/* $OpenBSD$ */

/*
 * Copyright (c) 2026 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 <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "tmux.h"

/* Type of span in the scene. */
enum redraw_span_type {
	REDRAW_SPAN_PANE,	/* inside a pane */
	REDRAW_SPAN_OUTSIDE,	/* outside the window */
	REDRAW_SPAN_EMPTY,	/* inside the window but nothing visible */
	REDRAW_SPAN_STATUS,	/* pane status line */
	REDRAW_SPAN_BORDER,	/* pane border */
	REDRAW_SPAN_SCROLLBAR,	/* pane scrollbar */
};
#define REDRAW_SPAN_TYPES 6

/* Border connections to adjacent cells. */
#define REDRAW_BORDER_L 0x1
#define REDRAW_BORDER_R 0x2
#define REDRAW_BORDER_U 0x4
#define REDRAW_BORDER_D 0x8

/* Span flags. */
#define REDRAW_BORDER_IS_ARROW 0x1
#define REDRAW_SCROLLBAR_LEFT 0x2
#define REDRAW_SCROLLBAR_RIGHT 0x4

/* Draw operations. */
#define REDRAW_DRAW_PANE 0x1
#define REDRAW_DRAW_BORDER 0x2
#define REDRAW_DRAW_STATUS 0x4
#define REDRAW_DRAW_SCROLLBAR 0x8
#define REDRAW_DRAW_ALL 0xff

/* Data for a span. */
struct redraw_span_data {
	enum redraw_span_type	type;

	union {
		struct {
			/* Pane this span belongs to. */
			struct window_pane	*wp;

			/* Position of span inside the pane. */
			u_int			 px;
			u_int			 py;
		} p;

		struct {
			/* Adjacent panes on each side. */
			struct window_pane	*top_wp;
			struct window_pane	*bottom_wp;
			struct window_pane	*left_wp;
			struct window_pane	*right_wp;

			/*
			 * The pane this span belongs if that is known when the
			 * scene is built. This is used for the half coloured
			 * active pane indicator.
			 */
			struct window_pane	*style_wp;

			/* Cell type for this span. */
			int			 cell_type;
			int			 cell_mask;

			/* Line styles for this span. */
			enum pane_lines		 top_lines;
			enum pane_lines		 bottom_lines;
			enum pane_lines		 left_lines;
			enum pane_lines		 right_lines;

			/* Flags for this span. */
			int			 flags;
		} b;

		struct {
			/* The pane and the offset into the status line. */
			struct window_pane	*wp;
			u_int			 offset;
		} st;

		struct {
			/* Pane this span belongs to. */
			struct window_pane	*wp;

			/* Line within the scrollbar. */
			u_int			 y;

			/* Full height of scrollbar. */
			u_int			 height;

			/* Flags for this span. */
			int			 flags;
		} sb;
	};
};

/* A span of cells of the same type inside a line. */
struct redraw_span {
	u_int				x;
	u_int				width;
	struct redraw_span_data		data;

	TAILQ_ENTRY(redraw_span)	entry;
};
TAILQ_HEAD(redraw_spans, redraw_span);

/* A visible line on the client. */
struct redraw_line {
	struct redraw_spans	spans[REDRAW_SPAN_TYPES];
};

/* A scene representing all the spans on the client. */
struct redraw_scene {
	struct client		*c;
	struct window		*w;

	u_int			 sx;
	u_int			 sy;
	u_int			 ox;
	u_int			 oy;

	struct redraw_line	*lines;
};

/* Cell for building the scene. */
struct redraw_build_cell {
	struct redraw_span_data	 data;
};

/* Context for building the scene. */
struct redraw_build_ctx {
	struct client				*c;
	struct window				*w;

	u_int					 ox;
	u_int					 oy;
	u_int					 sx;
	u_int					 sy;

	int					 sb;
	int					 sbp;
	int					 ind;

	struct redraw_build_cell		*cells;
};

/* Initialize the context for building scene. */
static void
screen_redraw_set_context(struct client *c, struct redraw_build_ctx *bctx)
{
	struct session	*s = c->session;
	struct window	*w = s->curw->window;
	struct options	*oo = w->options;

	memset(bctx, 0, sizeof *bctx);
	bctx->c = c;
	bctx->w = w;
	tty_window_offset(&c->tty, &bctx->ox, &bctx->oy, &bctx->sx, &bctx->sy);

	bctx->sb = options_get_number(oo, "pane-scrollbars");
	bctx->sbp = options_get_number(oo, "pane-scrollbars-position");
	bctx->ind = options_get_number(oo, "pane-border-indicators");
}

/* Return a cell. */
static struct redraw_build_cell *
screen_redraw_cell(struct redraw_build_ctx *bctx, u_int x, u_int y)
{
	return (&bctx->cells[(y * bctx->sx) + x]);
}

