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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: screen-write.c,v 1.139 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 <stdlib.h>
#include <string.h>

#include "tmux.h"

static void	screen_write_initctx(struct screen_write_ctx *,
		    struct tty_ctx *);
static void	screen_write_collect_clear(struct screen_write_ctx *, u_int,
		    u_int);
static void	screen_write_collect_scroll(struct screen_write_ctx *);
static void	screen_write_collect_flush(struct screen_write_ctx *, int);

static int	screen_write_overwrite(struct screen_write_ctx *,
		    struct grid_cell *, u_int);
static const struct grid_cell *screen_write_combine(struct screen_write_ctx *,
		    const struct utf8_data *, u_int *);

static const struct grid_cell screen_write_pad_cell = {
	GRID_FLAG_PADDING, 0, 8, 8, { { 0 }, 0, 0, 0 }
};

struct screen_write_collect_item {
	u_int			 x;
	int			 wrapped;

	u_int			 used;
	char			 data[256];

	struct grid_cell	 gc;

	TAILQ_ENTRY(screen_write_collect_item) entry;
};
struct screen_write_collect_line {
	TAILQ_HEAD(, screen_write_collect_item) items;
};

static void
screen_write_offset_timer(__unused int fd, __unused short events, void *data)
{
	struct window	*w = data;

	tty_update_window_offset(w);
}

/* Set cursor position. */
static void
screen_write_set_cursor(struct screen_write_ctx *ctx, int cx, int cy)
{
	struct window_pane	*wp = ctx->wp;
	struct window		*w;
	struct screen		*s = ctx->s;
	struct timeval		 tv = { .tv_usec = 10000 };

	if (cx != -1 && (u_int)cx == s->cx && cy != -1 && (u_int)cy == s->cy)
		return;

	if (cx != -1)
		s->cx = cx;
	if (cy != -1)
		s->cy = cy;

	if (wp == NULL)
		return;
	w = wp->window;

	if (!event_initialized(&w->offset_timer))
		evtimer_set(&w->offset_timer, screen_write_offset_timer, w);
	if (!evtimer_pending(&w->offset_timer, NULL))
		evtimer_add(&w->offset_timer, &tv);
}

/* Initialize writing with a window. */
void
screen_write_start(struct screen_write_ctx *ctx, struct window_pane *wp,
    struct screen *s)
{
	char	tmp[32];
	u_int	y;

	memset(ctx, 0, sizeof *ctx);

	ctx->wp = wp;
	if (wp != NULL && s == NULL)
		ctx->s = wp->screen;
	else
		ctx->s = s;

	ctx->list = xcalloc(screen_size_y(ctx->s), sizeof *ctx->list);
	for (y = 0; y < screen_size_y(ctx->s); y++)
		TAILQ_INIT(&ctx->list[y].items);
	ctx->item = xcalloc(1, sizeof *ctx->item);

	ctx->scrolled = 0;
	ctx->bg = 8;

	if (wp != NULL) {
		snprintf(tmp, sizeof tmp, "pane %%%u (at %u,%u)", wp->id,
		    wp->xoff, wp->yoff);
	}
	log_debug("%s: size %ux%u, %s", __func__, screen_size_x(ctx->s),
	    screen_size_y(ctx->s), wp == NULL ? "no pane" : tmp);
}

/* Finish writing. */
void
screen_write_stop(struct screen_write_ctx *ctx)
{
	screen_write_collect_end(ctx);
	screen_write_collect_flush(ctx, 0);

	log_debug("%s: %u cells (%u written, %u skipped)", __func__,
	    ctx->cells, ctx->written, ctx->skipped);

	free(ctx->item);
	free(ctx->list); /* flush will have emptied */
}

/* Reset screen state. */
void
screen_write_reset(struct screen_write_ctx *ctx)
{
	struct screen	*s = ctx->s;

	screen_reset_tabs(s);
	screen_write_scrollregion(ctx, 0, screen_size_y(s) - 1);

	s->mode &= ~(MODE_INSERT|MODE_KCURSOR|MODE_KKEYPAD|MODE_FOCUSON);
	s->mode &= ~(ALL_MOUSE_MODES|MODE_MOUSE_UTF8|MODE_MOUSE_SGR);

	screen_write_clearscreen(ctx, 8);
	screen_write_cursormove(ctx, 0, 0);
}

/* Write character. */
void
screen_write_putc(struct screen_write_ctx *ctx, const struct grid_cell *gcp,
    u_char ch)
{
	struct grid_cell	gc;

	memcpy(&gc, gcp, sizeof gc);

	utf8_set(&gc.data, ch);
	screen_write_cell(ctx, &gc);
}

/* Calculate string length, with embedded formatting. */
size_t
screen_write_cstrlen(const char *fmt, ...)
{
	va_list	ap;
	char   *msg, *msg2, *ptr, *ptr2;
	size_t	size;

	va_start(ap, fmt);
	xvasprintf(&msg, fmt, ap);
	va_end(ap);
	msg2 = xmalloc(strlen(msg) + 1);

	ptr = msg;
	ptr2 = msg2;
	while (*ptr != '\0') {
		if (ptr[0] == '#' && ptr[1] == '[') {
			while (*ptr != ']' && *ptr != '\0')
				ptr++;
			if (*ptr == ']')
				ptr++;
			continue;
		}
		*ptr2++ = *ptr++;
	}
	*ptr2 = '\0';

	size = screen_write_strlen("%s", msg2);

	free(msg);
	free(msg2);

	return (size);
}

/* Calculate string length. */
size_t
screen_write_strlen(const char *fmt, ...)
{
	va_list			ap;
	char   	       	       *msg;
	struct utf8_data	ud;
	u_char 	      	       *ptr;
	size_t			left, size = 0;
	enum utf8_state		more;

	va_start(ap, fmt);
	xvasprintf(&msg, fmt, ap);
	va_end(ap);

	ptr = msg;
	while (*ptr != '\0') {
		if (*ptr > 0x7f && utf8_open(&ud, *ptr) == UTF8_MORE) {
			ptr++;

			left = strlen(ptr);
			if (left < (size_t)ud.size - 1)
				break;
			while ((more = utf8_append(&ud, *ptr)) == UTF8_MORE)
				ptr++;
			ptr++;

