text: /* $OpenBSD$ */
  
  /*
   * 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 void	screen_write_collect_clear(struct screen_write_ctx *, u_int,
  		    u_int);
  static int	screen_write_collect_clear_end(struct screen_write_ctx *, u_int,
  		    u_int, u_int);
  static int	screen_write_collect_clear_start(struct screen_write_ctx *,
  		    u_int, u_int, u_int);
  static void	screen_write_collect_scroll(struct screen_write_ctx *);
  static void	screen_write_collect_flush(struct screen_write_ctx *, int,
  		    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 *);
  
  static const struct grid_cell screen_write_pad_cell = {
  	{ { 0 }, 0, 0, 0 }, 0, GRID_FLAG_PADDING, 0, 8, 8
  };
  
  struct screen_write_collect_item {
  	u_int			 x;
  	int			 wrapped;
  
  	enum { TEXT, CLEAR_END, CLEAR_START } type;
  	u_int			 used;
  	u_int			 bg;
  
  	struct grid_cell	 gc;
  
  	TAILQ_ENTRY(screen_write_collect_item) entry;
  };
  struct screen_write_collect_line {
  	u_int					 bg;
  	char					*data;
  	TAILQ_HEAD(, screen_write_collect_item)  items;
  };
  
  static void
  screen_write_offset_timer(__unused int fd, __unused short events, void *data)
  {
  	struct window	*w = data;
  
  	tty_update_window_offset(w);
  }
  
  /* Set cursor position. */
  static void
  screen_write_set_cursor(struct screen_write_ctx *ctx, int cx, int cy)
  {
  	struct window_pane	*wp = ctx->wp;
  	struct window		*w;
  	struct screen		*s = ctx->s;
  	struct timeval		 tv = { .tv_usec = 10000 };
  
  	if (cx != -1 && (u_int)cx == s->cx && cy != -1 && (u_int)cy == s->cy)
  		return;
  
  	if (cx != -1) {
  		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;
  
  	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("adding %%%u to deferred redraw", 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);
  
  	if (ctx->wp != NULL) {
  		tty_default_colours(&ttyctx->defaults, ctx->wp);
  		ttyctx->palette = ctx->wp->palette;
  	} else {
  		memcpy(&ttyctx->defaults, &grid_default_cell,
  		    sizeof ttyctx->defaults);
  		ttyctx->palette = NULL;
  	}
  
  	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;
  
  	if (ctx->init_ctx_cb != NULL)
  		ctx->init_ctx_cb(ctx, ttyctx);
  	else {
  		ttyctx->redraw_cb = screen_write_redraw_cb;
  		if (ctx->wp == NULL)
  			ttyctx->set_client_cb = NULL;
  		else
  			ttyctx->set_client_cb = screen_write_set_client_cb;
  		ttyctx->arg = ctx->wp;
  	}
  
  	if (ctx->wp != NULL &&
  	    (~ctx->flags & SCREEN_WRITE_SYNC) &&
  	    (sync || ctx->wp != ctx->wp->window->active)) {
  		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 = xcalloc(1, sizeof *ctx->item);
  
  	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__);
  
  	log_debug("%s: %u cells (%u written, %u skipped)", __func__,
  	    ctx->cells, ctx->written, ctx->skipped);
  	if (ctx->wp != NULL) {
  		ctx->wp->written += ctx->written;
  		ctx->wp->skipped += ctx->skipped;
  	}
  
  	free(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 > 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 horizontal line on screen. */
  void
  screen_write_vline(struct screen_write_ctx *ctx, u_int ny, int top, int bottom)
  {
  	struct screen		*s = ctx->s;
  	struct grid_cell	 gc;
  	u_int			 cx, cy, i;
  
  	cx = s->cx;
  	cy = s->cy;
  
  	memcpy(&gc, &grid_default_cell, sizeof gc);
  	gc.attr |= GRID_ATTR_CHARSET;
  
  	screen_write_putc(ctx, &gc, top ? 'w' : 'x');
  	for (i = 1; i < ny - 1; i++) {
  		screen_write_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;
  
