/* $OpenBSD: screen-write.c,v 1.285 2026/07/26 09:02:08 nicm Exp $ */

/*
 * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

#include <stdlib.h>
#include <string.h>

#include "tmux.h"

static struct screen_write_citem *screen_write_collect_trim(
                    struct screen_write_ctx *, u_int, u_int, u_int, int *);
static void     screen_write_collect_insert(struct screen_write_ctx *,
                    struct screen_write_citem *);
static void     screen_write_collect_insert_clear(struct screen_write_ctx *,
                    u_int, u_int, u_int);
static void     screen_write_collect_clear(struct screen_write_ctx *, u_int,
                    u_int);
static void     screen_write_collect_scroll(struct screen_write_ctx *, u_int);
static void     screen_write_collect_flush(struct screen_write_ctx *, int,
                    const char *);
static int      screen_write_overwrite(struct screen_write_ctx *,
                    struct grid_cell *, u_int);
static int      screen_write_combine(struct screen_write_ctx *,
                    const struct grid_cell *);
static void     screen_write_flush_dirty(struct window_pane *);

struct screen_write_citem {
        u_int                           x;
        int                             wrapped;

        enum { TEXT, CLEAR }            type;
        u_int                           used;
        u_int                           bg;

        struct grid_cell                gc;

        TAILQ_ENTRY(screen_write_citem) entry;
};
struct screen_write_cline {
        char                            *data;
        TAILQ_HEAD(, screen_write_citem) items;
};
TAILQ_HEAD(, screen_write_citem)  screen_write_citem_freelist =
    TAILQ_HEAD_INITIALIZER(screen_write_citem_freelist);

static struct screen_write_citem *
screen_write_get_citem(void)
{
    struct screen_write_citem   *ci;

    ci = TAILQ_FIRST(&screen_write_citem_freelist);
    if (ci != NULL) {
            TAILQ_REMOVE(&screen_write_citem_freelist, ci, entry);
            memset(ci, 0, sizeof *ci);
            return (ci);
    }
    return (xcalloc(1, sizeof *ci));
}

static void
screen_write_free_citem(struct screen_write_citem *ci)
{
        TAILQ_INSERT_TAIL(&screen_write_citem_freelist, ci, entry);
}

static void
screen_write_offset_timer(__unused int fd, __unused short events, void *data)
{
        struct window   *w = data;

        tty_update_window_offset(w);
}

/* Set cursor position. */
static void
screen_write_set_cursor(struct screen_write_ctx *ctx, int cx, int cy)
{
        struct window_pane      *wp = ctx->wp;
        struct window           *w;
        struct screen           *s = ctx->s;
        struct timeval           tv = { .tv_usec = 10000 };

        if (cx != -1 && (u_int)cx == s->cx && cy != -1 && (u_int)cy == s->cy)
                return;

        if (cx != -1) {
                if ((u_int)cx > screen_size_x(s)) /* allow last column */
                        cx = screen_size_x(s) - 1;
                s->cx = cx;
        }
        if (cy != -1) {
                if ((u_int)cy > screen_size_y(s) - 1)
                        cy = screen_size_y(s) - 1;
                s->cy = cy;
        }

        if (wp == NULL)
                return;
        w = wp->window;

        if (!event_initialized(&w->offset_timer))
                evtimer_set(&w->offset_timer, screen_write_offset_timer, w);
        if (!evtimer_pending(&w->offset_timer, NULL))
                evtimer_add(&w->offset_timer, &tv);
}

/* Do a full redraw. */
static void
screen_write_redraw_cb(const struct tty_ctx *ttyctx)
{
        struct window_pane      *wp = ttyctx->arg;

        if (wp != NULL)
                wp->flags |= PANE_REDRAW;
}

/* Update context for client. */
static int
screen_write_set_client_cb(struct tty_ctx *ttyctx, struct client *c)
{
        struct window_pane      *wp = ttyctx->arg;

        if (ttyctx->flags & TTY_CTX_INVISIBLE_PANES) {
                if (session_has(c->session, wp->window))
                        return (1);
                return (0);
        }

        if (c->session->curw->window != wp->window)
                return (0);
        if (wp->layout_cell == NULL)
                return (0);

        if (wp->flags & (PANE_REDRAW|PANE_DROP))
                return (-1);
        if (c->flags & CLIENT_REDRAWWINDOW) {
                /*
                 * Redraw is already deferred to redraw the window - redraw this
                 * one also when that happens.
                 */
                log_debug("%s: adding %%%u to deferred redraw", __func__,
                    wp->id);
                wp->flags |= (PANE_REDRAW|PANE_REDRAWSCROLLBAR);
                return (-1);
        }

        if (tty_window_offset(&c->tty, &ttyctx->wox, &ttyctx->woy, &ttyctx->wsx,
            &ttyctx->wsy))
                ttyctx->flags |= TTY_CTX_WINDOW_BIGGER;
        else
                ttyctx->flags &= ~TTY_CTX_WINDOW_BIGGER;

        ttyctx->xoff = ttyctx->rxoff = wp->xoff;
        ttyctx->yoff = ttyctx->ryoff = wp->yoff;

        if (status_at_line(c) == 0)
                ttyctx->yoff += status_line_size(c);

        return (1);
}

/* Return 1 if there is a floating window pane overlapping this pane. */
static int
screen_write_pane_is_obscured(struct screen_write_ctx *ctx)
{
        struct window_pane      *wp = ctx->wp;

        if (ctx->wp == NULL)
                return (0);
        if (ctx->flags & SCREEN_WRITE_CHECKED_IF_OBSCURED) {
                if (ctx->flags & SCREEN_WRITE_OBSCURED)
                        return (1);
                return (0);
        }
        ctx->flags |= SCREEN_WRITE_CHECKED_IF_OBSCURED;

        if (ctx->wp->xoff < 0 ||
            ctx->wp->yoff < 0 ||
            ctx->wp->xoff + ctx->wp->sx > ctx->wp->window->sx ||
            ctx->wp->yoff + ctx->wp->sy > ctx->wp->window->sy) {
                ctx->flags |= SCREEN_WRITE_OBSCURED;
                return (1);
        }

