screen.c - tmux - Rivoreo Source Code Repositories

 /* $Id: screen.c,v 1.4 2007-08-27 08:15:39 nicm Exp $ */

 /*
  * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
  *
  * 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 <string.h>

 #include "tmux.h"

 /*
  * Virtual screen and basic ANSI terminal emulator.
  *
  * XXX Most of this file sucks. There be memory corruption somewhere here.
  */

 size_t	 screen_store_attributes(struct buffer *, u_char);
 size_t	 screen_store_colours(struct buffer *, u_char);
 void	 screen_free_lines(struct screen *, u_int, u_int);
 void	 screen_make_lines(struct screen *, u_int, u_int);
 void	 screen_move_lines(struct screen *, u_int, u_int, u_int);
 void	 screen_fill_lines(
 	     struct screen *, u_int, u_int, u_char, u_char, u_char);
 uint16_t screen_extract(u_char *);
 void	 screen_write_character(struct screen *, u_char);
 void	 screen_cursor_up_scroll(struct screen *, u_int);
 void	 screen_cursor_down_scroll(struct screen *, u_int);
 void	 screen_scroll_up(struct screen *, u_int);
 void	 screen_scroll_down(struct screen *, u_int);
 void	 screen_fill_screen(struct screen *, u_char, u_char, u_char);
 void	 screen_fill_line(struct screen *, u_int, u_char, u_char, u_char);
 void	 screen_fill_end_of_screen(
     	     struct screen *, u_int, u_int, u_char, u_char, u_char);
 void	 screen_fill_end_of_line(
     	     struct screen *, u_int, u_int, u_char, u_char, u_char);
 void	 screen_fill_start_of_line(
     	     struct screen *, u_int, u_int, u_char, u_char, u_char);
 void	 screen_insert_lines(struct screen *, u_int, u_int);
 void	 screen_delete_lines(struct screen *, u_int, u_int);
 void	 screen_insert_characters(struct screen *, u_int, u_int, u_int);
 void	 screen_delete_characters(struct screen *, u_int, u_int, u_int);

 #define SCREEN_DEFDATA ' '
 #define SCREEN_DEFATTR 0
 #define SCREEN_DEFCOLR 0x88

 #define screen_last_y(s) ((s)->sy - 1)
 #define screen_last_x(s) ((s)->sx - 1)

 #define screen_range_y(lx, rx) (((rx) - (lx)) + 1)
 #define screen_range_x(ux, lx) (((lx) - (ux)) + 1)

 #define screen_offset_y(py, ny) ((py) + (ny) - 1)
 #define screen_offset_x(px, nx) ((px) + (nx) - 1)

 /* Create a new screen. */
 void
 screen_create(struct screen *s, u_int sx, u_int sy)
 {
 	s->sx = sx;
 	s->sy = sy;
 	s->cx = 0;
 	s->cy = 0;

 	s->ry_upper = 0;
 	s->ry_lower = screen_last_y(s);

 	s->attr = SCREEN_DEFATTR;
 	s->colr = SCREEN_DEFCOLR;

 	s->mode = MODE_CURSOR;
 	*s->title = '\0';

 	s->grid_data = xmalloc(sy * (sizeof *s->grid_data));
 	s->grid_attr = xmalloc(sy * (sizeof *s->grid_attr));
 	s->grid_colr = xmalloc(sy * (sizeof *s->grid_colr));
 	screen_make_lines(s, 0, screen_last_y(s));
 	screen_fill_screen(s, SCREEN_DEFDATA, 0, SCREEN_DEFCOLR);
 }

 /* Resize screen. */
 void
 screen_resize(struct screen *s, u_int sx, u_int sy)
 {
 	u_int	i, ox, oy, ny;

 	if (sx < 1)
 		sx = 1;
 	if (sy < 1)
 		sy = 1;

 	ox = s->sx;
 	oy = s->sy;
 	s->sx = sx;
 	s->sy = sy;

 	log_debug("resizing screen (%u, %u) -> (%u, %u)", ox, oy, sx, sy);

 	if (sy < oy) {
 		ny = oy - sy;
 		if (ny > s->cy)
 			ny = s->cy;

 		if (ny != 0) {
 			log_debug("removing %u lines from top", ny);
 			for (i = 0; i < ny; i++) {
 				log_debug("freeing line %u", i);
 				xfree(s->grid_data[i]);
 				xfree(s->grid_attr[i]);
 				xfree(s->grid_colr[i]);
 			}
 			memmove(s->grid_data, s->grid_data + ny,
 			    (oy - ny) * (sizeof *s->grid_data));
 			memmove(s->grid_attr, s->grid_attr + ny,
 			    (oy - ny) * (sizeof *s->grid_attr));
 			memmove(s->grid_colr, s->grid_colr + ny,
 			    (oy - ny) * (sizeof *s->grid_colr));
 			s->cy -= ny;
 		}
 		if (ny < oy - sy) {
 			log_debug(
 			    "removing %u lines from bottom", oy - sy - ny);
 			for (i = sy; i < oy - ny; i++) {
 				log_debug("freeing line %u", i);
 				  xfree(s->grid_data[i]);
 				  xfree(s->grid_attr[i]);
 				  xfree(s->grid_colr[i]);
 			}
 			if (s->cy >= sy)
 				s->cy = sy - 1;
 		}
 	}
 	if (sy != oy) {
 		s->grid_data = xrealloc(s->grid_data, sy, sizeof *s->grid_data);
 		s->grid_attr = xrealloc(s->grid_attr, sy, sizeof *s->grid_attr);
 		s->grid_colr = xrealloc(s->grid_colr, sy, sizeof *s->grid_colr);
 	}
 	if (sy > oy) {
 		for (i = oy; i < sy; i++) {
 			log_debug("allocating line %u", i);
 			s->grid_data[i] = xmalloc(sx);
 			s->grid_attr[i] = xmalloc(sx);
 			s->grid_colr[i] = xmalloc(sx);
 			screen_fill_line(s, i,
 			    SCREEN_DEFDATA, SCREEN_DEFATTR, SCREEN_DEFCOLR);
 		}
 		sy = oy;
 	}

 	if (sx != ox) {
 		for (i = 0; i < sy; i++) {
 			log_debug("adjusting line %u to %u", i, sx);
 			s->grid_data[i] = xrealloc(s->grid_data[i], sx, 1);
 			s->grid_attr[i] = xrealloc(s->grid_attr[i], sx, 1);
 			s->grid_colr[i] = xrealloc(s->grid_colr[i], sx, 1);
 			if (sx > ox) {
 				screen_fill_end_of_line(s, ox, i,
 				    SCREEN_DEFDATA, SCREEN_DEFATTR,
 				    SCREEN_DEFCOLR);
 			}
 		}
 		if (s->cx >= sx)
 			s->cx = sx - 1;
 	}
 }