  	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;
  }
  
  /* Clear a mode. */
  void
  screen_write_mode_clear(struct screen_write_ctx *ctx, int mode)
  {
  	struct screen	*s = ctx->s;
  
  	s->mode &= ~mode;
  }
  
  /* Cursor up by ny. */
  void
  screen_write_cursorup(struct screen_write_ctx *ctx, u_int ny)
  {
  	struct screen	*s = ctx->s;
  	u_int		 cx = s->cx, cy = s->cy;
  
  	if (ny == 0)
  		ny = 1;
  
  	if (cy < s->rupper) {
  		/* Above region. */
  		if (ny > cy)
  			ny = cy;
  	} else {
  		/* Below region. */
  		if (ny > cy - s->rupper)
  			ny = cy - s->rupper;
  	}
  	if (cx == screen_size_x(s))
  		cx--;
  
  	cy -= ny;
  
  	screen_write_set_cursor(ctx, cx, cy);
  }
  
  /* Cursor down by ny. */
  void
  screen_write_cursordown(struct screen_write_ctx *ctx, u_int ny)
  {
  	struct screen	*s = ctx->s;
  	u_int		 cx = s->cx, cy = s->cy;
  
  	if (ny == 0)
  		ny = 1;
  
  	if (cy > s->rlower) {
  		/* Below region. */
  		if (ny > screen_size_y(s) - 1 - cy)
  			ny = screen_size_y(s) - 1 - cy;
  	} else {
  		/* Above region. */
  		if (ny > s->rlower - cy)
  			ny = s->rlower - cy;
  	}
  	if (cx == screen_size_x(s))
  	    cx--;
  	else if (ny == 0)
  		return;
  
  	cy += ny;
  
  	screen_write_set_cursor(ctx, cx, cy);
  }
  
  /* Cursor right by nx. */
  void
  screen_write_cursorright(struct screen_write_ctx *ctx, u_int nx)
  {
  	struct screen	*s = ctx->s;
  	u_int		 cx = s->cx, cy = s->cy;
  
  	if (nx == 0)
  		nx = 1;
  
  	if (nx > screen_size_x(s) - 1 - cx)
  		nx = screen_size_x(s) - 1 - cx;
  	if (nx == 0)
  		return;
  
  	cx += nx;
  
  	screen_write_set_cursor(ctx, cx, cy);
  }
  
  /* Cursor left by nx. */
  void
  screen_write_cursorleft(struct screen_write_ctx *ctx, u_int nx)
  {
  	struct screen	*s = ctx->s;
  	u_int		 cx = s->cx, cy = s->cy;
  
  	if (nx == 0)
  		nx = 1;
  
  	if (nx > cx)
  		nx = cx;
  	if (nx == 0)
  		return;
  
  	cx -= nx;
  
  	screen_write_set_cursor(ctx, cx, cy);
  }
  
  /* Backspace; cursor left unless at start of wrapped line when can move up. */
  void
  screen_write_backspace(struct screen_write_ctx *ctx)
  {
  	struct screen		*s = ctx->s;
  	struct grid_line	*gl;
  	u_int			 cx = s->cx, cy = s->cy;
  
  	if (cx == 0) {
  		if (cy == 0)
  			return;
  		gl = grid_get_line(s->grid, s->grid->hsize + cy - 1);
  		if (gl->flags & GRID_LINE_WRAPPED) {
  			cy--;
  			cx = screen_size_x(s) - 1;
  		}
  	} else
  		cx--;
  
  	screen_write_set_cursor(ctx, cx, cy);
  }
  
  /* VT100 alignment test. */
  void
  screen_write_alignmenttest(struct screen_write_ctx *ctx)
  {
  	struct screen		*s = ctx->s;
  	struct tty_ctx	 	 ttyctx;
  	struct grid_cell       	 gc;
  	u_int			 xx, yy;
  
  	memcpy(&gc, &grid_default_cell, sizeof gc);
  	utf8_set(&gc.data, 'E');
  
  	for (yy = 0; yy < screen_size_y(s); yy++) {
  		for (xx = 0; xx < screen_size_x(s); xx++)
  			grid_view_set_cell(s->grid, xx, yy, &gc);
  	}
  
  	screen_write_set_cursor(ctx, 0, 0);
  
  	s->rupper = 0;
  	s->rlower = screen_size_y(s) - 1;
  
  	screen_write_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);
  
