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Support for windows larger than visible on the attached client. This has
been a limitation for a long time.

There are two new options, window-size and default-size, and a new
command, resize-window. The force-width and force-height options and the
session_width and session_height formats have been removed.

The new window-size option tells tmux how to work out the size of
windows: largest means it picks the size of the largest session,
smallest the smallest session (similar to the old behaviour) and manual
means that it does not automatically resize windows. The default is
currently largest but this may change. aggressive-resize modifies the
choice of session for largest and smallest as it did before.

If a window is in a session attached to a client that is too small, only
part of the window is shown. tmux attempts to keep the cursor visible,
so the part of the window displayed is changed as the cursor moves (with
a small delay, to try and avoid excess redrawing when applications
redraw status lines or similar that are not currently visible). The
offset of the visible portion of the window is shown in status-right.

Drawing windows which are larger than the client is not as efficient as
those which fit, particularly when the cursor moves, so it is
recommended to avoid using this on slow machines or networks (set
window-size to smallest or manual).

The resize-window command can be used to resize a window manually. If it
is used, the window-size option is automatically set to manual for the
window (undo this with "setw -u window-size"). resize-window works in a
similar way to resize-pane (-U -D -L -R -x -y flags) but also has -a and
-A flags. -a sets the window to the size of the smallest client (what it
would be if window-size was smallest) and -A the largest.

For the same behaviour as force-width or force-height, use resize-window
-x or -y, and "setw -u window-size" to revert to automatic sizing..

If the global window-size option is set to manual, the default-size
option is used for new windows. If -x or -y is used with new-session,
that sets the default-size option for the new session.

The maximum size of a window is 10000x10000. But expect applications to
complain and much higher memory use if making a window excessively
big. The minimum size is the size required for the current layout
including borders.

The refresh-client command can be used to pan around a window, -U -D -L
-R moves up, down, left or right and -c returns to automatic cursor
tracking. The position is reset when the current window is changed.

/* $OpenBSD: window.c,v 1.213 2018/10/18 08:38:01 nicm Exp $ */

/*
 * Copyright (c) 2007 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 <sys/ioctl.h>

#include <errno.h>
#include <fcntl.h>
#include <fnmatch.h>
#include <signal.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>
#include <util.h>
#include <vis.h>

#include "tmux.h"

/*
 * Each window is attached to a number of panes, each of which is a pty. This
 * file contains code to handle them.
 *
 * A pane has two buffers attached, these are filled and emptied by the main
 * server poll loop. Output data is received from pty's in screen format,
 * translated and returned as a series of escape sequences and strings via
 * input_parse (in input.c). Input data is received as key codes and written
 * directly via input_key.
 *
 * Each pane also has a "virtual" screen (screen.c) which contains the current
 * state and is redisplayed when the window is reattached to a client.
 *
 * Windows are stored directly on a global array and wrapped in any number of
 * winlink structs to be linked onto local session RB trees. A reference count
 * is maintained and a window removed from the global list and destroyed when
 * it reaches zero.
 */

/* Global window list. */
struct windows windows;

/* Global panes tree. */
struct window_pane_tree all_window_panes;
static u_int	next_window_pane_id;
static u_int	next_window_id;
static u_int	next_active_point;

static void	window_destroy(struct window *);

static struct window_pane *window_pane_create(struct window *, u_int, u_int,
		    u_int);
static void	window_pane_destroy(struct window_pane *);

static void	window_pane_read_callback(struct bufferevent *, void *);
static void	window_pane_error_callback(struct bufferevent *, short, void *);

static int	winlink_next_index(struct winlinks *, int);

static struct window_pane *window_pane_choose_best(struct window_pane **,
		    u_int);

RB_GENERATE(windows, window, entry, window_cmp);
RB_GENERATE(winlinks, winlink, entry, winlink_cmp);
RB_GENERATE(window_pane_tree, window_pane, tree_entry, window_pane_cmp);

int
window_cmp(struct window *w1, struct window *w2)
{
	return (w1->id - w2->id);
}

int
winlink_cmp(struct winlink *wl1, struct winlink *wl2)
{
	return (wl1->idx - wl2->idx);
}

int
window_pane_cmp(struct window_pane *wp1, struct window_pane *wp2)
{
	return (wp1->id - wp2->id);
}

struct winlink *
winlink_find_by_window(struct winlinks *wwl, struct window *w)
{
	struct winlink	*wl;

	RB_FOREACH(wl, winlinks, wwl) {
		if (wl->window == w)
			return (wl);
	}

	return (NULL);
}

struct winlink *
winlink_find_by_index(struct winlinks *wwl, int idx)
{
	struct winlink	wl;

	if (idx < 0)
		fatalx("bad index");

	wl.idx = idx;
	return (RB_FIND(winlinks, wwl, &wl));
}

struct winlink *
winlink_find_by_window_id(struct winlinks *wwl, u_int id)
{
	struct winlink *wl;