        while ((wp = TAILQ_PREV(wp, window_panes, zentry)) != NULL) {
                if (window_pane_is_floating(wp) &&
                    ((wp->yoff >= ctx->wp->yoff &&
                    wp->yoff <= ctx->wp->yoff + (int)ctx->wp->sy) ||
                    (wp->yoff + (int)wp->sy >= ctx->wp->yoff &&
                    wp->yoff + wp->sy <= ctx->wp->yoff + ctx->wp->sy)) &&
                    ((wp->xoff >= ctx->wp->xoff &&
                    wp->xoff <= ctx->wp->xoff + (int)ctx->wp->sx) ||
                    (wp->xoff + (int)wp->sx >= ctx->wp->xoff &&
                    wp->xoff + wp->sx <= ctx->wp->xoff + ctx->wp->sx))) {
                        ctx->flags |= SCREEN_WRITE_OBSCURED;
                        return (1);
                }
        }
        return (0);
}

/* Should we draw to the TTY? */
static int
screen_write_should_draw_lines(struct screen_write_ctx *ctx, u_int y, u_int ny)
{
        struct window_pane      *wp = ctx->wp;
        struct screen           *s = ctx->s;
        u_int                    sy = screen_size_y(s);
        bitstr_t                *bs;

        if (wp != NULL && (wp->flags & (PANE_REDRAW|PANE_DROP)))
                return (0);
        if (s->mode & MODE_SYNC) {
                if (wp != NULL && y < sy && ny != 0) {
                        bs = wp->sync_dirty;
                        if (ny > sy - y)
                                ny = sy - y;
                        if (bs == NULL || wp->sync_dirty_size != sy) {
                                if (bs != NULL && wp->sync_dirty_size != sy) {
                                        y = 0;
                                        ny = sy;
                                }
                                free(bs);

                                bs = wp->sync_dirty = bit_alloc(sy);
                                if (bs == NULL)
                                        fatal("bit_alloc failed");
                                wp->sync_dirty_size = sy;
                        }
                        bit_nset(bs, y, y + ny - 1);
                }
                return (0);
        }
        return (1);
}

/* Should we draw this line to the TTY? */
static int
screen_write_should_draw_line(struct screen_write_ctx *ctx, u_int y)
{
        return (screen_write_should_draw_lines(ctx, y, 1));
}

/* Set up context for TTY command. */
static void
screen_write_initctx(struct screen_write_ctx *ctx, struct tty_ctx *ttyctx,
    int is_sync, int check_obscured)
{
        struct screen           *s = ctx->s;
        struct colour_palette   *palette = NULL;

        memset(ttyctx, 0, sizeof *ttyctx);

        ttyctx->s = s;
        ttyctx->sx = screen_size_x(s);
        ttyctx->sy = screen_size_y(s);

        ttyctx->ocx = s->cx;
        ttyctx->ocy = s->cy;
        ttyctx->orlower = s->rlower;
        ttyctx->orupper = s->rupper;

        if (check_obscured && screen_write_pane_is_obscured(ctx))
                ttyctx->flags |= TTY_CTX_PANE_OBSCURED;

        memcpy(&ttyctx->defaults, &grid_default_cell, sizeof ttyctx->defaults);
        ttyctx->style_ctx.defaults = &ttyctx->defaults;
        ttyctx->style_ctx.hyperlinks = ctx->s->hyperlinks;

        if (ctx->init_ctx_cb != NULL) {
                ctx->init_ctx_cb(ctx, ttyctx);
                if (ttyctx->style_ctx.palette != NULL) {
                        palette = ttyctx->style_ctx.palette;
                        if (ttyctx->defaults.fg == 8)
                                ttyctx->defaults.fg = palette->fg;
                        if (ttyctx->defaults.bg == 8)
                                ttyctx->defaults.bg = palette->bg;
                }
        } else {
                ttyctx->redraw_cb = screen_write_redraw_cb;
                if (ctx->wp != NULL) {
                        tty_default_colours(&ttyctx->defaults, ctx->wp,
                            &ttyctx->style_ctx.dim);
                        ttyctx->style_ctx.palette = &ctx->wp->palette;
                        ttyctx->set_client_cb = screen_write_set_client_cb;
                        ttyctx->arg = ctx->wp;
                }
        }

        if (~ctx->flags & SCREEN_WRITE_SYNC) {
                /*
                 * For the active pane or for an overlay (no pane), we want to
                 * only use synchronized updates if requested (commands that
                 * move the cursor); for other panes, always use it, since the
                 * cursor will have to move.
                 */
                if (ctx->wp != NULL && ctx->wp != ctx->wp->window->active)
                        ttyctx->flags |= TTY_CTX_SYNC;
                else {
                        if (ctx->wp == NULL)
                                ttyctx->flags |= TTY_CTX_OVERLAY_SYNC;
                        if (is_sync)
                                ttyctx->flags |= TTY_CTX_SYNC;
                }
                tty_write(tty_cmd_syncstart, ttyctx);
                ctx->flags |= SCREEN_WRITE_SYNC;
        }
}

/* Make write list. */
void
screen_write_make_list(struct screen *s)
{
        u_int   y;

        s->write_list = xcalloc(screen_size_y(s), sizeof *s->write_list);
        for (y = 0; y < screen_size_y(s); y++)
                TAILQ_INIT(&s->write_list[y].items);
}

/* Free write list. */
void
screen_write_free_list(struct screen *s)
{
        u_int   y;

        for (y = 0; y < screen_size_y(s); y++)
                free(s->write_list[y].data);
        free(s->write_list);
}

/* Set up for writing. */
static void
screen_write_init(struct screen_write_ctx *ctx, struct screen *s)
{
        memset(ctx, 0, sizeof *ctx);

        ctx->s = s;

        if (ctx->s->write_list == NULL)
                screen_write_make_list(ctx->s);
        ctx->item = screen_write_get_citem();

        ctx->scrolled = 0;
        ctx->bg = 8;
}

/* Initialize writing with a pane. */
void
screen_write_start_pane(struct screen_write_ctx *ctx, struct window_pane *wp,
    struct screen *s)
{
        if (s == NULL)
                s = wp->screen;
        screen_write_init(ctx, s);
        ctx->wp = wp;

        if (log_get_level() != 0) {
                log_debug("%s: size %ux%u, pane %%%u (at %u,%u)",
                    __func__, screen_size_x(ctx->s), screen_size_y(ctx->s),
                    wp->id, wp->xoff, wp->yoff);
        }
}

