]     = "\e[32~",
	[KEY_F(21)]     = "\e[33~",
	[KEY_F(22)]     = "\e[34~",
	[KEY_RESIZE]    = "",
#ifdef KEY_EVENT
	[KEY_EVENT]     = "",
#endif
};

static void puttab(Vt *t, int count);
static void process_nonprinting(Vt *t, wchar_t wc);
static void send_curs(Vt *t);

__attribute__ ((const))
static attr_t build_attrs(attr_t curattrs)
{
	return ((curattrs & ~A_COLOR) | COLOR_PAIR(curattrs & 0xff))
	    >> NCURSES_ATTR_SHIFT;
}

static void row_set(Row *row, int start, int len, Buffer *t)
{
	Cell cell = {
		.text = L'\0',
		.attr = t ? build_attrs(t->curattrs) : 0,
		.fg = t ? t->curfg : -1,
		.bg = t ? t->curbg : -1,
	};

	for (int i = start; i < len + start; i++)
		row->cells[i] = cell;
	row->dirty = true;
}

static void row_roll(Row *start, Row *end, int count)
{
	int n = end - start;

	count %= n;
	if (count < 0)
		count += n;

	if (count) {
		char buf[count * sizeof(Row)];
		memcpy(buf, start, count * sizeof(Row));
		memmove(start, start + count, (n - count) * sizeof(Row));
		memcpy(end - count, buf, count * sizeof(Row));
		for (Row *row = start; row < end; row++)
			row->dirty = true;
	}
}

static void buffer_clear(Buffer *b)
{
	Cell cell = {
		.text = L'\0',
		.attr = A_NORMAL,
		.fg = -1,
		.bg = -1,
	};

	for (int i = 0; i < b->rows; i++) {
		Row *row = b->lines + i;
		for (int j = 0; j < b->cols; j++) {
			row->cells[j] = cell;
			row->dirty = true;
		}
	}
}

static void buffer_free(Buffer *b)
{
	for (int i = 0; i < b->rows; i++)
		free(b->lines[i].cells);
	free(b->lines);
	for (int i = 0; i < b->scroll_size; i++)
		free(b->scroll_buf[i].cells);
	free(b->scroll_buf);
	free(b->tabs);
}

static void buffer_scroll(Buffer *b, int s)
{
	/* work in screenfuls */
	int ssz = b->scroll_bot - b->scroll_top;
	if (s > ssz) {
		buffer_scroll(b, ssz);
		buffer_scroll(b, s - ssz);
		return;
	}
	if (s < -ssz) {
		buffer_scroll(b, -ssz);
		buffer_scroll(b, s + ssz);
		return;
	}

	b->scroll_above += s;
	if (b->scroll_above >= b->scroll_size)
		b->scroll_above = b->scroll_size;

	if (s > 0 && b->scroll_size) {
		for (int i = 0; i < s; i++) {
			Row tmp = b->scroll_top[i];
			b->scroll_top[i] = b->scroll_buf[b->scroll_index];
			b->scroll_buf[b->scroll_index] = tmp;

			b->scroll_index++;
			if (b->scroll_index == b->scroll_size)
				b->scroll_index = 0;
		}
	}
	row_roll(b->scroll_top, b->scroll_bot, s);
	if (s < 0 && b->scroll_size) {
		for (int i = (-s) - 1; i >= 0; i--) {
			b->scroll_index--;
			if (b->scroll_index == -1)
				b->scroll_index = b->scroll_size - 1;

			Row tmp = b->scroll_top[i];
			b->scroll_top[i] = b->scroll_buf[b->scroll_index];
			b->scroll_buf[b->scroll_index] = tmp;
			b->scroll_top[i].dirty = true;
		}
	}
}

static void buffer_resize(Buffer *b, int rows, int cols)
{
	Row *lines = b->lines;

	if (b->rows != rows) {
		if (b->curs_row >= lines + rows) {
			/* scroll up instead of simply chopping off bottom */
			buffer_scroll(b, (b->curs_row - b->lines) - rows + 1);
		}
		while (b->rows > rows) {
			free(lines[b->rows - 1].cells);
			b->rows--;
		}

		lines = realloc(lines, sizeof(Row) * rows);
	}

	if (b->maxcols < cols) {
		for (int row = 0; row < b->rows; row++) {
			lines[row].cells = realloc(lines[row].cells, sizeof(Cell) * cols);
			if (b->cols < cols)
				row_set(lines + row, b->cols, cols - b->cols, NULL);
			lines[row].dirty = true;
		}
		Row *sbuf = b->scroll_buf;
		for (int row = 0; row < b->scroll_size; row++) {
			sbuf[row].cells = realloc(sbuf[row].cells, sizeof(Cell) * cols);
			if (b->cols < cols)
				row_set(sbuf + row, b->cols, cols - b->cols, NULL);
		}
		b->tabs = realloc(b->tabs, sizeof(*b->tabs) * cols);
		for (int col = b->cols; col < cols; col++)
			b->tabs[col] = !(col & 7);
		b->maxcols = cols;
		b->cols = cols;
	} else if (b->cols != cols) {
		for (int row = 0; row < b->rows; row++)
			lines[row].dirty = true;
		b->cols = cols;
	}

	int deltarows = 0;
	if (b->rows < rows) {
		while (b->rows < rows) {
			lines[b->rows].cells = calloc(b->maxcols, sizeof(Cell));
			row_set(lines + b->rows, 0, b->maxcols, b);
			b->rows++;
		}

		/* prepare for backfill */
		if (b->curs_row >= b->scroll_bot - 1) {
			deltarows = b->lines + rows - b->curs_row - 1;
			if (deltarows > b->scroll_above)
				deltarows = b->scroll_above;
		}
	}

	b->curs_row += lines - b->lines;
	b->scroll_top = lines;
	b->scroll_bot = lines + rows;
	b->lines = lines;