			if (more == UTF8_DONE)
				size += ud.width;
		} else {
			if (*ptr > 0x1f && *ptr < 0x7f)
				size++;
			ptr++;
		}
	}

	free(msg);
	return (size);
}

/* Write simple string (no UTF-8 or maximum length). */
void
screen_write_puts(struct screen_write_ctx *ctx, const struct grid_cell *gcp,
    const char *fmt, ...)
{
	va_list	ap;

	va_start(ap, fmt);
	screen_write_vnputs(ctx, -1, gcp, fmt, ap);
	va_end(ap);
}

/* Write string with length limit (-1 for unlimited). */
void
screen_write_nputs(struct screen_write_ctx *ctx, ssize_t maxlen,
    const struct grid_cell *gcp, const char *fmt, ...)
{
	va_list	ap;

	va_start(ap, fmt);
	screen_write_vnputs(ctx, maxlen, gcp, fmt, ap);
	va_end(ap);
}

void
screen_write_vnputs(struct screen_write_ctx *ctx, ssize_t maxlen,
    const struct grid_cell *gcp, const char *fmt, va_list ap)
{
	struct grid_cell	gc;
	struct utf8_data       *ud = &gc.data;
	char   		       *msg;
	u_char 		       *ptr;
	size_t		 	left, size = 0;
	enum utf8_state		more;

	memcpy(&gc, gcp, sizeof gc);
	xvasprintf(&msg, fmt, ap);

	ptr = msg;
	while (*ptr != '\0') {
		if (*ptr > 0x7f && utf8_open(ud, *ptr) == UTF8_MORE) {
			ptr++;

			left = strlen(ptr);
			if (left < (size_t)ud->size - 1)
				break;
			while ((more = utf8_append(ud, *ptr)) == UTF8_MORE)
				ptr++;
			ptr++;

			if (more != UTF8_DONE)
				continue;
			if (maxlen > 0 && size + ud->width > (size_t)maxlen) {
				while (size < (size_t)maxlen) {
					screen_write_putc(ctx, &gc, ' ');
					size++;
				}
				break;
			}
			size += ud->width;
			screen_write_cell(ctx, &gc);
		} else {
			if (maxlen > 0 && size + 1 > (size_t)maxlen)
				break;

			if (*ptr == '\001')
				gc.attr ^= GRID_ATTR_CHARSET;
			else if (*ptr > 0x1f && *ptr < 0x7f) {
				size++;
				screen_write_putc(ctx, &gc, *ptr);
			}
			ptr++;
		}
	}

	free(msg);
}

/* Write string, similar to nputs, but with embedded formatting (#[]). */
void
screen_write_cnputs(struct screen_write_ctx *ctx, ssize_t maxlen,
    const struct grid_cell *gcp, const char *fmt, ...)
{
	struct grid_cell	 gc;
	struct utf8_data	*ud = &gc.data;
	va_list			 ap;
	char			*msg;
	u_char 			*ptr, *last;
	size_t			 left, size = 0;
	enum utf8_state		 more;

	memcpy(&gc, gcp, sizeof gc);

	va_start(ap, fmt);
	xvasprintf(&msg, fmt, ap);
	va_end(ap);

	ptr = msg;
	while (*ptr != '\0') {
		if (ptr[0] == '#' && ptr[1] == '[') {
			ptr += 2;
			last = ptr + strcspn(ptr, "]");
			if (*last == '\0') {
				/* No ]. Not much point in doing anything. */
				break;
			}
			*last = '\0';

			style_parse(gcp, &gc, ptr);
			ptr = last + 1;
			continue;
		}

		if (*ptr > 0x7f && utf8_open(ud, *ptr) == UTF8_MORE) {
			ptr++;

			left = strlen(ptr);
			if (left < (size_t)ud->size - 1)
				break;
			while ((more = utf8_append(ud, *ptr)) == UTF8_MORE)
				ptr++;
			ptr++;

			if (more != UTF8_DONE)
				continue;
			if (maxlen > 0 && size + ud->width > (size_t)maxlen) {
				while (size < (size_t)maxlen) {
					screen_write_putc(ctx, &gc, ' ');
					size++;
				}
				break;
			}
			size += ud->width;
			screen_write_cell(ctx, &gc);
		} else {
			if (maxlen > 0 && size + 1 > (size_t)maxlen)
				break;

			if (*ptr > 0x1f && *ptr < 0x7f) {
				size++;
				screen_write_putc(ctx, &gc, *ptr);
			}
			ptr++;
		}
	}

	free(msg);
}

/* Copy from another screen. Assumes target region is big enough. */
void
screen_write_copy(struct screen_write_ctx *ctx, struct screen *src, u_int px,
    u_int py, u_int nx, u_int ny, bitstr_t *mbs, const struct grid_cell *mgc)
{
	struct screen		*s = ctx->s;
	struct grid		*gd = src->grid;
	struct grid_cell	 gc;
	u_int		 	 xx, yy, cx, cy, b;

	if (nx == 0 || ny == 0)
		return;

	cx = s->cx;
	cy = s->cy;

	for (yy = py; yy < py + ny; yy++) {
		for (xx = px; xx < px + nx; xx++) {
			grid_get_cell(gd, xx, yy, &gc);
			if (mbs != NULL) {
				b = (yy * screen_size_x(src)) + xx;
				if (bit_test(mbs, b)) {
					gc.attr = mgc->attr;
					gc.fg = mgc->fg;
					gc.bg = mgc->bg;
				}
			}
			if (xx + gc.data.width <= px + nx)
				screen_write_cell(ctx, &gc);
		}
		cy++;
		screen_write_cursormove(ctx, cx, cy);
	}
}

/*
 * Copy from another screen but without the selection stuff. Also assumes the
 * target region is already big enough and already cleared.
 */
void
screen_write_fast_copy(struct screen_write_ctx *ctx, struct screen *src,
    u_int px, u_int py, u_int nx, u_int ny)
{
	struct screen		*s = ctx->s;
	struct grid		*gd = src->grid;
	struct grid_cell	 gc;
	u_int		 	 xx, yy, cx, cy;

	if (nx == 0 || ny == 0)
		return;

	cy = s->cy;
	for (yy = py; yy < py + ny; yy++) {
		if (yy >= gd->hsize + gd->sy)
			break;
		cx = s->cx;
		for (xx = px; xx < px + nx; xx++) {
			if (xx >= grid_get_line(gd, yy)->cellsize)
				break;
			grid_get_cell(gd, xx, yy, &gc);
			if (xx + gc.data.width > px + nx)
				break;
			if (!grid_cells_equal(&gc, &grid_default_cell))
				grid_view_set_cell(ctx->s->grid, cx, cy, &gc);
			cx++;
		}
		cy++;
	}
}