/* Initialize writing with a callback. */
void
screen_write_start_callback(struct screen_write_ctx *ctx, struct screen *s,
    screen_write_init_ctx_cb cb, void *arg)
{
        screen_write_init(ctx, s);

        ctx->init_ctx_cb = cb;
        ctx->arg = arg;

        if (log_get_level() != 0) {
                log_debug("%s: size %ux%u, with callback", __func__,
                    screen_size_x(ctx->s), screen_size_y(ctx->s));
        }
}

/* Initialize writing. */
void
screen_write_start(struct screen_write_ctx *ctx, struct screen *s)
{
        screen_write_init(ctx, s);

        if (log_get_level() != 0) {
                log_debug("%s: size %ux%u, no pane", __func__,
                    screen_size_x(ctx->s), screen_size_y(ctx->s));
        }
}

/* Finish writing. */
void
screen_write_stop(struct screen_write_ctx *ctx)
{
        screen_write_collect_end(ctx);
        screen_write_collect_flush(ctx, 0, __func__);

        screen_write_free_citem(ctx->item);
}

/* Reset screen state. */
void
screen_write_reset(struct screen_write_ctx *ctx)
{
        struct screen   *s = ctx->s;

        screen_reset_tabs(s);
        screen_write_scrollregion(ctx, 0, screen_size_y(s) - 1);

        s->mode = MODE_CURSOR|MODE_WRAP;

        if (options_get_number(global_options, "extended-keys") == 2)
                s->mode = (s->mode & ~EXTENDED_KEY_MODES)|MODE_KEYS_EXTENDED;

        screen_write_clearscreen(ctx, 8);
        screen_write_set_cursor(ctx, 0, 0);
}

/* Write character. */
void
screen_write_putc(struct screen_write_ctx *ctx, const struct grid_cell *gcp,
    u_char ch)
{
        struct grid_cell        gc;

        memcpy(&gc, gcp, sizeof gc);

        utf8_set(&gc.data, ch);
        screen_write_cell(ctx, &gc);
}

/* Calculate string length. */
size_t
screen_write_strlen(const char *fmt, ...)
{
        va_list                 ap;
        char                   *msg;
        struct utf8_data        ud;
        u_char                 *ptr;
        size_t                  left, size = 0;
        enum utf8_state         more;

        va_start(ap, fmt);
        xvasprintf(&msg, fmt, ap);
        va_end(ap);

        ptr = msg;
        while (*ptr != '\0') {
                if (*ptr > 0x7f && utf8_open(&ud, *ptr) == UTF8_MORE) {
                        ptr++;

                        left = strlen(ptr);
                        if (left < (size_t)ud.size - 1)
                                break;
                        while ((more = utf8_append(&ud, *ptr)) == UTF8_MORE)
                                ptr++;
                        ptr++;

                        if (more == UTF8_DONE)
                                size += ud.width;
                } else {
                        if (*ptr == '\t' || (*ptr > 0x1f && *ptr < 0x7f))
                                size++;
                        ptr++;
                }
        }

        free(msg);
        return (size);
}

/* Write string wrapped over lines. */
int
screen_write_text(struct screen_write_ctx *ctx, u_int cx, u_int width,
    u_int lines, int more, const struct grid_cell *gcp, const char *fmt, ...)
{
        struct screen           *s = ctx->s;
        va_list                  ap;
        char                    *tmp;
        u_int                    cy = s->cy, i, end, next, idx = 0, at, left;
        struct utf8_data        *text;
        struct grid_cell         gc;

        memcpy(&gc, gcp, sizeof gc);

        va_start(ap, fmt);
        xvasprintf(&tmp, fmt, ap);
        va_end(ap);

        text = utf8_fromcstr(tmp);
        free(tmp);

        left = (cx + width) - s->cx;
        for (;;) {
                /* Find the end of what can fit on the line. */
                at = 0;
                for (end = idx; text[end].size != 0; end++) {
                        if (text[end].size == 1 && text[end].data[0] == '\n')
                                break;
                        if (at + text[end].width > left)
                                break;
                        at += text[end].width;
                }

                /*
                 * If we're on a space, that's the end. If not, walk back to
                 * try and find one.
                 */
                if (text[end].size == 0)
                        next = end;
                else if (text[end].size == 1 && text[end].data[0] == '\n')
                        next = end + 1;
                else if (text[end].size == 1 && text[end].data[0] == ' ')
                        next = end + 1;
                else {
                        for (i = end; i > idx; i--) {
                                if (text[i].size == 1 && text[i].data[0] == ' ')
                                        break;
                        }
                        if (i != idx) {
                                next = i + 1;
                                end = i;
                        } else
                                next = end;
                }

                /* Print the line. */
                for (i = idx; i < end; i++) {
                        utf8_copy(&gc.data, &text[i]);
                        screen_write_cell(ctx, &gc);
                }

                /* If at the bottom, stop. */
                idx = next;
                if (s->cy == cy + lines - 1 || text[idx].size == 0)
                        break;

                screen_write_cursormove(ctx, cx, s->cy + 1, 0);
                left = width;
        }

        /*
         * Fail if on the last line and there is more to come or at the end, or
         * if the text was not entirely consumed.
         */
        if ((s->cy == cy + lines - 1 && (!more || s->cx == cx + width)) ||
            text[idx].size != 0) {
                free(text);
                return (0);
        }
        free(text);

        /*
         * If no more to come, move to the next line. Otherwise, leave on
         * the same line (except if at the end).
         */
        if (!more || s->cx == cx + width)
                screen_write_cursormove(ctx, cx, s->cy + 1, 0);
        return (1);
}

