Return to screen-write.c CVS log

Up to [local] / src / usr.bin / tmux

Be more sophisticated about enabling synchronized updates when there is
an overlay and treat it like the active pane (use for commands which
move the cursor only). When there is an overlay also use it for all
panes and not just the active pane. GitHub issue 2826.

/* $OpenBSD: screen-write.c,v 1.199 2021/08/17 08:44:52 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 struct screen_write_citem *screen_write_collect_trim(
		    struct screen_write_ctx *, u_int, u_int, u_int, int *);
static void	screen_write_collect_clear(struct screen_write_ctx *, u_int,
		    u_int);
static void	screen_write_collect_scroll(struct screen_write_ctx *, u_int);
static void	screen_write_collect_flush(struct screen_write_ctx *, int,
		    const char *);

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 *);

struct screen_write_citem {
	u_int				x;
	int				wrapped;

	enum { TEXT, CLEAR }		type;
	u_int				used;
	u_int				bg;

	struct grid_cell		gc;

	TAILQ_ENTRY(screen_write_citem) entry;
};
struct screen_write_cline {
	char				*data;
	TAILQ_HEAD(, screen_write_citem) items;
};
TAILQ_HEAD(, screen_write_citem)  screen_write_citem_freelist =
    TAILQ_HEAD_INITIALIZER(screen_write_citem_freelist);

static struct screen_write_citem *
screen_write_get_citem(void)
{
    struct screen_write_citem	*ci;

    ci = TAILQ_FIRST(&screen_write_citem_freelist);
    if (ci != NULL) {
        TAILQ_REMOVE(&screen_write_citem_freelist, ci, entry);
        memset(ci, 0, sizeof *ci);
        return (ci);
    }
    return (xcalloc(1, sizeof *ci));
}

static void
screen_write_free_citem(struct screen_write_citem *ci)
{
    TAILQ_INSERT_TAIL(&screen_write_citem_freelist, ci, entry);
}

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) {
		if ((u_int)cx > screen_size_x(s)) /* allow last column */
			cx = screen_size_x(s) - 1;
		s->cx = cx;
	}
	if (cy != -1) {
		if ((u_int)cy > screen_size_y(s) - 1)
			cy = screen_size_y(s) - 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);
}

/* Do a full redraw. */
static void
screen_write_redraw_cb(const struct tty_ctx *ttyctx)
{
	struct window_pane	*wp = ttyctx->arg;

	if (wp != NULL)
		wp->flags |= PANE_REDRAW;
}

/* Update context for client. */
static int
screen_write_set_client_cb(struct tty_ctx *ttyctx, struct client *c)
{
	struct window_pane	*wp = ttyctx->arg;

	if (c->session->curw->window != wp->window)
		return (0);
	if (wp->layout_cell == NULL)
		return (0);

	if (wp->flags & (PANE_REDRAW|PANE_DROP))
		return (-1);
	if (c->flags & CLIENT_REDRAWPANES) {
		/*
		 * Redraw is already deferred to redraw another pane - redraw
		 * this one also when that happens.
		 */
		log_debug("%s: adding %%%u to deferred redraw", __func__,
		    wp->id);
		wp->flags |= PANE_REDRAW;
		return (-1);
	}

	ttyctx->bigger = tty_window_offset(&c->tty, &ttyctx->wox, &ttyctx->woy,
	    &ttyctx->wsx, &ttyctx->wsy);

	ttyctx->xoff = ttyctx->rxoff = wp->xoff;
	ttyctx->yoff = ttyctx->ryoff = wp->yoff;

	if (status_at_line(c) == 0)
		ttyctx->yoff += status_line_size(c);

	return (1);
}

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

	memset(ttyctx, 0, sizeof *ttyctx);

	ttyctx->s = s;
	ttyctx->sx = screen_size_x(s);
	ttyctx->sy = screen_size_y(s);

	ttyctx->ocx = s->cx;
	ttyctx->ocy = s->cy;
	ttyctx->orlower = s->rlower;
	ttyctx->orupper = s->rupper;

