grid.c - tmux - Rivoreo Source Code Repositories

 /* $Id: grid.c,v 1.14 2009-03-28 20:17:29 nicm Exp $ */

 /*
  * Copyright (c) 2008 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"

 /*
  * Grid data. This is the basic data structure that represents what is shown on
  * screen.
  *
  * A grid is a grid of cells (struct grid_cell). Lines are not allocated until
  * cells in that line are written to. The grid is split into history and
  * viewable data with the history starting at row (line) 0 and extending to
  * (hsize - 1); from hsize to hsize + (sy - 1) is the viewable data. All
  * functions in this file work on absolute coordinates, grid-view.c has
  * functions which work on the screen data.
  */

 /* Default grid cell data. */
 const struct grid_cell grid_default_cell = { 0, 0, 8, 8, ' ' };

 #define grid_put_cell(gd, px, py, gc) do {			\
 	memcpy(&gd->data[py][px], gc, sizeof gd->data[py][px]);	\
 } while (0)
 #define grid_put_utf8(gd, px, py, gc) do {			\
 	memcpy(&gd->udata[py][px], gc, sizeof gd->udata[py][px]); \
 } while (0)

 int	grid_check_x(struct grid *, u_int);
 int	grid_check_y(struct grid *, u_int);

 #ifdef DEBUG
 int
 grid_check_x(struct grid *gd, u_int px)
 {
 	if ((px) >= (gd)->sx)
 		log_fatalx("x out of range: %u", px);
 	return (0);
 }

 int
 grid_check_y(struct grid *gd, u_int py)
 {
 	if ((py) >= (gd)->hsize + (gd)->sy)
 		log_fatalx("y out of range: %u", py);
 	return (0);
 }
 #else
 int
 grid_check_x(struct grid *gd, u_int px)
 {
 	if ((px) >= (gd)->sx) {
 		log_debug("x out of range: %u", px);
 		return (-1);
 	}
 	return (0);
 }

 int
 grid_check_y(struct grid *gd, u_int py)
 {
 	if ((py) >= (gd)->hsize + (gd)->sy) {
 		log_debug("y out of range: %u", py);
 		return (-1);
 	}
 	return (0);
 }
 #endif

 /* Create a new grid. */
 struct grid *
 grid_create(u_int sx, u_int sy, u_int hlimit)
 {
 	struct grid	*gd;

 	gd = xmalloc(sizeof *gd);
 	gd->sx = sx;
 	gd->sy = sy;

 	gd->hsize = 0;
 	gd->hlimit = hlimit;

 	gd->size = xcalloc(gd->sy, sizeof *gd->size);
 	gd->data = xcalloc(gd->sy, sizeof *gd->data);

 	gd->usize = xcalloc(gd->sy, sizeof *gd->usize);
 	gd->udata = xcalloc(gd->sy, sizeof *gd->udata);

 	return (gd);
 }

 /* Destroy grid. */
 void
 grid_destroy(struct grid *gd)
 {
 	u_int	yy;

 	for (yy = 0; yy < gd->hsize + gd->sy; yy++) {
 		if (gd->udata[yy] != NULL)
 			xfree(gd->udata[yy]);
 		if (gd->data[yy] != NULL)
 			xfree(gd->data[yy]);
 	}

 	if (gd->udata != NULL)
 		xfree(gd->udata);
 	if (gd->usize != NULL)
 		xfree(gd->usize);

 	if (gd->data != NULL)
 		xfree(gd->data);
 	if (gd->size != NULL)
 		xfree(gd->size);

 	xfree(gd);
 }

 /* Compare grids. */
 int
 grid_compare(struct grid *ga, struct grid *gb)
 {
 	struct grid_cell	*gca, *gcb;
 	u_int			 xx, yy;

 	if (ga->sx != gb->sx || ga->sy != ga->sy)
 		return (1);

 	for (yy = 0; yy < ga->sy; yy++) {
 		if (ga->size[yy] != gb->size[yy])
 			return (1);
 		for (xx = 0; xx < ga->sx; xx++) {
 			gca = &ga->data[yy][xx];
 			gcb = &gb->data[yy][xx];
 			if (memcmp(gca, gcb, sizeof (struct grid_cell)) != 0)
 				return (1);
 			/* XXX */
 		}
 	}

 	return (0);
 }

 /* Scroll a line into the history. */
 void
 grid_scroll_line(struct grid *gd)
 {
 	u_int	yy;