/* Write simple string (no maximum length). */
void
screen_write_puts(struct screen_write_ctx *ctx, const struct grid_cell *gcp,
    const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        screen_write_vnputs(ctx, -1, gcp, fmt, ap);
        va_end(ap);
}

/* Write string with length limit (-1 for unlimited). */
void
screen_write_nputs(struct screen_write_ctx *ctx, ssize_t maxlen,
    const struct grid_cell *gcp, const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        screen_write_vnputs(ctx, maxlen, gcp, fmt, ap);
        va_end(ap);
}

void
screen_write_vnputs(struct screen_write_ctx *ctx, ssize_t maxlen,
    const struct grid_cell *gcp, const char *fmt, va_list ap)
{
        struct grid_cell        gc;
        struct utf8_data       *ud = &gc.data;
        char                   *msg;
        u_char                 *ptr;
        size_t                  left, size = 0;
        enum utf8_state         more;

        memcpy(&gc, gcp, sizeof gc);
        xvasprintf(&msg, fmt, ap);

        ptr = msg;
        while (*ptr != '\0') {
                if (*ptr > 0x7f && utf8_open(ud, *ptr) == UTF8_MORE) {
                        ptr++;

                        left = strlen(ptr);
                        if (left < (size_t)ud->size - 1)
                                break;
                        while ((more = utf8_append(ud, *ptr)) == UTF8_MORE)
                                ptr++;
                        ptr++;

                        if (more != UTF8_DONE)
                                continue;
                        if (maxlen > 0 && size + ud->width > (size_t)maxlen) {
                                while (size < (size_t)maxlen) {
                                        screen_write_putc(ctx, &gc, ' ');
                                        size++;
                                }
                                break;
                        }
                        size += ud->width;
                        screen_write_cell(ctx, &gc);
                } else {
                        if (maxlen > 0 && size + 1 > (size_t)maxlen)
                                break;

                        if (*ptr == '\001')
                                gc.attr ^= GRID_ATTR_CHARSET;
                        else if (*ptr == '\n') {
                                screen_write_linefeed(ctx, 0, 8);
                                screen_write_carriagereturn(ctx);
                        } else if (*ptr == '\t' || (*ptr > 0x1f && *ptr < 0x7f)) {
                                size++;
                                screen_write_putc(ctx, &gc, *ptr);
                        }
                        ptr++;
                }
        }

        free(msg);
}

/*
 * Copy from another screen but without the selection stuff. Assumes the target
 * region is already big enough.
 */
void
screen_write_fast_copy(struct screen_write_ctx *ctx, struct screen *src,
    u_int px, u_int py, u_int nx, u_int ny)
{
        struct screen           *s = ctx->s;
        struct window_pane      *wp = ctx->wp;
        struct tty_ctx           ttyctx;
        struct grid             *gd = src->grid;
        struct grid_line        *gl, *sgl;
        struct grid_cell         gc;
        u_int                    xx, yy, cx = s->cx, cy = s->cy;
        int                      xoff = 0, yoff = 0;
        struct visible_ranges   *r;

        if (nx == 0 || ny == 0)
                return;
        if (wp != NULL) {
                xoff = wp->xoff;
                yoff = wp->yoff;
        }

        for (yy = py; yy < py + ny; yy++) {
                if (yy >= gd->hsize + gd->sy)
                        break;
                s->cx = cx;
                screen_write_initctx(ctx, &ttyctx, 0, 0);
                r = window_visible_ranges(wp, xoff + s->cx, s->cy + yoff, nx,
                    NULL);
                for (xx = px; xx < px + nx; xx++) {
                        gl = grid_get_line(gd, yy);
                        sgl = grid_get_line(s->grid, s->cy);
                        if (xx >= gl->cellsize && s->cx >= sgl->cellsize)
                                break;

                        grid_get_cell(gd, xx, yy, &gc);
                        if (xx + gc.data.width > px + nx)
                                break;
                        grid_view_set_cell(s->grid, s->cx, s->cy, &gc);

                        if (!window_position_is_visible(r, xoff + s->cx))
                                break;
                        ttyctx.cell = &gc;
                        ttyctx.flags &= (TTY_CTX_OVERLAY_SYNC|TTY_CTX_SYNC);
                        tty_write(tty_cmd_cell, &ttyctx);
                        ttyctx.ocx++;

                        s->cx++;
                }
                s->cy++;
        }

        s->cx = cx;
        s->cy = cy;
}

/* Select character set for drawing border lines. */
static void
screen_write_box_border_set(enum box_lines lines, int cell_type,
    struct grid_cell *gc)
{
        switch (lines) {
        case BOX_LINES_NONE:
                break;
        case BOX_LINES_DOUBLE:
                gc->attr &= ~GRID_ATTR_CHARSET;
                utf8_copy(&gc->data, tty_acs_double_borders(cell_type));
                break;
        case BOX_LINES_HEAVY:
                gc->attr &= ~GRID_ATTR_CHARSET;
                utf8_copy(&gc->data, tty_acs_heavy_borders(cell_type));
                break;
        case BOX_LINES_ROUNDED:
                gc->attr &= ~GRID_ATTR_CHARSET;
                utf8_copy(&gc->data, tty_acs_rounded_borders(cell_type));
                break;
        case BOX_LINES_SIMPLE:
                gc->attr &= ~GRID_ATTR_CHARSET;
                utf8_set(&gc->data, SIMPLE_BORDERS[cell_type]);
                break;
        case BOX_LINES_PADDED:
                gc->attr &= ~GRID_ATTR_CHARSET;
                utf8_set(&gc->data, PADDED_BORDERS[cell_type]);
                break;
        case BOX_LINES_SINGLE:
        case BOX_LINES_DEFAULT:
                gc->attr |= GRID_ATTR_CHARSET;
                utf8_set(&gc->data, CELL_BORDERS[cell_type]);
                break;
        }
}