/* Reset cell to either empty or outside the window. */
static void
screen_redraw_reset_cell(struct redraw_build_ctx *bctx, u_int x, u_int y)
{
	struct redraw_build_cell	*bc = screen_redraw_cell(bctx, x, y);
	struct window			*w = bctx->w;

	memset(bc, 0, sizeof *bc);
	if (bctx->ox + x <= w->sx && bctx->oy + y <= w->sy)
		bc->data.type = REDRAW_SPAN_EMPTY;
	else
		bc->data.type = REDRAW_SPAN_OUTSIDE;
}

/* Convert window position to scene position. */
static int
screen_redraw_window_scene(struct redraw_build_ctx *bctx, int wx, int wy,
    u_int *x, u_int *y)
{
	if (wx < 0 || wy < 0)
		return (0);
	if ((u_int)wx > bctx->w->sx || (u_int)wy > bctx->w->sy)
		return (0);
	if (wx < (int)bctx->ox || wy < (int)bctx->oy)
		return (0);
	wx -= bctx->ox;
	wy -= bctx->oy;

	if (wx < 0 || wy < 0)
		return (0);
	if ((u_int)wx >= bctx->sx || (u_int)wy >= bctx->sy)
		return (0);
	*x = wx;
	*y = wy;
	return (1);
}

/* Convert pane position to scene. */
static int
screen_redraw_pane_scene(struct redraw_build_ctx *bctx,
    struct window_pane *wp, int px, int py, u_int *x, u_int *y)
{
	int	wx = wp->xoff + px, wy = wp->yoff + py;

	return (screen_redraw_window_scene(bctx, wx, wy, x, y));
}

/* Convert redraw border mask to a cell type. */
static int
screen_redraw_get_cell_type(int mask)
{
	switch (mask) {
	case REDRAW_BORDER_L|REDRAW_BORDER_R|REDRAW_BORDER_U|REDRAW_BORDER_D:
		return (CELL_JOIN);
	case REDRAW_BORDER_L|REDRAW_BORDER_R|REDRAW_BORDER_U:
		return (CELL_BOTTOMJOIN);
	case REDRAW_BORDER_L|REDRAW_BORDER_R|REDRAW_BORDER_D:
		return (CELL_TOPJOIN);
	case REDRAW_BORDER_L|REDRAW_BORDER_R:
	case REDRAW_BORDER_L:
	case REDRAW_BORDER_R:
		return (CELL_LEFTRIGHT);
	case REDRAW_BORDER_L|REDRAW_BORDER_U|REDRAW_BORDER_D:
		return (CELL_RIGHTJOIN);
	case REDRAW_BORDER_L|REDRAW_BORDER_U:
		return (CELL_BOTTOMRIGHT);
	case REDRAW_BORDER_L|REDRAW_BORDER_D:
		return (CELL_TOPRIGHT);
	case REDRAW_BORDER_R|REDRAW_BORDER_U|REDRAW_BORDER_D:
		return (CELL_LEFTJOIN);
	case REDRAW_BORDER_R|REDRAW_BORDER_U:
		return (CELL_BOTTOMLEFT);
	case REDRAW_BORDER_R|REDRAW_BORDER_D:
		return (CELL_TOPLEFT);
	case REDRAW_BORDER_U|REDRAW_BORDER_D:
	case REDRAW_BORDER_U:
	case REDRAW_BORDER_D:
		return (CELL_TOPBOTTOM);
	}
	return (CELL_OUTSIDE);
}

/* Return if this cell has exactly two panes with a shared border. */
static int
screen_redraw_two_panes(struct window *w, enum layout_type *type)
{
	struct window_pane	*wp;
	u_int			 count = 0;

	TAILQ_FOREACH(wp, &w->panes, entry) {
		if (window_pane_is_floating(wp) || wp->layout_cell == NULL)
			continue;
		count++;
		if (count > 2 || wp->layout_cell->parent == NULL)
			return (0);
		*type = wp->layout_cell->parent->type;
	}
	return (count == 2);
}


/* Clear the cells covered by a floating pane. */
static void
screen_redraw_clear_floating_pane(struct redraw_build_ctx *bctx,
    struct window_pane *wp, int	sb_w, int sb_left)
{
	enum pane_lines	 pane_lines;
	u_int		 x, y;
	int		 left, right, top, bottom, wx, wy;

	if (!window_pane_is_floating(wp))
		return;

	pane_lines = window_pane_get_pane_lines(wp);
	if (pane_lines == PANE_LINES_NONE) {
		left = wp->xoff;
		right = wp->xoff + (int)wp->sx - 1;
		top = wp->yoff;
		bottom = wp->yoff + (int)wp->sy - 1;
	} else {
		left = wp->xoff - 1;
		right = wp->xoff + (int)wp->sx;
		top = wp->yoff - 1;
		bottom = wp->yoff + (int)wp->sy;
	}
	if (sb_left)
		left -= sb_w;
	else
		right += sb_w;

	for (wy = top; wy <= bottom; wy++) {
		for (wx = left; wx <= right; wx++) {
			if (screen_redraw_window_scene(bctx, wx, wy, &x, &y))
				screen_redraw_reset_cell(bctx, x, y);
		}
	}
}