/* Draw a horizontal line on screen. */
void
screen_write_hline(struct screen_write_ctx *ctx, u_int nx, int left, int right)
{
	struct screen		*s = ctx->s;
	struct grid_cell	 gc;
	u_int			 cx, cy, i;

	cx = s->cx;
	cy = s->cy;

	memcpy(&gc, &grid_default_cell, sizeof gc);
	gc.attr |= GRID_ATTR_CHARSET;

	screen_write_putc(ctx, &gc, left ? 't' : 'q');
	for (i = 1; i < nx - 1; i++)
		screen_write_putc(ctx, &gc, 'q');
	screen_write_putc(ctx, &gc, right ? 'u' : 'q');

	screen_write_cursormove(ctx, cx, cy);
}

/* Draw a horizontal line on screen. */
void
screen_write_vline(struct screen_write_ctx *ctx, u_int ny, int top, int bottom)
{
	struct screen		*s = ctx->s;
	struct grid_cell	 gc;
	u_int			 cx, cy, i;

	cx = s->cx;
	cy = s->cy;

	memcpy(&gc, &grid_default_cell, sizeof gc);
	gc.attr |= GRID_ATTR_CHARSET;

	screen_write_putc(ctx, &gc, top ? 'w' : 'x');
	for (i = 1; i < ny - 1; i++) {
		screen_write_cursormove(ctx, cx, cy + i);
		screen_write_putc(ctx, &gc, 'x');
	}
	screen_write_cursormove(ctx, cx, cy + ny - 1);
	screen_write_putc(ctx, &gc, bottom ? 'v' : 'x');

	screen_write_cursormove(ctx, cx, cy);
}

/* Draw a box on screen. */
void
screen_write_box(struct screen_write_ctx *ctx, u_int nx, u_int ny)
{
	struct screen		*s = ctx->s;
	struct grid_cell	 gc;
	u_int			 cx, cy, i;

	cx = s->cx;
	cy = s->cy;

	memcpy(&gc, &grid_default_cell, sizeof gc);
	gc.attr |= GRID_ATTR_CHARSET;

	screen_write_putc(ctx, &gc, 'l');
	for (i = 1; i < nx - 1; i++)
		screen_write_putc(ctx, &gc, 'q');
	screen_write_putc(ctx, &gc, 'k');

	screen_write_cursormove(ctx, cx, cy + ny - 1);
	screen_write_putc(ctx, &gc, 'm');
	for (i = 1; i < nx - 1; i++)
		screen_write_putc(ctx, &gc, 'q');
	screen_write_putc(ctx, &gc, 'j');

	for (i = 1; i < ny - 1; i++) {
		screen_write_cursormove(ctx, cx, cy + i);
		screen_write_putc(ctx, &gc, 'x');
	}
	for (i = 1; i < ny - 1; i++) {
		screen_write_cursormove(ctx, cx + nx - 1, cy + i);
		screen_write_putc(ctx, &gc, 'x');
	}

	screen_write_cursormove(ctx, cx, cy);
}

/*
 * Write a preview version of a window. Assumes target area is big enough and
 * already cleared.
 */
void
screen_write_preview(struct screen_write_ctx *ctx, struct screen *src, u_int nx,
    u_int ny)
{
	struct screen		*s = ctx->s;
	struct grid_cell	 gc;
	u_int			 cx, cy, px, py;

	cx = s->cx;
	cy = s->cy;

	/*
	 * If the cursor is on, pick the area around the cursor, otherwise use
	 * the top left.
	 */
	if (src->mode & MODE_CURSOR) {
		px = src->cx;
		if (px < nx / 3)
			px = 0;
		else
			px = px - nx / 3;
		if (px + nx > screen_size_x(src)) {
			if (nx > screen_size_x(src))
				px = 0;
			else
				px = screen_size_x(src) - nx;
		}
		py = src->cy;
		if (py < ny / 3)
			py = 0;
		else
			py = py - ny / 3;
		if (py + ny > screen_size_y(src)) {
			if (ny > screen_size_y(src))
				py = 0;
			else
				py = screen_size_y(src) - ny;
		}
	} else {
		px = 0;
		py = 0;
	}

	screen_write_fast_copy(ctx, src, px, src->grid->hsize + py, nx, ny);

	if (src->mode & MODE_CURSOR) {
		grid_view_get_cell(src->grid, src->cx, src->cy, &gc);
		gc.attr |= GRID_ATTR_REVERSE;
		screen_write_cursormove(ctx, cx + (src->cx - px),
		    cy + (src->cy - py));
		screen_write_cell(ctx, &gc);
	}
}

/* Set up context for TTY command. */
static void
screen_write_initctx(struct screen_write_ctx *ctx, struct tty_ctx *ttyctx)
{
	struct screen	*s = ctx->s;

	memset(ttyctx, 0, sizeof *ttyctx);

	ttyctx->wp = ctx->wp;

	ttyctx->ocx = s->cx;
	ttyctx->ocy = s->cy;

	ttyctx->orlower = s->rlower;
	ttyctx->orupper = s->rupper;
}

/* Set a mode. */
void
screen_write_mode_set(struct screen_write_ctx *ctx, int mode)
{
	struct screen	*s = ctx->s;

	s->mode |= mode;
}

/* Clear a mode. */
void
screen_write_mode_clear(struct screen_write_ctx *ctx, int mode)
{
	struct screen	*s = ctx->s;

	s->mode &= ~mode;
}

/* Cursor up by ny. */
void
screen_write_cursorup(struct screen_write_ctx *ctx, u_int ny)
{
	struct screen	*s = ctx->s;
	u_int		 cx = s->cx, cy = s->cy;

	if (ny == 0)
		ny = 1;

	if (cy < s->rupper) {
		/* Above region. */
		if (ny > cy)
			ny = cy;
	} else {
		/* Below region. */
		if (ny > cy - s->rupper)
			ny = cy - s->rupper;
	}
	if (cx == screen_size_x(s))
		cx--;

