Return to grid.c CVS log

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

Add support for BCE (background colour erase). This makes various escape
sequences (notable EL and ED but also IL, DL, ICH, DCH) create blank
cells using the current background colour rather than the default
colour.

On modern systems BCE doesn't really have many benefits, but most other
terminals now support it, some (lazy) applications rely on it, and it is
not hard to include now that we have pane background colours anyway.

Mostly written by Sean Haugh.

/* $OpenBSD: grid.c,v 1.58 2016/10/13 20:27:27 nicm Exp $ */

/*
 * Copyright (c) 2008 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"

/*
 * 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, { { ' ' }, 0, 1, 1 }
};
const struct grid_cell_entry grid_default_entry = {
	0, { .data = { 0, 8, 8, ' ' } }
};

static void	grid_expand_line(struct grid *, u_int, u_int, u_int);
static void	grid_empty_line(struct grid *, u_int, u_int);

static void	grid_reflow_copy(struct grid_line *, u_int, struct grid_line *,
		    u_int, u_int);
static void	grid_reflow_join(struct grid *, u_int *, struct grid_line *,
		    u_int);
static void	grid_reflow_split(struct grid *, u_int *, struct grid_line *,
		    u_int, u_int);
static void	grid_reflow_move(struct grid *, u_int *, struct grid_line *);

static size_t	grid_string_cells_fg(const struct grid_cell *, int *);
static size_t	grid_string_cells_bg(const struct grid_cell *, int *);
static void	grid_string_cells_code(const struct grid_cell *,
		    const struct grid_cell *, char *, size_t, int);

/* Copy default into a cell. */
static void
grid_clear_cell(struct grid *gd, u_int px, u_int py, u_int bg)
{
	gd->linedata[py].celldata[px] = grid_default_entry;
	gd->linedata[py].celldata[px].data.bg = bg;
}

/* Check grid y position. */
static 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);
}

/* Compare grid cells. Return 1 if equal, 0 if not. */
int
grid_cells_equal(const struct grid_cell *gca, const struct grid_cell *gcb)
{
	if (gca->fg != gcb->fg || gca->bg != gcb->bg)
		return (0);
	if (gca->attr != gcb->attr || gca->flags != gcb->flags)
		return (0);
	if (gca->data.width != gcb->data.width)
		return (0);
	if (gca->data.size != gcb->data.size)
		return (0);
	return (memcmp(gca->data.data, gcb->data.data, gca->data.size) == 0);
}

/* 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->flags = GRID_HISTORY;

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

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

	return (gd);
}

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

	for (yy = 0; yy < gd->hsize + gd->sy; yy++) {
		gl = &gd->linedata[yy];
		free(gl->celldata);
		free(gl->extddata);
	}

	free(gd->linedata);

	free(gd);
}

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

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

	for (yy = 0; yy < ga->sy; yy++) {
		gla = &ga->linedata[yy];
		glb = &gb->linedata[yy];
		if (gla->cellsize != glb->cellsize)
			return (1);
		for (xx = 0; xx < gla->cellsize; xx++) {
			grid_get_cell(ga, xx, yy, &gca);
			grid_get_cell(gb, xx, yy, &gcb);
			if (!grid_cells_equal(&gca, &gcb))
				return (1);
		}
	}

	return (0);
}

/*
 * Collect lines from the history if at the limit. Free the top (oldest) 10%
 * and shift up.
 */
void
grid_collect_history(struct grid *gd, u_int bg)
{
	u_int	yy;

	if (gd->hsize < gd->hlimit)
		return;

	yy = gd->hlimit / 10;
	if (yy < 1)
		yy = 1;

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

/*
 * Scroll the entire visible screen, moving one line into the history. Just
 * allocate a new line at the bottom and move the history size indicator.
 */
void
grid_scroll_history(struct grid *gd, u_int bg)
{
	u_int	yy;

	yy = gd->hsize + gd->sy;
	gd->linedata = xreallocarray(gd->linedata, yy + 1,
	    sizeof *gd->linedata);
	grid_empty_line(gd, yy, bg);

	gd->hscrolled++;
	gd->hsize++;
}

/* Clear the history. */
void
grid_clear_history(struct grid *gd)
{
	grid_clear_lines(gd, 0, gd->hsize, 8);
	grid_move_lines(gd, 0, gd->hsize, gd->sy, 8);

	gd->hscrolled = 0;
	gd->hsize = 0;

	gd->linedata = xreallocarray(gd->linedata, gd->sy,
	    sizeof *gd->linedata);
}

/* Scroll a region up, moving the top line into the history. */
void
grid_scroll_history_region(struct grid *gd, u_int upper, u_int lower)
{
	struct grid_line	*gl_history, *gl_upper, *gl_lower;
	u_int			 yy;