	/* perform backfill */
	if (deltarows > 0) {
		buffer_scroll(b, -deltarows);
		b->curs_row += deltarows;
	}
}

static bool buffer_init(Buffer *b, int rows, int cols, int scroll_size)
{
	b->curattrs = A_NORMAL;	/* white text over black background */
	b->curfg = b->curbg = -1;
	if (scroll_size < 0)
		scroll_size = 0;
	if (scroll_size && !(b->scroll_buf = calloc(scroll_size, sizeof(Row))))
		return false;
	b->scroll_size = scroll_size;
	buffer_resize(b, rows, cols);
	return true;
}

static void buffer_boundry(Buffer *b, Row **bs, Row **be, Row **as, Row **ae) {
	if (bs)
		*bs = NULL;
	if (be)
		*be = NULL;
	if (as)
		*as = NULL;
	if (ae)
		*ae = NULL;
	if (!b->scroll_size)
		return;

	if (b->scroll_above) {
		if (bs)
			*bs = &b->scroll_buf[(b->scroll_index - b->scroll_above + b->scroll_size) % b->scroll_size];
		if (be)
			*be = &b->scroll_buf[(b->scroll_index-1 + b->scroll_size) % b->scroll_size];
	}
	if (b->scroll_below) {
		if (as)
			*as = &b->scroll_buf[b->scroll_index];
		if (ae)
			*ae = &b->scroll_buf[(b->scroll_index + b->scroll_below-1) % b->scroll_size];
	}
}

static Row *buffer_row_first(Buffer *b) {
	Row *bstart;
	if (!b->scroll_size || !b->scroll_above)
		return b->lines;
	buffer_boundry(b, &bstart, NULL, NULL, NULL);
	return bstart;
}

static Row *buffer_row_last(Buffer *b) {
	Row *aend;
	if (!b->scroll_size || !b->scroll_below)
		return b->lines + b->rows - 1;
	buffer_boundry(b, NULL, NULL, NULL, &aend);
	return aend;
}

static Row *buffer_row_next(Buffer *b, Row *row)
{
	Row *before_start, *before_end, *after_start, *after_end;
	Row *first = b->lines, *last = b->lines + b->rows - 1;

	if (!row)
		return NULL;

	buffer_boundry(b, &before_start, &before_end, &after_start, &after_end);

	if (row >= first && row < last)
		return ++row;
	if (row == last)
		return after_start;
	if (row == before_end)
		return first;
	if (row == after_end)
		return NULL;
	if (row == &b->scroll_buf[b->scroll_size - 1])
		return b->scroll_buf;
	return ++row;
}

static Row *buffer_row_prev(Buffer *b, Row *row)
{
	Row *before_start, *before_end, *after_start, *after_end;
	Row *first = b->lines, *last = b->lines + b->rows - 1;

	if (!row)
		return NULL;

	buffer_boundry(b, &before_start, &before_end, &after_start, &after_end);

	if (row > first && row <= last)
		return --row;
	if (row == first)
		return before_end;
	if (row == before_start)
		return NULL;
	if (row == after_start)
		return last;
	if (row == b->scroll_buf)
		return &b->scroll_buf[b->scroll_size - 1];
	return --row;
}

static void cursor_clamp(Vt *t)
{
	Buffer *b = t->buffer;
	Row *lines = t->relposmode ? b->scroll_top : b->lines;
	int rows = t->relposmode ? b->scroll_bot - b->scroll_top : b->rows;

	if (b->curs_row < lines)
		b->curs_row = lines;
	if (b->curs_row >= lines + rows)
		b->curs_row = lines + rows - 1;
	if (b->curs_col < 0)
		b->curs_col = 0;
	if (b->curs_col >= b->cols)
		b->curs_col = b->cols - 1;
}

static void cursor_line_down(Vt *t)
{
	Buffer *b = t->buffer;
	row_set(b->curs_row, b->cols, b->maxcols - b->cols, NULL);
	b->curs_row++;
	if (b->curs_row < b->scroll_bot)
		return;

	vt_noscroll(t);

	b->curs_row = b->scroll_bot - 1;
	buffer_scroll(b, 1);
	row_set(b->curs_row, 0, b->cols, b);
}

static void cursor_save(Vt *t)
{
	Buffer *b = t->buffer;
	b->curs_srow = b->curs_row - b->lines;
	b->curs_scol = b->curs_col;
}

static void cursor_restore(Vt *t)
{
	Buffer *b = t->buffer;
	b->curs_row = b->lines + b->curs_srow;
	b->curs_col = b->curs_scol;
	cursor_clamp(t);
}

static void attributes_save(Vt *t)
{
	Buffer *b = t->buffer;
	b->savattrs = b->curattrs;
	b->savfg = b->curfg;
	b->savbg = b->curbg;
	t->savgraphmode = t->graphmode;
}

static void attributes_restore(Vt *t)
{
	Buffer *b = t->buffer;
	b->curattrs = b->savattrs;
	b->curfg = b->savfg;
	b->curbg = b->savbg;
	t->graphmode = t->savgraphmode;
}

static void new_escape_sequence(Vt *t)
{
	t->escaped = true;
	t->elen = 0;
	t->ebuf[0] = '\0';
}

static void cancel_escape_sequence(Vt *t)
{
	t->escaped = false;
	t->elen = 0;
	t->ebuf[0] = '\0';
}

static bool is_valid_csi_ender(int c)
{
	return (c >= 'a' && c <= 'z')
	    || (c >= 'A' && c <= 'Z')
	    || (c == '@' || c == '`');
}

/* interprets a 'set attribute' (SGR) CSI escape sequence */
static void interpret_csi_sgr(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	if (pcount == 0) {
		/* special case: reset attributes */
		b->curattrs = A_NORMAL;
		b->curfg = b->curbg = -1;
		return;
	}

	for (int i = 0; i < pcount; i++) {
		switch (param[i]) {
		case 0:
			b->curattrs = A_NORMAL;
			b->curfg = b->curbg = -1;
			break;
		case 1:
			b->curattrs |= A_BOLD;
			break;
		case 2:
			b->curattrs |= A_DIM;
			break;
#ifdef A_ITALIC
		case 3:
			b->curattrs |= A_ITALIC;
			break;
#endif
		case 4:
			b->curattrs |= A_UNDERLINE;
			break;
		case 5:
			b->curattrs |= A_BLINK;
			break;
		case 7:
			b->curattrs |= A_REVERSE;
			break;
		case 8:
			b->curattrs |= A_INVIS;
			break;
		case 22:
			b->curattrs &= ~(A_BOLD | A_DIM);
			break;
#ifdef A_ITALIC
		case 23:
			b->curattrs &= ~A_ITALIC;
			break;
#endif
		case 24:
			b->curattrs &= ~A_UNDERLINE;
			break;
		case 25:
			b->curattrs &= ~A_BLINK;
			break;
		case 27:
			b->curattrs &= ~A_REVERSE;
			break;
		case 28:
			b->curattrs &= ~A_INVIS;
			break;
		case 30 ... 37:	/* fg */
			b->curfg = param[i] - 30;
			break;
		case 38:
			if ((i + 2) < pcount && param[i + 1] == 5) {
				b->curfg = param[i + 2];
				i += 2;
			}
			break;
		case 39:
			b->curfg = -1;
			break;
		case 40 ... 47:	/* bg */
			b->curbg = param[i] - 40;
			break;
		case 48:
			if ((i + 2) < pcount && param[i + 1] == 5) {
				b->curbg = param[i + 2];
				i += 2;
			}
			break;
		case 49:
			b->curbg = -1;
			break;
		case 90 ... 97:	/* hi fg */
			b->curfg = param[i] - 82;
			break;
		case 100 ... 107: /* hi bg */
			b->curbg = param[i] - 92;
			break;
		default:
			break;
		}
	}
}