	cy -= ny;

	screen_write_set_cursor(ctx, cx, cy);
}

/* Cursor down by ny. */
void
screen_write_cursordown(struct screen_write_ctx *ctx, u_int ny)
{
	struct screen	*s = ctx->s;
	u_int		 cx = s->cx, cy = s->cy;

	if (ny == 0)
		ny = 1;

	if (cy > s->rlower) {
		/* Below region. */
		if (ny > screen_size_y(s) - 1 - cy)
			ny = screen_size_y(s) - 1 - cy;
	} else {
		/* Above region. */
		if (ny > s->rlower - cy)
			ny = s->rlower - cy;
	}
	if (cx == screen_size_x(s))
	    cx--;
	else if (ny == 0)
		return;

	cy += ny;

	screen_write_set_cursor(ctx, cx, cy);
}

/* Cursor right by nx. */
void
screen_write_cursorright(struct screen_write_ctx *ctx, u_int nx)
{
	struct screen	*s = ctx->s;
	u_int		 cx = s->cx, cy = s->cy;

	if (nx == 0)
		nx = 1;

	if (nx > screen_size_x(s) - 1 - cx)
		nx = screen_size_x(s) - 1 - cx;
	if (nx == 0)
		return;

	cx += nx;

	screen_write_set_cursor(ctx, cx, cy);
}

/* Cursor left by nx. */
void
screen_write_cursorleft(struct screen_write_ctx *ctx, u_int nx)
{
	struct screen	*s = ctx->s;
	u_int		 cx = s->cx, cy = s->cy;

	if (nx == 0)
		nx = 1;

	if (nx > cx)
		nx = cx;
	if (nx == 0)
		return;

	cx -= nx;

	screen_write_set_cursor(ctx, cx, cy);
}

/* Backspace; cursor left unless at start of wrapped line when can move up. */
void
screen_write_backspace(struct screen_write_ctx *ctx)
{
	struct screen		*s = ctx->s;
	struct grid_line	*gl;
	u_int			 cx = s->cx, cy = s->cy;

	if (cx == 0) {
		if (cy == 0)
			return;
		gl = grid_get_line(s->grid, s->grid->hsize + cy - 1);
		if (gl->flags & GRID_LINE_WRAPPED) {
			cy--;
			cx = screen_size_x(s) - 1;
		}
	} else
		cx--;

	screen_write_set_cursor(ctx, cx, cy);
}

/* VT100 alignment test. */
void
screen_write_alignmenttest(struct screen_write_ctx *ctx)
{
	struct screen		*s = ctx->s;
	struct tty_ctx	 	 ttyctx;
	struct grid_cell       	 gc;
	u_int			 xx, yy;

	memcpy(&gc, &grid_default_cell, sizeof gc);
	utf8_set(&gc.data, 'E');

	for (yy = 0; yy < screen_size_y(s); yy++) {
		for (xx = 0; xx < screen_size_x(s); xx++)
			grid_view_set_cell(s->grid, xx, yy, &gc);
	}

	screen_write_set_cursor(ctx, 0, 0);

	s->rupper = 0;
	s->rlower = screen_size_y(s) - 1;

	screen_write_collect_clear(ctx, 0, screen_size_y(s) - 1);
	tty_write(tty_cmd_alignmenttest, &ttyctx);
}

/* Insert nx characters. */
void
screen_write_insertcharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;

	if (nx == 0)
		nx = 1;

	if (nx > screen_size_x(s) - s->cx)
		nx = screen_size_x(s) - s->cx;
	if (nx == 0)
		return;

	if (s->cx > screen_size_x(s) - 1)
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	grid_view_insert_cells(s->grid, s->cx, s->cy, nx, bg);

	screen_write_collect_flush(ctx, 0);
	ttyctx.num = nx;
	tty_write(tty_cmd_insertcharacter, &ttyctx);
}

/* Delete nx characters. */
void
screen_write_deletecharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;

	if (nx == 0)
		nx = 1;

	if (nx > screen_size_x(s) - s->cx)
		nx = screen_size_x(s) - s->cx;
	if (nx == 0)
		return;

	if (s->cx > screen_size_x(s) - 1)
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	grid_view_delete_cells(s->grid, s->cx, s->cy, nx, bg);

	screen_write_collect_flush(ctx, 0);
	ttyctx.num = nx;
	tty_write(tty_cmd_deletecharacter, &ttyctx);
}

/* Clear nx characters. */
void
screen_write_clearcharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;

	if (nx == 0)
		nx = 1;

	if (nx > screen_size_x(s) - s->cx)
		nx = screen_size_x(s) - s->cx;
	if (nx == 0)
		return;

	if (s->cx > screen_size_x(s) - 1)
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	grid_view_clear(s->grid, s->cx, s->cy, nx, 1, bg);

	screen_write_collect_flush(ctx, 0);
	ttyctx.num = nx;
	tty_write(tty_cmd_clearcharacter, &ttyctx);
}

/* Insert ny lines. */
void
screen_write_insertline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
{
	struct screen	*s = ctx->s;
	struct grid	*gd = s->grid;
	struct tty_ctx	 ttyctx;

	if (ny == 0)
		ny = 1;

	if (s->cy < s->rupper || s->cy > s->rlower) {
		if (ny > screen_size_y(s) - s->cy)
			ny = screen_size_y(s) - s->cy;
		if (ny == 0)
			return;

		screen_write_initctx(ctx, &ttyctx);
		ttyctx.bg = bg;

		grid_view_insert_lines(gd, s->cy, ny, bg);

		screen_write_collect_flush(ctx, 0);
		ttyctx.num = ny;
		tty_write(tty_cmd_insertline, &ttyctx);
		return;
	}

	if (ny > s->rlower + 1 - s->cy)
		ny = s->rlower + 1 - s->cy;
	if (ny == 0)
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	if (s->cy < s->rupper || s->cy > s->rlower)
		grid_view_insert_lines(gd, s->cy, ny, bg);
	else
		grid_view_insert_lines_region(gd, s->rlower, s->cy, ny, bg);

	screen_write_collect_flush(ctx, 0);
	ttyctx.num = ny;
	tty_write(tty_cmd_insertline, &ttyctx);
}