/* Draw a horizontal line on screen. */
void
screen_write_hline(struct screen_write_ctx *ctx, u_int nx, int left, int right,
   enum box_lines lines, const struct grid_cell *border_gc)
{
        struct screen           *s = ctx->s;
        struct grid_cell         gc;
        u_int                    cx, cy, i;

        cx = s->cx;
        cy = s->cy;

        if (border_gc != NULL)
                memcpy(&gc, border_gc, sizeof gc);
        else
                memcpy(&gc, &grid_default_cell, sizeof gc);
        gc.attr |= GRID_ATTR_CHARSET;

        if (left)
                screen_write_box_border_set(lines, CELL_URD, &gc);
        else
                screen_write_box_border_set(lines, CELL_LR, &gc);
        screen_write_cell(ctx, &gc);

        screen_write_box_border_set(lines, CELL_LR, &gc);
        for (i = 1; i < nx - 1; i++)
                screen_write_cell(ctx, &gc);

        if (right)
                screen_write_box_border_set(lines, CELL_ULD, &gc);
        else
                screen_write_box_border_set(lines, CELL_LR, &gc);
        screen_write_cell(ctx, &gc);

        screen_write_set_cursor(ctx, cx, cy);
}

/* Draw a vertical line on screen. */
void
screen_write_vline(struct screen_write_ctx *ctx, u_int ny, int top, int bottom,
    const struct grid_cell *gcp)
{
        struct screen           *s = ctx->s;
        struct grid_cell         gc;
        u_int                    cx, cy, i;

        cx = s->cx;
        cy = s->cy;

        if (gcp != NULL)
                memcpy(&gc, gcp, sizeof gc);
        else
                memcpy(&gc, &grid_default_cell, sizeof gc);
        gc.attr |= GRID_ATTR_CHARSET;

        screen_write_putc(ctx, &gc, top ? 'w' : 'x');
        for (i = 1; i < ny - 1; i++) {
                screen_write_set_cursor(ctx, cx, cy + i);
                screen_write_putc(ctx, &gc, 'x');
        }
        screen_write_set_cursor(ctx, cx, cy + ny - 1);
        screen_write_putc(ctx, &gc, bottom ? 'v' : 'x');

        screen_write_set_cursor(ctx, cx, cy);
}

/* Draw a menu on screen. */
void
screen_write_menu(struct screen_write_ctx *ctx, struct menu *menu, int choice,
    enum box_lines lines, const struct grid_cell *menu_gc,
    const struct grid_cell *border_gc, const struct grid_cell *choice_gc)
{
        struct screen           *s = ctx->s;
        struct grid_cell         default_gc;
        const struct grid_cell  *gc = &default_gc;
        u_int                    cx, cy, i, j, width = menu->width;
        const char              *name;

        cx = s->cx;
        cy = s->cy;

        memcpy(&default_gc, menu_gc, sizeof default_gc);

        screen_write_box(ctx, menu->width + 4, menu->count + 2, lines,
            border_gc, menu->title);

        for (i = 0; i < menu->count; i++) {
                name = menu->items[i].name;
                if (name == NULL) {
                        screen_write_cursormove(ctx, cx, cy + 1 + i, 0);
                        screen_write_hline(ctx, width + 4, 1, 1, lines,
                            border_gc);
                        continue;
                }

                if (choice >= 0 && i == (u_int)choice && *name != '-')
                        gc = choice_gc;

                screen_write_cursormove(ctx, cx + 1, cy + 1 + i, 0);
                for (j = 0; j < width + 2; j++)
                        screen_write_putc(ctx, gc, ' ');

                screen_write_cursormove(ctx, cx + 2, cy + 1 + i, 0);
                if (*name == '-') {
                        default_gc.attr |= GRID_ATTR_DIM;
                        format_draw(ctx, gc, width, name + 1, NULL, 0);
                        default_gc.attr &= ~GRID_ATTR_DIM;
                        continue;
                }

                format_draw(ctx, gc, width, name, NULL, 0);
                gc = &default_gc;
        }

        screen_write_set_cursor(ctx, cx, cy);
}

/* Draw a box on screen. */
void
screen_write_box(struct screen_write_ctx *ctx, u_int nx, u_int ny,
    enum box_lines lines, const struct grid_cell *gcp, const char *title)
{
        struct screen           *s = ctx->s;
        struct grid_cell         gc;
        u_int                    cx, cy, i;

        cx = s->cx;
        cy = s->cy;

        if (gcp != NULL)
                memcpy(&gc, gcp, sizeof gc);
        else
                memcpy(&gc, &grid_default_cell, sizeof gc);

        gc.attr |= GRID_ATTR_CHARSET;
        gc.flags |= GRID_FLAG_NOPALETTE;

        /* Draw top border */
        screen_write_box_border_set(lines, CELL_RD, &gc);
        screen_write_cell(ctx, &gc);
        screen_write_box_border_set(lines, CELL_LR, &gc);
        for (i = 1; i < nx - 1; i++)
                screen_write_cell(ctx, &gc);
        screen_write_box_border_set(lines, CELL_LD, &gc);
        screen_write_cell(ctx, &gc);

        /* Draw bottom border */
        screen_write_set_cursor(ctx, cx, cy + ny - 1);
        screen_write_box_border_set(lines, CELL_RU, &gc);
        screen_write_cell(ctx, &gc);
        screen_write_box_border_set(lines, CELL_LR, &gc);
        for (i = 1; i < nx - 1; i++)
                screen_write_cell(ctx, &gc);
        screen_write_box_border_set(lines, CELL_LU, &gc);
        screen_write_cell(ctx, &gc);

        /* Draw sides */
        screen_write_box_border_set(lines, CELL_UD, &gc);
        for (i = 1; i < ny - 1; i++) {
                /* left side */
                screen_write_set_cursor(ctx, cx, cy + i);
                screen_write_cell(ctx, &gc);
                /* right side */
                screen_write_set_cursor(ctx, cx + nx - 1, cy + i);
                screen_write_cell(ctx, &gc);
        }

        if (title != NULL) {
                gc.attr &= ~GRID_ATTR_CHARSET;
                screen_write_cursormove(ctx, cx + 2, cy, 0);
                format_draw(ctx, &gc, nx - 4, title, NULL, 0);
        }

        screen_write_set_cursor(ctx, cx, cy);
}

/*
 * Write a preview version of a window. Assumes target area is big enough and
 * already cleared.
 */
void
screen_write_preview(struct screen_write_ctx *ctx, struct screen *src, u_int nx,
    u_int ny)
{
        struct screen           *s = ctx->s;
        struct grid_cell         gc;
        u_int                    cx, cy, px, py;

        cx = s->cx;
        cy = s->cy;