/* interprets an 'erase display' (ED) escape sequence */
static void interpret_csi_ed(Vt *t, int param[], int pcount)
{
	Row *row, *start, *end;
	Buffer *b = t->buffer;

	attributes_save(t);
	b->curattrs = A_NORMAL;
	b->curfg = b->curbg = -1;

	if (pcount && param[0] == 2) {
		start = b->lines;
		end = b->lines + b->rows;
	} else if (pcount && param[0] == 1) {
		start = b->lines;
		end = b->curs_row;
		row_set(b->curs_row, 0, b->curs_col + 1, b);
	} else {
		row_set(b->curs_row, b->curs_col, b->cols - b->curs_col, b);
		start = b->curs_row + 1;
		end = b->lines + b->rows;
	}

	for (row = start; row < end; row++)
		row_set(row, 0, b->cols, b);

	attributes_restore(t);
}

/* interprets a 'move cursor' (CUP) escape sequence */
static void interpret_csi_cup(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	Row *lines = t->relposmode ? b->scroll_top : b->lines;

	if (pcount == 0) {
		b->curs_row = lines;
		b->curs_col = 0;
	} else if (pcount == 1) {
		b->curs_row = lines + param[0] - 1;
		b->curs_col = 0;
	} else {
		b->curs_row = lines + param[0] - 1;
		b->curs_col = param[1] - 1;
	}

	cursor_clamp(t);
}

/* Interpret the 'relative mode' sequences: CUU, CUD, CUF, CUB, CNL,
 * CPL, CHA, HPR, VPA, VPR, HPA */
static void interpret_csi_c(Vt *t, char verb, int param[], int pcount)
{
	Buffer *b = t->buffer;
	int n = (pcount && param[0] > 0) ? param[0] : 1;

	switch (verb) {
	case 'A':
		b->curs_row -= n;
		break;
	case 'B':
	case 'e':
		b->curs_row += n;
		break;
	case 'C':
	case 'a':
		b->curs_col += n;
		break;
	case 'D':
		b->curs_col -= n;
		break;
	case 'E':
		b->curs_row += n;
		b->curs_col = 0;
		break;
	case 'F':
		b->curs_row -= n;
		b->curs_col = 0;
		break;
	case 'G':
	case '`':
		b->curs_col = n - 1;
		break;
	case 'd':
		b->curs_row = b->lines + n - 1;
		break;
	}

	cursor_clamp(t);
}

/* Interpret the 'erase line' escape sequence */
static void interpret_csi_el(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	switch (pcount ? param[0] : 0) {
	case 1:
		row_set(b->curs_row, 0, b->curs_col + 1, b);
		break;
	case 2:
		row_set(b->curs_row, 0, b->cols, b);
		break;
	default:
		row_set(b->curs_row, b->curs_col, b->cols - b->curs_col, b);
		break;
	}
}

/* Interpret the 'insert blanks' sequence (ICH) */
static void interpret_csi_ich(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	Row *row = b->curs_row;
	int n = (pcount && param[0] > 0) ? param[0] : 1;

	if (b->curs_col + n > b->cols)
		n = b->cols - b->curs_col;

	for (int i = b->cols - 1; i >= b->curs_col + n; i--)
		row->cells[i] = row->cells[i - n];

	row_set(row, b->curs_col, n, b);
}

/* Interpret the 'delete chars' sequence (DCH) */
static void interpret_csi_dch(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	Row *row = b->curs_row;
	int n = (pcount && param[0] > 0) ? param[0] : 1;

	if (b->curs_col + n > b->cols)
		n = b->cols - b->curs_col;

	for (int i = b->curs_col; i < b->cols - n; i++)
		row->cells[i] = row->cells[i + n];

	row_set(row, b->cols - n, n, b);
}

/* Interpret an 'insert line' sequence (IL) */
static void interpret_csi_il(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	int n = (pcount && param[0] > 0) ? param[0] : 1;

	if (b->curs_row + n >= b->scroll_bot) {
		for (Row *row = b->curs_row; row < b->scroll_bot; row++)
			row_set(row, 0, b->cols, b);
	} else {
		row_roll(b->curs_row, b->scroll_bot, -n);
		for (Row *row = b->curs_row; row < b->curs_row + n; row++)
			row_set(row, 0, b->cols, b);
	}
}

/* Interpret a 'delete line' sequence (DL) */
static void interpret_csi_dl(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	int n = (pcount && param[0] > 0) ? param[0] : 1;

	if (b->curs_row + n >= b->scroll_bot) {
		for (Row *row = b->curs_row; row < b->scroll_bot; row++)
			row_set(row, 0, b->cols, b);
	} else {
		row_roll(b->curs_row, b->scroll_bot, n);
		for (Row *row = b->scroll_bot - n; row < b->scroll_bot; row++)
			row_set(row, 0, b->cols, b);
	}
}

/* Interpret an 'erase characters' (ECH) sequence */
static void interpret_csi_ech(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	int n = (pcount && param[0] > 0) ? param[0] : 1;

	if (b->curs_col + n > b->cols)
		n = b->cols - b->curs_col;

	row_set(b->curs_row, b->curs_col, n, b);
}

/* Interpret a 'set scrolling region' (DECSTBM) sequence */
static void interpret_csi_decstbm(Vt *t, int param[], int pcount)
{
	Buffer *b = t->buffer;
	int new_top, new_bot;

	switch (pcount) {
	case 0:
		b->scroll_top = b->lines;
		b->scroll_bot = b->lines + b->rows;
		break;
	case 2:
		new_top = param[0] - 1;
		new_bot = param[1];