	RB_FOREACH(wl, winlinks, wwl) {
		if (wl->window->id == id)
			return (wl);
	}
	return (NULL);
}

static int
winlink_next_index(struct winlinks *wwl, int idx)
{
	int	i;

	i = idx;
	do {
		if (winlink_find_by_index(wwl, i) == NULL)
			return (i);
		if (i == INT_MAX)
			i = 0;
		else
			i++;
	} while (i != idx);
	return (-1);
}

u_int
winlink_count(struct winlinks *wwl)
{
	struct winlink	*wl;
	u_int		 n;

	n = 0;
	RB_FOREACH(wl, winlinks, wwl)
		n++;

	return (n);
}

struct winlink *
winlink_add(struct winlinks *wwl, int idx)
{
	struct winlink	*wl;

	if (idx < 0) {
		if ((idx = winlink_next_index(wwl, -idx - 1)) == -1)
			return (NULL);
	} else if (winlink_find_by_index(wwl, idx) != NULL)
		return (NULL);

	wl = xcalloc(1, sizeof *wl);
	wl->idx = idx;
	RB_INSERT(winlinks, wwl, wl);

	return (wl);
}

void
winlink_set_window(struct winlink *wl, struct window *w)
{
	if (wl->window != NULL) {
		TAILQ_REMOVE(&wl->window->winlinks, wl, wentry);
		window_remove_ref(wl->window, __func__);
	}
	TAILQ_INSERT_TAIL(&w->winlinks, wl, wentry);
	wl->window = w;
	window_add_ref(w, __func__);
}

void
winlink_remove(struct winlinks *wwl, struct winlink *wl)
{
	struct window	*w = wl->window;

	if (w != NULL) {
		TAILQ_REMOVE(&w->winlinks, wl, wentry);
		window_remove_ref(w, __func__);
	}

	RB_REMOVE(winlinks, wwl, wl);
	free(wl->status_text);
	free(wl);
}

struct winlink *
winlink_next(struct winlink *wl)
{
	return (RB_NEXT(winlinks, wwl, wl));
}

struct winlink *
winlink_previous(struct winlink *wl)
{
	return (RB_PREV(winlinks, wwl, wl));
}

struct winlink *
winlink_next_by_number(struct winlink *wl, struct session *s, int n)
{
	for (; n > 0; n--) {
		if ((wl = RB_NEXT(winlinks, wwl, wl)) == NULL)
			wl = RB_MIN(winlinks, &s->windows);
	}

	return (wl);
}

struct winlink *
winlink_previous_by_number(struct winlink *wl, struct session *s, int n)
{
	for (; n > 0; n--) {
		if ((wl = RB_PREV(winlinks, wwl, wl)) == NULL)
			wl = RB_MAX(winlinks, &s->windows);
	}

	return (wl);
}

void
winlink_stack_push(struct winlink_stack *stack, struct winlink *wl)
{
	if (wl == NULL)
		return;

	winlink_stack_remove(stack, wl);
	TAILQ_INSERT_HEAD(stack, wl, sentry);
}

void
winlink_stack_remove(struct winlink_stack *stack, struct winlink *wl)
{
	struct winlink	*wl2;

	if (wl == NULL)
		return;

	TAILQ_FOREACH(wl2, stack, sentry) {
		if (wl2 == wl) {
			TAILQ_REMOVE(stack, wl, sentry);
			return;
		}
	}
}

struct window *
window_find_by_id_str(const char *s)
{
	const char	*errstr;
	u_int		 id;

	if (*s != '@')
		return (NULL);

	id = strtonum(s + 1, 0, UINT_MAX, &errstr);
	if (errstr != NULL)
		return (NULL);
	return (window_find_by_id(id));
}

struct window *
window_find_by_id(u_int id)
{
	struct window	w;

	w.id = id;
	return (RB_FIND(windows, &windows, &w));
}

void
window_update_activity(struct window *w)
{
	gettimeofday(&w->activity_time, NULL);
	alerts_queue(w, WINDOW_ACTIVITY);
}

struct window *
window_create(u_int sx, u_int sy)
{
	struct window	*w;

	w = xcalloc(1, sizeof *w);
	w->name = NULL;
	w->flags = WINDOW_STYLECHANGED;

	TAILQ_INIT(&w->panes);
	w->active = NULL;

	w->lastlayout = -1;
	w->layout_root = NULL;

	w->sx = sx;
	w->sy = sy;

	w->options = options_create(global_w_options);

	w->references = 0;
	TAILQ_INIT(&w->winlinks);

	w->id = next_window_id++;
	RB_INSERT(windows, &windows, w);

	window_update_activity(w);

	return (w);
}

struct window *
window_create_spawn(const char *name, int argc, char **argv, const char *path,
    const char *shell, const char *cwd, struct environ *env,
    struct termios *tio, u_int sx, u_int sy, u_int hlimit, char **cause)
{
	struct window		*w;
	struct window_pane	*wp;

	w = window_create(sx, sy);
	wp = window_add_pane(w, NULL, 0, 0, hlimit);
	layout_init(w, wp);

	if (window_pane_spawn(wp, argc, argv, path, shell, cwd,
	    env, tio, cause) != 0) {
		window_destroy(w);
		return (NULL);
	}

	w->active = TAILQ_FIRST(&w->panes);
	if (name != NULL) {
		w->name = xstrdup(name);
		options_set_number(w->options, "automatic-rename", 0);
	} else
		w->name = default_window_name(w);

	notify_window("window-pane-changed", w);

	return (w);
}

static void
window_destroy(struct window *w)
{
	log_debug("window @%u destroyed (%d references)", w->id, w->references);