  	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);
  	ctx->s->write_list[s->cy].bg = 1 + bg;
  	ctx->item->used = 0;
  }
  
  /* 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_collect_item *ci = ctx->item;
  
  	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);
  
  	if (!screen_write_collect_clear_end(ctx, s->cy, s->cx, bg)) {
  		ci->x = s->cx;
  		ci->type = CLEAR_END;
  		ci->bg = bg;
  		TAILQ_INSERT_TAIL(&ctx->s->write_list[s->cy].items, ci, entry);
  		ctx->item = xcalloc(1, sizeof *ctx->item);
  	}
  }
  
  /* 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_collect_item *ci = ctx->item;
  
  	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);
  
  	if (!screen_write_collect_clear_start(ctx, s->cy, s->cx, bg)) {
  		ci->x = s->cx;
  		ci->type = CLEAR_START;
  		ci->bg = bg;
  		TAILQ_INSERT_TAIL(&ctx->s->write_list[s->cy].items, ci, entry);
  		ctx->item = xcalloc(1, sizeof *ctx->item);
  	}
  }
  
  /* 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;
  
  	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;
  	else
  		gl->flags &= ~GRID_LINE_WRAPPED;
  
  	log_debug("%s: at %u,%u (region %u-%u)", __func__, s->cx, s->cy,
  	    s->rupper, s->rlower);
  
  	if (bg != ctx->bg) {
  		screen_write_collect_flush(ctx, 1, __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);
  		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);
  	}
  	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);
  }
  
  /* Clear to start of a collected line. */
  static int
  screen_write_collect_clear_start(struct screen_write_ctx *ctx, u_int y, u_int x,
      u_int bg)
  {
  	struct screen_write_collect_item	*ci, *tmp;
  	size_t					 size = 0;
  	u_int					 items = 0;
  	int					 redundant = 0;
  
  	if (TAILQ_EMPTY(&ctx->s->write_list[y].items))
  		return (0);
  	TAILQ_FOREACH_SAFE(ci, &ctx->s->write_list[y].items, entry, tmp) {
  		switch (ci->type) {
  		case CLEAR_START:
  			if (ci->x >= x) {
  				if (ci->bg == bg)
  					redundant = 1;
  				continue;
  			}
  			break;
  		case CLEAR_END:
  			if (ci->x <= x)
  				ci->x = x;
  			continue;
  		case TEXT:
  			if (ci->x > x)
  				continue;
  			break;
  		}
  		items++;
  		size += ci->used;
  		TAILQ_REMOVE(&ctx->s->write_list[y].items, ci, entry);
  		free(ci);
  	}
  	ctx->skipped += size;
  	log_debug("%s: dropped %u items (%zu bytes) (line %u)", __func__, items,
  	    size, y);
  	return (redundant);
  }
  
  /* Clear to end of a collected line. */
  static int
  screen_write_collect_clear_end(struct screen_write_ctx *ctx, u_int y, u_int x,
      u_int bg)
  {
  	struct screen_write_collect_item	*ci, *tmp;
  	size_t					 size = 0;
  	int					 redundant = 0;
  	u_int					 items = 0;
  
  	if (TAILQ_EMPTY(&ctx->s->write_list[y].items))
  		return (0);
  	TAILQ_FOREACH_SAFE(ci, &ctx->s->write_list[y].items, entry, tmp) {
  		switch (ci->type) {
  		case CLEAR_START:
  			if (ci->x >= x)
  				ci->x = x;
  			continue;
  		case CLEAR_END:
  			if (ci->x <= x) {
  				if (ci->bg == bg)
  					redundant = 1;
  				continue;
  			}
  			break;
  		case TEXT:
  			if (ci->x < x)
  				continue;
  			break;
  		}
  		items++;
  		size += ci->used;
  		TAILQ_REMOVE(&ctx->s->write_list[y].items, ci, entry);
  		free(ci);
  	}
  	ctx->skipped += size;
  	log_debug("%s: dropped %u items (%zu bytes) (line %u)", __func__, items,
  	    size, y);
  	return (redundant);
  }
  