/* Mark pane inside data. */
static void
screen_redraw_mark_pane_inside(struct redraw_build_ctx *bctx,
    struct window_pane *wp)
{
	struct redraw_build_cell	*bc;
	u_int				 px, py, x, y;

	for (py = 0; py < wp->sy; py++) {
		for (px = 0; px < wp->sx; px++) {
			if (!screen_redraw_pane_scene(bctx, wp, px, py, &x, &y))
				continue;
			bc = screen_redraw_cell(bctx, x, y);
			memset(bc, 0, sizeof *bc);
			bc->data.type = REDRAW_SPAN_PANE;
			bc->data.p.wp = wp;
			bc->data.p.px = px;
			bc->data.p.py = py;
		}
	}
}

/* Mark scrollbar data. */
static void
screen_redraw_mark_pane_scrollbar(struct redraw_build_ctx *bctx,
    struct window_pane *wp, int sb_w, int sb_left)
{
	struct redraw_build_cell	*bc;
	u_int			 x, y;
	int			 wx, wy, sx, ex;
	u_int			 sy;

	if (sb_w == 0)
		return;

	if (sb_left) {
		sx = wp->xoff - sb_w;
		ex = wp->xoff - 1;
	} else {
		sx = wp->xoff + (int)wp->sx;
		ex = sx + sb_w - 1;
	}

	for (sy = 0; sy < wp->sy; sy++) {
		wy = wp->yoff + (int)sy;
		for (wx = sx; wx <= ex; wx++) {
			if (!screen_redraw_window_scene(bctx, wx, wy, &x, &y))
				continue;
			bc = screen_redraw_cell(bctx, x, y);
			memset(bc, 0, sizeof *bc);
			bc->data.type = REDRAW_SPAN_SCROLLBAR;
			bc->data.sb.wp = wp;
			bc->data.sb.y = sy;
			bc->data.sb.height = wp->sy;
			if (sb_left)
				bc->data.sb.flags |= REDRAW_SCROLLBAR_LEFT;
			else
				bc->data.sb.flags |= REDRAW_SCROLLBAR_RIGHT;
		}
	}
}

/*
 * Mark one border cell. If a non-border cell is being marked as a border,
 * replace it. If it is already a border, merge it.
 */
static void
screen_redraw_mark_border_cell(struct redraw_build_ctx *bctx, int wx, int wy,
    struct window_pane *wp, int top_owner, int bottom_owner, int mask)
{
	struct redraw_build_cell	*bc;
	enum pane_lines			 pane_lines;
	u_int				 x, y;

	if (!screen_redraw_window_scene(bctx, wx, wy, &x, &y))
		return;
	bc = screen_redraw_cell(bctx, x, y);

	if (bc->data.type != REDRAW_SPAN_BORDER) {
		if (bc->data.type != REDRAW_SPAN_EMPTY)
			return;
		memset(bc, 0, sizeof *bc);
		bc->data.type = REDRAW_SPAN_BORDER;
	}
	pane_lines = window_pane_get_pane_lines(wp);
	if (top_owner) {
		bc->data.b.top_wp = wp;
		bc->data.b.top_lines = pane_lines;
	}
	if (bottom_owner) {
		bc->data.b.bottom_wp = wp;
		bc->data.b.bottom_lines = pane_lines;
	}

	if (mask & (REDRAW_BORDER_U|REDRAW_BORDER_D)) {
		if (wx < wp->xoff) {
			bc->data.b.right_wp = wp;
			bc->data.b.right_lines = pane_lines;
		} else if (wx >= wp->xoff + (int)wp->sx) {
			bc->data.b.left_wp = wp;
			bc->data.b.left_lines = pane_lines;
		}
	}

	mask |= bc->data.b.cell_mask;
	bc->data.b.cell_mask = mask;
	bc->data.b.cell_type = screen_redraw_get_cell_type(mask);
}

/* Mark area available for pane status line. */
static void
screen_redraw_mark_border_status(struct redraw_build_ctx *bctx,
    struct window_pane *wp, int left, int right, int top, int bottom)
{
	struct redraw_build_cell	*bc;
	u_int				 x, y, offset = 0;
	int				 pane_status, wy, sx, ex, wx;

	pane_status = window_pane_get_pane_status(wp);
	if (pane_status == PANE_STATUS_OFF)
		return;
	if (pane_status == PANE_STATUS_TOP)
		wy = top;
	else
		wy = bottom;

	sx = left + 1;
	ex = right - 1;
	if (bctx->ind == PANE_BORDER_ARROWS || bctx->ind == PANE_BORDER_BOTH) {
		wx = wp->xoff + 1;
		if (wx >= sx && wx <= ex)
			sx = wx + 1;
	}
	if (sx > ex)
		return;

	for (wx = sx; wx <= ex; wx++, offset++) {
		if (!screen_redraw_window_scene(bctx, wx, wy, &x, &y))
			continue;
		bc = screen_redraw_cell(bctx, x, y);
		if (bc->data.type != REDRAW_SPAN_BORDER)
			continue;
		bc->data.type = REDRAW_SPAN_STATUS;
		bc->data.st.wp = wp;
		bc->data.st.offset = offset;
	}
}