	RB_REMOVE(windows, &windows, w);

	if (w->layout_root != NULL)
		layout_free_cell(w->layout_root);
	if (w->saved_layout_root != NULL)
		layout_free_cell(w->saved_layout_root);
	free(w->old_layout);

	if (event_initialized(&w->name_event))
		evtimer_del(&w->name_event);

	if (event_initialized(&w->alerts_timer))
		evtimer_del(&w->alerts_timer);
	if (event_initialized(&w->offset_timer))
		event_del(&w->offset_timer);

	options_free(w->options);

	window_destroy_panes(w);

	free(w->name);
	free(w);
}

int
window_pane_destroy_ready(struct window_pane *wp)
{
	int	n;

	if (wp->pipe_fd != -1) {
		if (EVBUFFER_LENGTH(wp->pipe_event->output) != 0)
			return (0);
		if (ioctl(wp->fd, FIONREAD, &n) != -1 && n > 0)
			return (0);
	}

	if (~wp->flags & PANE_EXITED)
		return (0);
	return (1);
}

void
window_add_ref(struct window *w, const char *from)
{
	w->references++;
	log_debug("%s: @%u %s, now %d", __func__, w->id, from, w->references);
}

void
window_remove_ref(struct window *w, const char *from)
{
	w->references--;
	log_debug("%s: @%u %s, now %d", __func__, w->id, from, w->references);

	if (w->references == 0)
		window_destroy(w);
}

void
window_set_name(struct window *w, const char *new_name)
{
	free(w->name);
	utf8_stravis(&w->name, new_name, VIS_OCTAL|VIS_CSTYLE|VIS_TAB|VIS_NL);
	notify_window("window-renamed", w);
}

void
window_resize(struct window *w, u_int sx, u_int sy)
{
	w->sx = sx;
	w->sy = sy;
}

int
window_has_pane(struct window *w, struct window_pane *wp)
{
	struct window_pane	*wp1;

	TAILQ_FOREACH(wp1, &w->panes, entry) {
		if (wp1 == wp)
			return (1);
	}
	return (0);
}

int
window_set_active_pane(struct window *w, struct window_pane *wp)
{
	log_debug("%s: pane %%%u (was %%%u)", __func__, wp->id, w->active->id);
	if (wp == w->active)
		return (0);
	w->last = w->active;
	w->active = wp;
	w->active->active_point = next_active_point++;
	w->active->flags |= PANE_CHANGED;
	tty_update_window_offset(w);
	notify_window("window-pane-changed", w);
	return (1);
}

void
window_redraw_active_switch(struct window *w, struct window_pane *wp)
{
	const struct grid_cell	*gc;

	if (wp == w->active)
		return;

	/*
	 * If window-style and window-active-style are the same, we don't need
	 * to redraw panes when switching active panes.
	 */
	gc = options_get_style(w->options, "window-active-style");
	if (style_equal(gc, options_get_style(w->options, "window-style")))
		return;

	/*
	 * If the now active or inactive pane do not have a custom style or if
	 * the palette is different, they need to be redrawn.
	 */
	if (window_pane_get_palette(w->active, w->active->colgc.fg) != -1 ||
	    window_pane_get_palette(w->active, w->active->colgc.bg) != -1 ||
	    style_equal(&grid_default_cell, &w->active->colgc))
		w->active->flags |= PANE_REDRAW;
	if (window_pane_get_palette(wp, wp->colgc.fg) != -1 ||
	    window_pane_get_palette(wp, wp->colgc.bg) != -1 ||
	    style_equal(&grid_default_cell, &wp->colgc))
		wp->flags |= PANE_REDRAW;
}

struct window_pane *
window_get_active_at(struct window *w, u_int x, u_int y)
{
	struct window_pane	*wp;

	TAILQ_FOREACH(wp, &w->panes, entry) {
                if (!window_pane_visible(wp))
                        continue;
		if (x < wp->xoff || x > wp->xoff + wp->sx)
			continue;
		if (y < wp->yoff || y > wp->yoff + wp->sy)
			continue;
		return (wp);
	}
	return (NULL);
}

struct window_pane *
window_find_string(struct window *w, const char *s)
{
	u_int	x, y;

	x = w->sx / 2;
	y = w->sy / 2;

	if (strcasecmp(s, "top") == 0)
		y = 0;
	else if (strcasecmp(s, "bottom") == 0)
		y = w->sy - 1;
	else if (strcasecmp(s, "left") == 0)
		x = 0;
	else if (strcasecmp(s, "right") == 0)
		x = w->sx - 1;
	else if (strcasecmp(s, "top-left") == 0) {
		x = 0;
		y = 0;
	} else if (strcasecmp(s, "top-right") == 0) {
		x = w->sx - 1;
		y = 0;
	} else if (strcasecmp(s, "bottom-left") == 0) {
		x = 0;
		y = w->sy - 1;
	} else if (strcasecmp(s, "bottom-right") == 0) {
		x = w->sx - 1;
		y = w->sy - 1;
	} else
		return (NULL);

	return (window_get_active_at(w, x, y));
}

int
window_zoom(struct window_pane *wp)
{
	struct window		*w = wp->window;
	struct window_pane	*wp1;

	if (w->flags & WINDOW_ZOOMED)
		return (-1);

	if (window_count_panes(w) == 1)
		return (-1);

	if (w->active != wp)
		window_set_active_pane(w, wp);

	TAILQ_FOREACH(wp1, &w->panes, entry) {
		wp1->saved_layout_cell = wp1->layout_cell;
		wp1->layout_cell = NULL;
	}

	w->saved_layout_root = w->layout_root;
	layout_init(w, wp);
	w->flags |= WINDOW_ZOOMED;
	notify_window("window-layout-changed", w);

	return (0);
}

int
window_unzoom(struct window *w)
{
	struct window_pane	*wp;

	if (!(w->flags & WINDOW_ZOOMED))
		return (-1);

	w->flags &= ~WINDOW_ZOOMED;
	layout_free(w);
	w->layout_root = w->saved_layout_root;
	w->saved_layout_root = NULL;