	/* Create a space for a new line. */
	yy = gd->hsize + gd->sy;
	gd->linedata = xreallocarray(gd->linedata, yy + 1,
	    sizeof *gd->linedata);

	/* Move the entire screen down to free a space for this line. */
	gl_history = &gd->linedata[gd->hsize];
	memmove(gl_history + 1, gl_history, gd->sy * sizeof *gl_history);

	/* Adjust the region and find its start and end. */
	upper++;
	gl_upper = &gd->linedata[upper];
	lower++;
	gl_lower = &gd->linedata[lower];

	/* Move the line into the history. */
	memcpy(gl_history, gl_upper, sizeof *gl_history);

	/* Then move the region up and clear the bottom line. */
	memmove(gl_upper, gl_upper + 1, (lower - upper) * sizeof *gl_upper);
	memset(gl_lower, 0, sizeof *gl_lower);

	/* Move the history offset down over the line. */
	gd->hscrolled++;
	gd->hsize++;
}

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

	gl = &gd->linedata[py];
	if (sx <= gl->cellsize)
		return;

	gl->celldata = xreallocarray(gl->celldata, sx, sizeof *gl->celldata);
	for (xx = gl->cellsize; xx < sx; xx++)
		grid_clear_cell(gd, xx, py, bg);
	gl->cellsize = sx;
}

/* Empty a line and set background colour if needed. */
static void
grid_empty_line(struct grid *gd, u_int py, u_int bg)
{
	memset(&gd->linedata[py], 0, sizeof gd->linedata[py]);
	if (bg != 8)
		grid_expand_line(gd, py, gd->sx, bg);
}

/* Peek at grid line. */
const struct grid_line *
grid_peek_line(struct grid *gd, u_int py)
{
	if (grid_check_y(gd, py) != 0)
		return (NULL);
	return (&gd->linedata[py]);
}

/* Get cell for reading. */
void
grid_get_cell(struct grid *gd, u_int px, u_int py, struct grid_cell *gc)
{
	struct grid_line	*gl;
	struct grid_cell_entry	*gce;

	if (grid_check_y(gd, py) != 0 || px >= gd->linedata[py].cellsize) {
		memcpy(gc, &grid_default_cell, sizeof *gc);
		return;
	}

	gl = &gd->linedata[py];
	gce = &gl->celldata[px];

	if (gce->flags & GRID_FLAG_EXTENDED) {
		if (gce->offset >= gl->extdsize)
			memcpy(gc, &grid_default_cell, sizeof *gc);
		else
			memcpy(gc, &gl->extddata[gce->offset], sizeof *gc);
		return;
	}

	gc->flags = gce->flags & ~(GRID_FLAG_FG256|GRID_FLAG_BG256);
	gc->attr = gce->data.attr;
	gc->fg = gce->data.fg;
	if (gce->flags & GRID_FLAG_FG256)
		gc->fg |= COLOUR_FLAG_256;
	gc->bg = gce->data.bg;
	if (gce->flags & GRID_FLAG_BG256)
		gc->bg |= COLOUR_FLAG_256;
	utf8_set(&gc->data, gce->data.data);
}

/* Set cell at relative position. */
void
grid_set_cell(struct grid *gd, u_int px, u_int py, const struct grid_cell *gc)
{
	struct grid_line	*gl;
	struct grid_cell_entry	*gce;
	struct grid_cell 	*gcp;
	int			 extended;

	if (grid_check_y(gd, py) != 0)
		return;

	grid_expand_line(gd, py, px + 1, 8);

	gl = &gd->linedata[py];
	gce = &gl->celldata[px];

	if (px + 1 > gl->cellused)
		gl->cellused = px + 1;

	extended = (gce->flags & GRID_FLAG_EXTENDED);
	if (!extended && (gc->data.size != 1 || gc->data.width != 1))
		extended = 1;
	if (!extended && ((gc->fg & COLOUR_FLAG_RGB) ||
	    (gc->bg & COLOUR_FLAG_RGB)))
		extended = 1;
	if (extended) {
		gl->flags |= GRID_LINE_EXTENDED;