	memcpy(&ttyctx->defaults, &grid_default_cell, sizeof ttyctx->defaults);
	if (ctx->init_ctx_cb != NULL) {
		ctx->init_ctx_cb(ctx, ttyctx);
		if (ttyctx->palette != NULL) {
			ttyctx->defaults.fg = ttyctx->palette->fg;
			ttyctx->defaults.bg = ttyctx->palette->bg;
		}
	} else {
		ttyctx->redraw_cb = screen_write_redraw_cb;
		if (ctx->wp != NULL) {
			tty_default_colours(&ttyctx->defaults, ctx->wp);
			ttyctx->palette = &ctx->wp->palette;
			ttyctx->set_client_cb = screen_write_set_client_cb;
			ttyctx->arg = ctx->wp;
		}
	}

	if (~ctx->flags & SCREEN_WRITE_SYNC) {
		/*
		 * For the active pane or for an overlay (no pane), we want to
		 * only use synchronized updates if requested (commands that
		 * move the cursor); for other panes, always use it, since the
		 * cursor will have to move.
		 */
		if (ctx->wp != NULL) {
			if (ctx->wp != ctx->wp->window->active)
				ttyctx->num = 1;
			else
				ttyctx->num = sync;
		} else
			ttyctx->num = 0x10|sync;
		tty_write(tty_cmd_syncstart, ttyctx);
		ctx->flags |= SCREEN_WRITE_SYNC;
	}
}

/* Make write list. */
void
screen_write_make_list(struct screen *s)
{
	u_int	y;

	s->write_list = xcalloc(screen_size_y(s), sizeof *s->write_list);
	for (y = 0; y < screen_size_y(s); y++)
		TAILQ_INIT(&s->write_list[y].items);
}

/* Free write list. */
void
screen_write_free_list(struct screen *s)
{
	u_int	y;

	for (y = 0; y < screen_size_y(s); y++)
		free(s->write_list[y].data);
	free(s->write_list);
}

/* Set up for writing. */
static void
screen_write_init(struct screen_write_ctx *ctx, struct screen *s)
{
	memset(ctx, 0, sizeof *ctx);

	ctx->s = s;

	if (ctx->s->write_list == NULL)
		screen_write_make_list(ctx->s);
	ctx->item = screen_write_get_citem();

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

/* Initialize writing with a pane. */
void
screen_write_start_pane(struct screen_write_ctx *ctx, struct window_pane *wp,
    struct screen *s)
{
	if (s == NULL)
		s = wp->screen;
	screen_write_init(ctx, s);
	ctx->wp = wp;

	if (log_get_level() != 0) {
		log_debug("%s: size %ux%u, pane %%%u (at %u,%u)",
		    __func__, screen_size_x(ctx->s), screen_size_y(ctx->s),
		    wp->id, wp->xoff, wp->yoff);
	}
}

/* Initialize writing with a callback. */
void
screen_write_start_callback(struct screen_write_ctx *ctx, struct screen *s,
    screen_write_init_ctx_cb cb, void *arg)
{
	screen_write_init(ctx, s);

	ctx->init_ctx_cb = cb;
	ctx->arg = arg;

	if (log_get_level() != 0) {
		log_debug("%s: size %ux%u, with callback", __func__,
		    screen_size_x(ctx->s), screen_size_y(ctx->s));
	}
}

/* Initialize writing. */
void
screen_write_start(struct screen_write_ctx *ctx, struct screen *s)
{
	screen_write_init(ctx, s);

	if (log_get_level() != 0) {
		log_debug("%s: size %ux%u, no pane", __func__,
		    screen_size_x(ctx->s), screen_size_y(ctx->s));
	}
}

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

	screen_write_free_citem(ctx->item);
}

/* 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_CURSOR | MODE_WRAP;

	screen_write_clearscreen(ctx, 8);
	screen_write_set_cursor(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. */
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 string wrapped over lines. */
int
screen_write_text(struct screen_write_ctx *ctx, u_int cx, u_int width,
    u_int lines, int more, const struct grid_cell *gcp, const char *fmt, ...)
{
	struct screen		*s = ctx->s;
	va_list			 ap;
	char			*tmp;
	u_int			 cy = s->cy, i, end, next, idx = 0, at, left;
	struct utf8_data	*text;
	struct grid_cell	 gc;

	memcpy(&gc, gcp, sizeof gc);