	TAILQ_FOREACH(wp, &w->panes, entry) {
		wp->layout_cell = wp->saved_layout_cell;
		wp->saved_layout_cell = NULL;
	}
	layout_fix_panes(w);
	notify_window("window-layout-changed", w);

	return (0);
}

struct window_pane *
window_add_pane(struct window *w, struct window_pane *other, int before,
    int full_size, u_int hlimit)
{
	struct window_pane	*wp;

	if (other == NULL)
		other = w->active;

	wp = window_pane_create(w, w->sx, w->sy, hlimit);
	if (TAILQ_EMPTY(&w->panes)) {
		log_debug("%s: @%u at start", __func__, w->id);
		TAILQ_INSERT_HEAD(&w->panes, wp, entry);
	} else if (before) {
		log_debug("%s: @%u before %%%u", __func__, w->id, wp->id);
		if (full_size)
			TAILQ_INSERT_HEAD(&w->panes, wp, entry);
		else
			TAILQ_INSERT_BEFORE(other, wp, entry);
	} else {
		log_debug("%s: @%u after %%%u", __func__, w->id, wp->id);
		if (full_size)
			TAILQ_INSERT_TAIL(&w->panes, wp, entry);
		else
			TAILQ_INSERT_AFTER(&w->panes, other, wp, entry);
	}
	return (wp);
}

void
window_lost_pane(struct window *w, struct window_pane *wp)
{
	log_debug("%s: @%u pane %%%u", __func__, w->id, wp->id);

	if (wp == marked_pane.wp)
		server_clear_marked();

	if (wp == w->active) {
		w->active = w->last;
		w->last = NULL;
		if (w->active == NULL) {
			w->active = TAILQ_PREV(wp, window_panes, entry);
			if (w->active == NULL)
				w->active = TAILQ_NEXT(wp, entry);
		}
		if (w->active != NULL) {
			w->active->flags |= PANE_CHANGED;
			notify_window("window-pane-changed", w);
		}
	} else if (wp == w->last)
		w->last = NULL;
}

void
window_remove_pane(struct window *w, struct window_pane *wp)
{
	window_lost_pane(w, wp);

	TAILQ_REMOVE(&w->panes, wp, entry);
	window_pane_destroy(wp);
}

struct window_pane *
window_pane_at_index(struct window *w, u_int idx)
{
	struct window_pane	*wp;
	u_int			 n;

	n = options_get_number(w->options, "pane-base-index");
	TAILQ_FOREACH(wp, &w->panes, entry) {
		if (n == idx)
			return (wp);
		n++;
	}
	return (NULL);
}

struct window_pane *
window_pane_next_by_number(struct window *w, struct window_pane *wp, u_int n)
{
	for (; n > 0; n--) {
		if ((wp = TAILQ_NEXT(wp, entry)) == NULL)
			wp = TAILQ_FIRST(&w->panes);
	}

	return (wp);
}

struct window_pane *
window_pane_previous_by_number(struct window *w, struct window_pane *wp,
    u_int n)
{
	for (; n > 0; n--) {
		if ((wp = TAILQ_PREV(wp, window_panes, entry)) == NULL)
			wp = TAILQ_LAST(&w->panes, window_panes);
	}

	return (wp);
}

int
window_pane_index(struct window_pane *wp, u_int *i)
{
	struct window_pane	*wq;
	struct window		*w = wp->window;

	*i = options_get_number(w->options, "pane-base-index");
	TAILQ_FOREACH(wq, &w->panes, entry) {
		if (wp == wq) {
			return (0);
		}
		(*i)++;
	}

	return (-1);
}

u_int
window_count_panes(struct window *w)
{
	struct window_pane	*wp;
	u_int			 n;

	n = 0;
	TAILQ_FOREACH(wp, &w->panes, entry)
		n++;
	return (n);
}

void
window_destroy_panes(struct window *w)
{
	struct window_pane	*wp;

	while (!TAILQ_EMPTY(&w->panes)) {
		wp = TAILQ_FIRST(&w->panes);
		TAILQ_REMOVE(&w->panes, wp, entry);
		window_pane_destroy(wp);
	}
}

const char *
window_printable_flags(struct winlink *wl)
{
	struct session	*s = wl->session;
	static char	 flags[32];
	int		 pos;

	pos = 0;
	if (wl->flags & WINLINK_ACTIVITY)
		flags[pos++] = '#';
	if (wl->flags & WINLINK_BELL)
		flags[pos++] = '!';
	if (wl->flags & WINLINK_SILENCE)
		flags[pos++] = '~';
	if (wl == s->curw)
		flags[pos++] = '*';
	if (wl == TAILQ_FIRST(&s->lastw))
		flags[pos++] = '-';
	if (server_check_marked() && wl == marked_pane.wl)
		flags[pos++] = 'M';
	if (wl->window->flags & WINDOW_ZOOMED)
		flags[pos++] = 'Z';
	flags[pos] = '\0';
	return (flags);
}

struct window_pane *
window_pane_find_by_id_str(const char *s)
{
	const char	*errstr;
	u_int		 id;

	if (*s != '%')
		return (NULL);

	id = strtonum(s + 1, 0, UINT_MAX, &errstr);
	if (errstr != NULL)
		return (NULL);
	return (window_pane_find_by_id(id));
}

struct window_pane *
window_pane_find_by_id(u_int id)
{
	struct window_pane	wp;

	wp.id = id;
	return (RB_FIND(window_pane_tree, &all_window_panes, &wp));
}

static struct window_pane *
window_pane_create(struct window *w, u_int sx, u_int sy, u_int hlimit)
{
	struct window_pane	*wp;
	char			 host[HOST_NAME_MAX + 1];