/* Delete ny lines. */
void
screen_write_deleteline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
{
	struct screen	*s = ctx->s;
	struct grid	*gd = s->grid;
	struct tty_ctx	 ttyctx;

	if (ny == 0)
		ny = 1;

	if (s->cy < s->rupper || s->cy > s->rlower) {
		if (ny > screen_size_y(s) - s->cy)
			ny = screen_size_y(s) - s->cy;
		if (ny == 0)
			return;

		screen_write_initctx(ctx, &ttyctx);
		ttyctx.bg = bg;

		grid_view_delete_lines(gd, s->cy, ny, bg);

		screen_write_collect_flush(ctx, 0);
		ttyctx.num = ny;
		tty_write(tty_cmd_deleteline, &ttyctx);
		return;
	}

	if (ny > s->rlower + 1 - s->cy)
		ny = s->rlower + 1 - s->cy;
	if (ny == 0)
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	if (s->cy < s->rupper || s->cy > s->rlower)
		grid_view_delete_lines(gd, s->cy, ny, bg);
	else
		grid_view_delete_lines_region(gd, s->rlower, s->cy, ny, bg);

	screen_write_collect_flush(ctx, 0);
	ttyctx.num = ny;
	tty_write(tty_cmd_deleteline, &ttyctx);
}

/* Clear line at cursor. */
void
screen_write_clearline(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen		*s = ctx->s;
	struct grid_line	*gl;
	struct tty_ctx		 ttyctx;
	u_int			 sx = screen_size_x(s);

	gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
	if (gl->cellsize == 0 && bg == 8)
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	grid_view_clear(s->grid, 0, s->cy, sx, 1, bg);

	screen_write_collect_clear(ctx, s->cy, 1);
	screen_write_collect_flush(ctx, 0);
	tty_write(tty_cmd_clearline, &ttyctx);
}

/* Clear to end of line from cursor. */
void
screen_write_clearendofline(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen		*s = ctx->s;
	struct grid_line	*gl;
	struct tty_ctx		 ttyctx;
	u_int			 sx = screen_size_x(s);

	gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
	if (s->cx > sx - 1 || (s->cx >= gl->cellsize && bg == 8))
		return;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	grid_view_clear(s->grid, s->cx, s->cy, sx - s->cx, 1, bg);

	if (s->cx == 0)
		screen_write_collect_clear(ctx, s->cy, 1);
	screen_write_collect_flush(ctx, 0);
	tty_write(tty_cmd_clearendofline, &ttyctx);
}

/* Clear to start of line from cursor. */
void
screen_write_clearstartofline(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;
	u_int		 sx = screen_size_x(s);

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	if (s->cx > sx - 1)
		grid_view_clear(s->grid, 0, s->cy, sx, 1, bg);
	else
		grid_view_clear(s->grid, 0, s->cy, s->cx + 1, 1, bg);

	if (s->cx > sx - 1)
		screen_write_collect_clear(ctx, s->cy, 1);
	screen_write_collect_flush(ctx, 0);
	tty_write(tty_cmd_clearstartofline, &ttyctx);
}

/* Move cursor to px,py. */
void
screen_write_cursormove(struct screen_write_ctx *ctx, u_int px, u_int py)
{
	struct screen	*s = ctx->s;

	if (px > screen_size_x(s) - 1)
		px = screen_size_x(s) - 1;
	if (py > screen_size_y(s) - 1)
		py = screen_size_y(s) - 1;

	screen_write_set_cursor(ctx, px, py);
}

/* Reverse index (up with scroll). */
void
screen_write_reverseindex(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	if (s->cy == s->rupper)
		grid_view_scroll_region_down(s->grid, s->rupper, s->rlower, bg);
	else if (s->cy > 0)
		screen_write_set_cursor(ctx, -1, s->cy - 1);

	screen_write_collect_flush(ctx, 0);
	tty_write(tty_cmd_reverseindex, &ttyctx);
}

/* Set scroll region. */
void
screen_write_scrollregion(struct screen_write_ctx *ctx, u_int rupper,
    u_int rlower)
{
	struct screen	*s = ctx->s;

	if (rupper > screen_size_y(s) - 1)
		rupper = screen_size_y(s) - 1;
	if (rlower > screen_size_y(s) - 1)
		rlower = screen_size_y(s) - 1;
	if (rupper >= rlower)	/* cannot be one line */
		return;

	screen_write_collect_flush(ctx, 0);

	/* Cursor moves to top-left. */
	screen_write_set_cursor(ctx, 0, 0);

	s->rupper = rupper;
	s->rlower = rlower;
}

/* Line feed. */
void
screen_write_linefeed(struct screen_write_ctx *ctx, int wrapped, u_int bg)
{
	struct screen		*s = ctx->s;
	struct grid		*gd = s->grid;
	struct grid_line	*gl;

	gl = grid_get_line(gd, gd->hsize + s->cy);
	if (wrapped)
		gl->flags |= GRID_LINE_WRAPPED;
	else
		gl->flags &= ~GRID_LINE_WRAPPED;

	log_debug("%s: at %u,%u (region %u-%u)", __func__, s->cx, s->cy,
	    s->rupper, s->rlower);

	if (bg != ctx->bg) {
		screen_write_collect_flush(ctx, 1);
		ctx->bg = bg;
	}

	if (s->cy == s->rlower) {
		grid_view_scroll_region_up(gd, s->rupper, s->rlower, bg);
		screen_write_collect_scroll(ctx);
		ctx->scrolled++;
	} else if (s->cy < screen_size_y(s) - 1)
		screen_write_set_cursor(ctx, -1, s->cy + 1);
}

/* Scroll up. */
void
screen_write_scrollup(struct screen_write_ctx *ctx, u_int lines, u_int bg)
{
	struct screen	*s = ctx->s;
	struct grid	*gd = s->grid;
	u_int		 i;

	if (lines == 0)
		lines = 1;
	else if (lines > s->rlower - s->rupper + 1)
		lines = s->rlower - s->rupper + 1;

	if (bg != ctx->bg) {
		screen_write_collect_flush(ctx, 1);
		ctx->bg = bg;
	}

	for (i = 0; i < lines; i++) {
		grid_view_scroll_region_up(gd, s->rupper, s->rlower, bg);
		screen_write_collect_scroll(ctx);
	}
	ctx->scrolled += lines;
}

/* Carriage return (cursor to start of line). */
void
screen_write_carriagereturn(struct screen_write_ctx *ctx)
{
	screen_write_set_cursor(ctx, 0, -1);
}