 /* Draw a set of lines on the screen. */
 void
 screen_draw(struct screen *s, struct buffer *b, u_int uy, u_int ly)
 {
 	u_char		 attr, colr;
 	size_t		 size;
 	u_int		 i, j;
 	uint16_t	 n;

 	if (uy > screen_last_y(s) || ly > screen_last_y(s) || ly < uy)
 		fatalx("bad range");

 	/* XXX. This is naive and rough right now. */
 	attr = 0;
 	colr = SCREEN_DEFCOLR;

 	input_store_zero(b, CODE_CURSOROFF);

 	input_store_one(b, CODE_ATTRIBUTES, 0);

 	for (j = uy; j <= ly; j++) {
 		input_store_two(b, CODE_CURSORMOVE, j + 1, 1);

 		for (i = 0; i <= screen_last_x(s); i++) {

 			size = BUFFER_USED(b);
 			input_store_one(b, CODE_ATTRIBUTES, 0);

 			n = 0;
 			if (s->grid_attr[j][i] != attr) {
 				attr = s->grid_attr[j][i];
 				n += screen_store_attributes(b, attr);
 				if (attr == 0)
 				colr = SCREEN_DEFCOLR;
 			}
 			if (s->grid_colr[j][i] != colr) {
 				colr = s->grid_colr[j][i];
 				n += screen_store_colours(b, colr);
 			}
 			if (n == 0)
 				buffer_reverse_add(b, 4);
 			else {
 				size = BUFFER_USED(b) - size;
 				memcpy(BUFFER_IN(b) - size + 2, &n, 2);
 			}

 			input_store8(b, s->grid_data[j][i]);
 		}
 	}

 	size = BUFFER_USED(b);
 	input_store_one(b, CODE_ATTRIBUTES, 0);
 	n = screen_store_attributes(b, s->attr);
 	n += screen_store_colours(b, s->colr);
 	size = BUFFER_USED(b) - size;
 	memcpy(BUFFER_IN(b) - size + 2, &n, 2);

 	input_store_two(b, CODE_CURSORMOVE, s->cy + 1, s->cx + 1);

 	if (s->mode & MODE_CURSOR)
 		input_store_zero(b, CODE_CURSORON);
 }

 /* Store screen atttributes in buffer. */
 size_t
 screen_store_attributes(struct buffer *b, u_char attr)
 {
 	size_t	n;

 	if (attr == 0) {
 		input_store16(b, 0);
 		return (1);
 	}

 	n = 0;
 	if (attr & ATTR_BRIGHT) {
 		input_store16(b, 1);
 		n++;
 	}
 	if (attr & ATTR_DIM) {
 		input_store16(b, 2);
 		n++;
 	}
 	if (attr & ATTR_ITALICS) {
 		input_store16(b, 3);
 		n++;
 	}
 	if (attr & ATTR_UNDERSCORE) {
 		input_store16(b, 4);
 		n++;
 	}
 	if (attr & ATTR_BLINK) {
 		input_store16(b, 5);
 		n++;
 	}
 	if (attr & ATTR_REVERSE) {
 		input_store16(b, 7);
 		n++;
 	}
 	if (attr & ATTR_HIDDEN) {
 		input_store16(b, 8);
 		n++;
 	}
 	return (n);
 }

 /* Store screen colours in buffer. */
 size_t
 screen_store_colours(struct buffer *b, u_char colr)
 {
 	uint16_t	v;

 	v = colr >> 4;
 	if (v == 8)
 		v = 9;
 	input_store16(b, 30 + v);
 	v = colr & 0xf;
 	if (v == 8)
 		v = 9;
 	input_store16(b, 40 + v);

 	return (2);
 }

 /* Make a range of lines. */
 void
 screen_make_lines(struct screen *s, u_int uy, u_int ly)
 {
 	u_int	i;

 	log_debug("making lines %u:%u", uy, ly);

 	if (uy > screen_last_y(s) || ly > screen_last_y(s) || ly < uy)
 		fatalx("bad range");

 	for (i = uy; i <= ly; i++) {
 		s->grid_data[i] = xmalloc(s->sx);
 		s->grid_attr[i] = xmalloc(s->sx);
 		s->grid_colr[i] = xmalloc(s->sx);
 	}
 }

 /* Free a range of lines. */
 void
 screen_free_lines(struct screen *s, u_int uy, u_int ly)
 {
 	u_int	i;

 	log_debug("freeing lines %u:%u", uy, ly);

 	if (uy > screen_last_y(s) || ly > screen_last_y(s) || ly < uy)
 		fatalx("bad range");

 	for (i = uy; i <= ly; i++) {
 		xfree(s->grid_data[i]);
 		s->grid_data[i] = (u_char *) 0xffffffff;
 		xfree(s->grid_attr[i]);
 		s->grid_attr[i] = (u_char *) 0xffffffff;
 		xfree(s->grid_colr[i]);
 		s->grid_colr[i] = (u_char *) 0xffffffff;
 	}
 }

 /* Move a range of lines. */
 void
 screen_move_lines(struct screen *s, u_int dy, u_int uy, u_int ly)
 {
 	u_int	ny;

 	log_debug("moving lines %u:%u to %u", uy, ly, dy);

 	ny = (ly - uy) + 1;

 	if (uy > screen_last_y(s) || ly > screen_last_y(s) || ly < uy)
 		fatalx("bad range");
 	if (dy > screen_last_y(s))
 		fatalx("bad destination");
 	if (dy + ny - 1 > screen_last_y(s))
 		fatalx("bad size");
 	if (dy == uy)
 		fatalx("null move");

 	memmove(
 	    &s->grid_data[dy], &s->grid_data[uy], ny * (sizeof *s->grid_data));
 	memmove(
 	    &s->grid_attr[dy], &s->grid_attr[uy], ny * (sizeof *s->grid_attr));
 	memmove(
 	    &s->grid_colr[dy], &s->grid_colr[uy], ny * (sizeof *s->grid_colr));
 }

 /* Fill a range of lines. */
 void
 screen_fill_lines(
     struct screen *s, u_int uy, u_int ly, u_char data, u_char attr, u_char colr)
 {
 	u_int	i;

 	log_debug("filling lines %u:%u", uy, ly);

 	if (uy > screen_last_y(s) || ly > screen_last_y(s) || ly < uy)
 		fatalx("bad range");

 	for (i = uy; i <= ly; i++)
 		screen_fill_line(s, i, data, attr, colr);
 }

 /* Update screen with character. */
 void
 screen_character(struct screen *s, u_char ch)
 {
 	switch (ch) {
 	case '\n':	/* LF */
 		screen_cursor_down_scroll(s, 1);
 		break;
 	case '\r':	/* CR */
 		s->cx = 0;
 		break;
 	case '\010':	/* BS */
 		if (s->cx > 0)
 			s->cx--;
 		break;
 	default:
 		if (ch < ' ')
 			fatalx("bad control");
 		screen_write_character(s, ch);
 		break;
 	}
 }