/* Mark where indicator arrows will go, if enabled. */
static void
screen_redraw_mark_border_arrows(struct redraw_build_ctx *bctx,
    struct window_pane *wp, int left, int right, int top, int bottom)
{
	struct redraw_build_cell	*bc;
	u_int				 x, y;
	int				 wx, wy;

	if (bctx->ind != PANE_BORDER_ARROWS && bctx->ind != PANE_BORDER_BOTH)
		return;

	wx = wp->xoff + 1;
	if (wx >= left && wx <= right) {
		wy = top;
		if (screen_redraw_window_scene(bctx, wx, wy, &x, &y)) {
			bc = screen_redraw_cell(bctx, x, y);
			if (bc->data.type == REDRAW_SPAN_BORDER)
				bc->data.b.flags |= REDRAW_BORDER_IS_ARROW;
		}
		wy = bottom;
		if (screen_redraw_window_scene(bctx, wx, wy, &x, &y)) {
			bc = screen_redraw_cell(bctx, x, y);
			if (bc->data.type == REDRAW_SPAN_BORDER)
				bc->data.b.flags |= REDRAW_BORDER_IS_ARROW;
		}
	}

	wy = wp->yoff + 1;
	if (wy >= top && wy <= bottom) {
		wx = left;
		if (screen_redraw_window_scene(bctx, wx, wy, &x, &y)) {
			bc = screen_redraw_cell(bctx, x, y);
			if (bc->data.type == REDRAW_SPAN_BORDER)
				bc->data.b.flags |= REDRAW_BORDER_IS_ARROW;
		}
		wx = right;
		if (screen_redraw_window_scene(bctx, wx, wy, &x, &y)) {
			bc = screen_redraw_cell(bctx, x, y);
			if (bc->data.type == REDRAW_SPAN_BORDER)
				bc->data.b.flags |= REDRAW_BORDER_IS_ARROW;
		}
	}
}

/* Mark pane borders. */
static void
screen_redraw_mark_pane_borders(struct redraw_build_ctx *bctx,
    struct window_pane *wp, int sb_w, int sb_left)
{
	enum pane_lines pane_lines = window_pane_get_pane_lines(wp);
	int		pane_status, left, right, top, bottom, wx, wy;
	int		draw_top, draw_bottom, draw_left, draw_right, mask = 0;

	if (window_pane_is_floating(wp) && pane_lines == PANE_LINES_NONE)
		return;
	pane_status = window_pane_get_pane_status(wp);

	left = wp->xoff - 1;
	right = wp->xoff + (int)wp->sx;
	if (sb_w != 0) {
		if (sb_left)
			left -= sb_w;
		else
			right += sb_w;
	}
	top = wp->yoff - 1;
	bottom = wp->yoff + (int)wp->sy;

	draw_left = (left >= 0);
	draw_right = (right <= (int)bctx->w->sx);
	draw_top = (top >= 0);
	draw_bottom = (bottom <= (int)bctx->w->sy);

	if (pane_status == PANE_STATUS_TOP)
		draw_bottom = 0;
	else if (pane_status == PANE_STATUS_BOTTOM)
		draw_top = 0;

	if (draw_top) {
		for (wx = left; wx <= right; wx++) {
			mask = 0;
			if (wx > left)
				mask |= REDRAW_BORDER_L;
			if (wx < right)
				mask |= REDRAW_BORDER_R;
			screen_redraw_mark_border_cell(bctx, wx, top, wp,
			    0, 1, mask);
		}
	}
	if (draw_bottom) {
		for (wx = left; wx <= right; wx++) {
			mask = 0;
			if (wx > left)
				mask |= REDRAW_BORDER_L;
			if (wx < right)
				mask |= REDRAW_BORDER_R;
			screen_redraw_mark_border_cell(bctx, wx, bottom, wp,
			    1, 0, ((wx > left) ? REDRAW_BORDER_L : 0) |
			    ((wx < right) ? REDRAW_BORDER_R : 0));
		}
	}
	if (draw_left) {
		for (wy = top; wy <= bottom; wy++) {
			mask = 0;
			if (wy > top)
				mask |= REDRAW_BORDER_U;
			if (wy < bottom)
				mask |= REDRAW_BORDER_D;
			screen_redraw_mark_border_cell(bctx, left, wy, wp,
			    0, 0, mask);
		}
	}
	if (draw_right) {
		for (wy = top; wy <= bottom; wy++) {
			mask = 0;
			if (wy > top)
				mask |= REDRAW_BORDER_U;
			if (wy < bottom)
				mask |= REDRAW_BORDER_D;
			screen_redraw_mark_border_cell(bctx, right, wy, wp,
			    0, 0, mask);
		}
	}

	screen_redraw_mark_border_status(bctx, wp, left, right, top, bottom);
	screen_redraw_mark_border_arrows(bctx, wp, left, right, top, bottom);
}