/* Clear to end of screen from cursor. */
void
screen_write_clearendofscreen(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct grid	*gd = s->grid;
	struct tty_ctx	 ttyctx;
	u_int		 sx = screen_size_x(s), sy = screen_size_y(s);

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	/* Scroll into history if it is enabled and clearing entire screen. */
	if (s->cx == 0 && s->cy == 0 && (gd->flags & GRID_HISTORY))
		grid_view_clear_history(gd, bg);
	else {
		if (s->cx <= sx - 1)
			grid_view_clear(gd, s->cx, s->cy, sx - s->cx, 1, bg);
		grid_view_clear(gd, 0, s->cy + 1, sx, sy - (s->cy + 1), bg);
	}

	screen_write_collect_clear(ctx, s->cy + 1, sy - (s->cy + 1));
	screen_write_collect_flush(ctx, 0);
	tty_write(tty_cmd_clearendofscreen, &ttyctx);
}

/* Clear to start of screen. */
void
screen_write_clearstartofscreen(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;
	u_int		 sx = screen_size_x(s);

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	if (s->cy > 0)
		grid_view_clear(s->grid, 0, 0, sx, s->cy, bg);
	if (s->cx > sx - 1)
		grid_view_clear(s->grid, 0, s->cy, sx, 1, bg);
	else
		grid_view_clear(s->grid, 0, s->cy, s->cx + 1, 1, bg);

	screen_write_collect_clear(ctx, 0, s->cy);
	screen_write_collect_flush(ctx, 0);
	tty_write(tty_cmd_clearstartofscreen, &ttyctx);
}

/* Clear entire screen. */
void
screen_write_clearscreen(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen	*s = ctx->s;
	struct tty_ctx	 ttyctx;
	u_int		 sx = screen_size_x(s), sy = screen_size_y(s);

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.bg = bg;

	/* Scroll into history if it is enabled. */
	if (s->grid->flags & GRID_HISTORY)
		grid_view_clear_history(s->grid, bg);
	else
		grid_view_clear(s->grid, 0, 0, sx, sy, bg);

	screen_write_collect_clear(ctx, 0, sy);
	tty_write(tty_cmd_clearscreen, &ttyctx);
}

/* Clear entire history. */
void
screen_write_clearhistory(struct screen_write_ctx *ctx)
{
	struct screen	*s = ctx->s;
	struct grid	*gd = s->grid;

	grid_move_lines(gd, 0, gd->hsize, gd->sy, 8);
	gd->hscrolled = gd->hsize = 0;
}

/* Clear a collected line. */
static void
screen_write_collect_clear(struct screen_write_ctx *ctx, u_int y, u_int n)
{
	struct screen_write_collect_item	*ci, *tmp;
	u_int					 i;
	size_t					 size;

	for (i = y ; i < y + n; i++) {
		if (TAILQ_EMPTY(&ctx->list[i].items))
			continue;
		size = 0;
		TAILQ_FOREACH_SAFE(ci, &ctx->list[i].items, entry, tmp) {
			size += ci->used;
			TAILQ_REMOVE(&ctx->list[i].items, ci, entry);
			free(ci);
		}
		ctx->skipped += size;
		log_debug("%s: dropped %zu bytes (line %u)", __func__, size, i);
	}
}

/* Scroll collected lines up. */
static void
screen_write_collect_scroll(struct screen_write_ctx *ctx)
{
	struct screen				*s = ctx->s;
	struct screen_write_collect_line	*cl;
	u_int					 y;

	log_debug("%s: at %u,%u (region %u-%u)", __func__, s->cx, s->cy,
	    s->rupper, s->rlower);

	screen_write_collect_clear(ctx, s->rupper, 1);
	for (y = s->rupper; y < s->rlower; y++) {
		cl = &ctx->list[y + 1];
		TAILQ_CONCAT(&ctx->list[y].items, &cl->items, entry);
		TAILQ_INIT(&cl->items);
	}
}

/* Flush collected lines. */
static void
screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only)
{
	struct screen				*s = ctx->s;
	struct screen_write_collect_item	*ci, *tmp;
	u_int					 y, cx, cy, items = 0;
	struct tty_ctx				 ttyctx;
	size_t					 written = 0;

	if (ctx->scrolled != 0) {
		log_debug("%s: scrolled %u (region %u-%u)", __func__,
		    ctx->scrolled, s->rupper, s->rlower);
		if (ctx->scrolled > s->rlower - s->rupper + 1)
			ctx->scrolled = s->rlower - s->rupper + 1;

		screen_write_initctx(ctx, &ttyctx);
		ttyctx.num = ctx->scrolled;
		ttyctx.bg = ctx->bg;
		tty_write(tty_cmd_scrollup, &ttyctx);
	}
	ctx->scrolled = 0;
	ctx->bg = 8;

	if (scroll_only)
		return;

	cx = s->cx; cy = s->cy;
	for (y = 0; y < screen_size_y(s); y++) {
		TAILQ_FOREACH_SAFE(ci, &ctx->list[y].items, entry, tmp) {
			screen_write_cursormove(ctx, ci->x, y);
			screen_write_initctx(ctx, &ttyctx);
			ttyctx.cell = &ci->gc;
			ttyctx.wrapped = ci->wrapped;
			ttyctx.ptr = ci->data;
			ttyctx.num = ci->used;
			tty_write(tty_cmd_cells, &ttyctx);

			items++;
			written += ci->used;

			TAILQ_REMOVE(&ctx->list[y].items, ci, entry);
			free(ci);
		}
	}
	s->cx = cx; s->cy = cy;

	log_debug("%s: flushed %u items (%zu bytes)", __func__, items, written);
	ctx->written += written;
}