 /* Extract 16-bit value from pointer. */
 uint16_t
 screen_extract(u_char *ptr)
 {
 	uint16_t	n;

 	memcpy(&n, ptr, sizeof n);
 	return (n);
 }

 /* Update screen with escape sequence. */
 void
 screen_sequence(struct screen *s, u_char *ptr)
 {
 	uint16_t	ua, ub;

 	ptr++;
 	log_debug("processing code %hhu", *ptr);
 	switch (*ptr++) {
 	case CODE_CURSORUP:
 		ua = screen_extract(ptr);
 		if (ua > s->cy)
 			ua = s->cy;
 		s->cy -= ua;
 		break;
 	case CODE_CURSORDOWN:
 		ua = screen_extract(ptr);
 		if (s->cy + ua > screen_last_y(s))
 			ua = screen_last_y(s) - s->cy;
 		s->cy += ua;
 		break;
 	case CODE_CURSORLEFT:
 		ua = screen_extract(ptr);
 		if (ua > s->cx)
 			ua = s->cx;
 		s->cx -= ua;
 		break;
 	case CODE_CURSORRIGHT:
 		ua = screen_extract(ptr);
 		if (s->cx + ua > screen_last_x(s))
 			ua = screen_last_x(s) - s->cx;
 		s->cx += ua;
 		break;
 	case CODE_CURSORMOVE:
 		ua = screen_extract(ptr);
 		ptr += 2;
 		ub = screen_extract(ptr);
 		if (ub > s->sx)
 			ub = s->sx;
 		s->cx = ub - 1;
 		if (ua > s->sy)
 			ua = s->sy;
 		s->cy = ua - 1;
 		break;
 	case CODE_CLEARENDOFSCREEN:
 		screen_fill_end_of_screen(
 		    s, s->cx, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
 		break;
 	case CODE_CLEARSCREEN:
 		screen_fill_screen(s, SCREEN_DEFDATA, s->attr, s->colr);
 		break;
 	case CODE_CLEARENDOFLINE:
 		screen_fill_end_of_line(
 		    s, s->cx, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
 		break;
 	case CODE_CLEARSTARTOFLINE:
 		screen_fill_start_of_line(
 		    s, s->cx, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
 		break;
 	case CODE_CLEARLINE:
 		screen_fill_line(s, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
 		break;
 	case CODE_INSERTLINE:
 		ua = screen_extract(ptr);
 		screen_insert_lines(s, s->cy, ua);
 		break;
 	case CODE_DELETELINE:
 		ua = screen_extract(ptr);
 		screen_delete_lines(s, s->cy, ua);
 		break;
 	case CODE_INSERTCHARACTER:
 		ua = screen_extract(ptr);
 		screen_insert_characters(s, s->cx, s->cy, ua);
 		break;
 	case CODE_DELETECHARACTER:
 		ua = screen_extract(ptr);
 		screen_delete_characters(s, s->cx, s->cy, ua);
 		break;
 	case CODE_CURSORON:
 		s->mode |= MODE_CURSOR;
 		break;
 	case CODE_CURSOROFF:
 		s->mode &= ~MODE_CURSOR;
 		break;
 	case CODE_CURSORDOWNSCROLL:
 		ua = screen_extract(ptr);
 		screen_cursor_down_scroll(s, ua);
 		break;
 	case CODE_CURSORUPSCROLL:
 		ua = screen_extract(ptr);
 		screen_cursor_up_scroll(s, ua);
 		break;
 	case CODE_SCROLLREGION:
 		ua = screen_extract(ptr);
 		ptr += 2;
 		ub = screen_extract(ptr);
 		if (ua > s->sy)
 			ua = s->sy;
 		s->ry_upper = ua - 1;
 		if (ub > s->sy)
 			ub = s->sy;
 		s->ry_lower = ub - 1;
 		break;
 	case CODE_INSERTOFF:
 		s->mode &= ~MODE_INSERT;
 		break;
 	case CODE_INSERTON:
 		s->mode |= MODE_INSERT;
 		break;
 	case CODE_KCURSOROFF:
 		s->mode &= ~MODE_KCURSOR;
 		break;
 	case CODE_KCURSORON:
 		s->mode |= MODE_KCURSOR;
 		break;
 	case CODE_KKEYPADOFF:
 		s->mode &= ~MODE_KKEYPAD;
 		break;
 	case CODE_KKEYPADON:
 		s->mode |= MODE_KKEYPAD;
 		break;
 	case CODE_TITLE:
 		ua = screen_extract(ptr);
 		ptr += 2;
 		log_debug("new title: %u:%.*s", ua, (int) ua, ptr);
 		if (ua > MAXTITLELEN - 1)
 			ua = MAXTITLELEN - 1;
 		memcpy(s->title, ptr, ua);
 		s->title[ua] = '\0';
 		break;
 	case CODE_ATTRIBUTES:
 		ua = screen_extract(ptr);
 		if (ua == 0) {
 			s->attr = 0;
 			s->colr = SCREEN_DEFCOLR;
 			break;
 		}

 		while (ua-- > 0) {
 			ptr += 2;
 			ub = screen_extract(ptr);
 			switch (ub) {
 			case 0:
 			case 10:
 				s->attr = 0;
 				s->colr = SCREEN_DEFCOLR;
 				break;
 			case 1:
 				s->attr |= ATTR_BRIGHT;
 				break;
 			case 2:
 				s->attr |= ATTR_DIM;
 				break;
 			case 3:
 				s->attr |= ATTR_ITALICS;
 				break;
 			case 4:
 				s->attr |= ATTR_UNDERSCORE;
 				break;
 			case 5:
 				s->attr |= ATTR_BLINK;
 				break;
 			case 7:
 				s->attr |= ATTR_REVERSE;
 				break;
 			case 8:
 				s->attr |= ATTR_HIDDEN;
 				break;
 			case 23:
 				s->attr &= ~ATTR_ITALICS;
 				break;
 			case 24:
 				s->attr &= ~ATTR_UNDERSCORE;
 				break;
 			case 30:
 			case 31:
 			case 32:
 			case 33:
 			case 34:
 			case 35:
 			case 36:
 			case 37:
 				s->colr &= 0x0f;
 				s->colr |= (ub - 30) << 4;
 				break;
 			case 39:
 				s->colr &= 0x0f;
 				s->colr |= 0x80;
 				break;
 			case 40:
 			case 41:
 			case 42:
 			case 43:
 			case 44:
 			case 45:
 			case 46:
 			case 47:
 				s->colr &= 0xf0;
 				s->colr |= ub - 40;
 				break;
 			case 49:
 				s->colr &= 0xf0;
 				s->colr |= 0x08;
 				break;
 			}
 		}
 	}
 }

 /* Write a single character to the screen at the cursor and move forward. */
 void
 screen_write_character(struct screen *s, u_char ch)
 {
 	s->grid_data[s->cy][s->cx] = ch;
 	s->grid_attr[s->cy][s->cx] = s->attr;
 	s->grid_colr[s->cy][s->cx] = s->colr;

 	s->cx++;
 	if (s->cx > screen_last_x(s)) {
 		s->cx = 0;
 		screen_cursor_down_scroll(s, 1);
 	}
 }

