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Some terminals don't correctly clear their let's-wrap flag after changing the
scroll region (which moves the cursor to 0,0). This means that if the cursor
was at the edge of the screen, any further output after scroll region change
incorrectly causes a line wrap. Add a workaround to move the cursor to position
0 if it is at the screen edge before changing scroll region.

/* $OpenBSD: tty.c,v 1.55 2009/10/21 09:36:53 nicm Exp $ */

/*
 * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
 *
 * 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 <sys/ioctl.h>

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

#include "tmux.h"

void	tty_fill_acs(struct tty *);

int	tty_try_256(struct tty *, u_char, const char *);
int	tty_try_88(struct tty *, u_char, const char *);

void	tty_attributes_fg(struct tty *, const struct grid_cell *);
void	tty_attributes_bg(struct tty *, const struct grid_cell *);

void	tty_redraw_region(struct tty *, const struct tty_ctx *);
void	tty_emulate_repeat(
	    struct tty *, enum tty_code_code, enum tty_code_code, u_int);
void	tty_cell(struct tty *,
    	    const struct grid_cell *, const struct grid_utf8 *);

void
tty_init(struct tty *tty, int fd, char *term)
{
	char	*path;

	memset(tty, 0, sizeof *tty);
	tty->log_fd = -1;

	if (term == NULL || *term == '\0')
		tty->termname = xstrdup("unknown");
	else
		tty->termname = xstrdup(term);

	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
		fatal("fcntl failed");
	tty->fd = fd;

	if ((path = ttyname(fd)) == NULL)
		fatalx("ttyname failed");
	tty->path = xstrdup(path);

	tty->flags = 0;
	tty->term_flags = 0;
}

void
tty_resize(struct tty *tty)
{
	struct winsize	ws;

	if (ioctl(tty->fd, TIOCGWINSZ, &ws) != -1) {
		tty->sx = ws.ws_col;
		tty->sy = ws.ws_row;
	}
	if (tty->sx == 0)
		tty->sx = 80;
	if (tty->sy == 0)
		tty->sy = 24;

	tty->cx = UINT_MAX;
	tty->cy = UINT_MAX;

	tty->rupper = UINT_MAX;
	tty->rlower = UINT_MAX;
}

int
tty_open(struct tty *tty, const char *overrides, char **cause)
{
	int	fd;

	if (debug_level > 3) {
		fd = open("tmux.out", O_WRONLY|O_CREAT|O_TRUNC, 0644);
		if (fd != -1 && fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
			fatal("fcntl failed");
		tty->log_fd = fd;
	}

	tty->term = tty_term_find(tty->termname, tty->fd, overrides, cause);
	if (tty->term == NULL) {
		tty_close(tty);
		return (-1);
	}
	tty->flags |= TTY_OPENED;

	tty->in = buffer_create(BUFSIZ);
	tty->out = buffer_create(BUFSIZ);

	tty->flags &= ~(TTY_NOCURSOR|TTY_FREEZE|TTY_ESCAPE);

	tty_start_tty(tty);

	tty_keys_init(tty);

	tty_fill_acs(tty);

	return (0);
}

void
tty_start_tty(struct tty *tty)
{
	struct termios	 tio;
	int		 what, mode;

	if (tty->fd == -1)
		return;

	if ((mode = fcntl(tty->fd, F_GETFL)) == -1)
		fatal("fcntl failed");
	if (fcntl(tty->fd, F_SETFL, mode|O_NONBLOCK) == -1)
		fatal("fcntl failed");

	if (tcgetattr(tty->fd, &tty->tio) != 0)
		fatal("tcgetattr failed");
	memcpy(&tio, &tty->tio, sizeof tio);
	tio.c_iflag &= ~(IXON|IXOFF|ICRNL|INLCR|IGNCR|IMAXBEL|ISTRIP);
	tio.c_iflag |= IGNBRK;
	tio.c_oflag &= ~(OPOST|ONLCR|OCRNL|ONLRET);
	tio.c_lflag &= ~(IEXTEN|ICANON|ECHO|ECHOE|ECHONL|ECHOCTL|
	    ECHOPRT|ECHOKE|ECHOCTL|ISIG);
	tio.c_cc[VMIN] = 1;
        tio.c_cc[VTIME] = 0;
	if (tcsetattr(tty->fd, TCSANOW, &tio) != 0)
		fatal("tcsetattr failed");

	what = 0;
	if (ioctl(tty->fd, TIOCFLUSH, &what) != 0)
		fatal("ioctl(TIOCFLUSH)");

	tty_putcode(tty, TTYC_SMCUP);

	tty_putcode(tty, TTYC_SGR0);
	memcpy(&tty->cell, &grid_default_cell, sizeof tty->cell);