/* Finish and store collected cells. */
void
screen_write_collect_end(struct screen_write_ctx *ctx)
{
	struct screen				*s = ctx->s;
	struct screen_write_collect_item	*ci = ctx->item;
	struct grid_cell			 gc;
	u_int					 xx;

	if (ci->used == 0)
		return;
	ci->data[ci->used] = '\0';

	ci->x = s->cx;
	TAILQ_INSERT_TAIL(&ctx->list[s->cy].items, ci, entry);
	ctx->item = xcalloc(1, sizeof *ctx->item);

	log_debug("%s: %u %s (at %u,%u)", __func__, ci->used, ci->data, s->cx,
	    s->cy);

	if (s->cx != 0) {
		for (xx = s->cx; xx > 0; xx--) {
			grid_view_get_cell(s->grid, xx, s->cy, &gc);
			if (~gc.flags & GRID_FLAG_PADDING)
				break;
			grid_view_set_cell(s->grid, xx, s->cy,
			    &grid_default_cell);
		}
		if (gc.data.width > 1) {
			grid_view_set_cell(s->grid, xx, s->cy,
			    &grid_default_cell);
		}
	}

	memcpy(&gc, &ci->gc, sizeof gc);
	grid_view_set_cells(s->grid, s->cx, s->cy, &gc, ci->data, ci->used);
	screen_write_set_cursor(ctx, s->cx + ci->used, -1);

	for (xx = s->cx; xx < screen_size_x(s); xx++) {
		grid_view_get_cell(s->grid, xx, s->cy, &gc);
		if (~gc.flags & GRID_FLAG_PADDING)
			break;
		grid_view_set_cell(s->grid, xx, s->cy, &grid_default_cell);
	}
}

/* Write cell data, collecting if necessary. */
void
screen_write_collect_add(struct screen_write_ctx *ctx,
    const struct grid_cell *gc)
{
	struct screen				*s = ctx->s;
	struct screen_write_collect_item	*ci;
	u_int					 sx = screen_size_x(s);
	int					 collect;

	/*
	 * Don't need to check that the attributes and whatnot are still the
	 * same - input_parse will end the collection when anything that isn't
	 * a plain character is encountered. Also nothing should make it here
	 * that isn't a single ASCII character.
	 */

	collect = 1;
	if (gc->data.width != 1 || gc->data.size != 1 || *gc->data.data >= 0x7f)
		collect = 0;
	else if (gc->attr & GRID_ATTR_CHARSET)
		collect = 0;
	else if (~s->mode & MODE_WRAP)
		collect = 0;
	else if (s->mode & MODE_INSERT)
		collect = 0;
	else if (s->sel != NULL)
		collect = 0;
	if (!collect) {
		screen_write_collect_end(ctx);
		screen_write_collect_flush(ctx, 0);
		screen_write_cell(ctx, gc);
		return;
	}
	ctx->cells++;

	if (s->cx > sx - 1 || ctx->item->used > sx - 1 - s->cx)
		screen_write_collect_end(ctx);
	ci = ctx->item; /* may have changed */

	if (s->cx > sx - 1) {
		log_debug("%s: wrapped at %u,%u", __func__, s->cx, s->cy);
		ci->wrapped = 1;
		screen_write_linefeed(ctx, 1, 8);
		screen_write_set_cursor(ctx, 0, -1);
	}

	if (ci->used == 0)
		memcpy(&ci->gc, gc, sizeof ci->gc);
	ci->data[ci->used++] = gc->data.data[0];
	if (ci->used == (sizeof ci->data) - 1)
		screen_write_collect_end(ctx);
}

/* Write cell data. */
void
screen_write_cell(struct screen_write_ctx *ctx, const struct grid_cell *gc)
{
	struct screen		*s = ctx->s;
	struct grid		*gd = s->grid;
	struct grid_line	*gl;
	struct grid_cell_entry	*gce;
	struct grid_cell 	 tmp_gc, now_gc;
	struct tty_ctx		 ttyctx;
	u_int			 sx = screen_size_x(s), sy = screen_size_y(s);
	u_int		 	 width = gc->data.width, xx, last, cx, cy;
	int			 selected, skip = 1;

	/* Ignore padding cells. */
	if (gc->flags & GRID_FLAG_PADDING)
		return;
	ctx->cells++;

	/* If the width is zero, combine onto the previous character. */
	if (width == 0) {
		screen_write_collect_flush(ctx, 0);
		if ((gc = screen_write_combine(ctx, &gc->data, &xx)) != 0) {
			cx = s->cx; cy = s->cy;
			screen_write_cursormove(ctx, xx, s->cy);
			screen_write_initctx(ctx, &ttyctx);
			ttyctx.cell = gc;
			tty_write(tty_cmd_cell, &ttyctx);
			s->cx = cx; s->cy = cy;
		}
		return;
	}

	/* Flush any existing scrolling. */
	screen_write_collect_flush(ctx, 1);

	/* If this character doesn't fit, ignore it. */
	if ((~s->mode & MODE_WRAP) &&
	    width > 1 &&
	    (width > sx || (s->cx != sx && s->cx > sx - width)))
		return;

	/* If in insert mode, make space for the cells. */
	if (s->mode & MODE_INSERT) {
		grid_view_insert_cells(s->grid, s->cx, s->cy, width, 8);
		skip = 0;
	}

	/* Check this will fit on the current line and wrap if not. */
	if ((s->mode & MODE_WRAP) && s->cx > sx - width) {
		log_debug("%s: wrapped at %u,%u", __func__, s->cx, s->cy);
		screen_write_linefeed(ctx, 1, 8);
		screen_write_set_cursor(ctx, 0, -1);
		screen_write_collect_flush(ctx, 1);
	}

	/* Sanity check cursor position. */
	if (s->cx > sx - width || s->cy > sy - 1)
		return;
	screen_write_initctx(ctx, &ttyctx);

	/* Handle overwriting of UTF-8 characters. */
	gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
	if (gl->flags & GRID_LINE_EXTENDED) {
		grid_view_get_cell(gd, s->cx, s->cy, &now_gc);
		if (screen_write_overwrite(ctx, &now_gc, width))
			skip = 0;
	}

	/*
	 * If the new character is UTF-8 wide, fill in padding cells. Have
	 * already ensured there is enough room.
	 */
	for (xx = s->cx + 1; xx < s->cx + width; xx++) {
		log_debug("%s: new padding at %u,%u", __func__, xx, s->cy);
		grid_view_set_cell(gd, xx, s->cy, &screen_write_pad_cell);
		skip = 0;
	}