 /* Move cursor up and scroll if necessary. */
 void
 screen_cursor_up_scroll(struct screen *s, u_int ny)
 {
 	if (s->cy < ny) {
 		screen_scroll_down(s, ny - s->cy);
 		s->cy = 0;
 	} else
 		s->cy -= ny;
 }

 /* Move cursor down and scroll if necessary. */
 void
 screen_cursor_down_scroll(struct screen *s, u_int ny)
 {
 	if (screen_last_y(s) - s->cy < ny) {
 		screen_scroll_up(s, ny - (screen_last_y(s) - s->cy));
 		s->cy = screen_last_y(s);
 	} else
 		s->cy += ny;
 }

 /* Scroll screen up. */
 void
 screen_scroll_up(struct screen *s, u_int ny)
 {
 	if (s->ry_upper == 0 && s->ry_lower == screen_last_y(s)) {
 		screen_delete_lines(s, 0, ny);
 		return;
 	}

 	fatalx("unimplemented");
 }

 /* Scroll screen down. */
 void
 screen_scroll_down(struct screen *s, u_int ny)
 {
 	if (s->ry_upper == 0 && s->ry_lower == screen_last_y(s)) {
 		screen_insert_lines(s, 0, ny);
 		return;
 	}

 	fatalx("unimplemented");
 }

 /* Fill entire screen. */
 void
 screen_fill_screen(struct screen *s, u_char data, u_char attr, u_char colr)
 {
 	screen_fill_end_of_screen(s, 0, 0, data, attr, colr);
 }

 /* Fill single line. */
 void
 screen_fill_line(
     struct screen *s, u_int py, u_char data, u_char attr, u_char colr)
 {
 	screen_fill_end_of_line(s, 0, py, data, attr, colr);
 }

 /* Fill to end of screen. */
 void
 screen_fill_end_of_screen(
     struct screen *s, u_int px, u_int py, u_char data, u_char attr, u_char colr)
 {
 	if (py > screen_last_y(s))
 		return;

 	if (px != 0) {
 		screen_fill_end_of_line(s, px, py, data, attr, colr);
 		if (py++ > screen_last_y(s))
 			return;
 	}

 	while (py <= screen_last_y(s)) {
 		screen_fill_line(s, py, data, attr, colr);
 		py++;
 	}
 }

 /* Fill to end of line. */
 void
 screen_fill_end_of_line(
     struct screen *s, u_int px, u_int py, u_char data, u_char attr, u_char colr)
 {
 	if (px > screen_last_x(s))
 		return;
 	if (py > screen_last_y(s))
 		return;

 	memset(&s->grid_data[py][px], data, s->sx - px);
 	memset(&s->grid_attr[py][px], attr, s->sx - px);
 	memset(&s->grid_colr[py][px], colr, s->sx - px);
 }

 /* Fill to start of line. */
 void
 screen_fill_start_of_line(
     struct screen *s, u_int px, u_int py, u_char data, u_char attr, u_char colr)
 {
 	if (px > screen_last_x(s))
 		return;
 	if (py > screen_last_y(s))
 		return;

 	memset(s->grid_data[py], data, px);
 	memset(s->grid_attr[py], attr, px);
 	memset(s->grid_colr[py], colr, px);
 }

 /* Insert lines. */
 void
 screen_insert_lines(struct screen *s, u_int py, u_int ny)
 {
 	if (py > screen_last_y(s))
 		return;

 	if (py + ny > screen_last_y(s))
 		ny = screen_last_y(s) - py;
 	log_debug("inserting lines: %u,%u", py, ny);

 	screen_free_lines(s, (screen_last_y(s) - ny) + 1, screen_last_y(s));

 	if (py != screen_last_y(s))
 		screen_move_lines(s, py + ny, py, screen_last_y(s) - ny);

 	screen_fill_lines(
 	    s, py, py + ny - 1, SCREEN_DEFDATA, SCREEN_DEFATTR, SCREEN_DEFCOLR);
 }

 /* Delete lines. */
 void
 screen_delete_lines(struct screen *s, u_int py, u_int ny)
 {
 	if (py > screen_last_y(s))
 		return;

 	if (py + ny > screen_last_y(s))
 		ny = screen_last_y(s) - py;
 	log_debug("deleting lines: %u,%u", py, ny);

 	screen_free_lines(s, py, py + ny - 1);

 	if (py != screen_last_y(s))
 		screen_move_lines(s, py, py + ny, screen_last_y(s));

 	screen_make_lines(s, (screen_last_y(s) - ny) + 1, screen_last_y(s));
 	screen_fill_lines(s, (screen_last_y(s) - ny) + 1,
 	    screen_last_y(s), SCREEN_DEFDATA, SCREEN_DEFATTR, SCREEN_DEFCOLR);
 }

 /* Insert characters. */
 void
 screen_insert_characters(struct screen *s, u_int px, u_int py, u_int nx)
 {
 	u_int	lx, rx;

 	if (px > screen_last_x(s) || py > screen_last_y(s))
 		return;

 	lx = px;
 	rx = screen_offset_x(px, nx);
 	if (rx > screen_last_x(s))
 		rx = screen_last_x(s);

 	/*
 	 * Inserting a range from lx to rx, inclusive.
 	 *
 	 * - If rx is not the last x, move from lx to rx + 1.
 	 * - Clear the range from lx to rx.
 	 */
 	if (rx != screen_last_x(s)) {
 		nx = screen_range_x(rx + 1, screen_last_x(s));
 		memmove(&s->grid_data[py][rx + 1], &s->grid_data[py][lx], nx);
 		memmove(&s->grid_attr[py][rx + 1], &s->grid_attr[py][lx], nx);
 		memmove(&s->grid_colr[py][rx + 1], &s->grid_colr[py][lx], nx);
 	}
 	memset(&s->grid_data[py][lx], SCREEN_DEFDATA, screen_range_x(lx, rx));
 	memset(&s->grid_attr[py][lx], SCREEN_DEFATTR, screen_range_x(lx, rx));
 	memset(&s->grid_colr[py][lx], SCREEN_DEFCOLR, screen_range_x(lx, rx));
 }

 /* Delete characters. */
 void
 screen_delete_characters(struct screen *s, u_int px, u_int py, u_int nx)
 {
 	u_int	lx, rx;

 	if (px > screen_last_x(s) || py > screen_last_y(s))
 		return;

 	lx = px;
 	rx = screen_offset_x(px, nx);
 	if (rx > screen_last_x(s))
 		rx = screen_last_x(s);