		if (~gce->flags & GRID_FLAG_EXTENDED) {
			gl->extddata = xreallocarray(gl->extddata,
			    gl->extdsize + 1, sizeof *gl->extddata);
			gce->offset = gl->extdsize++;
			gce->flags = gc->flags | GRID_FLAG_EXTENDED;
		}

		if (gce->offset >= gl->extdsize)
			fatalx("offset too big");
		gcp = &gl->extddata[gce->offset];
		memcpy(gcp, gc, sizeof *gcp);
		return;
	}

	gce->flags = gc->flags;
	gce->data.attr = gc->attr;
	gce->data.fg = gc->fg & 0xff;
	if (gc->fg & COLOUR_FLAG_256)
		gce->flags |= GRID_FLAG_FG256;
	gce->data.bg = gc->bg & 0xff;
	if (gc->bg & COLOUR_FLAG_256)
		gce->flags |= GRID_FLAG_BG256;
	gce->data.data = gc->data.data[0];
}

/* Clear area. */
void
grid_clear(struct grid *gd, u_int px, u_int py, u_int nx, u_int ny, u_int bg)
{
	u_int	xx, yy;

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

	if (px == 0 && nx == gd->sx) {
		grid_clear_lines(gd, py, ny, bg);
		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 (px + nx >= gd->sx && px < gd->linedata[yy].cellused)
			gd->linedata[yy].cellused = px;
		if (px > gd->linedata[yy].cellsize && bg == 8)
			continue;
		if (px + nx >= gd->linedata[yy].cellsize && bg == 8) {
			gd->linedata[yy].cellsize = px;
			continue;
		}
		grid_expand_line(gd, yy, px + nx, bg);
		for (xx = px; xx < px + nx; xx++)
			grid_clear_cell(gd, xx, yy, bg);
	}
}

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

	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++) {
		gl = &gd->linedata[yy];
		free(gl->celldata);
		free(gl->extddata);
		grid_empty_line(gd, yy, bg);
	}
}

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

	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, bg);
	}

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

	/* Wipe any lines that have been moved (without freeing them). */
	for (yy = py; yy < py + ny; yy++) {
		if (yy < dy || yy >= dy + ny)
			grid_empty_line(gd, yy, bg);
	}
}

/* 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 bg)
{
	struct grid_line	*gl;
	u_int			 xx;

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

	if (grid_check_y(gd, py) != 0)
		return;
	gl = &gd->linedata[py];

	grid_expand_line(gd, py, px + nx, 8);
	grid_expand_line(gd, py, dx + nx, 8);
	memmove(&gl->celldata[dx], &gl->celldata[px],
	    nx * sizeof *gl->celldata);

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

/* Get ANSI foreground sequence. */
static size_t
grid_string_cells_fg(const struct grid_cell *gc, int *values)
{
	size_t	n;
	u_char	r, g, b;

	n = 0;
	if (gc->fg & COLOUR_FLAG_256) {
		values[n++] = 38;
		values[n++] = 5;
		values[n++] = gc->fg & 0xff;
	} else if (gc->fg & COLOUR_FLAG_RGB) {
		values[n++] = 38;
		values[n++] = 2;
		colour_split_rgb(gc->fg, &r, &g, &b);
		values[n++] = r;
		values[n++] = g;
		values[n++] = b;
	} else {
		switch (gc->fg) {
		case 0:
		case 1:
		case 2:
		case 3:
		case 4:
		case 5:
		case 6:
		case 7:
			values[n++] = gc->fg + 30;
			break;
		case 8:
			values[n++] = 39;
			break;
		case 90:
		case 91:
		case 92:
		case 93:
		case 94:
		case 95:
		case 96:
		case 97:
			values[n++] = gc->fg;
			break;
		}
	}
	return (n);
}