	tty_putcode(tty, TTYC_SMKX);
	tty_putcode(tty, TTYC_ENACS);
	tty_putcode(tty, TTYC_CLEAR);

	tty_putcode(tty, TTYC_CNORM);
	if (tty_term_has(tty->term, TTYC_KMOUS))
		tty_puts(tty, "\033[?1000l");

	tty->cx = UINT_MAX;
	tty->cy = UINT_MAX;

	tty->rlower = UINT_MAX;
	tty->rupper = UINT_MAX;

	tty->mode = MODE_CURSOR;

	tty->flags |= TTY_STARTED;
}

void
tty_stop_tty(struct tty *tty)
{
	struct winsize	ws;
	int		mode;

	if (!(tty->flags & TTY_STARTED))
		return;
	tty->flags &= ~TTY_STARTED;

	/*
	 * Be flexible about error handling and try not kill the server just
	 * because the fd is invalid. Things like ssh -t can easily leave us
	 * with a dead tty.
	 */
	if ((mode = fcntl(tty->fd, F_GETFL)) == -1)
		return;
	if (fcntl(tty->fd, F_SETFL, mode & ~O_NONBLOCK) == -1)
		return;
	if (ioctl(tty->fd, TIOCGWINSZ, &ws) == -1)
		return;
	if (tcsetattr(tty->fd, TCSANOW, &tty->tio) == -1)
		return;

	tty_raw(tty, tty_term_string2(tty->term, TTYC_CSR, 0, ws.ws_row - 1));
	tty_raw(tty, tty_term_string(tty->term, TTYC_RMACS));
	tty_raw(tty, tty_term_string(tty->term, TTYC_SGR0));
	tty_raw(tty, tty_term_string(tty->term, TTYC_RMKX));
	tty_raw(tty, tty_term_string(tty->term, TTYC_CLEAR));

	tty_raw(tty, tty_term_string(tty->term, TTYC_CNORM));
	if (tty_term_has(tty->term, TTYC_KMOUS))
		tty_raw(tty, "\033[?1000l");

	tty_raw(tty, tty_term_string(tty->term, TTYC_RMCUP));
}

void
tty_fill_acs(struct tty *tty)
{
	const char *ptr;

	memset(tty->acs, 0, sizeof tty->acs);
	if (!tty_term_has(tty->term, TTYC_ACSC))
		return;

	ptr = tty_term_string(tty->term, TTYC_ACSC);
	if (strlen(ptr) % 2 != 0)
		return;
	for (; *ptr != '\0'; ptr += 2)
		tty->acs[(u_char) ptr[0]] = ptr[1];
}

u_char
tty_get_acs(struct tty *tty, u_char ch)
{
	if (tty->acs[ch] != '\0')
		return (tty->acs[ch]);
	return (ch);
}

void
tty_close(struct tty *tty)
{
	if (tty->log_fd != -1) {
		close(tty->log_fd);
		tty->log_fd = -1;
	}

	tty_stop_tty(tty);

	if (tty->flags & TTY_OPENED) {
		tty_term_free(tty->term);
		tty_keys_free(tty);

		buffer_destroy(tty->in);
		buffer_destroy(tty->out);

		tty->flags &= ~TTY_OPENED;
	}

	if (tty->fd != -1) {
		close(tty->fd);
		tty->fd = -1;
	}
}

void
tty_free(struct tty *tty)
{
	tty_close(tty);

	if (tty->path != NULL)
		xfree(tty->path);
	if (tty->termname != NULL)
		xfree(tty->termname);
}

void
tty_raw(struct tty *tty, const char *s)
{
	write(tty->fd, s, strlen(s));
}

void
tty_putcode(struct tty *tty, enum tty_code_code code)
{
	tty_puts(tty, tty_term_string(tty->term, code));
}

void
tty_putcode1(struct tty *tty, enum tty_code_code code, int a)
{
	if (a < 0)
		return;
	tty_puts(tty, tty_term_string1(tty->term, code, a));
}

void
tty_putcode2(struct tty *tty, enum tty_code_code code, int a, int b)
{
	if (a < 0 || b < 0)
		return;
	tty_puts(tty, tty_term_string2(tty->term, code, a, b));
}

void
tty_puts(struct tty *tty, const char *s)
{
	if (*s == '\0')
		return;
	buffer_write(tty->out, s, strlen(s));

	if (tty->log_fd != -1)
		write(tty->log_fd, s, strlen(s));
}

void
tty_putc(struct tty *tty, u_char ch)
{
	u_int	sx;

	if (tty->cell.attr & GRID_ATTR_CHARSET)
		ch = tty_get_acs(tty, ch);
	buffer_write8(tty->out, ch);

	if (ch >= 0x20 && ch != 0x7f) {
		sx = tty->sx;
		if (tty->term->flags & TERM_EARLYWRAP)
			sx--;