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

	text = utf8_fromcstr(tmp);
	free(tmp);

	left = (cx + width) - s->cx;
	for (;;) {
		/* Find the end of what can fit on the line. */
		at = 0;
		for (end = idx; text[end].size != 0; end++) {
			if (text[end].size == 1 && text[end].data[0] == '\n')
				break;
			if (at + text[end].width > left)
				break;
			at += text[end].width;
		}

		/*
		 * If we're on a space, that's the end. If not, walk back to
		 * try and find one.
		 */
		if (text[end].size == 0)
			next = end;
		else if (text[end].size == 1 && text[end].data[0] == '\n')
			next = end + 1;
		else if (text[end].size == 1 && text[end].data[0] == ' ')
			next = end + 1;
		else {
			for (i = end; i > idx; i--) {
				if (text[i].size == 1 && text[i].data[0] == ' ')
					break;
			}
			if (i != idx) {
				next = i + 1;
				end = i;
			} else
				next = end;
		}

		/* Print the line. */
		for (i = idx; i < end; i++) {
			utf8_copy(&gc.data, &text[i]);
			screen_write_cell(ctx, &gc);
		}

		/* If at the bottom, stop. */
		idx = next;
		if (s->cy == cy + lines - 1 || text[idx].size == 0)
			break;

		screen_write_cursormove(ctx, cx, s->cy + 1, 0);
		left = width;
	}

	/*
	 * Fail if on the last line and there is more to come or at the end, or
	 * if the text was not entirely consumed.
	 */
	if ((s->cy == cy + lines - 1 && (!more || s->cx == cx + width)) ||
	    text[idx].size != 0) {
		free(text);
		return (0);
	}
	free(text);

	/*
	 * If no more to come, move to the next line. Otherwise, leave on
	 * the same line (except if at the end).
	 */
	if (!more || s->cx == cx + width)
		screen_write_cursormove(ctx, cx, s->cy + 1, 0);
	return (1);
}

/* Write simple string (no 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 == '\n') {
				screen_write_linefeed(ctx, 0, 8);
				screen_write_carriagereturn(ctx);
			} else if (*ptr > 0x1f && *ptr < 0x7f) {
				size++;
				screen_write_putc(ctx, &gc, *ptr);
			}
			ptr++;
		}
	}

	free(msg);
}

/*
 * Copy from another screen but without the selection stuff. Assumes the target
 * region is already big enough.
 */
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;
			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_set_cursor(ctx, cx, cy);
}

/* Draw a vertical 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_set_cursor(ctx, cx, cy + i);
		screen_write_putc(ctx, &gc, 'x');
	}
	screen_write_set_cursor(ctx, cx, cy + ny - 1);
	screen_write_putc(ctx, &gc, bottom ? 'v' : 'x');

	screen_write_set_cursor(ctx, cx, cy);
}

/* Draw a menu on screen. */
void
screen_write_menu(struct screen_write_ctx *ctx, struct menu *menu,
    int choice, const struct grid_cell *choice_gc)
{
	struct screen		*s = ctx->s;
	struct grid_cell	 default_gc;
	const struct grid_cell	*gc = &default_gc;
	u_int			 cx, cy, i, j;
	const char		*name;