/* Get ANSI background sequence. */
static size_t
grid_string_cells_bg(const struct grid_cell *gc, int *values)
{
	size_t	n;
	u_char	r, g, b;

	n = 0;
	if (gc->bg & COLOUR_FLAG_256) {
		values[n++] = 48;
		values[n++] = 5;
		values[n++] = gc->bg & 0xff;
	} else if (gc->bg & COLOUR_FLAG_RGB) {
		values[n++] = 48;
		values[n++] = 2;
		colour_split_rgb(gc->bg, &r, &g, &b);
		values[n++] = r;
		values[n++] = g;
		values[n++] = b;
	} else {
		switch (gc->bg) {
		case 0:
		case 1:
		case 2:
		case 3:
		case 4:
		case 5:
		case 6:
		case 7:
			values[n++] = gc->bg + 40;
			break;
		case 8:
			values[n++] = 49;
			break;
		case 100:
		case 101:
		case 102:
		case 103:
		case 104:
		case 105:
		case 106:
		case 107:
			values[n++] = gc->bg - 10;
			break;
		}
	}
	return (n);
}

/*
 * Returns ANSI code to set particular attributes (colour, bold and so on)
 * given a current state. The output buffer must be able to hold at least 57
 * bytes.
 */
static void
grid_string_cells_code(const struct grid_cell *lastgc,
    const struct grid_cell *gc, char *buf, size_t len, int escape_c0)
{
	int	oldc[64], newc[64], s[128];
	size_t	noldc, nnewc, n, i;
	u_int	attr = gc->attr;
	u_int	lastattr = lastgc->attr;
	char	tmp[64];

	struct {
		u_int	mask;
		u_int	code;
	} attrs[] = {
		{ GRID_ATTR_BRIGHT, 1 },
		{ GRID_ATTR_DIM, 2 },
		{ GRID_ATTR_ITALICS, 3 },
		{ GRID_ATTR_UNDERSCORE, 4 },
		{ GRID_ATTR_BLINK, 5 },
		{ GRID_ATTR_REVERSE, 7 },
		{ GRID_ATTR_HIDDEN, 8 }
	};
	n = 0;

	/* If any attribute is removed, begin with 0. */
	for (i = 0; i < nitems(attrs); i++) {
		if (!(attr & attrs[i].mask) && (lastattr & attrs[i].mask)) {
			s[n++] = 0;
			lastattr &= GRID_ATTR_CHARSET;
			break;
		}
	}
	/* For each attribute that is newly set, add its code. */
	for (i = 0; i < nitems(attrs); i++) {
		if ((attr & attrs[i].mask) && !(lastattr & attrs[i].mask))
			s[n++] = attrs[i].code;
	}

	/* If the foreground colour changed, append its parameters. */
	nnewc = grid_string_cells_fg(gc, newc);
	noldc = grid_string_cells_fg(lastgc, oldc);
	if (nnewc != noldc || memcmp(newc, oldc, nnewc * sizeof newc[0]) != 0) {
		for (i = 0; i < nnewc; i++)
			s[n++] = newc[i];
	}

	/* If the background colour changed, append its parameters. */
	nnewc = grid_string_cells_bg(gc, newc);
	noldc = grid_string_cells_bg(lastgc, oldc);
	if (nnewc != noldc || memcmp(newc, oldc, nnewc * sizeof newc[0]) != 0) {
		for (i = 0; i < nnewc; i++)
			s[n++] = newc[i];
	}

	/* If there are any parameters, append an SGR code. */
	*buf = '\0';
	if (n > 0) {
		if (escape_c0)
			strlcat(buf, "\\033[", len);
		else
			strlcat(buf, "\033[", len);
		for (i = 0; i < n; i++) {
			if (i + 1 < n)
				xsnprintf(tmp, sizeof tmp, "%d;", s[i]);
			else
				xsnprintf(tmp, sizeof tmp, "%d", s[i]);
			strlcat(buf, tmp, len);
		}
		strlcat(buf, "m", len);
	}

	/* Append shift in/shift out if needed. */
	if ((attr & GRID_ATTR_CHARSET) && !(lastattr & GRID_ATTR_CHARSET)) {
		if (escape_c0)
			strlcat(buf, "\\016", len);  /* SO */
		else
			strlcat(buf, "\016", len);  /* SO */
	}
	if (!(attr & GRID_ATTR_CHARSET) && (lastattr & GRID_ATTR_CHARSET)) {
		if (escape_c0)
			strlcat(buf, "\\017", len);  /* SI */
		else
			strlcat(buf, "\017", len);  /* SI */
	}
}