  	GRID_DEBUG(gd, "");

 	if (gd->hsize >= gd->hlimit - 1) {
 		/* If the limit is hit, free the bottom 10% and shift up. */
 		yy = gd->hlimit / 10;
 		if (yy < 1)
 			yy = 1;

 		grid_move_lines(gd, 0, yy, gd->hsize + gd->sy - yy);
 		gd->hsize -= yy;
 	}

 	yy = gd->hsize + gd->sy;

 	gd->size = xrealloc(gd->size, yy + 1, sizeof *gd->size);
 	gd->size[yy] = 0;
 	gd->data = xrealloc(gd->data, yy + 1, sizeof *gd->data);
 	gd->data[yy] = NULL;

 	gd->usize = xrealloc(gd->usize, yy + 1, sizeof *gd->usize);
 	gd->usize[yy] = 0;
 	gd->udata = xrealloc(gd->udata, yy + 1, sizeof *gd->udata);
 	gd->udata[yy] = NULL;

 	gd->hsize++;
 }

 /* Reduce line to fit to cell. */
 void
 grid_reduce_line(struct grid *gd, u_int py, u_int sx)
 {
 	if (sx < gd->size[py]) {
 		gd->data[py] = xrealloc(gd->data[py], sx, sizeof **gd->data);
 		gd->size[py] = sx;
 	}
 	if (sx < gd->usize[py]) {
 		gd->udata[py] = xrealloc(gd->udata[py], sx, sizeof **gd->udata);
 		gd->usize[py] = sx;
 	}
 }

 /* Expand line to fit to cell. */
 void
 grid_expand_line(struct grid *gd, u_int py, u_int sx)
 {
 	u_int	xx;

 	if (sx <= gd->size[py])
 		return;

 	gd->data[py] = xrealloc(gd->data[py], sx, sizeof **gd->data);
 	for (xx = gd->size[py]; xx < sx; xx++)
 		grid_put_cell(gd, xx, py, &grid_default_cell);
 	gd->size[py] = sx;
 }

 /* Expand line to fit to cell for UTF-8. */
 void
 grid_expand_line_utf8(struct grid *gd, u_int py, u_int sx)
 {
 	if (sx <= gd->usize[py])
 		return;

 	gd->udata[py] = xrealloc(gd->udata[py], sx, sizeof **gd->udata);
 	gd->usize[py] = sx;
 }

 /* Get cell for reading. */
 const struct grid_cell *
 grid_peek_cell(struct grid *gd, u_int px, u_int py)
 {
 	if (grid_check_x(gd, px) != 0)
 		return (&grid_default_cell);
 	if (grid_check_y(gd, py) != 0)
 		return (&grid_default_cell);

 	if (px >= gd->size[py])
 		return (&grid_default_cell);
 	return (&gd->data[py][px]);
 }

 /* Get cell at relative position (for writing). */
 struct grid_cell *
 grid_get_cell(struct grid *gd, u_int px, u_int py)
 {
 	if (grid_check_x(gd, px) != 0)
 		return (NULL);
 	if (grid_check_y(gd, py) != 0)
 		return (NULL);

 	grid_expand_line(gd, py, px + 1);
 	return (&gd->data[py][px]);
 }

 /* Set cell at relative position. */
 void
 grid_set_cell(
     struct grid *gd, u_int px, u_int py, const struct grid_cell *gc)
 {
 	if (grid_check_x(gd, px) != 0)
 		return;
 	if (grid_check_y(gd, py) != 0)
 		return;

 	grid_expand_line(gd, py, px + 1);
 	grid_put_cell(gd, px, py, gc);
 }

 /* Get UTF-8 for reading. */
 const struct grid_utf8 *
 grid_peek_utf8(struct grid *gd, u_int px, u_int py)
 {
 	if (grid_check_x(gd, px) != 0)
 		return (NULL);
 	if (grid_check_y(gd, py) != 0)
 		return (NULL);