 	/*
 	 * Deleting the range from lx to rx, inclusive.
 	 *
 	 * - If rx is not the last x, move the range from rx + 1 to lx.
 	 * - Clear the range from the last x - (rx - lx)  to the last x.
 	 */

 	if (rx != screen_last_x(s)) {
 		nx = screen_range_x(rx + 1, screen_last_x(s));
 		memmove(&s->grid_data[py][lx], &s->grid_data[py][rx + 1], nx);
 		memmove(&s->grid_attr[py][lx], &s->grid_attr[py][rx + 1], nx);
 		memmove(&s->grid_colr[py][lx], &s->grid_colr[py][rx + 1], nx);
 	}

 	/* If lx == rx, then nx = 1. */
 	nx = screen_range_x(lx, rx);
 	memset(&s->grid_data[py][s->sx - nx], SCREEN_DEFDATA, nx);
 	memset(&s->grid_attr[py][s->sx - nx], SCREEN_DEFATTR, nx);
 	memset(&s->grid_colr[py][s->sx - nx], SCREEN_DEFCOLR, nx);
 }
	/* $Id: screen.c,v 1.4 2007-08-27 08:15:39 nicm Exp $ */

	/*
	* Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
	*
	* 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 <string.h>

	#include "tmux.h"

	/*
	* Virtual screen and basic ANSI terminal emulator.
	*
	* XXX Most of this file sucks. There be memory corruption somewhere here.
	*/

	size_t screen_store_attributes(struct buffer *, u_char);
	size_t screen_store_colours(struct buffer *, u_char);
	void screen_free_lines(struct screen *, u_int, u_int);
	void screen_make_lines(struct screen *, u_int, u_int);
	void screen_move_lines(struct screen *, u_int, u_int, u_int);
	void screen_fill_lines(
	struct screen *, u_int, u_int, u_char, u_char, u_char);
	uint16_t screen_extract(u_char *);
	void screen_write_character(struct screen *, u_char);
	void screen_cursor_up_scroll(struct screen *, u_int);
	void screen_cursor_down_scroll(struct screen *, u_int);
	void screen_scroll_up(struct screen *, u_int);
	void screen_scroll_down(struct screen *, u_int);
	void screen_fill_screen(struct screen *, u_char, u_char, u_char);
	void screen_fill_line(struct screen *, u_int, u_char, u_char, u_char);
	void screen_fill_end_of_screen(
	struct screen *, u_int, u_int, u_char, u_char, u_char);
	void screen_fill_end_of_line(
	struct screen *, u_int, u_int, u_char, u_char, u_char);
	void screen_fill_start_of_line(
	struct screen *, u_int, u_int, u_char, u_char, u_char);
	void screen_insert_lines(struct screen *, u_int, u_int);
	void screen_delete_lines(struct screen *, u_int, u_int);
	void screen_insert_characters(struct screen *, u_int, u_int, u_int);
	void screen_delete_characters(struct screen *, u_int, u_int, u_int);

	#define SCREEN_DEFDATA ' '
	#define SCREEN_DEFATTR 0
	#define SCREEN_DEFCOLR 0x88

	#define screen_last_y(s) ((s)->sy - 1)
	#define screen_last_x(s) ((s)->sx - 1)

	#define screen_range_y(lx, rx) (((rx) - (lx)) + 1)
	#define screen_range_x(ux, lx) (((lx) - (ux)) + 1)

	#define screen_offset_y(py, ny) ((py) + (ny) - 1)
	#define screen_offset_x(px, nx) ((px) + (nx) - 1)

	/* Create a new screen. */
	void
	screen_create(struct screen *s, u_int sx, u_int sy)
	{
	s->sx = sx;
	s->sy = sy;
	s->cx = 0;
	s->cy = 0;

	s->ry_upper = 0;
	s->ry_lower = screen_last_y(s);

	s->attr = SCREEN_DEFATTR;
	s->colr = SCREEN_DEFCOLR;

	s->mode = MODE_CURSOR;
	*s->title = '\0';

	s->grid_data = xmalloc(sy * (sizeof *s->grid_data));
	s->grid_attr = xmalloc(sy * (sizeof *s->grid_attr));
	s->grid_colr = xmalloc(sy * (sizeof *s->grid_colr));
	screen_make_lines(s, 0, screen_last_y(s));
	screen_fill_screen(s, SCREEN_DEFDATA, 0, SCREEN_DEFCOLR);
	}

	/* Resize screen. */
	void
	screen_resize(struct screen *s, u_int sx, u_int sy)
	{
	u_int i, ox, oy, ny;

	if (sx < 1)
	sx = 1;
	if (sy < 1)
	sy = 1;

	ox = s->sx;
	oy = s->sy;
	s->sx = sx;
	s->sy = sy;

	log_debug("resizing screen (%u, %u) -> (%u, %u)", ox, oy, sx, sy);

	if (sy < oy) {
	ny = oy - sy;
	if (ny > s->cy)
	ny = s->cy;

	if (ny != 0) {
	log_debug("removing %u lines from top", ny);
	for (i = 0; i < ny; i++) {
	log_debug("freeing line %u", i);
	xfree(s->grid_data[i]);
	xfree(s->grid_attr[i]);
	xfree(s->grid_colr[i]);
	}
	memmove(s->grid_data, s->grid_data + ny,
	(oy - ny) * (sizeof *s->grid_data));
	memmove(s->grid_attr, s->grid_attr + ny,
	(oy - ny) * (sizeof *s->grid_attr));
	memmove(s->grid_colr, s->grid_colr + ny,
	(oy - ny) * (sizeof *s->grid_colr));
	s->cy -= ny;
	}
	if (ny < oy - sy) {
	log_debug(
	"removing %u lines from bottom", oy - sy - ny);
	for (i = sy; i < oy - ny; i++) {
	log_debug("freeing line %u", i);
	xfree(s->grid_data[i]);
	xfree(s->grid_attr[i]);
	xfree(s->grid_colr[i]);
	}
	if (s->cy >= sy)
	s->cy = sy - 1;
	}
	}
	if (sy != oy) {
	s->grid_data = xrealloc(s->grid_data, sy, sizeof *s->grid_data);
	s->grid_attr = xrealloc(s->grid_attr, sy, sizeof *s->grid_attr);
	s->grid_colr = xrealloc(s->grid_colr, sy, sizeof *s->grid_colr);
	}
	if (sy > oy) {
	for (i = oy; i < sy; i++) {
	log_debug("allocating line %u", i);
	s->grid_data[i] = xmalloc(sx);
	s->grid_attr[i] = xmalloc(sx);
	s->grid_colr[i] = xmalloc(sx);
	screen_fill_line(s, i,
	SCREEN_DEFDATA, SCREEN_DEFATTR, SCREEN_DEFCOLR);
	}
	sy = oy;
	}

	if (sx != ox) {
	for (i = 0; i < sy; i++) {
	log_debug("adjusting line %u to %u", i, sx);
	s->grid_data[i] = xrealloc(s->grid_data[i], sx, 1);
	s->grid_attr[i] = xrealloc(s->grid_attr[i], sx, 1);
	s->grid_colr[i] = xrealloc(s->grid_colr[i], sx, 1);
	if (sx > ox) {
	screen_fill_end_of_line(s, ox, i,
	SCREEN_DEFDATA, SCREEN_DEFATTR,
	SCREEN_DEFCOLR);
	}
	}
	if (s->cx >= sx)
	s->cx = sx - 1;
	}
	}