/* Convert cells into a string. */
char *
grid_string_cells(struct grid *gd, u_int px, u_int py, u_int nx,
    struct grid_cell **lastgc, int with_codes, int escape_c0, int trim)
{
	struct grid_cell	 gc;
	static struct grid_cell	 lastgc1;
	const char		*data;
	char			*buf, code[128];
	size_t			 len, off, size, codelen;
	u_int			 xx;
	const struct grid_line	*gl;

	if (lastgc != NULL && *lastgc == NULL) {
		memcpy(&lastgc1, &grid_default_cell, sizeof lastgc1);
		*lastgc = &lastgc1;
	}

	len = 128;
	buf = xmalloc(len);
	off = 0;

	gl = grid_peek_line(gd, py);
	for (xx = px; xx < px + nx; xx++) {
		if (gl == NULL || xx >= gl->cellsize)
			break;
		grid_get_cell(gd, xx, py, &gc);
		if (gc.flags & GRID_FLAG_PADDING)
			continue;

		if (with_codes) {
			grid_string_cells_code(*lastgc, &gc, code, sizeof code,
			    escape_c0);
			codelen = strlen(code);
			memcpy(*lastgc, &gc, sizeof **lastgc);
		} else
			codelen = 0;

		data = gc.data.data;
		size = gc.data.size;
		if (escape_c0 && size == 1 && *data == '\\') {
			data = "\\\\";
			size = 2;
		}

		while (len < off + size + codelen + 1) {
			buf = xreallocarray(buf, 2, len);
			len *= 2;
		}

		if (codelen != 0) {
			memcpy(buf + off, code, codelen);
			off += codelen;
		}
		memcpy(buf + off, data, size);
		off += size;
	}

	if (trim) {
		while (off > 0 && buf[off - 1] == ' ')
			off--;
	}
	buf[off] = '\0';

	return (buf);
}

/*
 * Duplicate a set of lines between two grids. If there aren't enough lines in
 * either source or destination, the number of lines is limited to the number
 * available.
 */
void
grid_duplicate_lines(struct grid *dst, u_int dy, struct grid *src, u_int sy,
    u_int ny)
{
	struct grid_line	*dstl, *srcl;
	u_int			 yy;

	if (dy + ny > dst->hsize + dst->sy)
		ny = dst->hsize + dst->sy - dy;
	if (sy + ny > src->hsize + src->sy)
		ny = src->hsize + src->sy - sy;
	grid_clear_lines(dst, dy, ny, 8);

	for (yy = 0; yy < ny; yy++) {
		srcl = &src->linedata[sy];
		dstl = &dst->linedata[dy];

		memcpy(dstl, srcl, sizeof *dstl);
		if (srcl->cellsize != 0) {
			dstl->celldata = xreallocarray(NULL,
			    srcl->cellsize, sizeof *dstl->celldata);
			memcpy(dstl->celldata, srcl->celldata,
			    srcl->cellsize * sizeof *dstl->celldata);
		} else
			dstl->celldata = NULL;

		if (srcl->extdsize != 0) {
			dstl->extdsize = srcl->extdsize;
			dstl->extddata = xreallocarray(NULL, dstl->extdsize,
			    sizeof *dstl->extddata);
			memcpy(dstl->extddata, srcl->extddata, dstl->extdsize *
			    sizeof *dstl->extddata);
		}

		sy++;
		dy++;
	}
}

/* Copy a section of a line. */
static void
grid_reflow_copy(struct grid_line *dst_gl, u_int to, struct grid_line *src_gl,
    u_int from, u_int to_copy)
{
	struct grid_cell_entry	*gce;
	u_int			 i, was;

	memcpy(&dst_gl->celldata[to], &src_gl->celldata[from],
	    to_copy * sizeof *dst_gl->celldata);

	for (i = to; i < to + to_copy; i++) {
		gce = &dst_gl->celldata[i];
		if (~gce->flags & GRID_FLAG_EXTENDED)
			continue;
		was = gce->offset;

		dst_gl->extddata = xreallocarray(dst_gl->extddata,
		    dst_gl->extdsize + 1, sizeof *dst_gl->extddata);
		gce->offset = dst_gl->extdsize++;
		memcpy(&dst_gl->extddata[gce->offset], &src_gl->extddata[was],
		    sizeof *dst_gl->extddata);
	}
}