        /*
         * If the cursor is on, pick the area around the cursor, otherwise use
         * the top left.
         */
        if (src->mode & MODE_CURSOR) {
                px = src->cx;
                if (px < nx / 3)
                        px = 0;
                else
                        px = px - nx / 3;
                if (px + nx > screen_size_x(src)) {
                        if (nx > screen_size_x(src))
                                px = 0;
                        else
                                px = screen_size_x(src) - nx;
                }
                py = src->cy;
                if (py < ny / 3)
                        py = 0;
                else
                        py = py - ny / 3;
                if (py + ny > screen_size_y(src)) {
                        if (ny > screen_size_y(src))
                                py = 0;
                        else
                                py = screen_size_y(src) - ny;
                }
        } else {
                px = 0;
                py = 0;
        }

        screen_write_fast_copy(ctx, src, px, src->grid->hsize + py, nx, ny);

        if (src->mode & MODE_CURSOR) {
                grid_view_get_cell(src->grid, src->cx, src->cy, &gc);
                gc.attr |= GRID_ATTR_REVERSE;
                screen_write_set_cursor(ctx, cx + (src->cx - px),
                    cy + (src->cy - py));
                screen_write_cell(ctx, &gc);
        }
}

/* Set a mode. */
void
screen_write_mode_set(struct screen_write_ctx *ctx, int mode)
{
        struct screen   *s = ctx->s;

        s->mode |= mode;

        if (log_get_level() != 0)
                log_debug("%s: %s", __func__, screen_mode_to_string(mode));
}

/* Clear a mode. */
void
screen_write_mode_clear(struct screen_write_ctx *ctx, int mode)
{
        struct screen   *s = ctx->s;

        s->mode &= ~mode;

        if (log_get_level() != 0)
                log_debug("%s: %s", __func__, screen_mode_to_string(mode));
}

/* Sync timeout callback. */
static void
screen_write_sync_callback(__unused int fd, __unused short events, void *arg)
{
        struct window_pane      *wp = arg;

        log_debug("%s: %%%u sync timer expired", __func__, wp->id);
        evtimer_del(&wp->sync_timer);

        if (wp->base.mode & MODE_SYNC) {
                wp->base.mode &= ~MODE_SYNC;
                screen_write_flush_dirty(wp);
        }
}

/* Start sync mode. */
void
screen_write_start_sync(struct window_pane *wp)
{
        struct timeval  tv = { .tv_sec = 1, .tv_usec = 0 };

        if (wp == NULL)
                return;

        wp->base.mode |= MODE_SYNC;
        if (!event_initialized(&wp->sync_timer))
                evtimer_set(&wp->sync_timer, screen_write_sync_callback, wp);
        evtimer_add(&wp->sync_timer, &tv);

        log_debug("%s: %%%u started sync mode", __func__, wp->id);
}

/* Stop sync mode. */
void
screen_write_stop_sync(struct window_pane *wp)
{
        if (wp == NULL || (~wp->base.mode & MODE_SYNC))
                return;

        if (event_initialized(&wp->sync_timer))
                evtimer_del(&wp->sync_timer);
        wp->base.mode &= ~MODE_SYNC;

        screen_write_flush_dirty(wp);

        log_debug("%s: %%%u stopped sync mode", __func__, wp->id);
}

/* Cursor up by ny. */
void
screen_write_cursorup(struct screen_write_ctx *ctx, u_int ny)
{
        struct screen   *s = ctx->s;
        u_int            cx = s->cx, cy = s->cy;

        if (ny == 0)
                ny = 1;

        if (cy < s->rupper) {
                /* Above region. */
                if (ny > cy)
                        ny = cy;
        } else {
                /* Below region. */
                if (ny > cy - s->rupper)
                        ny = cy - s->rupper;
        }
        if (cx == screen_size_x(s))
                cx--;

        cy -= ny;

        screen_write_set_cursor(ctx, cx, cy);
}

/* Cursor down by ny. */
void
screen_write_cursordown(struct screen_write_ctx *ctx, u_int ny)
{
        struct screen   *s = ctx->s;
        u_int            cx = s->cx, cy = s->cy;

        if (ny == 0)
                ny = 1;

        if (cy > s->rlower) {
                /* Below region. */
                if (ny > screen_size_y(s) - 1 - cy)
                        ny = screen_size_y(s) - 1 - cy;
        } else {
                /* Above region. */
                if (ny > s->rlower - cy)
                        ny = s->rlower - cy;
        }
        if (cx == screen_size_x(s))
            cx--;
        else if (ny == 0)
                return;

        cy += ny;

        screen_write_set_cursor(ctx, cx, cy);
}

/* Cursor right by nx. */
void
screen_write_cursorright(struct screen_write_ctx *ctx, u_int nx)
{
        struct screen   *s = ctx->s;
        u_int            cx = s->cx, cy = s->cy;

        if (nx == 0)
                nx = 1;

        if (nx > screen_size_x(s) - 1 - cx)
                nx = screen_size_x(s) - 1 - cx;
        if (nx == 0)
                return;

        cx += nx;

        screen_write_set_cursor(ctx, cx, cy);
}

/* Cursor left by nx. */
void
screen_write_cursorleft(struct screen_write_ctx *ctx, u_int nx)
{
        struct screen   *s = ctx->s;
        u_int            cx = s->cx, cy = s->cy;

        if (nx == 0)
                nx = 1;

        if (nx > cx)
                nx = cx;
        if (nx == 0)
                return;

        cx -= nx;

        screen_write_set_cursor(ctx, cx, cy);
}

/* Backspace; cursor left unless at start of wrapped line when can move up. */
void
screen_write_backspace(struct screen_write_ctx *ctx)
{
        struct screen           *s = ctx->s;
        struct grid_line        *gl;
        u_int                    cx = s->cx, cy = s->cy;