	wp = xcalloc(1, sizeof *wp);
	wp->window = w;

	wp->id = next_window_pane_id++;
	RB_INSERT(window_pane_tree, &all_window_panes, wp);

	wp->argc = 0;
	wp->argv = NULL;
	wp->shell = NULL;
	wp->cwd = NULL;

	wp->fd = -1;
	wp->event = NULL;

	wp->mode = NULL;
	wp->modeprefix = 1;

	wp->layout_cell = NULL;

	wp->xoff = 0;
	wp->yoff = 0;

	wp->sx = wp->osx = sx;
	wp->sy = wp->osx = sy;

	wp->pipe_fd = -1;
	wp->pipe_off = 0;
	wp->pipe_event = NULL;

	wp->saved_grid = NULL;

	memcpy(&wp->colgc, &grid_default_cell, sizeof wp->colgc);

	screen_init(&wp->base, sx, sy, hlimit);
	wp->screen = &wp->base;

	screen_init(&wp->status_screen, 1, 1, 0);

	if (gethostname(host, sizeof host) == 0)
		screen_set_title(&wp->base, host);

	input_init(wp);

	return (wp);
}

static void
window_pane_destroy(struct window_pane *wp)
{
	window_pane_reset_mode(wp);
	free(wp->searchstr);

	if (wp->fd != -1) {
		bufferevent_free(wp->event);
		close(wp->fd);
	}

	input_free(wp);

	screen_free(&wp->base);
	if (wp->saved_grid != NULL)
		grid_destroy(wp->saved_grid);

	if (wp->pipe_fd != -1) {
		bufferevent_free(wp->pipe_event);
		close(wp->pipe_fd);
	}

	if (event_initialized(&wp->resize_timer))
		event_del(&wp->resize_timer);

	RB_REMOVE(window_pane_tree, &all_window_panes, wp);

	free((void *)wp->cwd);
	free(wp->shell);
	cmd_free_argv(wp->argc, wp->argv);
	free(wp->palette);
	free(wp);
}

int
window_pane_spawn(struct window_pane *wp, int argc, char **argv,
    const char *path, const char *shell, const char *cwd, struct environ *env,
    struct termios *tio, char **cause)
{
	struct winsize	 ws;
	char		*argv0, *cmd, **argvp;
	const char	*ptr, *first, *home;
	struct termios	 tio2;
	sigset_t	 set, oldset;

	if (wp->fd != -1) {
		bufferevent_free(wp->event);
		close(wp->fd);
	}
	if (argc > 0) {
		cmd_free_argv(wp->argc, wp->argv);
		wp->argc = argc;
		wp->argv = cmd_copy_argv(argc, argv);
	}
	if (shell != NULL) {
		free(wp->shell);
		wp->shell = xstrdup(shell);
	}
	if (cwd != NULL) {
		free((void *)wp->cwd);
		wp->cwd = xstrdup(cwd);
	}
	wp->flags &= ~(PANE_STATUSREADY|PANE_STATUSDRAWN);

	cmd = cmd_stringify_argv(wp->argc, wp->argv);
	log_debug("%s: shell=%s", __func__, wp->shell);
	log_debug("%s: cmd=%s", __func__, cmd);
	log_debug("%s: cwd=%s", __func__, cwd);
	cmd_log_argv(wp->argc, wp->argv, __func__);
	environ_log(env, "%s: environment ", __func__);

	memset(&ws, 0, sizeof ws);
	ws.ws_col = screen_size_x(&wp->base);
	ws.ws_row = screen_size_y(&wp->base);

	sigfillset(&set);
	sigprocmask(SIG_BLOCK, &set, &oldset);
	switch (wp->pid = fdforkpty(ptm_fd, &wp->fd, wp->tty, NULL, &ws)) {
	case -1:
		wp->fd = -1;

		xasprintf(cause, "%s: %s", cmd, strerror(errno));
		free(cmd);

		sigprocmask(SIG_SETMASK, &oldset, NULL);
		return (-1);
	case 0:
		proc_clear_signals(server_proc, 1);
		sigprocmask(SIG_SETMASK, &oldset, NULL);

		cwd = NULL;
		if (chdir(wp->cwd) == 0)
			cwd = wp->cwd;
		else if ((home = find_home()) != NULL && chdir(home) == 0)
			cwd = home;
		else
			chdir("/");

		if (tcgetattr(STDIN_FILENO, &tio2) != 0)
			fatal("tcgetattr failed");
		if (tio != NULL)
			memcpy(tio2.c_cc, tio->c_cc, sizeof tio2.c_cc);
		tio2.c_cc[VERASE] = '\177';
		if (tcsetattr(STDIN_FILENO, TCSANOW, &tio2) != 0)
			fatal("tcgetattr failed");

		log_close();
		closefrom(STDERR_FILENO + 1);

		if (path != NULL)
			environ_set(env, "PATH", "%s", path);
		if (cwd != NULL)
			environ_set(env, "PWD", "%s", cwd);
		environ_set(env, "TMUX_PANE", "%%%u", wp->id);
		environ_push(env);

		setenv("SHELL", wp->shell, 1);
		ptr = strrchr(wp->shell, '/');