		if (tty->cx >= sx) {
			tty->cx = 1;
			if (tty->cy != tty->rlower)
				tty->cy++;
		} else
			tty->cx++;
	}

	if (tty->log_fd != -1)
		write(tty->log_fd, &ch, 1);
}

void
tty_pututf8(struct tty *tty, const struct grid_utf8 *gu)
{
	u_int	i;

	for (i = 0; i < UTF8_SIZE; i++) {
		if (gu->data[i] == 0xff)
			break;
		buffer_write8(tty->out, gu->data[i]);
		if (tty->log_fd != -1)
			write(tty->log_fd, &gu->data[i], 1);
	}

	tty->cx += gu->width;
}

void
tty_set_title(struct tty *tty, const char *title)
{
	if (strstr(tty->termname, "xterm") == NULL &&
	    strstr(tty->termname, "rxvt") == NULL &&
	    strcmp(tty->termname, "screen") != 0)
		return;

	tty_puts(tty, "\033]0;");
	tty_puts(tty, title);
	tty_putc(tty, '\007');
}

void
tty_update_mode(struct tty *tty, int mode)
{
	int	changed;

	if (tty->flags & TTY_NOCURSOR)
		mode &= ~MODE_CURSOR;

	changed = mode ^ tty->mode;
	if (changed & MODE_CURSOR) {
		if (mode & MODE_CURSOR)
			tty_putcode(tty, TTYC_CNORM);
		else
			tty_putcode(tty, TTYC_CIVIS);
	}
	if (changed & MODE_MOUSE) {
		if (mode & MODE_MOUSE)
			tty_puts(tty, "\033[?1000h");
		else
			tty_puts(tty, "\033[?1000l");
	}
	tty->mode = mode;
}

void
tty_emulate_repeat(
    struct tty *tty, enum tty_code_code code, enum tty_code_code code1, u_int n)
{
	if (tty_term_has(tty->term, code))
		tty_putcode1(tty, code, n);
	else {
		while (n-- > 0)
			tty_putcode(tty, code1);
	}
}

/*
 * Redraw scroll region using data from screen (already updated). Used when
 * CSR not supported, or window is a pane that doesn't take up the full
 * width of the terminal.
 */
void
tty_redraw_region(struct tty *tty, const struct tty_ctx *ctx)
{
	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int		 	 i;

	/*
	 * If region is >= 50% of the screen, just schedule a window redraw. In
	 * most cases, this is likely to be followed by some more scrolling -
	 * without this, the entire pane ends up being redrawn many times which
	 * can be much more data.
	 */
	if (ctx->orupper - ctx->orlower >= screen_size_y(s) / 2) {
		wp->flags |= PANE_REDRAW;
		return;
	}

	if (ctx->ocy < ctx->orupper || ctx->ocy > ctx->orlower) {
		for (i = ctx->ocy; i < screen_size_y(s); i++)
			tty_draw_line(tty, s, i, wp->xoff, wp->yoff);
	} else {
		for (i = ctx->orupper; i <= ctx->orlower; i++)
			tty_draw_line(tty, s, i, wp->xoff, wp->yoff);
	}
}

void
tty_draw_line(struct tty *tty, struct screen *s, u_int py, u_int ox, u_int oy)
{
	const struct grid_cell	*gc;
	struct grid_line	*gl;
	struct grid_cell	 tmpgc;
	const struct grid_utf8	*gu;
	u_int			 i, sx;

	tty_update_mode(tty, tty->mode & ~MODE_CURSOR);

	sx = screen_size_x(s);
	if (sx > s->grid->linedata[s->grid->hsize + py].cellsize)
		sx = s->grid->linedata[s->grid->hsize + py].cellsize;
	if (sx > tty->sx)
		sx = tty->sx;

	/*
	 * Don't move the cursor to the start permission if it will wrap there
	 * itself.
	 */
	gl = NULL;
	if (py != 0)
		gl = &s->grid->linedata[s->grid->hsize + py - 1];
	if (oy + py == 0 || (gl != NULL && !(gl->flags & GRID_LINE_WRAPPED)) ||
	    tty->cx < tty->sx || ox != 0 ||
	    (oy + py != tty->cy + 1 && tty->cy != s->rlower + oy))
		tty_cursor(tty, ox, oy + py);

	for (i = 0; i < sx; i++) {
		gc = grid_view_peek_cell(s->grid, i, py);

		gu = NULL;
		if (gc->flags & GRID_FLAG_UTF8)
			gu = grid_view_peek_utf8(s->grid, i, py);