  /* Clear collected lines. */
  static void
  screen_write_collect_clear(struct screen_write_ctx *ctx, u_int y, u_int n)
  {
  	struct screen_write_collect_item	*ci, *tmp;
  	struct screen_write_collect_line	*cl;
  	u_int					 i, items;
  	size_t					 size;
  
  	for (i = y; i < y + n; i++) {
  		if (TAILQ_EMPTY(&ctx->s->write_list[i].items))
  			continue;
  		items = 0;
  		size = 0;
  		cl = &ctx->s->write_list[i];
  		TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
  			items++;
  			size += ci->used;
  			TAILQ_REMOVE(&cl->items, ci, entry);
  			free(ci);
  		}
  		ctx->skipped += size;
  		log_debug("%s: dropped %u items (%zu bytes) (line %u)",
  		    __func__, items, size, y);
  	}
  }
  
  /* Scroll collected lines up. */
  static void
  screen_write_collect_scroll(struct screen_write_ctx *ctx)
  {
  	struct screen				*s = ctx->s;
  	struct screen_write_collect_line	*cl;
  	u_int					 y;
  	char					*saved;
  
  	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].bg = cl->bg;
  		ctx->s->write_list[y].data = cl->data;
  	}
  	ctx->s->write_list[s->rlower].bg = 1 + 8;
  	ctx->s->write_list[s->rlower].data = saved;
  }
  
  /* 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_collect_item	*ci, *tmp;
  	struct screen_write_collect_line	*cl;
  	u_int					 y, cx, cy, items = 0;
  	struct tty_ctx				 ttyctx;
  	size_t					 written = 0;
  
  	if (ctx->scrolled != 0) {
  		log_debug("%s: scrolled %u (region %u-%u)", __func__,
  		    ctx->scrolled, s->rupper, s->rlower);
  		if (ctx->scrolled > s->rlower - s->rupper + 1)
  			ctx->scrolled = s->rlower - s->rupper + 1;
  
  		screen_write_initctx(ctx, &ttyctx, 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];
  		if (cl->bg != 0) {
  			screen_write_set_cursor(ctx, 0, y);
  			screen_write_initctx(ctx, &ttyctx, 1);
  			ttyctx.bg = cl->bg - 1;
  			tty_write(tty_cmd_clearline, &ttyctx);
  		}
  		TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
  			screen_write_set_cursor(ctx, ci->x, y);
  			if (ci->type == CLEAR_END) {
  				screen_write_initctx(ctx, &ttyctx, 1);
  				ttyctx.bg = ci->bg;
  				tty_write(tty_cmd_clearendofline, &ttyctx);
  			} else if (ci->type == CLEAR_START) {
  				screen_write_initctx(ctx, &ttyctx, 1);
  				ttyctx.bg = ci->bg;
  				tty_write(tty_cmd_clearstartofline, &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++;
  			written += ci->used;
  
  			TAILQ_REMOVE(&cl->items, ci, entry);
  			free(ci);
  		}
  		cl->bg = 0;
  	}
  	s->cx = cx; s->cy = cy;
  
  	log_debug("%s: flushed %u items (%zu bytes) (%s)", __func__, items,
  	    written, from);
  	ctx->written += written;
  }
  
  /* Finish and store collected cells. */
  void
  screen_write_collect_end(struct screen_write_ctx *ctx)
  {
  	struct screen				*s = ctx->s;
  	struct screen_write_collect_item	*ci = ctx->item;
  	struct screen_write_collect_line	*cl = &s->write_list[s->cy];
  	struct grid_cell			 gc;
  	u_int					 xx;
  
  	if (ci->used == 0)
  		return;
  
  	ci->x = s->cx;
  	TAILQ_INSERT_TAIL(&cl->items, ci, entry);
  	ctx->item = xcalloc(1, sizeof *ctx->item);
  
  	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_collect_item	*ci;
  	u_int					 sx = screen_size_x(s);
  	int					 collect;
  