		/*
		 * If given one argument, assume it should be passed to sh -c;
		 * with more than one argument, use execvp(). If there is no
		 * arguments, create a login shell.
		 */
		if (wp->argc > 0) {
			if (wp->argc != 1) {
				/* Copy to ensure argv ends in NULL. */
				argvp = cmd_copy_argv(wp->argc, wp->argv);
				execvp(argvp[0], argvp);
				fatal("execvp failed");
			}
			first = wp->argv[0];

			if (ptr != NULL && *(ptr + 1) != '\0')
				xasprintf(&argv0, "%s", ptr + 1);
			else
				xasprintf(&argv0, "%s", wp->shell);
			execl(wp->shell, argv0, "-c", first, (char *)NULL);
			fatal("execl failed");
		}
		if (ptr != NULL && *(ptr + 1) != '\0')
			xasprintf(&argv0, "-%s", ptr + 1);
		else
			xasprintf(&argv0, "-%s", wp->shell);
		execl(wp->shell, argv0, (char *)NULL);
		fatal("execl failed");
	}
	log_debug("%s: master=%s", __func__, ttyname(wp->fd));
	log_debug("%s: slave=%s", __func__, wp->tty);

	sigprocmask(SIG_SETMASK, &oldset, NULL);
	setblocking(wp->fd, 0);

	wp->event = bufferevent_new(wp->fd, window_pane_read_callback, NULL,
	    window_pane_error_callback, wp);

	bufferevent_setwatermark(wp->event, EV_READ, 0, READ_SIZE);
	bufferevent_enable(wp->event, EV_READ|EV_WRITE);

	free(cmd);
	return (0);
}

static void
window_pane_read_callback(__unused struct bufferevent *bufev, void *data)
{
	struct window_pane	*wp = data;
	struct evbuffer		*evb = wp->event->input;
	size_t			 size = EVBUFFER_LENGTH(evb);
	char			*new_data;
	size_t			 new_size;

	new_size = size - wp->pipe_off;
	if (wp->pipe_fd != -1 && new_size > 0) {
		new_data = EVBUFFER_DATA(evb) + wp->pipe_off;
		bufferevent_write(wp->pipe_event, new_data, new_size);
	}

	log_debug("%%%u has %zu bytes", wp->id, size);
	input_parse(wp);

	wp->pipe_off = EVBUFFER_LENGTH(evb);
}

static void
window_pane_error_callback(__unused struct bufferevent *bufev,
    __unused short what, void *data)
{
	struct window_pane *wp = data;

	log_debug("%%%u error", wp->id);
	wp->flags |= PANE_EXITED;

	if (window_pane_destroy_ready(wp))
		server_destroy_pane(wp, 1);
}

void
window_pane_resize(struct window_pane *wp, u_int sx, u_int sy)
{
	if (sx == wp->sx && sy == wp->sy)
		return;
	wp->sx = sx;
	wp->sy = sy;

	screen_resize(&wp->base, sx, sy, wp->saved_grid == NULL);
	if (wp->mode != NULL)
		wp->mode->resize(wp, sx, sy);

	wp->flags |= PANE_RESIZE;
}

/*
 * Enter alternative screen mode. A copy of the visible screen is saved and the
 * history is not updated
 */
void
window_pane_alternate_on(struct window_pane *wp, struct grid_cell *gc,
    int cursor)
{
	struct screen	*s = &wp->base;
	u_int		 sx, sy;

	if (wp->saved_grid != NULL)
		return;
	if (!options_get_number(wp->window->options, "alternate-screen"))
		return;
	sx = screen_size_x(s);
	sy = screen_size_y(s);

	wp->saved_grid = grid_create(sx, sy, 0);
	grid_duplicate_lines(wp->saved_grid, 0, s->grid, screen_hsize(s), sy);
	if (cursor) {
		wp->saved_cx = s->cx;
		wp->saved_cy = s->cy;
	}
	memcpy(&wp->saved_cell, gc, sizeof wp->saved_cell);

	grid_view_clear(s->grid, 0, 0, sx, sy, 8);

	wp->base.grid->flags &= ~GRID_HISTORY;

	wp->flags |= PANE_REDRAW;
}

/* Exit alternate screen mode and restore the copied grid. */
void
window_pane_alternate_off(struct window_pane *wp, struct grid_cell *gc,
    int cursor)
{
	struct screen	*s = &wp->base;
	u_int		 sx, sy;

	if (wp->saved_grid == NULL)
		return;
	if (!options_get_number(wp->window->options, "alternate-screen"))
		return;
	sx = screen_size_x(s);
	sy = screen_size_y(s);

	/*
	 * If the current size is bigger, temporarily resize to the old size
	 * before copying back.
	 */
	if (sy > wp->saved_grid->sy)
		screen_resize(s, sx, wp->saved_grid->sy, 1);

	/* Restore the grid, cursor position and cell. */
	grid_duplicate_lines(s->grid, screen_hsize(s), wp->saved_grid, 0, sy);
	if (cursor)
		s->cx = wp->saved_cx;
	if (s->cx > screen_size_x(s) - 1)
		s->cx = screen_size_x(s) - 1;
	if (cursor)
		s->cy = wp->saved_cy;
	if (s->cy > screen_size_y(s) - 1)
		s->cy = screen_size_y(s) - 1;
	memcpy(gc, &wp->saved_cell, sizeof *gc);