		if (screen_check_selection(s, i, py)) {
			memcpy(&tmpgc, &s->sel.cell, sizeof tmpgc);
			tmpgc.data = gc->data;
			tmpgc.flags = gc->flags & 
			    ~(GRID_FLAG_FG256|GRID_FLAG_BG256);
			tmpgc.flags |= s->sel.cell.flags &
			    (GRID_FLAG_FG256|GRID_FLAG_BG256);
			tty_cell(tty, &tmpgc, gu);
		} else
			tty_cell(tty, gc, gu);
	}

	if (sx >= tty->sx) {
		tty_update_mode(tty, tty->mode);
		return;
	}
	tty_reset(tty);

	tty_cursor(tty, ox + sx, oy + py);
	if (screen_size_x(s) >= tty->sx && tty_term_has(tty->term, TTYC_EL))
		tty_putcode(tty, TTYC_EL);
	else {
		for (i = sx; i < screen_size_x(s); i++)
			tty_putc(tty, ' ');
	}
	tty_update_mode(tty, tty->mode);
}

void
tty_write(void (*cmdfn)(
    struct tty *, const struct tty_ctx *), const struct tty_ctx *ctx)
{
	struct window_pane	*wp = ctx->wp;
	struct client		*c;
	u_int		 	 i;

	if (wp == NULL)
		return;

	if (wp->window->flags & WINDOW_REDRAW || wp->flags & PANE_REDRAW)
		return;
	if (wp->window->flags & WINDOW_HIDDEN || !window_pane_visible(wp))
		return;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		if (c->flags & CLIENT_SUSPENDED)
			continue;

		if (c->session->curw->window == wp->window) {
			if (c->tty.flags & TTY_FREEZE || c->tty.term == NULL)
				continue;
			cmdfn(&c->tty, ctx);
		}
	}
}

void
tty_cmd_insertcharacter(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int			 i;

	if (wp->xoff != 0 || screen_size_x(s) < tty->sx) {
		tty_draw_line(tty, wp->screen, ctx->ocy, wp->xoff, wp->yoff);
		return;
	}

	tty_reset(tty);

 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	if (tty_term_has(tty->term, TTYC_ICH) ||
	    tty_term_has(tty->term, TTYC_ICH1))
		tty_emulate_repeat(tty, TTYC_ICH, TTYC_ICH1, ctx->num);
	else {
		tty_putcode(tty, TTYC_SMIR);
		for (i = 0; i < ctx->num; i++)
			tty_putc(tty, ' ');
		tty_putcode(tty, TTYC_RMIR);
	}
}

void
tty_cmd_deletecharacter(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;

	if (wp->xoff != 0 || screen_size_x(s) < tty->sx ||
	    (!tty_term_has(tty->term, TTYC_DCH) &&
	    !tty_term_has(tty->term, TTYC_DCH1))) {
		tty_draw_line(tty, wp->screen, ctx->ocy, wp->xoff, wp->yoff);
		return;
	}

	tty_reset(tty);

 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	if (tty_term_has(tty->term, TTYC_DCH) ||
	    tty_term_has(tty->term, TTYC_DCH1))
		tty_emulate_repeat(tty, TTYC_DCH, TTYC_DCH1, ctx->num);
}

void
tty_cmd_insertline(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;

 	if (wp->xoff != 0 || screen_size_x(s) < tty->sx ||
	    !tty_term_has(tty->term, TTYC_CSR)) {
		tty_redraw_region(tty, ctx);
		return;
	}

	tty_reset(tty);

 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	tty_emulate_repeat(tty, TTYC_IL, TTYC_IL1, ctx->num);
}

void
tty_cmd_deleteline(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;

 	if (wp->xoff != 0 || screen_size_x(s) < tty->sx ||
	    !tty_term_has(tty->term, TTYC_CSR)) {
		tty_redraw_region(tty, ctx);
		return;
	}

	tty_reset(tty);

 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	tty_emulate_repeat(tty, TTYC_DL, TTYC_DL1, ctx->num);
}

void
tty_cmd_clearline(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int		 	 i;

	tty_reset(tty);

 	tty_cursor_pane(tty, ctx, 0, ctx->ocy);

	if (wp->xoff == 0 && screen_size_x(s) >= tty->sx &&
	    tty_term_has(tty->term, TTYC_EL)) {
		tty_putcode(tty, TTYC_EL);
	} else {
		for (i = 0; i < screen_size_x(s); i++)
			tty_putc(tty, ' ');
	}
}

void
tty_cmd_clearendofline(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int		 	 i;

	tty_reset(tty);