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

	memcpy(&default_gc, &grid_default_cell, sizeof default_gc);

	screen_write_box(ctx, menu->width + 4, menu->count + 2);
	screen_write_cursormove(ctx, cx + 2, cy, 0);
	format_draw(ctx, &default_gc, menu->width, menu->title, NULL);

	for (i = 0; i < menu->count; i++) {
		name = menu->items[i].name;
		if (name == NULL) {
			screen_write_cursormove(ctx, cx, cy + 1 + i, 0);
			screen_write_hline(ctx, menu->width + 4, 1, 1);
		} else {
			if (choice >= 0 && i == (u_int)choice && *name != '-')
				gc = choice_gc;
			screen_write_cursormove(ctx, cx + 2, cy + 1 + i, 0);
			for (j = 0; j < menu->width; j++)
				screen_write_putc(ctx, gc, ' ');
			screen_write_cursormove(ctx, cx + 2, cy + 1 + i, 0);
			if (*name == '-') {
				name++;
				default_gc.attr |= GRID_ATTR_DIM;
				format_draw(ctx, gc, menu->width, name, NULL);
				default_gc.attr &= ~GRID_ATTR_DIM;
			} else
				format_draw(ctx, gc, menu->width, name, NULL);
			gc = &default_gc;
		}
	}

	screen_write_set_cursor(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;
	gc.flags |= GRID_FLAG_NOPALETTE;

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

	screen_write_set_cursor(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_set_cursor(ctx, cx + (src->cx - px),
		    cy + (src->cy - py));
		screen_write_cell(ctx, &gc);
	}
}

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

	s->mode |= mode;

	if (log_get_level() != 0)
		log_debug("%s: %s", __func__, screen_mode_to_string(mode));
}

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

	s->mode &= ~mode;

	if (log_get_level() != 0)
		log_debug("%s: %s", __func__, screen_mode_to_string(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_initctx(ctx, &ttyctx, 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, 0);
	ttyctx.bg = bg;

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

	screen_write_collect_flush(ctx, 0, __func__);
	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, 0);
	ttyctx.bg = bg;

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

	screen_write_collect_flush(ctx, 0, __func__);
	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, 0);
	ttyctx.bg = bg;

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

	screen_write_collect_flush(ctx, 0, __func__);
	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, 1);
		ttyctx.bg = bg;

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

		screen_write_collect_flush(ctx, 0, __func__);
		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, 1);
	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, __func__);

	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, 1);
		ttyctx.bg = bg;

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

		screen_write_collect_flush(ctx, 0, __func__);
		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, 1);
	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, __func__);
	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;
	u_int				 sx = screen_size_x(s);
	struct screen_write_citem	*ci = ctx->item;

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

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

	screen_write_collect_clear(ctx, s->cy, 1);
	ci->x = 0;
	ci->used = sx;
	ci->type = CLEAR;
	ci->bg = bg;
	TAILQ_INSERT_TAIL(&ctx->s->write_list[s->cy].items, ci, entry);
	ctx->item = screen_write_get_citem();
}

/* 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;
	u_int				 sx = screen_size_x(s);
	struct screen_write_citem	*ci = ctx->item, *before;

	if (s->cx == 0) {
		screen_write_clearline(ctx, bg);
		return;
	}

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

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

 	before = screen_write_collect_trim(ctx, s->cy, s->cx, sx - s->cx, NULL);
	ci->x = s->cx;
	ci->used = sx - s->cx;
	ci->type = CLEAR;
	ci->bg = bg;
	if (before == NULL)
		TAILQ_INSERT_TAIL(&ctx->s->write_list[s->cy].items, ci, entry);
	else
		TAILQ_INSERT_BEFORE(before, ci, entry);
	ctx->item = screen_write_get_citem();
}

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

	if (s->cx >= sx - 1) {
		screen_write_clearline(ctx, bg);
		return;
	}

	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);

	before = screen_write_collect_trim(ctx, s->cy, 0, s->cx + 1, NULL);
	ci->x = 0;
	ci->used = s->cx + 1;
	ci->type = CLEAR;
	ci->bg = bg;
	if (before == NULL)
		TAILQ_INSERT_TAIL(&ctx->s->write_list[s->cy].items, ci, entry);
	else
		TAILQ_INSERT_BEFORE(before, ci, entry);
	ctx->item = screen_write_get_citem();
}

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

	if (origin && py != -1 && (s->mode & MODE_ORIGIN)) {
		if ((u_int)py > s->rlower - s->rupper)
			py = s->rlower;
		else
			py += s->rupper;
	}