 	if (px >= gd->usize[py])
 		return (NULL);
 	return (&gd->udata[py][px]);
 }

 /* Get utf8 at relative position (for writing). */
 struct grid_utf8 *
 grid_get_utf8(struct grid *gd, u_int px, u_int py)
 {
 	if (grid_check_x(gd, px) != 0)
 		return (NULL);
 	if (grid_check_y(gd, py) != 0)
 		return (NULL);

 	grid_expand_line_utf8(gd, py, px + 1);
 	return (&gd->udata[py][px]);
 }

 /* Set utf8 at relative position. */
 void
 grid_set_utf8(
     struct grid *gd, u_int px, u_int py, const struct grid_utf8 *gc)
 {
 	if (grid_check_x(gd, px) != 0)
 		return;
 	if (grid_check_y(gd, py) != 0)
 		return;

 	grid_expand_line_utf8(gd, py, px + 1);
 	grid_put_utf8(gd, px, py, gc);
 }

 /*
  * Clear area. Note this is different from a fill as it just omits unallocated
  * cells.
  */
 void
 grid_clear(struct grid *gd, u_int px, u_int py, u_int nx, u_int ny)
 {
 	u_int	xx, yy;

  	GRID_DEBUG(gd, "px=%u, py=%u, nx=%u, ny=%u", px, py, nx, ny);

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

 	if (px == 0 && nx == gd->sx) {
 		grid_clear_lines(gd, py, ny);
 		return;
 	}

 	if (grid_check_x(gd, px) != 0)
 		return;
 	if (grid_check_x(gd, px + nx - 1) != 0)
 		return;
 	if (grid_check_y(gd, py) != 0)
 		return;
 	if (grid_check_y(gd, py + ny - 1) != 0)
 		return;

 	for (yy = py; yy < py + ny; yy++) {
 		for (xx = px; xx < px + nx; xx++) {
 			if (xx >= gd->size[yy])
 				break;
 			grid_put_cell(gd, xx, yy, &grid_default_cell);
 		}
 	}
 }

 /* Clear lines. This just frees and truncates the lines. */
 void
 grid_clear_lines(struct grid *gd, u_int py, u_int ny)
 {
 	u_int	yy;

  	GRID_DEBUG(gd, "py=%u, ny=%u", py, ny);

 	if (ny == 0)
 		return;

 	if (grid_check_y(gd, py) != 0)
 		return;
 	if (grid_check_y(gd, py + ny - 1) != 0)
 		return;

 	for (yy = py; yy < py + ny; yy++) {
 		if (gd->data[yy] != NULL) {
 			xfree(gd->data[yy]);
 			gd->data[yy] = NULL;
 			gd->size[yy] = 0;
 		}
 		if (gd->udata[yy] != NULL) {
 			xfree(gd->udata[yy]);
 			gd->udata[yy] = NULL;
 			gd->usize[yy] = 0;
 		}
 	}
 }

 /* Move a group of lines. */
 void
 grid_move_lines(struct grid *gd, u_int dy, u_int py, u_int ny)
 {
 	u_int	yy;

  	GRID_DEBUG(gd, "dy=%u, py=%u, ny=%u", dy, py, ny);

 	if (ny == 0 || py == dy)
 		return;

 	if (grid_check_y(gd, py) != 0)
 		return;
 	if (grid_check_y(gd, py + ny - 1) != 0)
 		return;
 	if (grid_check_y(gd, dy) != 0)
 		return;
 	if (grid_check_y(gd, dy + ny - 1) != 0)
 		return;

 	/* Free any lines which are being replaced. */
 	for (yy = dy; yy < dy + ny; yy++) {
 		if (yy >= py && yy < py + ny)
 			continue;
 		grid_clear_lines(gd, yy, 1);
 	}

 	memmove(&gd->data[dy], &gd->data[py], ny * (sizeof *gd->data));
 	memmove(&gd->size[dy], &gd->size[py], ny * (sizeof *gd->size));

 	memmove(&gd->udata[dy], &gd->udata[py], ny * (sizeof *gd->udata));
 	memmove(&gd->usize[dy], &gd->usize[py], ny * (sizeof *gd->usize));