	/* If no change, do not draw. */
	if (skip) {
		if (s->cx >= gl->cellsize)
			skip = grid_cells_equal(gc, &grid_default_cell);
		else {
			gce = &gl->celldata[s->cx];
			if (gce->flags & GRID_FLAG_EXTENDED)
				skip = 0;
			else if (gc->flags != gce->flags)
				skip = 0;
			else if (gc->attr != gce->data.attr)
				skip = 0;
			else if (gc->fg != gce->data.fg)
				skip = 0;
			else if (gc->bg != gce->data.bg)
				skip = 0;
			else if (gc->data.width != 1)
				skip = 0;
			else if (gc->data.size != 1)
				skip = 0;
			else if (gce->data.data != gc->data.data[0])
				skip = 0;
		}
	}

	/* Update the selected flag and set the cell. */
	selected = screen_check_selection(s, s->cx, s->cy);
	if (selected && (~gc->flags & GRID_FLAG_SELECTED)) {
		memcpy(&tmp_gc, gc, sizeof tmp_gc);
		tmp_gc.flags |= GRID_FLAG_SELECTED;
		grid_view_set_cell(gd, s->cx, s->cy, &tmp_gc);
	} else if (!selected && (gc->flags & GRID_FLAG_SELECTED)) {
		memcpy(&tmp_gc, gc, sizeof tmp_gc);
		tmp_gc.flags &= ~GRID_FLAG_SELECTED;
		grid_view_set_cell(gd, s->cx, s->cy, &tmp_gc);
	} else if (!skip)
		grid_view_set_cell(gd, s->cx, s->cy, gc);
	if (selected)
		skip = 0;

	/*
	 * Move the cursor. If not wrapping, stick at the last character and
	 * replace it.
	 */
	last = !(s->mode & MODE_WRAP);
	if (s->cx <= sx - last - width)
		screen_write_set_cursor(ctx, s->cx + width, -1);
	else
		screen_write_set_cursor(ctx,  sx - last, -1);

	/* Create space for character in insert mode. */
	if (s->mode & MODE_INSERT) {
		screen_write_collect_flush(ctx, 0);
		ttyctx.num = width;
		tty_write(tty_cmd_insertcharacter, &ttyctx);
	}

	/* Write to the screen. */
	if (!skip) {
		if (selected) {
			screen_select_cell(s, &tmp_gc, gc);
			ttyctx.cell = &tmp_gc;
		} else
			ttyctx.cell = gc;
		tty_write(tty_cmd_cell, &ttyctx);
		ctx->written++;
	} else
		ctx->skipped++;
}

/* Combine a UTF-8 zero-width character onto the previous. */
static const struct grid_cell *
screen_write_combine(struct screen_write_ctx *ctx, const struct utf8_data *ud,
    u_int *xx)
{
	struct screen		*s = ctx->s;
	struct grid		*gd = s->grid;
	static struct grid_cell	 gc;
	u_int			 n;

	/* Can't combine if at 0. */
	if (s->cx == 0)
		return (NULL);

	/* Empty data is out. */
	if (ud->size == 0)
		fatalx("UTF-8 data empty");

	/* Retrieve the previous cell. */
	for (n = 1; n <= s->cx; n++) {
		grid_view_get_cell(gd, s->cx - n, s->cy, &gc);
		if (~gc.flags & GRID_FLAG_PADDING)
			break;
	}
	if (n > s->cx)
		return (NULL);
	*xx = s->cx - n;

	/* Check there is enough space. */
	if (gc.data.size + ud->size > sizeof gc.data.data)
		return (NULL);

	log_debug("%s: %.*s onto %.*s at %u,%u", __func__, (int)ud->size,
	    ud->data, (int)gc.data.size, gc.data.data, *xx, s->cy);

	/* Append the data. */
	memcpy(gc.data.data + gc.data.size, ud->data, ud->size);
	gc.data.size += ud->size;

	/* Set the new cell. */
	grid_view_set_cell(gd, *xx, s->cy, &gc);

	return (&gc);
}

/*
 * UTF-8 wide characters are a bit of an annoyance. They take up more than one
 * cell on the screen, so following cells must not be drawn by marking them as
 * padding.
 *
 * So far, so good. The problem is, when overwriting a padding cell, or a UTF-8
 * character, it is necessary to also overwrite any other cells which covered
 * by the same character.
 */
static int
screen_write_overwrite(struct screen_write_ctx *ctx, struct grid_cell *gc,
    u_int width)
{
	struct screen		*s = ctx->s;
	struct grid		*gd = s->grid;
	struct grid_cell	 tmp_gc;
	u_int			 xx;
	int			 done = 0;

	if (gc->flags & GRID_FLAG_PADDING) {
		/*
		 * A padding cell, so clear any following and leading padding
		 * cells back to the character. Don't overwrite the current
		 * cell as that happens later anyway.
		 */
		xx = s->cx + 1;
		while (--xx > 0) {
			grid_view_get_cell(gd, xx, s->cy, &tmp_gc);
			if (~tmp_gc.flags & GRID_FLAG_PADDING)
				break;
			log_debug("%s: padding at %u,%u", __func__, xx, s->cy);
			grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
		}

		/* Overwrite the character at the start of this padding. */
		log_debug("%s: character at %u,%u", __func__, xx, s->cy);
		grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
		done = 1;
	}

	/*
	 * Overwrite any padding cells that belong to any UTF-8 characters
	 * we'll be overwriting with the current character.
	 */
	if (width != 1 ||
	    gc->data.width != 1 ||
	    gc->flags & GRID_FLAG_PADDING) {
		xx = s->cx + width - 1;
		while (++xx < screen_size_x(s)) {
			grid_view_get_cell(gd, xx, s->cy, &tmp_gc);
			if (~tmp_gc.flags & GRID_FLAG_PADDING)
				break;
			log_debug("%s: overwrite at %u,%u", __func__, xx, s->cy);
			grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
			done = 1;
		}
	}

	return (done);
}

/* Set external clipboard. */
void
screen_write_setselection(struct screen_write_ctx *ctx, u_char *str, u_int len)
{
	struct tty_ctx	ttyctx;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.ptr = str;
	ttyctx.num = len;

	tty_write(tty_cmd_setselection, &ttyctx);
}

/* Write unmodified string. */
void
screen_write_rawstring(struct screen_write_ctx *ctx, u_char *str, u_int len)
{
	struct tty_ctx	ttyctx;

	screen_write_initctx(ctx, &ttyctx);
	ttyctx.ptr = str;
	ttyctx.num = len;

	tty_write(tty_cmd_rawstring, &ttyctx);
}