		/* clamp to bounds */
		if (new_top < 0)
			new_top = 0;
		if (new_top >= b->rows)
			new_top = b->rows - 1;
		if (new_bot < 0)
			new_bot = 0;
		if (new_bot >= b->rows)
			new_bot = b->rows;

		/* check for range validity */
		if (new_top < new_bot) {
			b->scroll_top = b->lines + new_top;
			b->scroll_bot = b->lines + new_bot;
		}
		break;
	default:
		return;	/* malformed */
	}
	b->curs_row = b->scroll_top;
	b->curs_col = 0;
}

static void interpret_csi_mode(Vt *t, int param[], int pcount, bool set)
{
	for (int i = 0; i < pcount; i++) {
		switch (param[i]) {
		case 4: /* insert/replace mode */
			t->insert = set;
			break;
		}
	}
}

static void interpret_csi_priv_mode(Vt *t, int param[], int pcount, bool set)
{
	for (int i = 0; i < pcount; i++) {
		switch (param[i]) {
		case 1: /* set application/normal cursor key mode (DECCKM) */
			t->curskeymode = set;
			break;
		case 6: /* set origin to relative/absolute (DECOM) */
			t->relposmode = set;
			break;
		case 25: /* make cursor visible/invisible (DECCM) */
			t->curshid = !set;
			break;
		case 1049: /* combine 1047 + 1048 */
		case 47:   /* use alternate/normal screen buffer */
		case 1047:
			if (!set)
				buffer_clear(&t->buffer_alternate);
			t->buffer = set ? &t->buffer_alternate : &t->buffer_normal;
			vt_dirty(t);
			if (param[i] != 1049)
				break;
			/* fall through */
		case 1048: /* save/restore cursor */
			if (set)
				cursor_save(t);
			else
				cursor_restore(t);
			break;
		case 1000: /* enable/disable normal mouse tracking */
			t->mousetrack = set;
			break;
		}
	}
}

static void interpret_csi(Vt *t)
{
	Buffer *b = t->buffer;
	int csiparam[16];
	unsigned int param_count = 0;
	const char *p = t->ebuf + 1;
	char verb = t->ebuf[t->elen - 1];

	/* parse numeric parameters */
	for (p += (t->ebuf[1] == '?'); *p; p++) {
		if (IS_CONTROL(*p)) {
			process_nonprinting(t, *p);
		} else if (*p == ';') {
			if (param_count >= LENGTH(csiparam))
				return;	/* too long! */
			csiparam[param_count++] = 0;
		} else if (isdigit((unsigned char)*p)) {
			if (param_count == 0)
				csiparam[param_count++] = 0;
			csiparam[param_count - 1] *= 10;
			csiparam[param_count - 1] += *p - '0';
		}
	}

	if (t->ebuf[1] == '?') {
		switch (verb) {
		case 'h':
		case 'l': /* private set/reset mode */
			interpret_csi_priv_mode(t, csiparam, param_count, verb == 'h');
			break;
		}
		return;
	}

	/* delegate handling depending on command character (verb) */
	switch (verb) {
	case 'h':
	case 'l': /* set/reset mode */
		interpret_csi_mode(t, csiparam, param_count, verb == 'h');
		break;
	case 'm': /* set attribute */
		interpret_csi_sgr(t, csiparam, param_count);
		break;
	case 'J': /* erase display */
		interpret_csi_ed(t, csiparam, param_count);
		break;
	case 'H':
	case 'f': /* move cursor */
		interpret_csi_cup(t, csiparam, param_count);
		break;
	case 'A':
	case 'B':
	case 'C':
	case 'D':
	case 'E':
	case 'F':
	case 'G':
	case 'e':
	case 'a':
	case 'd':
	case '`': /* relative move */
		interpret_csi_c(t, verb, csiparam, param_count);
		break;
	case 'K': /* erase line */
		interpret_csi_el(t, csiparam, param_count);
		break;
	case '@': /* insert characters */
		interpret_csi_ich(t, csiparam, param_count);
		break;
	case 'P': /* delete characters */
		interpret_csi_dch(t, csiparam, param_count);
		break;
	case 'L': /* insert lines */
		interpret_csi_il(t, csiparam, param_count);
		break;
	case 'M': /* delete lines */
		interpret_csi_dl(t, csiparam, param_count);
		break;
	case 'X': /* erase chars */
		interpret_csi_ech(t, csiparam, param_count);
		break;
	case 'S': /* SU: scroll up */
		vt_scroll(t, param_count ? -csiparam[0] : -1);
		break;
	case 'T': /* SD: scroll down */
		vt_scroll(t, param_count ? csiparam[0] : 1);
		break;
	case 'Z': /* CBT: cursor backward tabulation */
		puttab(t, param_count ? -csiparam[0] : -1);
		break;
	case 'g': /* TBC: tabulation clear */
		switch (param_count ? csiparam[0] : 0) {
		case 0:
			b->tabs[b->curs_col] = false;
			break;
		case 3:
			memset(b->tabs, 0, sizeof(*b->tabs) * b->maxcols);
			break;
		}
		break;
	case 'r': /* set scrolling region */
		interpret_csi_decstbm(t, csiparam, param_count);
		break;
	case 's': /* save cursor location */
		cursor_save(t);
		break;
	case 'u': /* restore cursor location */
		cursor_restore(t);
		break;
	case 'n': /* query cursor location */
		if (param_count == 1 && csiparam[0] == 6)
			send_curs(t);
		break;
	default:
		break;
	}
}

/* Interpret an 'index' (IND) sequence */
static void interpret_csi_ind(Vt *t)
{
	Buffer *b = t->buffer;
	if (b->curs_row < b->lines + b->rows - 1)
		b->curs_row++;
}

/* Interpret a 'reverse index' (RI) sequence */
static void interpret_csi_ri(Vt *t)
{
	Buffer *b = t->buffer;
	if (b->curs_row > b->scroll_top)
		b->curs_row--;
	else {
		row_roll(b->scroll_top, b->scroll_bot, -1);
		row_set(b->scroll_top, 0, b->cols, b);
	}
}