	/* Draw a set of lines on the screen. */
	void
	screen_draw(struct screen s, struct buffer b, u_int uy, u_int ly)
	{
	u_char attr, colr;
	size_t size;
	u_int i, j;
	uint16_t n;

	if (uy > screen_last_y(s) \|\| ly > screen_last_y(s) \|\| ly < uy)
	fatalx("bad range");

	/* XXX. This is naive and rough right now. */
	attr = 0;
	colr = SCREEN_DEFCOLR;

	input_store_zero(b, CODE_CURSOROFF);

	input_store_one(b, CODE_ATTRIBUTES, 0);

	for (j = uy; j <= ly; j++) {
	input_store_two(b, CODE_CURSORMOVE, j + 1, 1);

	for (i = 0; i <= screen_last_x(s); i++) {

	size = BUFFER_USED(b);
	input_store_one(b, CODE_ATTRIBUTES, 0);

	n = 0;
	if (s->grid_attr[j][i] != attr) {
	attr = s->grid_attr[j][i];
	n += screen_store_attributes(b, attr);
	if (attr == 0)
	colr = SCREEN_DEFCOLR;
	}
	if (s->grid_colr[j][i] != colr) {
	colr = s->grid_colr[j][i];
	n += screen_store_colours(b, colr);
	}
	if (n == 0)
	buffer_reverse_add(b, 4);
	else {
	size = BUFFER_USED(b) - size;
	memcpy(BUFFER_IN(b) - size + 2, &n, 2);
	}

	input_store8(b, s->grid_data[j][i]);
	}
	}

	size = BUFFER_USED(b);
	input_store_one(b, CODE_ATTRIBUTES, 0);
	n = screen_store_attributes(b, s->attr);
	n += screen_store_colours(b, s->colr);
	size = BUFFER_USED(b) - size;
	memcpy(BUFFER_IN(b) - size + 2, &n, 2);

	input_store_two(b, CODE_CURSORMOVE, s->cy + 1, s->cx + 1);

	if (s->mode & MODE_CURSOR)
	input_store_zero(b, CODE_CURSORON);
	}

	/* Store screen atttributes in buffer. */
	size_t
	screen_store_attributes(struct buffer *b, u_char attr)
	{
	size_t n;

	if (attr == 0) {
	input_store16(b, 0);
	return (1);
	}

	n = 0;
	if (attr & ATTR_BRIGHT) {
	input_store16(b, 1);
	n++;
	}
	if (attr & ATTR_DIM) {
	input_store16(b, 2);
	n++;
	}
	if (attr & ATTR_ITALICS) {
	input_store16(b, 3);
	n++;
	}
	if (attr & ATTR_UNDERSCORE) {
	input_store16(b, 4);
	n++;
	}
	if (attr & ATTR_BLINK) {
	input_store16(b, 5);
	n++;
	}
	if (attr & ATTR_REVERSE) {
	input_store16(b, 7);
	n++;
	}
	if (attr & ATTR_HIDDEN) {
	input_store16(b, 8);
	n++;
	}
	return (n);
	}

	/* Store screen colours in buffer. */
	size_t
	screen_store_colours(struct buffer *b, u_char colr)
	{
	uint16_t v;

	v = colr >> 4;
	if (v == 8)
	v = 9;
	input_store16(b, 30 + v);
	v = colr & 0xf;
	if (v == 8)
	v = 9;
	input_store16(b, 40 + v);

	return (2);
	}

	/* Make a range of lines. */
	void
	screen_make_lines(struct screen *s, u_int uy, u_int ly)
	{
	u_int i;

	log_debug("making lines %u:%u", uy, ly);

	if (uy > screen_last_y(s) \|\| ly > screen_last_y(s) \|\| ly < uy)
	fatalx("bad range");

	for (i = uy; i <= ly; i++) {
	s->grid_data[i] = xmalloc(s->sx);
	s->grid_attr[i] = xmalloc(s->sx);
	s->grid_colr[i] = xmalloc(s->sx);
	}
	}

	/* Free a range of lines. */
	void
	screen_free_lines(struct screen *s, u_int uy, u_int ly)
	{
	u_int i;

	log_debug("freeing lines %u:%u", uy, ly);

	if (uy > screen_last_y(s) \|\| ly > screen_last_y(s) \|\| ly < uy)
	fatalx("bad range");

	for (i = uy; i <= ly; i++) {
	xfree(s->grid_data[i]);
	s->grid_data[i] = (u_char *) 0xffffffff;
	xfree(s->grid_attr[i]);
	s->grid_attr[i] = (u_char *) 0xffffffff;
	xfree(s->grid_colr[i]);
	s->grid_colr[i] = (u_char *) 0xffffffff;
	}
	}

	/* Move a range of lines. */
	void
	screen_move_lines(struct screen *s, u_int dy, u_int uy, u_int ly)
	{
	u_int ny;

	log_debug("moving lines %u:%u to %u", uy, ly, dy);

	ny = (ly - uy) + 1;

	if (uy > screen_last_y(s) \|\| ly > screen_last_y(s) \|\| ly < uy)
	fatalx("bad range");
	if (dy > screen_last_y(s))
	fatalx("bad destination");
	if (dy + ny - 1 > screen_last_y(s))
	fatalx("bad size");
	if (dy == uy)
	fatalx("null move");

	memmove(
	&s->grid_data[dy], &s->grid_data[uy], ny * (sizeof *s->grid_data));
	memmove(
	&s->grid_attr[dy], &s->grid_attr[uy], ny * (sizeof *s->grid_attr));
	memmove(
	&s->grid_colr[dy], &s->grid_colr[uy], ny * (sizeof *s->grid_colr));
	}

	/* Fill a range of lines. */
	void
	screen_fill_lines(
	struct screen *s, u_int uy, u_int ly, u_char data, u_char attr, u_char colr)
	{
	u_int i;

	log_debug("filling lines %u:%u", uy, ly);

	if (uy > screen_last_y(s) \|\| ly > screen_last_y(s) \|\| ly < uy)
	fatalx("bad range");

	for (i = uy; i <= ly; i++)
	screen_fill_line(s, i, data, attr, colr);
	}

	/* Update screen with character. */
	void
	screen_character(struct screen *s, u_char ch)
	{
	switch (ch) {
	case '\n': /* LF */
	screen_cursor_down_scroll(s, 1);
	break;
	case '\r': /* CR */
	s->cx = 0;
	break;
	case '\010': /* BS */
	if (s->cx > 0)
	s->cx--;
	break;
	default:
	if (ch < ' ')
	fatalx("bad control");
	screen_write_character(s, ch);
	break;
	}
	}