/*
 * Mark an entire pane in the build grid. Floating panes overwrite anything
 * already below them.
 */
static void
screen_redraw_mark_pane(struct redraw_build_ctx *bctx, struct window_pane *wp)
{
	int	sb_w = 0, sb_left = 0;

	if (!window_pane_is_visible(wp))
		return;

	if (window_pane_show_scrollbar(wp, bctx->sb))
		sb_w = wp->scrollbar_style.width + wp->scrollbar_style.pad;
	if (sb_w != 0 && bctx->sbp == PANE_SCROLLBARS_LEFT)
		sb_left = 1;

	screen_redraw_clear_floating_pane(bctx, wp, sb_w, sb_left);
	screen_redraw_mark_pane_inside(bctx, wp);
	screen_redraw_mark_pane_borders(bctx, wp, sb_w, sb_left);
	screen_redraw_mark_pane_scrollbar(bctx, wp, sb_w, sb_left);
}

/* Mark the indicator. */
static void
screen_redraw_mark_two_pane_colours(struct redraw_build_ctx *bctx)
{
	struct redraw_build_cell	*bc;
	struct redraw_span_data		*sd;
	enum layout_type		 type;
	u_int				 x, y, wx, wy;

	if (bctx->ind != PANE_BORDER_COLOUR && bctx->ind != PANE_BORDER_BOTH)
		return;
	if (!screen_redraw_two_panes(bctx->w, &type))
		return;

	for (y = 0; y < bctx->sy; y++) {
		for (x = 0; x < bctx->sx; x++) {
			bc = screen_redraw_cell(bctx, x, y);
			if (bc->data.type != REDRAW_SPAN_BORDER)
				continue;
			sd = &bc->data;

			wx = bctx->ox + x;
			wy = bctx->oy + y;

			if (type == LAYOUT_LEFTRIGHT &&
			    sd->b.left_wp != NULL &&
			    sd->b.right_wp != NULL) {
				if (wy <= bctx->w->sy / 2)
					sd->b.style_wp = sd->b.left_wp;
				else
					sd->b.style_wp = sd->b.right_wp;
			} else if (type == LAYOUT_TOPBOTTOM &&
			    sd->b.top_wp != NULL &&
			    sd->b.bottom_wp != NULL) {
				if (wx <= bctx->w->sx / 2)
					sd->b.style_wp = sd->b.top_wp;
				else
					sd->b.style_wp = sd->b.bottom_wp;
			}
		}
	}
}

/* Return true if two adjacent build data can be coalesced into one span. */
static int
screen_redraw_data_cmp(struct redraw_build_cell *a, struct redraw_build_cell *b)
{
	struct redraw_span_data	*ad = &a->data, *bd = &b->data;

	if (ad->type != bd->type)
		return (0);

	switch (ad->type) {
	case REDRAW_SPAN_PANE:
		if (ad->p.wp != bd->p.wp ||
		    ad->p.py != bd->p.py ||
		    ad->p.px + 1 != bd->p.px)
			return (0);
		return (1);
	case REDRAW_SPAN_BORDER:
		if (ad->b.top_wp != bd->b.top_wp ||
		    ad->b.bottom_wp != bd->b.bottom_wp ||
		    ad->b.left_wp != bd->b.left_wp ||
		    ad->b.right_wp != bd->b.right_wp ||
		    ad->b.style_wp != bd->b.style_wp ||
		    ad->b.top_lines != bd->b.top_lines ||
		    ad->b.bottom_lines != bd->b.bottom_lines ||
		    ad->b.left_lines != bd->b.left_lines ||
		    ad->b.right_lines != bd->b.right_lines ||
		    ad->b.cell_type != bd->b.cell_type ||
		    ad->b.cell_mask != bd->b.cell_mask ||
		    ad->b.flags != bd->b.flags)
			return (0);
		if (ad->b.flags & REDRAW_BORDER_IS_ARROW)
			return (0);
		return (1);
	case REDRAW_SPAN_STATUS:
		if (ad->st.wp != bd->st.wp ||
		    ad->st.offset + 1 != bd->st.offset)
			return (0);
		return (1);
	case REDRAW_SPAN_SCROLLBAR:
		if (ad->sb.wp != bd->sb.wp ||
		    ad->sb.y != bd->sb.y ||
		    ad->sb.height != bd->sb.height ||
		    ad->sb.flags != bd->sb.flags)
			return (0);
		return (1);
	case REDRAW_SPAN_OUTSIDE:
	case REDRAW_SPAN_EMPTY:
		return (1);
	}
	return (0);
}