/* Interpret a 'next line' (NEL) sequence */
static void interpret_csi_nel(Vt *t)
{
	Buffer *b = t->buffer;
	if (b->curs_row < b->lines + b->rows - 1) {
		b->curs_row++;
		b->curs_col = 0;
	}
}

/* Interpret a 'select character set' (SCS) sequence */
static void interpret_csi_scs(Vt *t)
{
	/* ESC ( sets G0, ESC ) sets G1 */
	t->charsets[!!(t->ebuf[0] == ')')] = (t->ebuf[1] == '0');
	t->graphmode = t->charsets[0];
}

/* Interpret an 'operating system command' (OSC) sequence */
static void interpret_osc(Vt *t)
{
	/* ESC ] command ; data BEL
	 * ESC ] command ; data ESC \\
	 * Note that BEL or ESC \\ have already been replaced with NUL.
	 */
	char *data = NULL;
	int command = strtoul(t->ebuf + 1, &data, 10);
	if (data && *data == ';') {
		switch (command) {
		case 0: /* icon name and window title */
		case 2: /* window title */
			if (t->title_handler)
				t->title_handler(t, data+1);
			break;
		case 1: /* icon name */
			break;
		default:
#ifndef NDEBUG
			fprintf(stderr, "unknown OSC command: %d\n", command);
#endif
			break;
		}
	}
}

static void try_interpret_escape_seq(Vt *t)
{
	char lastchar = t->ebuf[t->elen - 1];

	if (!*t->ebuf)
		return;

	switch (*t->ebuf) {
	case '#': /* ignore DECDHL, DECSWL, DECDWL, DECHCP, DECFPP */
		if (t->elen == 2) {
			if (lastchar == '8') { /* DECALN */
				interpret_csi_ed(t, (int []){ 2 }, 1);
				goto handled;
			}
			goto cancel;
		}
		break;
	case '(':
	case ')':
		if (t->elen == 2) {
			interpret_csi_scs(t);
			goto handled;
		}
		break;
	case ']': /* OSC - operating system command */
		if (lastchar == '\a' ||
		   (lastchar == '\\' && t->elen >= 2 && t->ebuf[t->elen - 2] == '\e')) {
			t->elen -= lastchar == '\a' ? 1 : 2;
			t->ebuf[t->elen] = '\0';
			interpret_osc(t);
			goto handled;
		}
		break;
	case '[': /* CSI - control sequence introducer */
		if (is_valid_csi_ender(lastchar)) {
			interpret_csi(t);
			goto handled;
		}
		break;
	case '7': /* DECSC: save cursor and attributes */
		attributes_save(t);
		cursor_save(t);
		goto handled;
	case '8': /* DECRC: restore cursor and attributes */
		attributes_restore(t);
		cursor_restore(t);
		goto handled;
	case 'D': /* IND: index */
		interpret_csi_ind(t);
		goto handled;
	case 'M': /* RI: reverse index */
		interpret_csi_ri(t);
		goto handled;
	case 'E': /* NEL: next line */
		interpret_csi_nel(t);
		goto handled;
	case 'H': /* HTS: horizontal tab set */
		t->buffer->tabs[t->buffer->curs_col] = true;
		goto handled;
	default:
		goto cancel;
	}

	if (t->elen + 1 >= sizeof(t->ebuf)) {
cancel:
#ifndef NDEBUG
		fprintf(stderr, "cancelled: \\033");
		for (unsigned int i = 0; i < t->elen; i++) {
			if (isprint(t->ebuf[i])) {
				fputc(t->ebuf[i], stderr);
			} else {
				fprintf(stderr, "\\%03o", t->ebuf[i]);
			}
		}
		fputc('\n', stderr);
#endif
handled:
		cancel_escape_sequence(t);
	}
}

static void puttab(Vt *t, int count)
{
	Buffer *b = t->buffer;
	int direction = count >= 0 ? 1 : -1;
	for (int col = b->curs_col + direction; count; col += direction) {
		if (col < 0) {
			b->curs_col = 0;
			break;
		}
		if (col >= b->cols) {
			b->curs_col = b->cols - 1;
			break;
		}
		if (b->tabs[col]) {
			b->curs_col = col;
			count -= direction;
		}
	}
}

static void process_nonprinting(Vt *t, wchar_t wc)
{
	Buffer *b = t->buffer;
	switch (wc) {
	case '\e': /* ESC */
		new_escape_sequence(t);
		break;
	case '\a': /* BEL */
		if (t->urgent_handler)
			t->urgent_handler(t);
		break;
	case '\b': /* BS */
		if (b->curs_col > 0)
			b->curs_col--;
		break;
	case '\t': /* HT */
		puttab(t, 1);
		break;
	case '\r': /* CR */
		b->curs_col = 0;
		break;
	case '\v': /* VT */
	case '\f': /* FF */
	case '\n': /* LF */
		cursor_line_down(t);
		break;
	case '\016': /* SO: shift out, invoke the G1 character set */
		t->graphmode = t->charsets[1];
		break;
	case '\017': /* SI: shift in, invoke the G0 character set */
		t->graphmode = t->charsets[0];
		break;
	}
}

static void is_utf8_locale(void)
{
	const char *cset = nl_langinfo(CODESET);
	if (!cset)
		cset = "ANSI_X3.4-1968";
	is_utf8 = !strcmp(cset, "UTF-8");
}

static wchar_t get_vt100_graphic(char c)
{
	static char vt100_acs[] = "`afgjklmnopqrstuvwxyz{|}~";