	/*
	 * Turn history back on (so resize can use it) and then resize back to
	 * the current size.
	 */
	wp->base.grid->flags |= GRID_HISTORY;
	if (sy > wp->saved_grid->sy || sx != wp->saved_grid->sx)
		screen_resize(s, sx, sy, 1);

	grid_destroy(wp->saved_grid);
	wp->saved_grid = NULL;

	wp->flags |= PANE_REDRAW;
}

void
window_pane_set_palette(struct window_pane *wp, u_int n, int colour)
{
	if (n > 0xff)
		return;

	if (wp->palette == NULL)
		wp->palette = xcalloc(0x100, sizeof *wp->palette);

	wp->palette[n] = colour;
	wp->flags |= PANE_REDRAW;
}

void
window_pane_unset_palette(struct window_pane *wp, u_int n)
{
	if (n > 0xff || wp->palette == NULL)
		return;

	wp->palette[n] = 0;
	wp->flags |= PANE_REDRAW;
}

void
window_pane_reset_palette(struct window_pane *wp)
{
	if (wp->palette == NULL)
		return;

	free(wp->palette);
	wp->palette = NULL;
	wp->flags |= PANE_REDRAW;
}

int
window_pane_get_palette(const struct window_pane *wp, int c)
{
	int	new;

	if (wp == NULL || wp->palette == NULL)
		return (-1);

	new = -1;
	if (c < 8)
		new = wp->palette[c];
	else if (c >= 90 && c <= 97)
		new = wp->palette[8 + c - 90];
	else if (c & COLOUR_FLAG_256)
		new = wp->palette[c & ~COLOUR_FLAG_256];
	if (new == 0)
		return (-1);
	return (new);
}

static void
window_pane_mode_timer(__unused int fd, __unused short events, void *arg)
{
	struct window_pane	*wp = arg;
	struct timeval		 tv = { .tv_sec = 10 };
	int			 n = 0;

	evtimer_del(&wp->modetimer);
	evtimer_add(&wp->modetimer, &tv);

	log_debug("%%%u in mode: last=%ld", wp->id, (long)wp->modelast);

	if (wp->modelast < time(NULL) - WINDOW_MODE_TIMEOUT) {
		if (ioctl(wp->fd, FIONREAD, &n) == -1 || n > 0)
			window_pane_reset_mode(wp);
	}
}

int
window_pane_set_mode(struct window_pane *wp, const struct window_mode *mode,
    struct cmd_find_state *fs, struct args *args)
{
	struct screen	*s;
	struct timeval	 tv = { .tv_sec = 10 };

	if (wp->mode != NULL)
		return (1);
	wp->mode = mode;

	wp->modelast = time(NULL);
	evtimer_set(&wp->modetimer, window_pane_mode_timer, wp);
	evtimer_add(&wp->modetimer, &tv);

	if ((s = wp->mode->init(wp, fs, args)) != NULL)
		wp->screen = s;
	wp->flags |= (PANE_REDRAW|PANE_CHANGED);

	server_status_window(wp->window);
	notify_pane("pane-mode-changed", wp);
	return (0);
}

void
window_pane_reset_mode(struct window_pane *wp)
{
	if (wp->mode == NULL)
		return;

	evtimer_del(&wp->modetimer);

	wp->mode->free(wp);
	wp->mode = NULL;
	wp->modeprefix = 1;

	wp->screen = &wp->base;
	wp->flags |= (PANE_REDRAW|PANE_CHANGED);

	server_status_window(wp->window);
	notify_pane("pane-mode-changed", wp);
}

void
window_pane_key(struct window_pane *wp, struct client *c, struct session *s,
    key_code key, struct mouse_event *m)
{
	struct window_pane	*wp2;

	if (KEYC_IS_MOUSE(key) && m == NULL)
		return;

	if (wp->mode != NULL) {
		wp->modelast = time(NULL);
		if (wp->mode->key != NULL)
			wp->mode->key(wp, c, s, (key & ~KEYC_XTERM), m);
		return;
	}

	if (wp->fd == -1 || wp->flags & PANE_INPUTOFF)
		return;

	input_key(wp, key, m);

	if (KEYC_IS_MOUSE(key))
		return;
	if (options_get_number(wp->window->options, "synchronize-panes")) {
		TAILQ_FOREACH(wp2, &wp->window->panes, entry) {
			if (wp2 != wp &&
			    wp2->mode == NULL &&
			    wp2->fd != -1 &&
			    (~wp2->flags & PANE_INPUTOFF) &&
			    window_pane_visible(wp2))
				input_key(wp2, key, NULL);
		}
	}
}

int
window_pane_visible(struct window_pane *wp)
{
	if (~wp->window->flags & WINDOW_ZOOMED)
		return (1);
	return (wp == wp->window->active);
}

u_int
window_pane_search(struct window_pane *wp, const char *searchstr)
{
	struct screen	*s = &wp->base;
	char		*newsearchstr, *line;
	u_int		 i;

	xasprintf(&newsearchstr, "*%s*", searchstr);

	for (i = 0; i < screen_size_y(s); i++) {
		line = grid_view_string_cells(s->grid, 0, i, screen_size_x(s));
		if (fnmatch(newsearchstr, line, 0) == 0) {
			free(line);
			break;
		}
		free(line);
	}

	free(newsearchstr);
	if (i == screen_size_y(s))
		return (0);
	return (i + 1);
}

/* Get MRU pane from a list. */
static struct window_pane *
window_pane_choose_best(struct window_pane **list, u_int size)
{
	struct window_pane	*next, *best;
	u_int			 i;

	if (size == 0)
		return (NULL);

	best = list[0];
	for (i = 1; i < size; i++) {
		next = list[i];
		if (next->active_point > best->active_point)
			best = next;
	}
	return (best);
}

/*
 * Find the pane directly above another. We build a list of those adjacent to
 * top edge and then choose the best.
 */
struct window_pane *
window_pane_find_up(struct window_pane *wp)
{
	struct window_pane	*next, *best, **list;
	u_int			 edge, left, right, end, size;
	int			 status, found;

	if (wp == NULL)
		return (NULL);
	status = options_get_number(wp->window->options, "pane-border-status");

	list = NULL;
	size = 0;

	edge = wp->yoff;
	if (edge == (status == 1 ? 1 : 0))
		edge = wp->window->sy + 1 - (status == 2 ? 1 : 0);

	left = wp->xoff;
	right = wp->xoff + wp->sx;