  	/*
  	 * Don't need to check that the attributes and whatnot are still the
  	 * same - input_parse will end the collection when anything that isn't
  	 * a plain character is encountered.
  	 */
  
  	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;
  	}
  	ctx->cells++;
  
  	if (s->cx > sx - 1 || ctx->item->used > sx - 1 - s->cx)
  		screen_write_collect_end(ctx);
  	ci = ctx->item; /* may have changed */
  
  	if (s->cx > sx - 1) {
  		log_debug("%s: wrapped at %u,%u", __func__, s->cx, s->cy);
  		ci->wrapped = 1;
  		screen_write_linefeed(ctx, 1, 8);
  		screen_write_set_cursor(ctx, 0, -1);
  	}
  
  	if (ci->used == 0)
  		memcpy(&ci->gc, gc, sizeof ci->gc);
  	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;
  	struct grid_line	*gl;
  	struct grid_cell_entry	*gce;
  	struct grid_cell 	 tmp_gc, now_gc;
  	struct tty_ctx		 ttyctx;
  	u_int			 sx = screen_size_x(s), sy = screen_size_y(s);
  	u_int		 	 width = gc->data.width, xx, last, cx, cy;
  	int			 selected, skip = 1;
  
  	/* Ignore padding cells. */
  	if (gc->flags & GRID_FLAG_PADDING)
  		return;
  	ctx->cells++;
  
  	/* If the width is zero, combine onto the previous character. */
  	if (width == 0) {
  		screen_write_collect_flush(ctx, 0, __func__);
  		if ((gc = screen_write_combine(ctx, &gc->data, &xx)) != 0) {
  			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_cell(gd, xx, s->cy, &screen_write_pad_cell);
  		skip = 0;
  	}
  
  	/* If no change, do not draw. */
  	if (skip) {
  		if (s->cx >= gl->cellsize)
  			skip = grid_cells_equal(gc, &grid_default_cell);
  		else {
  			gce = &gl->celldata[s->cx];
  			if (gce->flags & GRID_FLAG_EXTENDED)
  				skip = 0;
  			else if (gc->flags != gce->flags)
  				skip = 0;
  			else if (gc->attr != gce->data.attr)
  				skip = 0;
  			else if (gc->fg != gce->data.fg)
  				skip = 0;
  			else if (gc->bg != gce->data.bg)
  				skip = 0;
  			else if (gc->data.width != 1)
  				skip = 0;
  			else if (gc->data.size != 1)
  				skip = 0;
  			else if (gce->data.data != gc->data.data[0])
  				skip = 0;
  		}
  	}
  
  	/* Update the selected flag and set the cell. */
  	selected = screen_check_selection(s, s->cx, s->cy);
  	if (selected && (~gc->flags & GRID_FLAG_SELECTED)) {
  		memcpy(&tmp_gc, gc, sizeof tmp_gc);
  		tmp_gc.flags |= GRID_FLAG_SELECTED;
  		grid_view_set_cell(gd, s->cx, s->cy, &tmp_gc);
  	} else if (!selected && (gc->flags & GRID_FLAG_SELECTED)) {
  		memcpy(&tmp_gc, gc, sizeof tmp_gc);
  		tmp_gc.flags &= ~GRID_FLAG_SELECTED;
  		grid_view_set_cell(gd, s->cx, s->cy, &tmp_gc);
  	} else if (!skip)
  		grid_view_set_cell(gd, s->cx, s->cy, gc);
  	if (selected)
  		skip = 0;
  
  	/*
  	 * Move the cursor. If not wrapping, stick at the last character and
  	 * replace it.
  	 */
  	last = !(s->mode & MODE_WRAP);
  	if (s->cx <= sx - last - width)
  		screen_write_set_cursor(ctx, s->cx + width, -1);
  	else
  		screen_write_set_cursor(ctx,  sx - last, -1);
  
  	/* Create space for character in insert mode. */
  	if (s->mode & MODE_INSERT) {
  		screen_write_collect_flush(ctx, 0, __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);
  		ctx->written++;
  	} else
  		ctx->skipped++;
  }
  