	/*
	 * 5f-7e standard vt100
	 * 40-5e rxvt extension for extra curses acs chars
	 */
	static uint16_t const vt100_utf8[62] = {
		        0x2191, 0x2193, 0x2192, 0x2190, 0x2588, 0x259a, 0x2603, // 41-47
		     0,      0,      0,      0,      0,      0,      0,      0, // 48-4f
		     0,      0,      0,      0,      0,      0,      0,      0, // 50-57
		     0,      0,      0,      0,      0,      0,      0, 0x0020, // 58-5f
		0x25c6, 0x2592, 0x2409, 0x240c, 0x240d, 0x240a, 0x00b0, 0x00b1, // 60-67
		0x2424, 0x240b, 0x2518, 0x2510, 0x250c, 0x2514, 0x253c, 0x23ba, // 68-6f
		0x23bb, 0x2500, 0x23bc, 0x23bd, 0x251c, 0x2524, 0x2534, 0x252c, // 70-77
		0x2502, 0x2264, 0x2265, 0x03c0, 0x2260, 0x00a3, 0x00b7,         // 78-7e
	};

	if (is_utf8)
		return vt100_utf8[c - 0x41];
	else if (strchr(vt100_acs, c))
		return NCURSES_ACS(c);
	return '\0';
}

static void put_wc(Vt *t, wchar_t wc)
{
	int width = 0;

	if (!t->seen_input) {
		t->seen_input = 1;
		kill(-t->pid, SIGWINCH);
	}

	if (t->escaped) {
		if (t->elen + 1 < sizeof(t->ebuf)) {
			t->ebuf[t->elen] = wc;
			t->ebuf[++t->elen] = '\0';
			try_interpret_escape_seq(t);
		} else {
			cancel_escape_sequence(t);
		}
	} else if (IS_CONTROL(wc)) {
		process_nonprinting(t, wc);
	} else {
		if (t->graphmode) {
			if (wc >= 0x41 && wc <= 0x7e) {
				wchar_t gc = get_vt100_graphic(wc);
				if (gc)
					wc = gc;
			}
			width = 1;
		} else if ((width = wcwidth(wc)) < 1) {
			width = 1;
		}
		Buffer *b = t->buffer;
		Cell blank_cell = { L'\0', build_attrs(b->curattrs), b->curfg, b->curbg };
		if (width == 2 && b->curs_col == b->cols - 1) {
			b->curs_row->cells[b->curs_col++] = blank_cell;
			b->curs_row->dirty = true;
		}

		if (b->curs_col >= b->cols) {
			b->curs_col = 0;
			cursor_line_down(t);
		}

		if (t->insert) {
			Cell *src = b->curs_row->cells + b->curs_col;
			Cell *dest = src + width;
			size_t len = b->cols - b->curs_col - width;
			memmove(dest, src, len * sizeof *dest);
		}

		b->curs_row->cells[b->curs_col] = blank_cell;
		b->curs_row->cells[b->curs_col++].text = wc;
		b->curs_row->dirty = true;
		if (width == 2)
			b->curs_row->cells[b->curs_col++] = blank_cell;
	}
}

int vt_process(Vt *t)
{
	int res;
	unsigned int pos = 0;
	mbstate_t ps;
	memset(&ps, 0, sizeof(ps));

	if (t->pty < 0) {
		errno = EINVAL;
		return -1;
	}

	res = read(t->pty, t->rbuf + t->rlen, sizeof(t->rbuf) - t->rlen);
	if (res < 0)
		return -1;

	t->rlen += res;
	while (pos < t->rlen) {
		wchar_t wc;
		ssize_t len;

		len = (ssize_t)mbrtowc(&wc, t->rbuf + pos, t->rlen - pos, &ps);
		if (len == -2) {
			t->rlen -= pos;
			memmove(t->rbuf, t->rbuf + pos, t->rlen);
			return 0;
		}

		if (len == -1) {
			len = 1;
			wc = t->rbuf[pos];
		}

		pos += len ? len : 1;
		put_wc(t, wc);
	}

	t->rlen -= pos;
	memmove(t->rbuf, t->rbuf + pos, t->rlen);
	return 0;
}

void vt_default_colors_set(Vt *t, attr_t attrs, short fg, short bg)
{
	t->defattrs = attrs;
	t->deffg = fg;
	t->defbg = bg;
}

Vt *vt_create(int rows, int cols, int scroll_size)
{
	if (rows <= 0 || cols <= 0)
		return NULL;

	Vt *t = calloc(1, sizeof(Vt));
	if (!t)
		return NULL;

	t->pty = -1;
	t->deffg = t->defbg = -1;
	t->buffer = &t->buffer_normal;

	if (!buffer_init(&t->buffer_normal, rows, cols, scroll_size) ||
	    !buffer_init(&t->buffer_alternate, rows, cols, 0)) {
		free(t);
		return NULL;
	}

	return t;
}

void vt_resize(Vt *t, int rows, int cols)
{
	struct winsize ws = { .ws_row = rows, .ws_col = cols };

	if (rows <= 0 || cols <= 0)
		return;

	vt_noscroll(t);
	buffer_resize(&t->buffer_normal, rows, cols);
	buffer_resize(&t->buffer_alternate, rows, cols);
	cursor_clamp(t);
	ioctl(t->pty, TIOCSWINSZ, &ws);
	kill(-t->pid, SIGWINCH);
}

void vt_destroy(Vt *t)
{
	if (!t)
		return;
	buffer_free(&t->buffer_normal);
	buffer_free(&t->buffer_alternate);
	close(t->pty);
	free(t);
}

void vt_dirty(Vt *t)
{
	Buffer *b = t->buffer;
	for (Row *row = b->lines, *end = row + b->rows; row < end; row++)
		row->dirty = true;
}

void vt_draw(Vt *t, WINDOW *win, int srow, int scol)
{
	Buffer *b = t->buffer;

	if (srow != t->srow || scol != t->scol) {
		vt_dirty(t);
		t->srow = srow;
		t->scol = scol;
	}

	for (int i = 0; i < b->rows; i++) {
		Row *row = b->lines + i;

		if (!row->dirty)
			continue;

		wmove(win, srow + i, scol);
		Cell *cell = NULL;
		for (int j = 0; j < b->cols; j++) {
			Cell *prev_cell = cell;
			cell = row->cells + j;
			if (!prev_cell || cell->attr != prev_cell->attr
			    || cell->fg != prev_cell->fg
			    || cell->bg != prev_cell->bg) {
				if (cell->attr == A_NORMAL)
					cell->attr = t->defattrs;
				if (cell->fg == -1)
					cell->fg = t->deffg;
				if (cell->bg == -1)
					cell->bg = t->defbg;
				wattrset(win, cell->attr << NCURSES_ATTR_SHIFT);
				wcolor_set(win, vt_color_get(t, cell->fg, cell->bg), NULL);
			}

			if (is_utf8 && cell->text >= 128) {
				char buf[MB_CUR_MAX + 1];
				size_t len = wcrtomb(buf, cell->text, NULL);
				if (len > 0) {
					waddnstr(win, buf, len);
					if (wcwidth(cell->text) > 1)
						j++;
				}
			} else {
				waddch(win, cell->text > ' ' ? cell->text : ' ');
			}
		}