	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	if (wp->xoff == 0 && screen_size_x(s) >= tty->sx &&
	    tty_term_has(tty->term, TTYC_EL))
		tty_putcode(tty, TTYC_EL);
	else {
		for (i = ctx->ocx; i < screen_size_x(s); i++)
			tty_putc(tty, ' ');
	}
}

void
tty_cmd_clearstartofline(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	u_int		 	 i;

	tty_reset(tty);

	if (wp->xoff == 0 && tty_term_has(tty->term, TTYC_EL1)) {
		tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
		tty_putcode(tty, TTYC_EL1);
	} else {
		tty_cursor_pane(tty, ctx, 0, ctx->ocy);
		for (i = 0; i < ctx->ocx + 1; i++)
			tty_putc(tty, ' ');
	}
}

void
tty_cmd_reverseindex(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;

 	if (wp->xoff != 0 || screen_size_x(s) < tty->sx ||
	    !tty_term_has(tty->term, TTYC_CSR)) {
		tty_redraw_region(tty, ctx);
		return;
	}

	if (ctx->ocy == ctx->orupper) {
		tty_reset(tty);

		tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
		tty_cursor_pane(tty, ctx, ctx->ocx, ctx->orupper);

		tty_putcode(tty, TTYC_RI);
	}
}

void
tty_cmd_linefeed(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;

 	if (wp->xoff != 0 || screen_size_x(s) < tty->sx ||
	    !tty_term_has(tty->term, TTYC_CSR)) {
		tty_redraw_region(tty, ctx);
		return;
	}

	/*
	 * If this line wrapped naturally (ctx->num is nonzero), don't do
	 * anything - the cursor can just be moved to the last cell and wrap
	 * naturally.
	 */
	if (ctx->num && !(tty->term->flags & TERM_EARLYWRAP))
		return;

	if (ctx->ocy == ctx->orlower) {
		tty_reset(tty);

		tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
		tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

		tty_putc(tty, '\n');
	}
}

void
tty_cmd_clearendofscreen(struct tty *tty, const struct tty_ctx *ctx)
{
  	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int		 	 i, j;

	tty_reset(tty);

	tty_region_pane(tty, ctx, 0, screen_size_y(s) - 1);
	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	if (wp->xoff == 0 && screen_size_x(s) >= tty->sx &&
	    tty_term_has(tty->term, TTYC_EL)) {
		tty_putcode(tty, TTYC_EL);
		if (ctx->ocy != screen_size_y(s) - 1) {
			tty_cursor_pane(tty, ctx, 0, ctx->ocy + 1);
			for (i = ctx->ocy + 1; i < screen_size_y(s); i++) {
				tty_putcode(tty, TTYC_EL);
				if (i == screen_size_y(s) - 1)
					continue;
				tty_emulate_repeat(tty, TTYC_CUD, TTYC_CUD1, 1);
				tty->cy++;
			}
		}
	} else {
		for (i = ctx->ocx; i < screen_size_x(s); i++)
			tty_putc(tty, ' ');
		for (j = ctx->ocy; j < screen_size_y(s); j++) {
			tty_cursor_pane(tty, ctx, 0, j);
			for (i = 0; i < screen_size_x(s); i++)
				tty_putc(tty, ' ');
		}
	}
}

void
tty_cmd_clearstartofscreen(struct tty *tty, const struct tty_ctx *ctx)
{
 	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int		 	 i, j;

	tty_reset(tty);

	tty_region_pane(tty, ctx, 0, screen_size_y(s) - 1);
	tty_cursor_pane(tty, ctx, 0, 0);

	if (wp->xoff == 0 && screen_size_x(s) >= tty->sx &&
	    tty_term_has(tty->term, TTYC_EL)) {
		for (i = 0; i < ctx->ocy; i++) {
			tty_putcode(tty, TTYC_EL);
			tty_emulate_repeat(tty, TTYC_CUD, TTYC_CUD1, 1);
			tty->cy++;
		}
	} else {
		for (j = 0; j < ctx->ocy; j++) {
			tty_cursor_pane(tty, ctx, 0, j);
			for (i = 0; i < screen_size_x(s); i++)
				tty_putc(tty, ' ');
		}
	}
	for (i = 0; i <= ctx->ocx; i++)
		tty_putc(tty, ' ');
}

void
tty_cmd_clearscreen(struct tty *tty, const struct tty_ctx *ctx)
{
 	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int		 	 i, j;

	tty_reset(tty);

	tty_region_pane(tty, ctx, 0, screen_size_y(s) - 1);
	tty_cursor_pane(tty, ctx, 0, 0);

	if (wp->xoff == 0 && screen_size_x(s) >= tty->sx &&
	    tty_term_has(tty->term, TTYC_EL)) {
		for (i = 0; i < screen_size_y(s); i++) {
			tty_putcode(tty, TTYC_EL);
			if (i != screen_size_y(s) - 1) {
				tty_emulate_repeat(tty, TTYC_CUD, TTYC_CUD1, 1);
				tty->cy++;
			}
		}
	} else {
		for (j = 0; j < screen_size_y(s); j++) {
			tty_cursor_pane(tty, ctx, 0, j);
			for (i = 0; i < screen_size_x(s); i++)
				tty_putc(tty, ' ');
		}
	}
}