 	/* Wipe any lines that have been moved (without freeing them). */
 	for (yy = py; yy < py + ny; yy++) {
 		if (yy >= dy && yy < dy + ny)
 			continue;
 		gd->data[yy] = NULL;
 		gd->size[yy] = 0;
 		gd->udata[yy] = NULL;
 		gd->usize[yy] = 0;
 	}
 }

 /* Clear a group of cells. */
 void
 grid_clear_cells(struct grid *gd, u_int px, u_int py, u_int nx)
 {
 	u_int	xx;

  	GRID_DEBUG(gd, "px=%u, py=%u, nx=%u", px, py, nx);

 	if (nx == 0)
 		return;

 	if (grid_check_x(gd, px) != 0)
 		return;
 	if (grid_check_x(gd, px + nx - 1) != 0)
 		return;
 	if (grid_check_y(gd, py) != 0)
 		return;

 	for (xx = px; xx < px + nx; xx++) {
 		if (xx >= gd->size[py])
 			break;
 		grid_put_cell(gd, xx, py, &grid_default_cell);
 	}
 }

 /* Move a group of cells. */
 void
 grid_move_cells(struct grid *gd, u_int dx, u_int px, u_int py, u_int nx)
 {
 	u_int	xx;

  	GRID_DEBUG(gd, "dx=%u, px=%u, py=%u, nx=%u", dx, px, py, nx);

 	if (nx == 0 || px == dx)
 		return;

 	if (grid_check_x(gd, px) != 0)
 		return;
 	if (grid_check_x(gd, px + nx - 1) != 0)
 		return;
 	if (grid_check_x(gd, dx + nx - 1) != 0)
 		return;
 	if (grid_check_y(gd, py) != 0)
 		return;

 	grid_expand_line(gd, py, px + nx);
 	grid_expand_line(gd, py, dx + nx);
 	memmove(&gd->data[py][dx], &gd->data[py][px], nx * (sizeof **gd->data));

 	if (gd->udata[py] != NULL) {
 		grid_expand_line_utf8(gd, py, px + nx);
 		grid_expand_line_utf8(gd, py, dx + nx);
 		memmove(&gd->udata[py][dx],
 		    &gd->udata[py][px], nx * (sizeof **gd->udata));
 	}

 	/* Wipe any cells that have been moved. */
 	for (xx = px; xx < px + nx; xx++) {
 		if (xx >= dx && xx < dx + nx)
 			continue;
 		grid_put_cell(gd, xx, py, &grid_default_cell);
 	}
 }
	/* $Id: grid.c,v 1.14 2009-03-28 20:17:29 nicm Exp $ */

	/*
	* Copyright (c) 2008 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"

	/*
	* Grid data. This is the basic data structure that represents what is shown on
	* screen.
	*
	* A grid is a grid of cells (struct grid_cell). Lines are not allocated until
	* cells in that line are written to. The grid is split into history and
	* viewable data with the history starting at row (line) 0 and extending to
	* (hsize - 1); from hsize to hsize + (sy - 1) is the viewable data. All
	* functions in this file work on absolute coordinates, grid-view.c has
	* functions which work on the screen data.
	*/

	/* Default grid cell data. */
	const struct grid_cell grid_default_cell = { 0, 0, 8, 8, ' ' };

	#define grid_put_cell(gd, px, py, gc) do { \
	memcpy(&gd->data[py][px], gc, sizeof gd->data[py][px]); \
	} while (0)
	#define grid_put_utf8(gd, px, py, gc) do { \
	memcpy(&gd->udata[py][px], gc, sizeof gd->udata[py][px]); \
	} while (0)

	int grid_check_x(struct grid *, u_int);
	int grid_check_y(struct grid *, u_int);

	#ifdef DEBUG
	int
	grid_check_x(struct grid *gd, u_int px)
	{
	if ((px) >= (gd)->sx)
	log_fatalx("x out of range: %u", px);
	return (0);
	}

	int
	grid_check_y(struct grid *gd, u_int py)
	{
	if ((py) >= (gd)->hsize + (gd)->sy)
	log_fatalx("y out of range: %u", py);
	return (0);
	}
	#else
	int
	grid_check_x(struct grid *gd, u_int px)
	{
	if ((px) >= (gd)->sx) {
	log_debug("x out of range: %u", px);
	return (-1);
	}
	return (0);
	}

	int
	grid_check_y(struct grid *gd, u_int py)
	{
	if ((py) >= (gd)->hsize + (gd)->sy) {
	log_debug("y out of range: %u", py);
	return (-1);
	}
	return (0);
	}
	#endif