  /* Combine a UTF-8 zero-width character onto the previous. */
  static const struct grid_cell *
  screen_write_combine(struct screen_write_ctx *ctx, const struct utf8_data *ud,
      u_int *xx)
  {
  	struct screen		*s = ctx->s;
  	struct grid		*gd = s->grid;
  	static struct grid_cell	 gc;
  	u_int			 n;
  
  	/* Can't combine if at 0. */
  	if (s->cx == 0)
  		return (NULL);
  
  	/* Empty data is out. */
  	if (ud->size == 0)
  		fatalx("UTF-8 data empty");
  
  	/* Retrieve the previous cell. */
  	for (n = 1; n <= s->cx; n++) {
  		grid_view_get_cell(gd, s->cx - n, s->cy, &gc);
  		if (~gc.flags & GRID_FLAG_PADDING)
  			break;
  	}
  	if (n > s->cx)
  		return (NULL);
  	*xx = s->cx - n;
  
  	/* Check there is enough space. */
  	if (gc.data.size + ud->size > sizeof gc.data.data)
  		return (NULL);
  
  	log_debug("%s: %.*s onto %.*s at %u,%u", __func__, (int)ud->size,
  	    ud->data, (int)gc.data.size, gc.data.data, *xx, s->cy);
  
  	/* Append the data. */
  	memcpy(gc.data.data + gc.data.size, ud->data, ud->size);
  	gc.data.size += ud->size;
  
  	/* Set the new cell. */
  	grid_view_set_cell(gd, *xx, s->cy, &gc);
  
  	return (&gc);
  }
  
  /*
   * UTF-8 wide characters are a bit of an annoyance. They take up more than one
   * cell on the screen, so following cells must not be drawn by marking them as
   * padding.
   *
   * So far, so good. The problem is, when overwriting a padding cell, or a UTF-8
   * character, it is necessary to also overwrite any other cells which covered
   * by the same character.
   */
  static int
  screen_write_overwrite(struct screen_write_ctx *ctx, struct grid_cell *gc,
      u_int width)
  {
  	struct screen		*s = ctx->s;
  	struct grid		*gd = s->grid;
  	struct grid_cell	 tmp_gc;
  	u_int			 xx;
  	int			 done = 0;
  
  	if (gc->flags & GRID_FLAG_PADDING) {
  		/*
  		 * A padding cell, so clear any following and leading padding
  		 * cells back to the character. Don't overwrite the current
  		 * cell as that happens later anyway.
  		 */
  		xx = s->cx + 1;
  		while (--xx > 0) {
  			grid_view_get_cell(gd, xx, s->cy, &tmp_gc);
  			if (~tmp_gc.flags & GRID_FLAG_PADDING)
  				break;
  			log_debug("%s: padding at %u,%u", __func__, xx, s->cy);
  			grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
  		}
  
  		/* Overwrite the character at the start of this padding. */
  		log_debug("%s: character at %u,%u", __func__, xx, s->cy);
  		grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
  		done = 1;
  	}
  
  	/*
  	 * Overwrite any padding cells that belong to any UTF-8 characters
  	 * we'll be overwriting with the current character.
  	 */
  	if (width != 1 ||
  	    gc->data.width != 1 ||
  	    gc->flags & GRID_FLAG_PADDING) {
  		xx = s->cx + width - 1;
  		while (++xx < screen_size_x(s)) {
  			grid_view_get_cell(gd, xx, s->cy, &tmp_gc);
  			if (~tmp_gc.flags & GRID_FLAG_PADDING)
  				break;
  			log_debug("%s: overwrite at %u,%u", __func__, xx,
  			    s->cy);
  			grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
  			done = 1;
  		}
  	}
  
  	return (done);
  }
  
  /* Set external clipboard. */
  void
  screen_write_setselection(struct screen_write_ctx *ctx, u_char *str, u_int len)
  {
  	struct tty_ctx	ttyctx;
  
  	screen_write_initctx(ctx, &ttyctx, 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_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_alternate_off(ctx->s, gc, cursor);
  
  	screen_write_initctx(ctx, &ttyctx, 1);
  	ttyctx.redraw_cb(&ttyctx);
  }
  