/* Convert the cells into spans. */
static void
screen_redraw_finish_scene(struct redraw_build_ctx *bctx,
    struct redraw_scene *scene)
{
	struct redraw_build_cell	*bc, *last;
	struct redraw_line		*line;
	struct redraw_span		*span;
	enum redraw_span_type		 type;
	u_int				 x, y, x0;

	for (y = 0; y < bctx->sy; y++) {
		line = &scene->lines[y];
		x = 0;
		while (x < bctx->sx) {
			x0 = x;
			last = screen_redraw_cell(bctx, x, y);
			x++;

			while (x < bctx->sx) {
				bc = screen_redraw_cell(bctx, x, y);
				if (!screen_redraw_data_cmp(last, bc))
					break;
				last = bc;
				x++;
			}
			bc = screen_redraw_cell(bctx, x0, y);
			type = bc->data.type;

			span = xcalloc(1, sizeof *span);
			span->x = x0;
			span->width = x - x0;
			span->data = bc->data;
			TAILQ_INSERT_TAIL(&line->spans[type], span, entry);
		}
	}
}


/*
 * Build and return a redraw scene for c. The caller owns the scene and must
 * free it with screen_redraw_free_scene().
 */
static struct redraw_scene *
screen_redraw_make_scene(struct client *c)
{
	struct redraw_build_ctx	 bctx;
	struct redraw_scene	*scene;
	struct window_pane	*wp;
	u_int			 x, y, type;
	size_t			 ncells;

	if (c->flags & CLIENT_SUSPENDED)
		return (NULL);
	screen_redraw_set_context(c, &bctx);

	scene = xcalloc(1, sizeof *scene);
	scene->c = c;
	scene->w = bctx.w;
	scene->sx = bctx.sx;
	scene->sy = bctx.sy;
	scene->ox = bctx.ox;
	scene->oy = bctx.oy;

	scene->lines = xcalloc(scene->sy, sizeof *scene->lines);
	for (y = 0; y < scene->sy; y++) {
		for (type = 0; type < REDRAW_SPAN_TYPES; type++)
			TAILQ_INIT(&scene->lines[y].spans[type]);
	}

	if (bctx.sx != 0 && bctx.sy > SIZE_MAX / bctx.sx)
		fatalx("%s: too many cells", __func__);
	ncells = (size_t)bctx.sx * bctx.sy;
	if (ncells > SIZE_MAX / sizeof *bctx.cells)
		fatalx("%s: too many cells", __func__);
	bctx.cells = xmalloc(ncells * sizeof *bctx.cells);
	for (y = 0; y < bctx.sy; y++) {
		for (x = 0; x < bctx.sx; x++)
			screen_redraw_reset_cell(&bctx, x, y);
	}

	TAILQ_FOREACH_REVERSE(wp, &bctx.w->z_index, window_panes_zindex, zentry)
	    screen_redraw_mark_pane(&bctx, wp);

	screen_redraw_mark_two_pane_colours(&bctx);
	screen_redraw_finish_scene(&bctx, scene);

	free(bctx.cells);
	return (scene);
}

/* Free a scene. */
static void
screen_redraw_free_scene(struct redraw_scene *scene)
{
	struct redraw_spans	*spans;
	struct redraw_span	*span, *span1;
	u_int			 y, type;

	for (y = 0; y < scene->sy; y++) {
		for (type = 0; type < REDRAW_SPAN_TYPES; type++) {
			spans = &scene->lines[y].spans[type];
			TAILQ_FOREACH_SAFE(span, spans, entry, span1) {
				TAILQ_REMOVE(spans, span, entry);
				free(span);
			}
		}
	}
	free(scene->lines);
	free(scene);
}

/* Is this span adjacent to this pane? */
static int
screen_redraw_span_has_pane(struct redraw_span *span, struct window_pane *wp)
{
	if (span->data.b.top_wp == wp)
		return (1);
	if (span->data.b.bottom_wp == wp)
		return (1);
	if (span->data.b.left_wp == wp)
		return (1);
	if (span->data.b.right_wp == wp)
		return (1);
	return (0);
}

/* Draw a pane span. */
static void
screen_redraw_draw_pane_span(struct redraw_scene *scene,
    struct redraw_span *span, u_int x, u_int y, u_int n)
{
	struct client		*c = scene->c;
	struct tty		*tty = &c->tty;
	struct window_pane	*wp = span->data.p.wp;
	struct screen		*s = wp->screen;
	struct grid_cell	 defaults;
	struct tty_style_ctx	 style_ctx;
	u_int			 px, py;

	//XXX sync?