        if (cx == 0) {
                if (cy == 0)
                        return;
                gl = grid_get_line(s->grid, s->grid->hsize + cy - 1);
                if (gl->flags & GRID_LINE_WRAPPED) {
                        cy--;
                        cx = screen_size_x(s) - 1;
                }
        } else
                cx--;

        screen_write_set_cursor(ctx, cx, cy);
}

/* Is this cell a single ASCII character? */
static int
screen_write_cell_is_single(const struct grid_cell *gc)
{
        if (gc->data.width != 1)
                return (0);
        if (gc->data.size != 1)
                return (0);
        if (*gc->data.data < 0x20 || *gc->data.data == 0x7f)
                return (0);
        if (gc->flags & GRID_FLAG_CLEARED)
                return (0);
        if (gc->flags & GRID_FLAG_PADDING)
                return (0);
        if (gc->flags & GRID_FLAG_TAB)
                return (0);
        return (1);
}

/* Redraw all visible cells on a line. */
static void
screen_write_redraw_line(struct screen_write_ctx *ctx, struct tty_ctx *ttyctx,
    u_int yy)
{
        struct window_pane      *wp = ctx->wp;
        struct screen           *s = ctx->s;
        struct grid_cell         gc, ngc;
        u_int                    sx = screen_size_x(s), cx, i;
        int                      xoff = wp->xoff, yoff = wp->yoff;
        struct visible_ranges   *r;
        struct visible_range    *ri;

        r = window_visible_ranges(wp, xoff, yoff + yy, sx, NULL);
        for (i = 0; i < r->used; i++) {
                ri = &r->ranges[i];
                if (ri->nx == 0)
                        continue;

                cx = ri->px - xoff;
                if (cx >= sx)
                        continue;
                if (cx + ri->nx > sx)
                        ttyctx->n = sx - cx;
                else
                        ttyctx->n = ri->nx;
                if (ttyctx->n == 0)
                        continue;
                ttyctx->ocx = cx;
                ttyctx->ocy = yy;

                if (ttyctx->n != 1) {
                        tty_write(tty_cmd_redrawline, ttyctx);
                        continue;
                }

                grid_view_get_cell(s->grid, cx, yy, &gc);
                if (!screen_write_cell_is_single(&gc)) {
                        tty_write(tty_cmd_redrawline, ttyctx);
                        continue;
                }
                if (~gc.flags & GRID_FLAG_SELECTED)
                        ttyctx->cell = &gc;
                else {
                        screen_select_cell(s, &ngc, &gc);
                        ttyctx->cell = &ngc;
                }
                tty_write(tty_cmd_cell, ttyctx);
        }
}

/* Redraw dirty lines. */
static void
screen_write_flush_dirty(struct window_pane *wp)
{
        struct screen_write_ctx  ctx;
        struct tty_ctx           ttyctx;
        struct screen           *s = &wp->base;
        u_int                    y, sy = screen_size_y(s), lines = 0;

        if (wp->sync_dirty == NULL)
                return;

        screen_write_start_pane(&ctx, wp, s);
        screen_write_initctx(&ctx, &ttyctx, 1, 1);

        for (y = 0; y < sy; y++) {
                if (bit_test(wp->sync_dirty, y)) {
                        screen_write_redraw_line(&ctx, &ttyctx, y);
                        lines++;
                }
        }
        log_debug("%s: %%%u had %u dirty lines", __func__, wp->id, lines);

        screen_write_stop(&ctx);
        screen_write_clear_dirty(wp);
}

/* Clear any dirty lines. */
void
screen_write_clear_dirty(struct window_pane *wp)
{
        if (wp != NULL && wp->sync_dirty != NULL) {
                free(wp->sync_dirty);
                wp->sync_dirty = NULL;
                wp->sync_dirty_size = 0;
        }
}

/* Redraw all visible cells in a pane. */
static void
screen_write_redraw_pane(struct screen_write_ctx *ctx, struct tty_ctx *ttyctx)
{
        struct screen   *s = ctx->s;
        u_int            yy;

        for (yy = 0; yy < screen_size_y(s); yy++)
                screen_write_redraw_line(ctx, ttyctx, yy);
}

/* VT100 alignment test. */
void
screen_write_alignmenttest(struct screen_write_ctx *ctx)
{
        struct screen           *s = ctx->s;
        struct tty_ctx           ttyctx;
        struct grid_cell         gc;
        u_int                    xx, yy;

        memcpy(&gc, &grid_default_cell, sizeof gc);
        utf8_set(&gc.data, 'E');

        for (yy = 0; yy < screen_size_y(s); yy++) {
                for (xx = 0; xx < screen_size_x(s); xx++)
                        grid_view_set_cell(s->grid, xx, yy, &gc);
        }

        screen_write_set_cursor(ctx, 0, 0);

        s->rupper = 0;
        s->rlower = screen_size_y(s) - 1;

        screen_write_collect_clear(ctx, 0, screen_size_y(s) - 1);

        screen_write_initctx(ctx, &ttyctx, 1, 1);

        if (!screen_write_should_draw_lines(ctx, 0, screen_size_y(s)))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_alignmenttest, &ttyctx);
                return;
        }

        screen_write_redraw_pane(ctx, &ttyctx);
}

/* Insert nx characters. */
void
screen_write_insertcharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
{
        struct screen   *s = ctx->s;
        struct tty_ctx   ttyctx;

        if (nx == 0)
                nx = 1;

        if (nx > screen_size_x(s) - s->cx)
                nx = screen_size_x(s) - s->cx;
        if (nx == 0)
                return;

        if (s->cx > screen_size_x(s) - 1)
                return;

        screen_write_initctx(ctx, &ttyctx, 0, 1);
        ttyctx.bg = bg;

        grid_view_insert_cells(s->grid, s->cx, s->cy, nx, bg);

        screen_write_collect_flush(ctx, 0, __func__);
        ttyctx.n = nx;

        if (!screen_write_should_draw_line(ctx, s->cy))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_insertcharacter, &ttyctx);
                return;
        }