	/* Extract 16-bit value from pointer. */
	uint16_t
	screen_extract(u_char *ptr)
	{
	uint16_t n;

	memcpy(&n, ptr, sizeof n);
	return (n);
	}

	/* Update screen with escape sequence. */
	void
	screen_sequence(struct screen s, u_char ptr)
	{
	uint16_t ua, ub;

	ptr++;
	log_debug("processing code %hhu", *ptr);
	switch (*ptr++) {
	case CODE_CURSORUP:
	ua = screen_extract(ptr);
	if (ua > s->cy)
	ua = s->cy;
	s->cy -= ua;
	break;
	case CODE_CURSORDOWN:
	ua = screen_extract(ptr);
	if (s->cy + ua > screen_last_y(s))
	ua = screen_last_y(s) - s->cy;
	s->cy += ua;
	break;
	case CODE_CURSORLEFT:
	ua = screen_extract(ptr);
	if (ua > s->cx)
	ua = s->cx;
	s->cx -= ua;
	break;
	case CODE_CURSORRIGHT:
	ua = screen_extract(ptr);
	if (s->cx + ua > screen_last_x(s))
	ua = screen_last_x(s) - s->cx;
	s->cx += ua;
	break;
	case CODE_CURSORMOVE:
	ua = screen_extract(ptr);
	ptr += 2;
	ub = screen_extract(ptr);
	if (ub > s->sx)
	ub = s->sx;
	s->cx = ub - 1;
	if (ua > s->sy)
	ua = s->sy;
	s->cy = ua - 1;
	break;
	case CODE_CLEARENDOFSCREEN:
	screen_fill_end_of_screen(
	s, s->cx, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
	break;
	case CODE_CLEARSCREEN:
	screen_fill_screen(s, SCREEN_DEFDATA, s->attr, s->colr);
	break;
	case CODE_CLEARENDOFLINE:
	screen_fill_end_of_line(
	s, s->cx, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
	break;
	case CODE_CLEARSTARTOFLINE:
	screen_fill_start_of_line(
	s, s->cx, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
	break;
	case CODE_CLEARLINE:
	screen_fill_line(s, s->cy, SCREEN_DEFDATA, s->attr, s->colr);
	break;
	case CODE_INSERTLINE:
	ua = screen_extract(ptr);
	screen_insert_lines(s, s->cy, ua);
	break;
	case CODE_DELETELINE:
	ua = screen_extract(ptr);
	screen_delete_lines(s, s->cy, ua);
	break;
	case CODE_INSERTCHARACTER:
	ua = screen_extract(ptr);
	screen_insert_characters(s, s->cx, s->cy, ua);
	break;
	case CODE_DELETECHARACTER:
	ua = screen_extract(ptr);
	screen_delete_characters(s, s->cx, s->cy, ua);
	break;
	case CODE_CURSORON:
	s->mode \|= MODE_CURSOR;
	break;
	case CODE_CURSOROFF:
	s->mode &= ~MODE_CURSOR;
	break;
	case CODE_CURSORDOWNSCROLL:
	ua = screen_extract(ptr);
	screen_cursor_down_scroll(s, ua);
	break;
	case CODE_CURSORUPSCROLL:
	ua = screen_extract(ptr);
	screen_cursor_up_scroll(s, ua);
	break;
	case CODE_SCROLLREGION:
	ua = screen_extract(ptr);
	ptr += 2;
	ub = screen_extract(ptr);
	if (ua > s->sy)
	ua = s->sy;
	s->ry_upper = ua - 1;
	if (ub > s->sy)
	ub = s->sy;
	s->ry_lower = ub - 1;
	break;
	case CODE_INSERTOFF:
	s->mode &= ~MODE_INSERT;
	break;
	case CODE_INSERTON:
	s->mode \|= MODE_INSERT;
	break;
	case CODE_KCURSOROFF:
	s->mode &= ~MODE_KCURSOR;
	break;
	case CODE_KCURSORON:
	s->mode \|= MODE_KCURSOR;
	break;
	case CODE_KKEYPADOFF:
	s->mode &= ~MODE_KKEYPAD;
	break;
	case CODE_KKEYPADON:
	s->mode \|= MODE_KKEYPAD;
	break;
	case CODE_TITLE:
	ua = screen_extract(ptr);
	ptr += 2;
	log_debug("new title: %u:%.*s", ua, (int) ua, ptr);
	if (ua > MAXTITLELEN - 1)
	ua = MAXTITLELEN - 1;
	memcpy(s->title, ptr, ua);
	s->title[ua] = '\0';
	break;
	case CODE_ATTRIBUTES:
	ua = screen_extract(ptr);
	if (ua == 0) {
	s->attr = 0;
	s->colr = SCREEN_DEFCOLR;
	break;
	}

	while (ua-- > 0) {
	ptr += 2;
	ub = screen_extract(ptr);
	switch (ub) {
	case 0:
	case 10:
	s->attr = 0;
	s->colr = SCREEN_DEFCOLR;
	break;
	case 1:
	s->attr \|= ATTR_BRIGHT;
	break;
	case 2:
	s->attr \|= ATTR_DIM;
	break;
	case 3:
	s->attr \|= ATTR_ITALICS;
	break;
	case 4:
	s->attr \|= ATTR_UNDERSCORE;
	break;
	case 5:
	s->attr \|= ATTR_BLINK;
	break;
	case 7:
	s->attr \|= ATTR_REVERSE;
	break;
	case 8:
	s->attr \|= ATTR_HIDDEN;
	break;
	case 23:
	s->attr &= ~ATTR_ITALICS;
	break;
	case 24:
	s->attr &= ~ATTR_UNDERSCORE;
	break;
	case 30:
	case 31:
	case 32:
	case 33:
	case 34:
	case 35:
	case 36:
	case 37:
	s->colr &= 0x0f;
	s->colr \|= (ub - 30) << 4;
	break;
	case 39:
	s->colr &= 0x0f;
	s->colr \|= 0x80;
	break;
	case 40:
	case 41:
	case 42:
	case 43:
	case 44:
	case 45:
	case 46:
	case 47:
	s->colr &= 0xf0;
	s->colr \|= ub - 40;
	break;
	case 49:
	s->colr &= 0xf0;
	s->colr \|= 0x08;
	break;
	}
	}
	}
	}

	/* Write a single character to the screen at the cursor and move forward. */
	void
	screen_write_character(struct screen *s, u_char ch)
	{
	s->grid_data[s->cy][s->cx] = ch;
	s->grid_attr[s->cy][s->cx] = s->attr;
	s->grid_colr[s->cy][s->cx] = s->colr;

	s->cx++;
	if (s->cx > screen_last_x(s)) {
	s->cx = 0;
	screen_cursor_down_scroll(s, 1);
	}
	}

	/* Move cursor up and scroll if necessary. */
	void
	screen_cursor_up_scroll(struct screen *s, u_int ny)
	{
	if (s->cy < ny) {
	screen_scroll_down(s, ny - s->cy);
	s->cy = 0;
	} else
	s->cy -= ny;
	}