	tty_default_colours(&defaults, wp);
	style_ctx.defaults = &defaults;
	style_ctx.palette = &wp->palette;
	style_ctx.hyperlinks = s->hyperlinks;

	px = span->data.p.px + (x - span->x);
	py = span->data.p.py;

	tty_draw_line(tty, s, px, py, n, x, y, &style_ctx);
}

/* Draw a border span. */
static void
screen_redraw_draw_border_span(struct redraw_scene *scene,
    struct redraw_span *span, u_int x, u_int y, u_int n)
{
	struct client	*c = scene->c;
	struct tty	*tty = &c->tty;

	tty_cursor(tty, x, y);
	for (x = 0; x < n; x++)
		tty_putc(tty, '-');
}

/* Draw a status span. */
static void
screen_redraw_draw_status_span(struct redraw_scene *scene,
    struct redraw_span *span, u_int x, u_int y, u_int n)
{
	struct client	*c = scene->c;
	struct tty	*tty = &c->tty;

	tty_cursor(tty, x, y);
	for (x = 0; x < n; x++)
		tty_putc(tty, 's');
}

/* Draw a scrollbar span. */
static void
screen_redraw_draw_scrollbar_span(struct redraw_scene *scene,
    struct redraw_span *span, u_int x, u_int y, u_int n)
{
	struct window_pane	*wp = span->data.sb.wp;
	struct screen		*s = wp->screen;
	struct tty		*tty = &scene->c->tty;
	struct style		*sb_style = &wp->scrollbar_style;
	struct grid_cell	 gc, slgc, *gcp;
	double			 pct_view;
	u_int			 total_height, slider_h, slider_y;
	u_int			 sb_h = span->data.sb.height;
	u_int			 sb_y = span->data.sb.y;
	u_int			 i, off, sb_w, sb_pad;
	int			 cm_y, cm_size;

	if (window_pane_mode(wp) == WINDOW_PANE_NO_MODE) {
		total_height = screen_size_y(s) + screen_hsize(s);
		if (total_height == 0)
			return;
		pct_view = (double)sb_h / total_height;
		slider_h = (double)sb_h * pct_view;
		slider_y = sb_h - slider_h;
	} else {
		if (TAILQ_FIRST(&wp->modes) == NULL)
			return;
		if (window_copy_get_current_offset(wp, &cm_y, &cm_size) == 0)
			return;
		total_height = cm_size + sb_h;
		if (total_height == 0)
			return;
		pct_view = (double)sb_h / total_height;
		slider_h = (double)sb_h * pct_view;
		slider_y = (sb_h + 1) * ((double)cm_y / total_height);
	}

	if (slider_h < 1)
		slider_h = 1;
	if (slider_y >= sb_h)
		slider_y = sb_h - 1;

	wp->sb_slider_y = slider_y;
	wp->sb_slider_h = slider_h;

	gc = sb_style->gc;
	memcpy(&slgc, &gc, sizeof slgc);
	slgc.fg = gc.bg;
	slgc.bg = gc.fg;

	sb_w = sb_style->width;
	sb_pad = sb_style->pad;
	off = x - span->x;

	tty_cursor(tty, x, y);
	for (i = 0; i < n; i++) {
		if (span->data.sb.flags & REDRAW_SCROLLBAR_LEFT) {
			if (off + i >= sb_w && off + i < sb_w + sb_pad) {
				tty_cell(tty, &grid_default_cell, NULL);
				continue;
			}
		} else {
			if (off + i < sb_pad) {
				tty_cell(tty, &grid_default_cell, NULL);
				continue;
			}
		}

		if (sb_y >= slider_y && sb_y < slider_y + slider_h)
			gcp = &slgc;
		else
			gcp = &gc;
		tty_cell(tty, gcp, NULL);
	}
}

/* Draw a span. */
static void
screen_redraw_draw_span(struct redraw_scene *scene, struct redraw_span *span,
    u_int y)
{
	struct client		*c = scene->c;
	struct tty		*tty = &c->tty;
	struct visible_ranges	*r;
	struct visible_range	*rr;
	u_int			 i, x, n;

	r = tty_check_overlay_range(tty, span->x, y, span->width);
	for (i = 0; i < r->used; i++) {
		rr = &r->ranges[i];
		if (rr->nx == 0)
			continue;
		x = rr->px;
		n = rr->nx;

		switch (span->data.type) {
		case REDRAW_SPAN_PANE:
			screen_redraw_draw_pane_span(scene, span, x, y, n);
			break;
		case REDRAW_SPAN_BORDER:
		case REDRAW_SPAN_EMPTY:
		case REDRAW_SPAN_OUTSIDE:
			screen_redraw_draw_border_span(scene, span, x, y, n);
			break;
		case REDRAW_SPAN_STATUS:
			screen_redraw_draw_status_span(scene, span, x, y, n);
			break;
		case REDRAW_SPAN_SCROLLBAR:
			screen_redraw_draw_scrollbar_span(scene, span, x, y, n);
			break;
		}
	}
}