		int x, y;
		getyx(win, y, x);
		(void)y;
		if (x && x < b->cols - 1)
			whline(win, ' ', b->cols - x);

		row->dirty = false;
	}

	wmove(win, srow + b->curs_row - b->lines, scol + b->curs_col);
}

void vt_scroll(Vt *t, int rows)
{
	Buffer *b = t->buffer;
	if (!b->scroll_size)
		return;
	if (rows < 0) { /* scroll back */
		if (rows < -b->scroll_above)
			rows = -b->scroll_above;
	} else { /* scroll forward */
		if (rows > b->scroll_below)
			rows = b->scroll_below;
	}
	buffer_scroll(b, rows);
	b->scroll_below -= rows;
}

void vt_noscroll(Vt *t)
{
	int scroll_below = t->buffer->scroll_below;
	if (scroll_below)
		vt_scroll(t, scroll_below);
}

static void reset_sigdfl()
{
	int signum;
	for (signum = 0; signum != _NSIG; ++signum)
		signal(signum, SIG_DFL);
}

pid_t vt_forkpty(Vt *t, const char *p, const char *argv[], const char *cwd, const char *env[], int *to, int *from)
{
	int vt2ed[2], ed2vt[2];
	struct winsize ws;
	ws.ws_row = t->buffer->rows;
	ws.ws_col = t->buffer->cols;
	ws.ws_xpixel = ws.ws_ypixel = 0;

	if (to && pipe(vt2ed)) {
		*to = -1;
		to = NULL;
	}
	if (from && pipe(ed2vt)) {
		*from = -1;
		from = NULL;
	}

	pid_t pid = forkpty(&t->pty, NULL, NULL, &ws);
	if (pid < 0)
		return -1;

	if (pid == 0) {
		setsid();

		sigset_t emptyset;
		sigemptyset(&emptyset);
		sigprocmask(SIG_SETMASK, &emptyset, NULL);

		if (to) {
			close(vt2ed[1]);
			dup2(vt2ed[0], STDIN_FILENO);
			close(vt2ed[0]);
		}

		if (from) {
			close(ed2vt[0]);
			dup2(ed2vt[1], STDOUT_FILENO);
			close(ed2vt[1]);
		}

		int maxfd = sysconf(_SC_OPEN_MAX);
		for (int fd = 3; fd < maxfd; fd++)
			if (close(fd) == -1 && errno == EBADF)
				break;

		for (const char **envp = env; envp && envp[0]; envp += 2)
			setenv(envp[0], envp[1], 1);
		setenv("TERM", vt_term, 1);

		if (cwd)
			chdir(cwd);

		reset_sigdfl();
		execvp(p, (char *const *)argv);
		fprintf(stderr, "\nexecv() failed.\nCommand: '%s'\n", argv[0]);
		exit(1);
	}

	if (to) {
		close(vt2ed[0]);
		*to = vt2ed[1];
	}

	if (from) {
		close(ed2vt[1]);
		*from = ed2vt[0];
	}

	return t->pid = pid;
}

int vt_pty_get(Vt *t)
{
	return t->pty;
}

ssize_t vt_write(Vt *t, const char *buf, size_t len)
{
	ssize_t ret = len;

	while (len > 0) {
		ssize_t res = write(t->pty, buf, len);
		if (res < 0) {
			if (errno != EAGAIN && errno != EINTR)
				return -1;
			continue;
		}
		buf += res;
		len -= res;
	}

	return ret;
}

static void send_curs(Vt *t)
{
	Buffer *b = t->buffer;
	char keyseq[16];
	snprintf(keyseq, sizeof keyseq, "\e[%d;%dR", (int)(b->curs_row - b->lines), b->curs_col);
	vt_write(t, keyseq, strlen(keyseq));
}

void vt_keypress(Vt *t, int keycode)
{
	vt_noscroll(t);

	if (keycode >= 0 && keycode <= KEY_MAX && keytable[keycode]) {
		switch (keycode) {
		case KEY_UP:
		case KEY_DOWN:
		case KEY_RIGHT:
		case KEY_LEFT: {
			char keyseq[3] = { '\e', (t->curskeymode ? 'O' : '['), keytable[keycode][0] };
			vt_write(t, keyseq, sizeof keyseq);
			break;
		}
		default:
			vt_write(t, keytable[keycode], strlen(keytable[keycode]));
		}
	} else if (keycode <= UCHAR_MAX) {
		char c = keycode;
		vt_write(t, &c, 1);
	} else {
#ifndef NDEBUG
		fprintf(stderr, "unhandled key %#o\n", keycode);
#endif
	}
}

void vt_mouse(Vt *t, int x, int y, mmask_t mask)
{
#ifdef NCURSES_MOUSE_VERSION
	char seq[6] = { '\e', '[', 'M' }, state = 0, button = 0;

	if (!t->mousetrack)
		return;

	if (mask & (BUTTON1_PRESSED | BUTTON1_CLICKED))
		button = 0;
	else if (mask & (BUTTON2_PRESSED | BUTTON2_CLICKED))
		button = 1;
	else if (mask & (BUTTON3_PRESSED | BUTTON3_CLICKED))
		button = 2;
	else if (mask & (BUTTON1_RELEASED | BUTTON2_RELEASED | BUTTON3_RELEASED))
		button = 3;

	if (mask & BUTTON_SHIFT)
		state |= 4;
	if (mask & BUTTON_ALT)
		state |= 8;
	if (mask & BUTTON_CTRL)
		state |= 16;

	seq[3] = 32 + button + state;
	seq[4] = 32 + x;
	seq[5] = 32 + y;

	vt_write(t, seq, sizeof seq);

	if (mask & (BUTTON1_CLICKED | BUTTON2_CLICKED | BUTTON3_CLICKED)) {
		/* send a button release event */
		button = 3;
		seq[3] = 32 + button + state;
		vt_write(t, seq, sizeof seq);
	}
#endif /* NCURSES_MOUSE_VERSION */
}

static unsigned int color_hash(short fg, short bg)
{
	if (fg == -1)
		fg = COLORS;
	if (bg == -1)
		bg = COLORS + 1;
	return fg * (COLORS + 2) + bg;
}

short vt_color_get(Vt *t, short fg, short bg)
{
	if (fg >= COLORS)
		fg = (t ? t->deffg : default_fg);
	if (bg >= COLORS)
		bg = (t ? t->defbg : default_bg);