void
tty_cmd_alignmenttest(struct tty *tty, const struct tty_ctx *ctx)
{
	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int			 i, j;

	tty_reset(tty);

	tty_region_pane(tty, ctx, 0, screen_size_y(s) - 1);

	for (j = 0; j < screen_size_y(s); j++) {
		tty_cursor_pane(tty, ctx, 0, j);
		for (i = 0; i < screen_size_x(s); i++)
			tty_putc(tty, 'E');
	}
}

void
tty_cmd_cell(struct tty *tty, const struct tty_ctx *ctx)
{
	struct window_pane	*wp = ctx->wp;
	struct screen		*s = wp->screen;
	u_int			 cx;

	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);

	/*
	 * Should the cursor be in the last cursor position ready for a natural
	 * wrap? If so - and it isn't - move to and rewrite the last cell.
	 */
	if (!(tty->term->flags & TERM_EARLYWRAP) &&
	    ctx->ocx + wp->xoff > tty->sx - ctx->last_width) {
		if (tty->cx < tty->sx) {
			cx = screen_size_x(s) - ctx->last_width;
			tty_cursor_pane(tty, ctx, cx, ctx->ocy);
			tty_cell(tty, &ctx->last_cell, &ctx->last_utf8);
		}
	} else
		tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);

	tty_cell(tty, ctx->cell, ctx->utf8);
}

void
tty_cmd_utf8character(struct tty *tty, const struct tty_ctx *ctx)
{
	struct window_pane	*wp = ctx->wp;

	/*
	 * Cannot rely on not being a partial character, so just redraw the
	 * whole line.
	 */
	tty_draw_line(tty, wp->screen, ctx->ocy, wp->xoff, wp->yoff);	
}

void
tty_cell(
    struct tty *tty, const struct grid_cell *gc, const struct grid_utf8 *gu)
{
	u_int	i;

	/* Skip last character if terminal is stupid. */
	if (tty->term->flags & TERM_EARLYWRAP &&
	    tty->cy == tty->sy - 1 && tty->cx == tty->sx - 1)
		return;

	/* If this is a padding character, do nothing. */
	if (gc->flags & GRID_FLAG_PADDING)
		return;

	/* Set the attributes. */
	tty_attributes(tty, gc);

	/* If not UTF-8, write directly. */
	if (!(gc->flags & GRID_FLAG_UTF8)) {
		if (gc->data < 0x20 || gc->data == 0x7f)
			return;
		tty_putc(tty, gc->data);
		return;
	}

	/* If the terminal doesn't support UTF-8, write underscores. */
	if (!(tty->flags & TTY_UTF8)) {
		for (i = 0; i < gu->width; i++)
			tty_putc(tty, '_');
		return;
	}

	/* Otherwise, write UTF-8. */
	tty_pututf8(tty, gu);
}

void
tty_reset(struct tty *tty)
{
	struct grid_cell	*gc = &tty->cell;

	if (memcmp(gc, &grid_default_cell, sizeof *gc) == 0)
		return;

	if (tty_term_has(tty->term, TTYC_RMACS) && gc->attr & GRID_ATTR_CHARSET)
		tty_putcode(tty, TTYC_RMACS);
	tty_putcode(tty, TTYC_SGR0);
	memcpy(gc, &grid_default_cell, sizeof *gc);
}

/* Set region inside pane. */
void
tty_region_pane(
    struct tty *tty, const struct tty_ctx *ctx, u_int rupper, u_int rlower)
{
  	struct window_pane	*wp = ctx->wp;

	tty_region(tty, wp->yoff + rupper, wp->yoff + rlower);
}

/* Set region at absolute position. */
void
tty_region(struct tty *tty, u_int rupper, u_int rlower)
{
	if (tty->rlower == rlower && tty->rupper == rupper)
		return;
	if (!tty_term_has(tty->term, TTYC_CSR))
		return;

	tty->rupper = rupper;
	tty->rlower = rlower;

	/*
	 * Some terminals (such as PuTTY) do not correctly reset the cursor to
	 * 0,0 if it is beyond the last column (they do not reset their wrap
	 * flag so further output causes a line feed). As a workaround, do an
	 * explicit move to 0 first.
	 */
	if (tty->cx >= tty->sx)
		tty_cursor(tty, 0, tty->cy);

	tty->cx = 0;
	tty->cy = 0;

	tty_putcode2(tty, TTYC_CSR, tty->rupper, tty->rlower);
}

/* Move cursor inside pane. */
void
tty_cursor_pane(struct tty *tty, const struct tty_ctx *ctx, u_int cx, u_int cy)
{
  	struct window_pane	*wp = ctx->wp;

	tty_cursor(tty, wp->xoff + cx, wp->yoff + cy);
}

/* Move cursor to absolute position. */
void
tty_cursor(struct tty *tty, u_int cx, u_int cy)
{
	struct tty_term	*term = tty->term;
	u_int		 thisx, thisy;
	int		 change;
	
	if (cx > tty->sx - 1)
		cx = tty->sx - 1;

	thisx = tty->cx;
	thisy = tty->cy;