/* Draw pane lines. */
static void
screen_redraw_draw_pane_lines(struct redraw_scene *scene, u_int status_lines,
    struct window_pane *wp, int flags)
{
	struct redraw_line	*line;
	struct redraw_spans	*spans;
	struct redraw_span	*span;
	u_int			 y, cy, top, bottom;

	if (wp->yoff < (int)scene->oy)
		top = 0;
	else
		top = wp->yoff - scene->oy;
	if (wp->yoff + wp->sy <= scene->oy)
		bottom = 0;
	else
		bottom = wp->yoff + wp->sy - scene->oy;
	if (bottom > scene->sy)
		bottom = scene->sy;

	for (y = top; y < bottom; y++) {
		line = &scene->lines[y];
		cy = status_lines + y;
		if (flags & REDRAW_DRAW_PANE) {
			spans = &line->spans[REDRAW_SPAN_PANE];
			TAILQ_FOREACH(span, spans, entry) {
				if (span->data.p.wp != wp)
					continue;
				screen_redraw_draw_span(scene, span, cy);
			}
		}
		if (flags & REDRAW_DRAW_SCROLLBAR) {
			spans = &line->spans[REDRAW_SPAN_SCROLLBAR];
			TAILQ_FOREACH(span, spans, entry) {
				if (span->data.sb.wp != wp)
					continue;
				cy = status_lines + y;
				screen_redraw_draw_span(scene, span, cy);
			}
		}
	}
}

/* Draw lines. */
static void
screen_redraw_draw_lines(struct redraw_scene *scene, u_int status_lines,
    int flags)
{
	struct redraw_line	*line;
	struct redraw_spans	*spans;
	struct redraw_span	*span;
	u_int			 y, cy, type;

	for (y = 0; y < scene->sy; y++) {
		line = &scene->lines[y];
		cy = status_lines + y;
		for (type = 0; type < REDRAW_SPAN_TYPES; type++) {
			if (flags != REDRAW_DRAW_ALL) {
				switch (type) {
				case REDRAW_SPAN_PANE:
					if (~flags & REDRAW_DRAW_PANE)
						continue;
					break;
				case REDRAW_SPAN_BORDER:
					if (~flags & REDRAW_DRAW_BORDER)
						continue;
					break;
				case REDRAW_SPAN_STATUS:
					if (~flags & REDRAW_DRAW_STATUS)
						continue;
					break;
				case REDRAW_SPAN_SCROLLBAR:
					if (~flags & REDRAW_DRAW_SCROLLBAR)
						continue;
					break;
				default:
					continue;
				}
			}
			spans = &line->spans[type];
			TAILQ_FOREACH(span, spans, entry)
				screen_redraw_draw_span(scene, span, cy);
		}
	}
}

/* Draw scene to client. */
static void
screen_redraw_draw(struct client *c, struct window_pane *wp, int flags)
{
	struct session		*s = c->session;
	struct tty		*tty = &c->tty;
	struct redraw_scene	*scene;
	u_int			 status_lines = 0;

	if (c->flags & CLIENT_SUSPENDED)
		return;

	scene = screen_redraw_make_scene(c); //XXX
	if (scene == NULL)
		return;

	if (options_get_number(s->options, "status-position") == 0)
		status_lines = status_line_size(c);

	tty_sync_start(tty);
	tty_update_mode(tty, 0, NULL);

	if (wp != NULL)
		screen_redraw_draw_pane_lines(scene, status_lines, wp, flags);
	else
		screen_redraw_draw_lines(scene, status_lines, flags);

	tty_reset(tty);
	tty_sync_end(tty);

	screen_redraw_free_scene(scene); //XXX
}

/* Draw screen. */
void
screen_redraw_screen(struct client *c)
{
	int	flags = 0;

	if (c->flags & CLIENT_REDRAWWINDOW)
		screen_redraw_draw(c, NULL, REDRAW_DRAW_ALL);
	else {
		if (c->flags & CLIENT_REDRAWBORDERS)
			flags |= (REDRAW_DRAW_BORDER|REDRAW_DRAW_STATUS);
		if (c->flags & CLIENT_REDRAWSTATUS)
			flags |= REDRAW_DRAW_STATUS;
		screen_redraw_draw(c, NULL, flags);
	}
	//XXX client status line
	//XXX overlays
}

/* Draw a single pane. */
void
screen_redraw_pane(struct client *c, struct window_pane *wp)
{
	screen_redraw_draw(c, wp, REDRAW_DRAW_PANE|REDRAW_DRAW_SCROLLBAR);
}

/* Draw a pane's scrollbar. */
void
screen_redraw_pane_scrollbar(struct client *c, struct window_pane *wp)
{
	screen_redraw_draw(c, wp, REDRAW_DRAW_SCROLLBAR);
}