	TAILQ_FOREACH(next, &wp->window->panes, entry) {
		if (next == wp)
			continue;
		if (next->yoff + next->sy + 1 != edge)
			continue;
		end = next->xoff + next->sx - 1;

		found = 0;
		if (next->xoff < left && end > right)
			found = 1;
		else if (next->xoff >= left && next->xoff <= right)
			found = 1;
		else if (end >= left && end <= right)
			found = 1;
		if (!found)
			continue;
		list = xreallocarray(list, size + 1, sizeof *list);
		list[size++] = next;
	}

	best = window_pane_choose_best(list, size);
	free(list);
	return (best);
}

/* Find the pane directly below another. */
struct window_pane *
window_pane_find_down(struct window_pane *wp)
{
	struct window_pane	*next, *best, **list;
	u_int			 edge, left, right, end, size;
	int			 status, found;

	if (wp == NULL)
		return (NULL);
	status = options_get_number(wp->window->options, "pane-border-status");

	list = NULL;
	size = 0;

	edge = wp->yoff + wp->sy + 1;
	if (edge >= wp->window->sy - (status == 2 ? 1 : 0))
		edge = (status == 1 ? 1 : 0);

	left = wp->xoff;
	right = wp->xoff + wp->sx;

	TAILQ_FOREACH(next, &wp->window->panes, entry) {
		if (next == wp)
			continue;
		if (next->yoff != edge)
			continue;
		end = next->xoff + next->sx - 1;

		found = 0;
		if (next->xoff < left && end > right)
			found = 1;
		else if (next->xoff >= left && next->xoff <= right)
			found = 1;
		else if (end >= left && end <= right)
			found = 1;
		if (!found)
			continue;
		list = xreallocarray(list, size + 1, sizeof *list);
		list[size++] = next;
	}

	best = window_pane_choose_best(list, size);
	free(list);
	return (best);
}

/* Find the pane directly to the left of another. */
struct window_pane *
window_pane_find_left(struct window_pane *wp)
{
	struct window_pane	*next, *best, **list;
	u_int			 edge, top, bottom, end, size;
	int			 found;

	if (wp == NULL)
		return (NULL);

	list = NULL;
	size = 0;

	edge = wp->xoff;
	if (edge == 0)
		edge = wp->window->sx + 1;

	top = wp->yoff;
	bottom = wp->yoff + wp->sy;

	TAILQ_FOREACH(next, &wp->window->panes, entry) {
		if (next == wp)
			continue;
		if (next->xoff + next->sx + 1 != edge)
			continue;
		end = next->yoff + next->sy - 1;

		found = 0;
		if (next->yoff < top && end > bottom)
			found = 1;
		else if (next->yoff >= top && next->yoff <= bottom)
			found = 1;
		else if (end >= top && end <= bottom)
			found = 1;
		if (!found)
			continue;
		list = xreallocarray(list, size + 1, sizeof *list);
		list[size++] = next;
	}

	best = window_pane_choose_best(list, size);
	free(list);
	return (best);
}

/* Find the pane directly to the right of another. */
struct window_pane *
window_pane_find_right(struct window_pane *wp)
{
	struct window_pane	*next, *best, **list;
	u_int			 edge, top, bottom, end, size;
	int			 found;

	if (wp == NULL)
		return (NULL);

	list = NULL;
	size = 0;

	edge = wp->xoff + wp->sx + 1;
	if (edge >= wp->window->sx)
		edge = 0;

	top = wp->yoff;
	bottom = wp->yoff + wp->sy;

	TAILQ_FOREACH(next, &wp->window->panes, entry) {
		if (next == wp)
			continue;
		if (next->xoff != edge)
			continue;
		end = next->yoff + next->sy - 1;

		found = 0;
		if (next->yoff < top && end > bottom)
			found = 1;
		else if (next->yoff >= top && next->yoff <= bottom)
			found = 1;
		else if (end >= top && end <= bottom)
			found = 1;
		if (!found)
			continue;
		list = xreallocarray(list, size + 1, sizeof *list);
		list[size++] = next;
	}

	best = window_pane_choose_best(list, size);
	free(list);
	return (best);
}

/* Clear alert flags for a winlink */
void
winlink_clear_flags(struct winlink *wl)
{
	struct winlink	*loop;

	wl->window->flags &= ~WINDOW_ALERTFLAGS;
	TAILQ_FOREACH(loop, &wl->window->winlinks, wentry) {
		if ((loop->flags & WINLINK_ALERTFLAGS) != 0) {
			loop->flags &= ~WINLINK_ALERTFLAGS;
			server_status_session(loop->session);
		}
	}
}

/* Shuffle window indexes up. */
int
winlink_shuffle_up(struct session *s, struct winlink *wl)
{
	int	 idx, last;

	idx = wl->idx + 1;

	/* Find the next free index. */
	for (last = idx; last < INT_MAX; last++) {
		if (winlink_find_by_index(&s->windows, last) == NULL)
			break;
	}
	if (last == INT_MAX)
		return (-1);

	/* Move everything from last - 1 to idx up a bit. */
	for (; last > idx; last--) {
		wl = winlink_find_by_index(&s->windows, last - 1);
		server_link_window(s, wl, s, last, 0, 0, NULL);
		server_unlink_window(s, wl);
	}

	return (idx);
}