	/* No change. */
	if (cx == thisx && cy == thisy)
		return;

	/* Very end of the line, just use absolute movement. */
	if (thisx > tty->sx - 1)
		goto absolute;

	/* Move to home position (0, 0). */
	if (cx == 0 && cy == 0 && tty_term_has(term, TTYC_HOME)) {
		tty_putcode(tty, TTYC_HOME);
		goto out;
	}

	/* Zero on the next line. */
	if (cx == 0 && cy == thisy + 1 && thisy != tty->rlower) {
		tty_putc(tty, '\r');
		tty_putc(tty, '\n');
		goto out;
	}

	/* Moving column or row. */
	if (cy == thisy) {
		/*
		 * Moving column only, row staying the same.
		 */

		/* To left edge. */
		if (cx == 0)	{
			tty_putc(tty, '\r');
			goto out;
		}

		/* One to the left. */
		if (cx == thisx - 1 && tty_term_has(term, TTYC_CUB1)) {
			tty_putcode(tty, TTYC_CUB1);
			goto out;
		}

		/* One to the right. */
		if (cx == thisx + 1 && tty_term_has(term, TTYC_CUF1)) {
			tty_putcode(tty, TTYC_CUF1);
			goto out;
		}

		/* Calculate difference. */
		change = thisx - cx;	/* +ve left, -ve right */

		/*
		 * Use HPA if change is larger than absolute, otherwise move
		 * the cursor with CUB/CUF.
		 */
		if (abs(change) > cx && tty_term_has(term, TTYC_HPA)) {
			tty_putcode1(tty, TTYC_HPA, cx);
			goto out;
		} else if (change > 0 && tty_term_has(term, TTYC_CUB)) {
			tty_putcode1(tty, TTYC_CUB, change);
			goto out;
		} else if (change < 0 && tty_term_has(term, TTYC_CUF)) {
			tty_putcode1(tty, TTYC_CUF, -change);
			goto out;
		}
	} else if (cx == thisx) {
		/*
		 * Moving row only, column staying the same.
		 */

		/* One above. */
		if (thisy != tty->rupper && 
		    cy == thisy - 1 && tty_term_has(term, TTYC_CUU1)) {
			tty_putcode(tty, TTYC_CUU1);
			goto out;
		}

		/* One below. */
		if (thisy != tty->rlower &&
		    cy == thisy + 1 && tty_term_has(term, TTYC_CUD1)) {
			tty_putcode(tty, TTYC_CUD1);
			goto out;
		}

		/* Calculate difference. */
		change = thisy - cy;	/* +ve up, -ve down */

		/*
		 * Try to use VPA if change is larger than absolute or if this change
		 * would cross the scroll region, otherwise use CUU/CUD.
		 */
		if (abs(change) > cy ||
		    (change < 0 && cy - change > tty->rlower) ||
		    (change > 0 && cy - change < tty->rupper)) {
			    if (tty_term_has(term, TTYC_VPA)) {
				    tty_putcode1(tty, TTYC_VPA, cy);
				    goto out;
			    }
		} else if (change > 0 && tty_term_has(term, TTYC_CUU)) {
			tty_putcode1(tty, TTYC_CUU, change);
			goto out;
		} else if (change < 0 && tty_term_has(term, TTYC_CUD)) {
			tty_putcode1(tty, TTYC_CUD, -change);
			goto out;
		}
	}

absolute:
	/* Absolute movement. */
	tty_putcode2(tty, TTYC_CUP, cy, cx);

out:
	tty->cx = cx;
	tty->cy = cy;
}

void
tty_attributes(struct tty *tty, const struct grid_cell *gc)
{
	struct grid_cell	*tc = &tty->cell;
	u_char			 changed;
	u_int			 fg, bg, attr;

	/*
	 * If no setab, try to use the reverse attribute as a best-effort for a
	 * non-default background. This is a bit of a hack but it doesn't do
	 * any serious harm and makes a couple of applications happier.
	 */
	fg = gc->fg; bg = gc->bg; attr = gc->attr;
	if (!tty_term_has(tty->term, TTYC_SETAB)) {
		if (attr & GRID_ATTR_REVERSE) {
			if (fg != 7 && fg != 8)
				attr &= ~GRID_ATTR_REVERSE;
		} else {
			if (bg != 0 && bg != 8)
				attr |= GRID_ATTR_REVERSE;
		}
	}