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

	log_debug("%s: from %u,%u to %u,%u", __func__, s->cx, s->cy, px, py);
	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;

	if (s->cy == s->rupper) {
		grid_view_scroll_region_down(s->grid, s->rupper, s->rlower, bg);
		screen_write_collect_flush(ctx, 0, __func__);

		screen_write_initctx(ctx, &ttyctx, 1);
		ttyctx.bg = bg;

		tty_write(tty_cmd_reverseindex, &ttyctx);
	} else if (s->cy > 0)
		screen_write_set_cursor(ctx, -1, s->cy - 1);

}

/* 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, __func__);

	/* 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;

	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, __func__);
		ctx->bg = bg;
	}

	if (s->cy == s->rlower) {
		grid_view_scroll_region_up(gd, s->rupper, s->rlower, bg);
		screen_write_collect_scroll(ctx, bg);
		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, __func__);
		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, bg);
	}
	ctx->scrolled += lines;
}

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

	screen_write_initctx(ctx, &ttyctx, 1);
	ttyctx.bg = bg;

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

	for (i = 0; i < lines; i++)
		grid_view_scroll_region_down(gd, s->rupper, s->rlower, bg);

	screen_write_collect_flush(ctx, 0, __func__);
	ttyctx.num = lines;
	tty_write(tty_cmd_scrolldown, &ttyctx);
}

/* 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, 1);
	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, __func__);
	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, 1);
	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, __func__);
	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, 1);
	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)
{
	grid_clear_history(ctx->s->grid);
}

/* Force a full redraw. */
void
screen_write_fullredraw(struct screen_write_ctx *ctx)
{
	struct tty_ctx	 ttyctx;

	screen_write_collect_flush(ctx, 0, __func__);

	screen_write_initctx(ctx, &ttyctx, 1);
	ttyctx.redraw_cb(&ttyctx);
}

/* Trim collected items. */
static struct screen_write_citem *
screen_write_collect_trim(struct screen_write_ctx *ctx, u_int y, u_int x,
    u_int used, int *wrapped)
{
	struct screen_write_cline	*cl = &ctx->s->write_list[y];
	struct screen_write_citem	*ci, *ci2, *tmp, *before = NULL;
	u_int				 sx = x, ex = x + used - 1;
	u_int				 csx, cex;

	if (TAILQ_EMPTY(&cl->items))
		return (NULL);
	TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
		csx = ci->x;
		cex = ci->x + ci->used - 1;

		/* Item is entirely before. */
		if (cex < sx) {
			log_debug("%s: %p %u-%u before %u-%u", __func__, ci,
			    csx, cex, sx, ex);
			continue;
		}

		/* Item is entirely after. */
		if (csx > ex) {
			log_debug("%s: %p %u-%u after %u-%u", __func__, ci,
			    csx, cex, sx, ex);
			before = ci;
			break;
		}

		/* Item is entirely inside. */
		if (csx >= sx && cex <= ex) {
			log_debug("%s: %p %u-%u inside %u-%u", __func__, ci,
			    csx, cex, sx, ex);
			TAILQ_REMOVE(&cl->items, ci, entry);
			screen_write_free_citem(ci);
			if (csx == 0 && ci->wrapped && wrapped != NULL)
				*wrapped = 1;
			continue;
		}

		/* Item under the start. */
		if (csx < sx && cex >= sx && cex <= ex) {
			log_debug("%s: %p %u-%u start %u-%u", __func__, ci,
			    csx, cex, sx, ex);
			ci->used = sx - csx;
			log_debug("%s: %p now %u-%u", __func__, ci, ci->x,
			    ci->x + ci->used + 1);
			continue;
		}

		/* Item covers the end. */
		if (cex > ex && csx >= sx && csx <= ex) {
			log_debug("%s: %p %u-%u end %u-%u", __func__, ci,
			    csx, cex, sx, ex);
			ci->x = ex + 1;
			ci->used = cex - ex;
			log_debug("%s: %p now %u-%u", __func__, ci, ci->x,
			    ci->x + ci->used + 1);
			before = ci;
			break;
		}