	/* Create a new grid. */
	struct grid *
	grid_create(u_int sx, u_int sy, u_int hlimit)
	{
	struct grid *gd;

	gd = xmalloc(sizeof *gd);
	gd->sx = sx;
	gd->sy = sy;

	gd->hsize = 0;
	gd->hlimit = hlimit;

	gd->size = xcalloc(gd->sy, sizeof *gd->size);
	gd->data = xcalloc(gd->sy, sizeof *gd->data);

	gd->usize = xcalloc(gd->sy, sizeof *gd->usize);
	gd->udata = xcalloc(gd->sy, sizeof *gd->udata);

	return (gd);
	}

	/* Destroy grid. */
	void
	grid_destroy(struct grid *gd)
	{
	u_int yy;

	for (yy = 0; yy < gd->hsize + gd->sy; yy++) {
	if (gd->udata[yy] != NULL)
	xfree(gd->udata[yy]);
	if (gd->data[yy] != NULL)
	xfree(gd->data[yy]);
	}

	if (gd->udata != NULL)
	xfree(gd->udata);
	if (gd->usize != NULL)
	xfree(gd->usize);

	if (gd->data != NULL)
	xfree(gd->data);
	if (gd->size != NULL)
	xfree(gd->size);

	xfree(gd);
	}

	/* Compare grids. */
	int
	grid_compare(struct grid ga, struct grid gb)
	{
	struct grid_cell gca, gcb;
	u_int xx, yy;

	if (ga->sx != gb->sx \|\| ga->sy != ga->sy)
	return (1);

	for (yy = 0; yy < ga->sy; yy++) {
	if (ga->size[yy] != gb->size[yy])
	return (1);
	for (xx = 0; xx < ga->sx; xx++) {
	gca = &ga->data[yy][xx];
	gcb = &gb->data[yy][xx];
	if (memcmp(gca, gcb, sizeof (struct grid_cell)) != 0)
	return (1);
	/* XXX */
	}
	}

	return (0);
	}

	/* Scroll a line into the history. */
	void
	grid_scroll_line(struct grid *gd)
	{
	u_int yy;

	GRID_DEBUG(gd, "");

	if (gd->hsize >= gd->hlimit - 1) {
	/* If the limit is hit, free the bottom 10% and shift up. */
	yy = gd->hlimit / 10;
	if (yy < 1)
	yy = 1;

	grid_move_lines(gd, 0, yy, gd->hsize + gd->sy - yy);
	gd->hsize -= yy;
	}

	yy = gd->hsize + gd->sy;

	gd->size = xrealloc(gd->size, yy + 1, sizeof *gd->size);
	gd->size[yy] = 0;
	gd->data = xrealloc(gd->data, yy + 1, sizeof *gd->data);
	gd->data[yy] = NULL;

	gd->usize = xrealloc(gd->usize, yy + 1, sizeof *gd->usize);
	gd->usize[yy] = 0;
	gd->udata = xrealloc(gd->udata, yy + 1, sizeof *gd->udata);
	gd->udata[yy] = NULL;

	gd->hsize++;
	}

	/* Reduce line to fit to cell. */
	void
	grid_reduce_line(struct grid *gd, u_int py, u_int sx)
	{
	if (sx < gd->size[py]) {
	gd->data[py] = xrealloc(gd->data[py], sx, sizeof **gd->data);
	gd->size[py] = sx;
	}
	if (sx < gd->usize[py]) {
	gd->udata[py] = xrealloc(gd->udata[py], sx, sizeof **gd->udata);
	gd->usize[py] = sx;
	}
	}

	/* Expand line to fit to cell. */
	void
	grid_expand_line(struct grid *gd, u_int py, u_int sx)
	{
	u_int xx;

	if (sx <= gd->size[py])
	return;

	gd->data[py] = xrealloc(gd->data[py], sx, sizeof **gd->data);
	for (xx = gd->size[py]; xx < sx; xx++)
	grid_put_cell(gd, xx, py, &grid_default_cell);
	gd->size[py] = sx;
	}