	if (!has_default_colors) {
		if (fg == -1)
			fg = (t && t->deffg != -1 ? t->deffg : default_fg);
		if (bg == -1)
			bg = (t && t->defbg != -1 ? t->defbg : default_bg);
	}

	if (!color2palette || (fg == -1 && bg == -1))
		return 0;
	unsigned int index = color_hash(fg, bg);
	if (color2palette[index] == 0) {
		short oldfg, oldbg;
		for (;;) {
			if (++color_pair_current >= color_pairs_max)
				color_pair_current = color_pairs_reserved + 1;
			pair_content(color_pair_current, &oldfg, &oldbg);
			unsigned int old_index = color_hash(oldfg, oldbg);
			if (color2palette[old_index] >= 0) {
				if (init_pair(color_pair_current, fg, bg) == OK) {
					color2palette[old_index] = 0;
					color2palette[index] = color_pair_current;
				}
				break;
			}
		}
	}

	short color_pair = color2palette[index];
	return color_pair >= 0 ? color_pair : -color_pair;
}

short vt_color_reserve(short fg, short bg)
{
	if (!color2palette || fg >= COLORS || bg >= COLORS)
		return 0;
	if (!has_default_colors && fg == -1)
		fg = default_fg;
	if (!has_default_colors && bg == -1)
		bg = default_bg;
	if (fg == -1 && bg == -1)
		return 0;
	unsigned int index = color_hash(fg, bg);
	if (color2palette[index] >= 0) {
		if (init_pair(color_pairs_reserved + 1, fg, bg) == OK)
			color2palette[index] = -(++color_pairs_reserved);
	}
	short color_pair = color2palette[index];
	return color_pair >= 0 ? color_pair : -color_pair;
}

static void init_colors(void)
{
	pair_content(0, &default_fg, &default_bg);
	if (default_fg == -1)
		default_fg = COLOR_WHITE;
	if (default_bg == -1)
		default_bg = COLOR_BLACK;
	has_default_colors = (use_default_colors() == OK);
	color_pairs_max = MIN(MAX_COLOR_PAIRS, SHRT_MAX);
	if (COLORS)
		color2palette = calloc((COLORS + 2) * (COLORS + 2), sizeof(short));
	/*
	 * XXX: On undefined color-pairs NetBSD curses pair_content() set fg
	 *      and bg to default colors while ncurses set them respectively to
	 *      0 and 0. Initialize all color-pairs in order to have consistent
	 *      behaviour despite the implementation used.
	 */
	for (short i = 1; i < color_pairs_max; i++)
		init_pair(i, 0, 0);
	vt_color_reserve(COLOR_WHITE, COLOR_BLACK);
}

void vt_init(void)
{
	init_colors();
	is_utf8_locale();
	char *term = getenv("DVTM_TERM");
	if (!term)
		term = "dvtm";
	snprintf(vt_term, sizeof vt_term, "%s%s", term, COLORS >= 256 ? "-256color" : "");
}

void vt_keytable_set(const char * const keytable_overlay[], int count)
{
	for (int k = 0; k < count && k < KEY_MAX; k++) {
		const char *keyseq = keytable_overlay[k];
		if (keyseq)
			keytable[k] = keyseq;
	}
}

void vt_shutdown(void)
{
	free(color2palette);
}

void vt_title_handler_set(Vt *t, vt_title_handler_t handler)
{
	t->title_handler = handler;
}

void vt_urgent_handler_set(Vt *t, vt_urgent_handler_t handler)
{
	t->urgent_handler = handler;
}

void vt_data_set(Vt *t, void *data)
{
	t->data = data;
}

void *vt_data_get(Vt *t)
{
	return t->data;
}

bool vt_cursor_visible(Vt *t)
{
	return t->buffer->scroll_below ? false : !t->curshid;
}

pid_t vt_pid_get(Vt *t)
{
	return t->pid;
}

size_t vt_content_get(Vt *t, char **buf, bool colored)
{
	Buffer *b = t->buffer;
	int lines = b->scroll_above + b->scroll_below + b->rows + 1;
	size_t size = lines * ((b->cols + 1) * ((colored ? 64 : 0) + MB_CUR_MAX));
	mbstate_t ps;
	memset(&ps, 0, sizeof(ps));

	if (!(*buf = malloc(size)))
		return 0;

	char *s = *buf;
	Cell *prev_cell = NULL;

	for (Row *row = buffer_row_first(b); row; row = buffer_row_next(b, row)) {
		size_t len = 0;
		char *last_non_space = s;
		for (int col = 0; col < b->cols; col++) {
			Cell *cell = row->cells + col;
			if (colored) {
				int esclen = 0;
				if (!prev_cell || cell->attr != prev_cell->attr) {
					attr_t attr = cell->attr << NCURSES_ATTR_SHIFT;
					esclen = sprintf(s, "\033[0%s%s%s%s%s%sm",
						attr & A_BOLD ? ";1" : "",
						attr & A_DIM ? ";2" : "",
						attr & A_UNDERLINE ? ";4" : "",
						attr & A_BLINK ? ";5" : "",
						attr & A_REVERSE ? ";7" : "",
						attr & A_INVIS ? ";8" : "");
					if (esclen > 0)
						s += esclen;
				}
				if (!prev_cell || cell->fg != prev_cell->fg || cell->attr != prev_cell->attr) {
					if (cell->fg == -1)
						esclen = sprintf(s, "\033[39m");
					else
						esclen = sprintf(s, "\033[38;5;%dm", cell->fg);
					if (esclen > 0)
						s += esclen;
				}
				if (!prev_cell || cell->bg != prev_cell->bg || cell->attr != prev_cell->attr) {
					if (cell->bg == -1)
						esclen = sprintf(s, "\033[49m");
					else
						esclen = sprintf(s, "\033[48;5;%dm", cell->bg);
					if (esclen > 0)
						s += esclen;
				}
				prev_cell = cell;
			}
			if (cell->text) {
				len = wcrtomb(s, cell->text, &ps);
				if (len > 0)
					s += len;
				last_non_space = s;
			} else if (len) {
				len = 0;
			} else {
				*s++ = ' ';
			}
		}

		s = last_non_space;
		*s++ = '\n';
	}

	return s - *buf;
}

int vt_content_start(Vt *t)
{
	return t->buffer->scroll_above;
}