		/* Item must cover both sides. */
		log_debug("%s: %p %u-%u under %u-%u", __func__, ci,
		    csx, cex, sx, ex);
		ci2 = screen_write_get_citem();
		ci2->type = ci->type;
		ci2->bg = ci->bg;
		memcpy(&ci2->gc, &ci->gc, sizeof ci2->gc);
		TAILQ_INSERT_AFTER(&cl->items, ci, ci2, entry);

		ci->used = sx - csx;
		ci2->x = ex + 1;
		ci2->used = cex - ex;

		log_debug("%s: %p now %u-%u (%p) and %u-%u (%p)", __func__, ci,
		    ci->x, ci->x + ci->used - 1, ci, ci2->x,
		    ci2->x + ci2->used - 1, ci2);
		before = ci2;
		break;
	}
	return (before);
}

/* Clear collected lines. */
static void
screen_write_collect_clear(struct screen_write_ctx *ctx, u_int y, u_int n)
{
	struct screen_write_cline	*cl;
	u_int				 i;

	for (i = y; i < y + n; i++) {
		cl = &ctx->s->write_list[i];
		TAILQ_CONCAT(&screen_write_citem_freelist, &cl->items, entry);
	}
}

/* Scroll collected lines up. */
static void
screen_write_collect_scroll(struct screen_write_ctx *ctx, u_int bg)
{
	struct screen			*s = ctx->s;
	struct screen_write_cline	*cl;
	u_int				 y;
	char				*saved;
	struct screen_write_citem	*ci;

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

	ci = screen_write_get_citem();
	ci->x = 0;
	ci->used = screen_size_x(s);
	ci->type = CLEAR;
	ci->bg = bg;
	TAILQ_INSERT_TAIL(&ctx->s->write_list[s->rlower].items, ci, entry);
}

/* Flush collected lines. */
static void
screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
    const char *from)
{
	struct screen			*s = ctx->s;
	struct screen_write_citem	*ci, *tmp;
	struct screen_write_cline	*cl;
	u_int				 y, cx, cy, last, items = 0;
	struct tty_ctx			 ttyctx;

	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, 1);
		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++) {
		cl = &ctx->s->write_list[y];
		last = UINT_MAX;
		TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
			if (last != UINT_MAX && ci->x <= last) {
				fatalx("collect list not in order: %u <= %u",
				    ci->x, last);
			}
			screen_write_set_cursor(ctx, ci->x, y);
			if (ci->type == CLEAR) {
				screen_write_initctx(ctx, &ttyctx, 1);
				ttyctx.bg = ci->bg;
				ttyctx.num = ci->used;
				tty_write(tty_cmd_clearcharacter, &ttyctx);
			} else {
				screen_write_initctx(ctx, &ttyctx, 0);
				ttyctx.cell = &ci->gc;
				ttyctx.wrapped = ci->wrapped;
				ttyctx.ptr = cl->data + ci->x;
				ttyctx.num = ci->used;
				tty_write(tty_cmd_cells, &ttyctx);
			}
			items++;

			TAILQ_REMOVE(&cl->items, ci, entry);
			screen_write_free_citem(ci);
			last = ci->x;
		}
	}
	s->cx = cx; s->cy = cy;

	log_debug("%s: flushed %u items (%s)", __func__, items, from);
}

/* Finish and store collected cells. */
void
screen_write_collect_end(struct screen_write_ctx *ctx)
{
	struct screen			*s = ctx->s;
	struct screen_write_citem	*ci = ctx->item, *before;
	struct screen_write_cline	*cl = &s->write_list[s->cy];
	struct grid_cell		 gc;
	u_int				 xx;
	int				 wrapped = ci->wrapped;

	if (ci->used == 0)
		return;

	before = screen_write_collect_trim(ctx, s->cy, s->cx, ci->used,
	    &wrapped);
	ci->x = s->cx;
	ci->wrapped = wrapped;
	if (before == NULL)
		TAILQ_INSERT_TAIL(&cl->items, ci, entry);
	else
		TAILQ_INSERT_BEFORE(before, ci, entry);
	ctx->item = screen_write_get_citem();

	log_debug("%s: %u %.*s (at %u,%u)", __func__, ci->used,
	    (int)ci->used, cl->data + ci->x, 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);
		}
	}

	grid_view_set_cells(s->grid, s->cx, s->cy, &ci->gc, cl->data + ci->x,
	    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_citem	*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.
	 */