	/* Expand line to fit to cell for UTF-8. */
	void
	grid_expand_line_utf8(struct grid *gd, u_int py, u_int sx)
	{
	if (sx <= gd->usize[py])
	return;

	gd->udata[py] = xrealloc(gd->udata[py], sx, sizeof **gd->udata);
	gd->usize[py] = sx;
	}

	/* Get cell for reading. */
	const struct grid_cell *
	grid_peek_cell(struct grid *gd, u_int px, u_int py)
	{
	if (grid_check_x(gd, px) != 0)
	return (&grid_default_cell);
	if (grid_check_y(gd, py) != 0)
	return (&grid_default_cell);

	if (px >= gd->size[py])
	return (&grid_default_cell);
	return (&gd->data[py][px]);
	}

	/* Get cell at relative position (for writing). */
	struct grid_cell *
	grid_get_cell(struct grid *gd, u_int px, u_int py)
	{
	if (grid_check_x(gd, px) != 0)
	return (NULL);
	if (grid_check_y(gd, py) != 0)
	return (NULL);

	grid_expand_line(gd, py, px + 1);
	return (&gd->data[py][px]);
	}

	/* Set cell at relative position. */
	void
	grid_set_cell(
	struct grid gd, u_int px, u_int py, const struct grid_cell gc)
	{
	if (grid_check_x(gd, px) != 0)
	return;
	if (grid_check_y(gd, py) != 0)
	return;

	grid_expand_line(gd, py, px + 1);
	grid_put_cell(gd, px, py, gc);
	}

	/* Get UTF-8 for reading. */
	const struct grid_utf8 *
	grid_peek_utf8(struct grid *gd, u_int px, u_int py)
	{
	if (grid_check_x(gd, px) != 0)
	return (NULL);
	if (grid_check_y(gd, py) != 0)
	return (NULL);

	if (px >= gd->usize[py])
	return (NULL);
	return (&gd->udata[py][px]);
	}

	/* Get utf8 at relative position (for writing). */
	struct grid_utf8 *
	grid_get_utf8(struct grid *gd, u_int px, u_int py)
	{
	if (grid_check_x(gd, px) != 0)
	return (NULL);
	if (grid_check_y(gd, py) != 0)
	return (NULL);

	grid_expand_line_utf8(gd, py, px + 1);
	return (&gd->udata[py][px]);
	}

	/* Set utf8 at relative position. */
	void
	grid_set_utf8(
	struct grid gd, u_int px, u_int py, const struct grid_utf8 gc)
	{
	if (grid_check_x(gd, px) != 0)
	return;
	if (grid_check_y(gd, py) != 0)
	return;

	grid_expand_line_utf8(gd, py, px + 1);
	grid_put_utf8(gd, px, py, gc);
	}

	/*
	* Clear area. Note this is different from a fill as it just omits unallocated
	* cells.
	*/
	void
	grid_clear(struct grid *gd, u_int px, u_int py, u_int nx, u_int ny)
	{
	u_int xx, yy;

	GRID_DEBUG(gd, "px=%u, py=%u, nx=%u, ny=%u", px, py, nx, ny);

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

	if (px == 0 && nx == gd->sx) {
	grid_clear_lines(gd, py, ny);
	return;
	}

	if (grid_check_x(gd, px) != 0)
	return;
	if (grid_check_x(gd, px + nx - 1) != 0)
	return;
	if (grid_check_y(gd, py) != 0)
	return;
	if (grid_check_y(gd, py + ny - 1) != 0)
	return;

	for (yy = py; yy < py + ny; yy++) {
	for (xx = px; xx < px + nx; xx++) {
	if (xx >= gd->size[yy])
	break;
	grid_put_cell(gd, xx, yy, &grid_default_cell);
	}
	}
	}

	/* Clear lines. This just frees and truncates the lines. */
	void
	grid_clear_lines(struct grid *gd, u_int py, u_int ny)
	{
	u_int yy;