/* Join line data. */
static void
grid_reflow_join(struct grid *dst, u_int *py, struct grid_line *src_gl,
    u_int new_x)
{
	struct grid_line	*dst_gl = &dst->linedata[(*py) - 1];
	u_int			 left, to_copy, ox, nx;

	/* How much is left on the old line? */
	left = new_x - dst_gl->cellused;

	/* Work out how much to append. */
	to_copy = src_gl->cellused;
	if (to_copy > left)
		to_copy = left;
	ox = dst_gl->cellused;
	nx = ox + to_copy;

	/* Resize the destination line. */
	dst_gl->celldata = xreallocarray(dst_gl->celldata, nx,
	    sizeof *dst_gl->celldata);
	dst_gl->cellsize = dst_gl->cellused = nx;

	/* Append as much as possible. */
	grid_reflow_copy(dst_gl, ox, src_gl, 0, to_copy);

	/* If there is any left in the source, split it. */
	if (src_gl->cellused > to_copy) {
		dst_gl->flags |= GRID_LINE_WRAPPED;

		src_gl->cellused -= to_copy;
		grid_reflow_split(dst, py, src_gl, new_x, to_copy);
	}
}

/* Split line data. */
static void
grid_reflow_split(struct grid *dst, u_int *py, struct grid_line *src_gl,
    u_int new_x, u_int offset)
{
	struct grid_line	*dst_gl = NULL;
	u_int			 to_copy;

	/* Loop and copy sections of the source line. */
	while (src_gl->cellused > 0) {
		/* Create new line. */
		if (*py >= dst->hsize + dst->sy)
			grid_scroll_history(dst, 8);
		dst_gl = &dst->linedata[*py];
		(*py)++;

		/* How much should we copy? */
		to_copy = new_x;
		if (to_copy > src_gl->cellused)
			to_copy = src_gl->cellused;

		/* Expand destination line. */
		dst_gl->celldata = xreallocarray(NULL, to_copy,
		    sizeof *dst_gl->celldata);
		dst_gl->cellsize = dst_gl->cellused = to_copy;
		dst_gl->flags |= GRID_LINE_WRAPPED;

		/* Copy the data. */
		grid_reflow_copy(dst_gl, 0, src_gl, offset, to_copy);

		/* Move offset and reduce old line size. */
		offset += to_copy;
		src_gl->cellused -= to_copy;
	}

	/* Last line is not wrapped. */
	if (dst_gl != NULL)
		dst_gl->flags &= ~GRID_LINE_WRAPPED;
}

/* Move line data. */
static void
grid_reflow_move(struct grid *dst, u_int *py, struct grid_line *src_gl)
{
	struct grid_line	*dst_gl;

	/* Create new line. */
	if (*py >= dst->hsize + dst->sy)
		grid_scroll_history(dst, 8);
	dst_gl = &dst->linedata[*py];
	(*py)++;

	/* Copy the old line. */
	memcpy(dst_gl, src_gl, sizeof *dst_gl);
	dst_gl->flags &= ~GRID_LINE_WRAPPED;

	/* Clear old line. */
	src_gl->celldata = NULL;
	src_gl->extddata = NULL;
}

/*
 * Reflow lines from src grid into dst grid of width new_x. Returns number of
 * lines fewer in the visible area. The source grid is destroyed.
 */
u_int
grid_reflow(struct grid *dst, struct grid *src, u_int new_x)
{
	u_int			 py, sy, line;
	int			 previous_wrapped;
	struct grid_line	*src_gl;

	py = 0;
	sy = src->sy;

	previous_wrapped = 0;
	for (line = 0; line < sy + src->hsize; line++) {
		src_gl = src->linedata + line;
		if (!previous_wrapped) {
			/* Wasn't wrapped. If smaller, move to destination. */
			if (src_gl->cellused <= new_x)
				grid_reflow_move(dst, &py, src_gl);
			else
				grid_reflow_split(dst, &py, src_gl, new_x, 0);
		} else {
			/* Previous was wrapped. Try to join. */
			grid_reflow_join(dst, &py, src_gl, new_x);
		}
		previous_wrapped = (src_gl->flags & GRID_LINE_WRAPPED);

		/* This is where we started scrolling. */
		if (line == sy + src->hsize - src->hscrolled - 1)
			dst->hscrolled = 0;
	}

	grid_destroy(src);

	if (py > sy)
		return (0);
	return (sy - py);
}