	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, __func__);
		screen_write_cell(ctx, gc);
		return;
	}

	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);
	if (ctx->s->write_list[s->cy].data == NULL)
		ctx->s->write_list[s->cy].data = xmalloc(screen_size_x(ctx->s));
	ctx->s->write_list[s->cy].data[s->cx + ci->used++] = gc->data.data[0];
}

/* 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;
	const struct utf8_data	*ud = &gc->data;
	const struct utf8_data	 zwj = { "\342\200\215", 0, 3, 0 };
	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;

	/*
	 * If this is a zero width joiner, set the flag so the next character
	 * will be treated as zero width and appended. Note that we assume a
	 * ZWJ will not change the width - the width of the first character is
	 * used.
	 */
	if (ud->size == 3 && memcmp(ud->data, "\342\200\215", 3) == 0) {
		log_debug("zero width joiner at %u,%u", s->cx, s->cy);
		ctx->flags |= SCREEN_WRITE_ZWJ;
		return;
	}

	/*
	 * If the width is zero, combine onto the previous character. We always
	 * combine with the cell to the left of the cursor position. In theory,
	 * the application could have moved the cursor somewhere else, but if
	 * they are silly enough to do that, who cares?
	 */
	if (ctx->flags & SCREEN_WRITE_ZWJ) {
		screen_write_collect_flush(ctx, 0, __func__);
		screen_write_combine(ctx, &zwj, &xx);
	}
	if (width == 0 || (ctx->flags & SCREEN_WRITE_ZWJ)) {
		ctx->flags &= ~SCREEN_WRITE_ZWJ;
		screen_write_collect_flush(ctx, 0, __func__);
		if ((gc = screen_write_combine(ctx, ud, &xx)) != NULL) {
			cx = s->cx; cy = s->cy;
			screen_write_set_cursor(ctx, xx, s->cy);
			screen_write_initctx(ctx, &ttyctx, 0);
			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, __func__);

	/* 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, __func__);
	}

	/* Sanity check cursor position. */
	if (s->cx > sx - width || s->cy > sy - 1)
		return;
	screen_write_initctx(ctx, &ttyctx, 0);

	/* 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_padding(gd, xx, s->cy);
		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, __func__);
		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);
	}
}

/* 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, 0);
	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, 0);
	ttyctx.ptr = str;
	ttyctx.num = len;

	tty_write(tty_cmd_rawstring, &ttyctx);
}

/* Turn alternate screen on. */
void
screen_write_alternateon(struct screen_write_ctx *ctx, struct grid_cell *gc,
    int cursor)
{
	struct tty_ctx		 ttyctx;
	struct window_pane	*wp = ctx->wp;

	if (wp != NULL && !options_get_number(wp->options, "alternate-screen"))
		return;

	screen_write_collect_flush(ctx, 0, __func__);
	screen_alternate_on(ctx->s, gc, cursor);

	screen_write_initctx(ctx, &ttyctx, 1);
	ttyctx.redraw_cb(&ttyctx);
}

/* Turn alternate screen off. */
void
screen_write_alternateoff(struct screen_write_ctx *ctx, struct grid_cell *gc,
    int cursor)
{
	struct tty_ctx		 ttyctx;
	struct window_pane	*wp = ctx->wp;

	if (wp != NULL && !options_get_number(wp->options, "alternate-screen"))
		return;

	screen_write_collect_flush(ctx, 0, __func__);
	screen_alternate_off(ctx->s, gc, cursor);

	screen_write_initctx(ctx, &ttyctx, 1);
	ttyctx.redraw_cb(&ttyctx);
}