	GRID_DEBUG(gd, "py=%u, ny=%u", py, ny);

	if (ny == 0)
	return;

	if (grid_check_y(gd, py) != 0)
	return;
	if (grid_check_y(gd, py + ny - 1) != 0)
	return;

	for (yy = py; yy < py + ny; yy++) {
	if (gd->data[yy] != NULL) {
	xfree(gd->data[yy]);
	gd->data[yy] = NULL;
	gd->size[yy] = 0;
	}
	if (gd->udata[yy] != NULL) {
	xfree(gd->udata[yy]);
	gd->udata[yy] = NULL;
	gd->usize[yy] = 0;
	}
	}
	}

	/* Move a group of lines. */
	void
	grid_move_lines(struct grid *gd, u_int dy, u_int py, u_int ny)
	{
	u_int yy;

	GRID_DEBUG(gd, "dy=%u, py=%u, ny=%u", dy, py, ny);

	if (ny == 0 \|\| py == dy)
	return;

	if (grid_check_y(gd, py) != 0)
	return;
	if (grid_check_y(gd, py + ny - 1) != 0)
	return;
	if (grid_check_y(gd, dy) != 0)
	return;
	if (grid_check_y(gd, dy + ny - 1) != 0)
	return;

	/* Free any lines which are being replaced. */
	for (yy = dy; yy < dy + ny; yy++) {
	if (yy >= py && yy < py + ny)
	continue;
	grid_clear_lines(gd, yy, 1);
	}

	memmove(&gd->data[dy], &gd->data[py], ny * (sizeof *gd->data));
	memmove(&gd->size[dy], &gd->size[py], ny * (sizeof *gd->size));

	memmove(&gd->udata[dy], &gd->udata[py], ny * (sizeof *gd->udata));
	memmove(&gd->usize[dy], &gd->usize[py], ny * (sizeof *gd->usize));

	/* Wipe any lines that have been moved (without freeing them). */
	for (yy = py; yy < py + ny; yy++) {
	if (yy >= dy && yy < dy + ny)
	continue;
	gd->data[yy] = NULL;
	gd->size[yy] = 0;
	gd->udata[yy] = NULL;
	gd->usize[yy] = 0;
	}
	}

	/* Clear a group of cells. */
	void
	grid_clear_cells(struct grid *gd, u_int px, u_int py, u_int nx)
	{
	u_int xx;

	GRID_DEBUG(gd, "px=%u, py=%u, nx=%u", px, py, nx);

	if (nx == 0)
	return;

	if (grid_check_x(gd, px) != 0)
	return;
	if (grid_check_x(gd, px + nx - 1) != 0)
	return;
	if (grid_check_y(gd, py) != 0)
	return;

	for (xx = px; xx < px + nx; xx++) {
	if (xx >= gd->size[py])
	break;
	grid_put_cell(gd, xx, py, &grid_default_cell);
	}
	}

	/* Move a group of cells. */
	void
	grid_move_cells(struct grid *gd, u_int dx, u_int px, u_int py, u_int nx)
	{
	u_int xx;

	GRID_DEBUG(gd, "dx=%u, px=%u, py=%u, nx=%u", dx, px, py, nx);

	if (nx == 0 \|\| px == dx)
	return;

	if (grid_check_x(gd, px) != 0)
	return;
	if (grid_check_x(gd, px + nx - 1) != 0)
	return;
	if (grid_check_x(gd, dx + nx - 1) != 0)
	return;
	if (grid_check_y(gd, py) != 0)
	return;

	grid_expand_line(gd, py, px + nx);
	grid_expand_line(gd, py, dx + nx);
	memmove(&gd->data[py][dx], &gd->data[py][px], nx * (sizeof **gd->data));

	if (gd->udata[py] != NULL) {
	grid_expand_line_utf8(gd, py, px + nx);
	grid_expand_line_utf8(gd, py, dx + nx);
	memmove(&gd->udata[py][dx],
	&gd->udata[py][px], nx * (sizeof **gd->udata));
	}

	/* Wipe any cells that have been moved. */
	for (xx = px; xx < px + nx; xx++) {
	if (xx >= dx && xx < dx + nx)
	continue;
	grid_put_cell(gd, xx, py, &grid_default_cell);
	}
	}