	/* If any bits are being cleared, reset everything. */
	if (tc->attr & ~attr)
		tty_reset(tty);

	/* Filter out attribute bits already set. */
	changed = attr & ~tc->attr;
	tc->attr = attr;

	/* Set the attributes. */
	if (changed & GRID_ATTR_BRIGHT)
		tty_putcode(tty, TTYC_BOLD);
	if (changed & GRID_ATTR_DIM)
		tty_putcode(tty, TTYC_DIM);
	if (changed & GRID_ATTR_ITALICS)
		tty_putcode(tty, TTYC_SMSO);
	if (changed & GRID_ATTR_UNDERSCORE)
		tty_putcode(tty, TTYC_SMUL);
	if (changed & GRID_ATTR_BLINK)
		tty_putcode(tty, TTYC_BLINK);
	if (changed & GRID_ATTR_REVERSE) {
		if (tty_term_has(tty->term, TTYC_REV))
			tty_putcode(tty, TTYC_REV);
		else if (tty_term_has(tty->term, TTYC_SMSO))
			tty_putcode(tty, TTYC_SMSO);
	}
	if (changed & GRID_ATTR_HIDDEN)
		tty_putcode(tty, TTYC_INVIS);
	if (changed & GRID_ATTR_CHARSET)
		tty_putcode(tty, TTYC_SMACS);

	/* Set foreground colour. */
	if (fg != tc->fg ||
	    (gc->flags & GRID_FLAG_FG256) != (tc->flags & GRID_FLAG_FG256)) {
		tty_attributes_fg(tty, gc);
		tc->fg = fg;
		tc->flags &= ~GRID_FLAG_FG256;
		tc->flags |= gc->flags & GRID_FLAG_FG256;
	}

	/* Set background colour. */
	if (bg != tc->bg ||
	    (gc->flags & GRID_FLAG_BG256) != (tc->flags & GRID_FLAG_BG256)) {
		tty_attributes_bg(tty, gc);
		tc->bg = bg;
		tc->flags &= ~GRID_FLAG_BG256;
		tc->flags |= gc->flags & GRID_FLAG_BG256;
	}
}

int
tty_try_256(struct tty *tty, u_char colour, const char *type)
{
	char	s[32];

	if (!(tty->term->flags & TERM_256COLOURS) &&
	    !(tty->term_flags & TERM_256COLOURS))
		return (-1);

	xsnprintf(s, sizeof s, "\033[%s;5;%hhum", type, colour);
	tty_puts(tty, s);
	return (0);
}

int
tty_try_88(struct tty *tty, u_char colour, const char *type)
{
	char	s[32];

	if (!(tty->term->flags & TERM_88COLOURS) &&
	    !(tty->term_flags & TERM_88COLOURS))
		return (-1);
	colour = colour_256to88(colour);

	xsnprintf(s, sizeof s, "\033[%s;5;%hhum", type, colour);
	tty_puts(tty, s);
	return (0);
}

void
tty_attributes_fg(struct tty *tty, const struct grid_cell *gc)
{
	u_char	fg;

	fg = gc->fg;
	if (gc->flags & GRID_FLAG_FG256) {
		if (tty_try_256(tty, fg, "38") == 0)
			return;
		if (tty_try_88(tty, fg, "38") == 0)
			return;
		fg = colour_256to16(fg);
		if (fg & 8) {
			fg &= 7;
			tty_putcode(tty, TTYC_BOLD);
			tty->cell.attr |= GRID_ATTR_BRIGHT;
		} else if (tty->cell.attr & GRID_ATTR_BRIGHT)
			tty_reset(tty);
	}

	if (fg == 8 &&
	    !(tty->term->flags & TERM_HASDEFAULTS) &&
	    !(tty->term_flags & TERM_HASDEFAULTS))
		fg = 7;
	if (fg == 8)
		tty_puts(tty, "\033[39m");
	else
		tty_putcode1(tty, TTYC_SETAF, fg);
}

void
tty_attributes_bg(struct tty *tty, const struct grid_cell *gc)
{
	u_char	bg;

	bg = gc->bg;
	if (gc->flags & GRID_FLAG_BG256) {
		if (tty_try_256(tty, bg, "48") == 0)
			return;
		if (tty_try_88(tty, bg, "48") == 0)
			return;
		bg = colour_256to16(bg);
		if (bg & 8)
			bg &= 7;
	}

	if (bg == 8 &&
	    !(tty->term->flags & TERM_HASDEFAULTS) &&
	    !(tty->term_flags & TERM_HASDEFAULTS))
		bg = 0;
	if (bg == 8)
		tty_puts(tty, "\033[49m");
	else
		tty_putcode1(tty, TTYC_SETAB, bg);
}