Adding upstream version 3.3a.upstream/3.3a

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2146 insertions, 0 deletions

diff --git a/screen-write.c b/screen-write.c
new file mode 100644
index 0000000..6b6a750
--- /dev/null
+++ b/screen-write.c
@@ -0,0 +1,2146 @@
+/* $OpenBSD$ */
+
+/*
+ * 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) {
+			if (ttyctx->defaults.fg == 8)
+				ttyctx->defaults.fg = ttyctx->palette->fg;
+			if (ttyctx->defaults.bg == 8)
+				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,
+	    BOX_LINES_DEFAULT, &default_gc, menu->title);
+
+	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,
+				    0);
+				default_gc.attr &= ~GRID_ATTR_DIM;
+			} else
+				format_draw(ctx, gc, menu->width, name, NULL,
+				    gc == choice_gc);
+			gc = &default_gc;
+		}
+	}
+
+	screen_write_set_cursor(ctx, cx, cy);
+}
+
+static void
+screen_write_box_border_set(enum box_lines box_lines, int cell_type,
+    struct grid_cell *gc)
+{
+	switch (box_lines) {
+        case BOX_LINES_NONE:
+		break;
+        case BOX_LINES_DOUBLE:
+                gc->attr &= ~GRID_ATTR_CHARSET;
+                utf8_copy(&gc->data, tty_acs_double_borders(cell_type));
+		break;
+        case BOX_LINES_HEAVY:
+                gc->attr &= ~GRID_ATTR_CHARSET;
+                utf8_copy(&gc->data, tty_acs_heavy_borders(cell_type));
+		break;
+        case BOX_LINES_ROUNDED:
+                gc->attr &= ~GRID_ATTR_CHARSET;
+                utf8_copy(&gc->data, tty_acs_rounded_borders(cell_type));
+		break;
+        case BOX_LINES_SIMPLE:
+                gc->attr &= ~GRID_ATTR_CHARSET;
+                utf8_set(&gc->data, SIMPLE_BORDERS[cell_type]);
+                break;
+        case BOX_LINES_PADDED:
+                gc->attr &= ~GRID_ATTR_CHARSET;
+                utf8_set(&gc->data, PADDED_BORDERS[cell_type]);
+                break;
+	case BOX_LINES_SINGLE:
+	case BOX_LINES_DEFAULT:
+		gc->attr |= GRID_ATTR_CHARSET;
+		utf8_set(&gc->data, CELL_BORDERS[cell_type]);
+		break;
+	}
+}
+
+/* Draw a box on screen. */
+void
+screen_write_box(struct screen_write_ctx *ctx, u_int nx, u_int ny,
+    enum box_lines lines, const struct grid_cell *gcp, const char *title)
+{
+	struct screen		*s = ctx->s;
+	struct grid_cell         gc;
+	u_int			 cx, cy, i;
+
+	cx = s->cx;
+	cy = s->cy;
+
+	if (gcp != NULL)
+		memcpy(&gc, gcp, sizeof gc);
+	else
+		memcpy(&gc, &grid_default_cell, sizeof gc);
+
+	gc.attr |= GRID_ATTR_CHARSET;
+	gc.flags |= GRID_FLAG_NOPALETTE;
+
+	/* Draw top border */
+	screen_write_box_border_set(lines, CELL_TOPLEFT, &gc);
+	screen_write_cell(ctx, &gc);
+	screen_write_box_border_set(lines, CELL_LEFTRIGHT, &gc);
+	for (i = 1; i < nx - 1; i++)
+		screen_write_cell(ctx, &gc);
+	screen_write_box_border_set(lines, CELL_TOPRIGHT, &gc);
+	screen_write_cell(ctx, &gc);
+
+	/* Draw bottom border */
+	screen_write_set_cursor(ctx, cx, cy + ny - 1);
+	screen_write_box_border_set(lines, CELL_BOTTOMLEFT, &gc);
+	screen_write_cell(ctx, &gc);
+	screen_write_box_border_set(lines, CELL_LEFTRIGHT, &gc);
+	for (i = 1; i < nx - 1; i++)
+		screen_write_cell(ctx, &gc);
+	screen_write_box_border_set(lines, CELL_BOTTOMRIGHT, &gc);
+	screen_write_cell(ctx, &gc);
+
+	/* Draw sides */
+	screen_write_box_border_set(lines, CELL_TOPBOTTOM, &gc);
+	for (i = 1; i < ny - 1; i++) {
+		/* left side */
+		screen_write_set_cursor(ctx, cx, cy + i);
+		screen_write_cell(ctx, &gc);
+		/* right side */
+		screen_write_set_cursor(ctx, cx + nx - 1, cy + i);
+		screen_write_cell(ctx, &gc);
+	}
+
+	if (title != NULL) {
+		gc.attr &= ~GRID_ATTR_CHARSET;
+		screen_write_cursormove(ctx, cx + 2, cy, 0);
+		format_draw(ctx, &gc, nx - 4, title, NULL, 0);
+	}
+
+	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) &&
+	    ctx->wp != NULL &&
+	    options_get_number(ctx->wp->options, "scroll-on-clear"))
+		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) &&
+	    ctx->wp != NULL &&
+	    options_get_number(ctx->wp->options, "scroll-on-clear"))
+		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);
+}