	/* Move cursor down and scroll if necessary. */
	void
	screen_cursor_down_scroll(struct screen *s, u_int ny)
	{
	if (screen_last_y(s) - s->cy < ny) {
	screen_scroll_up(s, ny - (screen_last_y(s) - s->cy));
	s->cy = screen_last_y(s);
	} else
	s->cy += ny;
	}

	/* Scroll screen up. */
	void
	screen_scroll_up(struct screen *s, u_int ny)
	{
	if (s->ry_upper == 0 && s->ry_lower == screen_last_y(s)) {
	screen_delete_lines(s, 0, ny);
	return;
	}

	fatalx("unimplemented");
	}

	/* Scroll screen down. */
	void
	screen_scroll_down(struct screen *s, u_int ny)
	{
	if (s->ry_upper == 0 && s->ry_lower == screen_last_y(s)) {
	screen_insert_lines(s, 0, ny);
	return;
	}

	fatalx("unimplemented");
	}

	/* Fill entire screen. */
	void
	screen_fill_screen(struct screen *s, u_char data, u_char attr, u_char colr)
	{
	screen_fill_end_of_screen(s, 0, 0, data, attr, colr);
	}

	/* Fill single line. */
	void
	screen_fill_line(
	struct screen *s, u_int py, u_char data, u_char attr, u_char colr)
	{
	screen_fill_end_of_line(s, 0, py, data, attr, colr);
	}

	/* Fill to end of screen. */
	void
	screen_fill_end_of_screen(
	struct screen *s, u_int px, u_int py, u_char data, u_char attr, u_char colr)
	{
	if (py > screen_last_y(s))
	return;

	if (px != 0) {
	screen_fill_end_of_line(s, px, py, data, attr, colr);
	if (py++ > screen_last_y(s))
	return;
	}

	while (py <= screen_last_y(s)) {
	screen_fill_line(s, py, data, attr, colr);
	py++;
	}
	}

	/* Fill to end of line. */
	void
	screen_fill_end_of_line(
	struct screen *s, u_int px, u_int py, u_char data, u_char attr, u_char colr)
	{
	if (px > screen_last_x(s))
	return;
	if (py > screen_last_y(s))
	return;

	memset(&s->grid_data[py][px], data, s->sx - px);
	memset(&s->grid_attr[py][px], attr, s->sx - px);
	memset(&s->grid_colr[py][px], colr, s->sx - px);
	}

	/* Fill to start of line. */
	void
	screen_fill_start_of_line(
	struct screen *s, u_int px, u_int py, u_char data, u_char attr, u_char colr)
	{
	if (px > screen_last_x(s))
	return;
	if (py > screen_last_y(s))
	return;

	memset(s->grid_data[py], data, px);
	memset(s->grid_attr[py], attr, px);
	memset(s->grid_colr[py], colr, px);
	}

	/* Insert lines. */
	void
	screen_insert_lines(struct screen *s, u_int py, u_int ny)
	{
	if (py > screen_last_y(s))
	return;

	if (py + ny > screen_last_y(s))
	ny = screen_last_y(s) - py;
	log_debug("inserting lines: %u,%u", py, ny);

	screen_free_lines(s, (screen_last_y(s) - ny) + 1, screen_last_y(s));

	if (py != screen_last_y(s))
	screen_move_lines(s, py + ny, py, screen_last_y(s) - ny);

	screen_fill_lines(
	s, py, py + ny - 1, SCREEN_DEFDATA, SCREEN_DEFATTR, SCREEN_DEFCOLR);
	}

	/* Delete lines. */
	void
	screen_delete_lines(struct screen *s, u_int py, u_int ny)
	{
	if (py > screen_last_y(s))
	return;

	if (py + ny > screen_last_y(s))
	ny = screen_last_y(s) - py;
	log_debug("deleting lines: %u,%u", py, ny);

	screen_free_lines(s, py, py + ny - 1);

	if (py != screen_last_y(s))
	screen_move_lines(s, py, py + ny, screen_last_y(s));

	screen_make_lines(s, (screen_last_y(s) - ny) + 1, screen_last_y(s));
	screen_fill_lines(s, (screen_last_y(s) - ny) + 1,
	screen_last_y(s), SCREEN_DEFDATA, SCREEN_DEFATTR, SCREEN_DEFCOLR);
	}

	/* Insert characters. */
	void
	screen_insert_characters(struct screen *s, u_int px, u_int py, u_int nx)
	{
	u_int lx, rx;

	if (px > screen_last_x(s) \|\| py > screen_last_y(s))
	return;

	lx = px;
	rx = screen_offset_x(px, nx);
	if (rx > screen_last_x(s))
	rx = screen_last_x(s);

	/*
	* Inserting a range from lx to rx, inclusive.
	*
	* - If rx is not the last x, move from lx to rx + 1.
	* - Clear the range from lx to rx.
	*/
	if (rx != screen_last_x(s)) {
	nx = screen_range_x(rx + 1, screen_last_x(s));
	memmove(&s->grid_data[py][rx + 1], &s->grid_data[py][lx], nx);
	memmove(&s->grid_attr[py][rx + 1], &s->grid_attr[py][lx], nx);
	memmove(&s->grid_colr[py][rx + 1], &s->grid_colr[py][lx], nx);
	}
	memset(&s->grid_data[py][lx], SCREEN_DEFDATA, screen_range_x(lx, rx));
	memset(&s->grid_attr[py][lx], SCREEN_DEFATTR, screen_range_x(lx, rx));
	memset(&s->grid_colr[py][lx], SCREEN_DEFCOLR, screen_range_x(lx, rx));
	}

	/* Delete characters. */
	void
	screen_delete_characters(struct screen *s, u_int px, u_int py, u_int nx)
	{
	u_int lx, rx;

	if (px > screen_last_x(s) \|\| py > screen_last_y(s))
	return;

	lx = px;
	rx = screen_offset_x(px, nx);
	if (rx > screen_last_x(s))
	rx = screen_last_x(s);

	/*
	* Deleting the range from lx to rx, inclusive.
	*
	* - If rx is not the last x, move the range from rx + 1 to lx.
	* - Clear the range from the last x - (rx - lx) to the last x.
	*/

	if (rx != screen_last_x(s)) {
	nx = screen_range_x(rx + 1, screen_last_x(s));
	memmove(&s->grid_data[py][lx], &s->grid_data[py][rx + 1], nx);
	memmove(&s->grid_attr[py][lx], &s->grid_attr[py][rx + 1], nx);
	memmove(&s->grid_colr[py][lx], &s->grid_colr[py][rx + 1], nx);
	}

	/* If lx == rx, then nx = 1. */
	nx = screen_range_x(lx, rx);
	memset(&s->grid_data[py][s->sx - nx], SCREEN_DEFDATA, nx);
	memset(&s->grid_attr[py][s->sx - nx], SCREEN_DEFATTR, nx);
	memset(&s->grid_colr[py][s->sx - nx], SCREEN_DEFCOLR, nx);
	}