        screen_write_redraw_line(ctx, &ttyctx, s->cy);
}

/* Delete nx characters. */
void
screen_write_deletecharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
{
        struct screen   *s = ctx->s;
        struct tty_ctx   ttyctx;

        if (nx == 0)
                nx = 1;

        if (nx > screen_size_x(s) - s->cx)
                nx = screen_size_x(s) - s->cx;
        if (nx == 0)
                return;

        if (s->cx > screen_size_x(s) - 1)
                return;

        screen_write_initctx(ctx, &ttyctx, 0, 1);
        ttyctx.bg = bg;

        grid_view_delete_cells(s->grid, s->cx, s->cy, nx, bg);

        screen_write_collect_flush(ctx, 0, __func__);
        ttyctx.n = nx;

        if (!screen_write_should_draw_line(ctx, s->cy))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_deletecharacter, &ttyctx);
                return;
        }

        screen_write_redraw_line(ctx, &ttyctx, s->cy);
}

/* Clear nx characters. */
void
screen_write_clearcharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
{
        struct screen   *s = ctx->s;
        struct tty_ctx   ttyctx;

        if (nx == 0)
                nx = 1;

        if (nx > screen_size_x(s) - s->cx)
                nx = screen_size_x(s) - s->cx;
        if (nx == 0)
                return;

        if (s->cx > screen_size_x(s) - 1)
                return;

        screen_write_initctx(ctx, &ttyctx, 0, 1);
        ttyctx.bg = bg;

        grid_view_clear(s->grid, s->cx, s->cy, nx, 1, bg);

        screen_write_collect_flush(ctx, 0, __func__);
        ttyctx.n = nx;

        if (!screen_write_should_draw_line(ctx, s->cy))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_clearcharacter, &ttyctx);
                return;
        }

        screen_write_redraw_line(ctx, &ttyctx, s->cy);
}

/* Insert ny lines. */
void
screen_write_insertline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
{
        struct screen   *s = ctx->s;
        struct grid     *gd = s->grid;
        struct tty_ctx   ttyctx;
        u_int            sy = screen_size_y(s);

        if (ny == 0)
                ny = 1;

        if (s->cy < s->rupper || s->cy > s->rlower) {
                if (ny > sy - s->cy)
                        ny = sy - s->cy;
                if (ny == 0)
                        return;

                screen_write_initctx(ctx, &ttyctx, 1, 1);
                ttyctx.bg = bg;

                grid_view_insert_lines(gd, s->cy, ny, bg);

                screen_write_collect_flush(ctx, 0, __func__);
                ttyctx.n = ny;

                if (!screen_write_should_draw_lines(ctx, s->cy, sy - s->cy))
                        return;
                if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                        tty_write(tty_cmd_insertline, &ttyctx);
                        return;
                }

                screen_write_redraw_pane(ctx, &ttyctx);
                return;
        }

        if (ny > s->rlower + 1 - s->cy)
                ny = s->rlower + 1 - s->cy;
        if (ny == 0)
                return;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        if (s->cy < s->rupper || s->cy > s->rlower)
                grid_view_insert_lines(gd, s->cy, ny, bg);
        else
                grid_view_insert_lines_region(gd, s->rlower, s->cy, ny, bg);

        screen_write_collect_flush(ctx, 0, __func__);
        ttyctx.n = ny;

        if (!screen_write_should_draw_lines(ctx, s->cy, s->rlower + 1 - s->cy))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_insertline, &ttyctx);
                return;
        }

        screen_write_redraw_pane(ctx, &ttyctx);
}

/* Delete ny lines. */
void
screen_write_deleteline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
{
        struct screen   *s = ctx->s;
        struct grid     *gd = s->grid;
        struct tty_ctx   ttyctx;
        u_int            sy = screen_size_y(s), ry;

        if (ny == 0)
                ny = 1;

        if (s->cy < s->rupper || s->cy > s->rlower) {
                if (ny > sy - s->cy)
                        ny = sy - s->cy;
                if (ny == 0)
                        return;

                screen_write_initctx(ctx, &ttyctx, 1, 1);
                ttyctx.bg = bg;

                grid_view_delete_lines(gd, s->cy, ny, bg);

                screen_write_collect_flush(ctx, 0, __func__);
                ttyctx.n = ny;

                ry = s->rlower + 1 - s->rupper;
                if (!screen_write_should_draw_lines(ctx, s->rupper, ry))
                        return;
                if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                        tty_write(tty_cmd_deleteline, &ttyctx);
                        return;
                }

                screen_write_redraw_pane(ctx, &ttyctx);
                return;
        }

        ry = s->rlower + 1 - s->cy;
        if (ny > ry)
                ny = ry;
        if (ny == 0)
                return;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        if (s->cy < s->rupper || s->cy > s->rlower)
                grid_view_delete_lines(gd, s->cy, ny, bg);
        else
                grid_view_delete_lines_region(gd, s->rlower, s->cy, ny, bg);

        screen_write_collect_flush(ctx, 0, __func__);
        ttyctx.n = ny;

        if (!screen_write_should_draw_lines(ctx, s->cy, ry))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_deleteline, &ttyctx);
                return;
        }

        screen_write_redraw_pane(ctx, &ttyctx);
}

/* Clear line at cursor. */
void
screen_write_clearline(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen                   *s = ctx->s;
        struct grid_line                *gl;
        u_int                            sx = screen_size_x(s);
        struct screen_write_citem       *ci = ctx->item;
        struct osc133_data               od;
        u_int                            flags;

        gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
        if (gl->cellsize == 0 && COLOUR_DEFAULT(bg))
                return;

        flags = gl->flags & GRID_LINE_OSC133_FLAGS;
        memcpy(&od, &gl->osc133_data, sizeof od);
        grid_view_clear(s->grid, 0, s->cy, sx, 1, bg);
        gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
        gl->flags |= flags;
        memcpy(&gl->osc133_data, &od, sizeof gl->osc133_data);

        screen_write_collect_clear(ctx, s->cy, 1);
        ci->x = 0;
        ci->used = sx;
        ci->type = CLEAR;
        ci->bg = bg;
        TAILQ_INSERT_TAIL(&ctx->s->write_list[s->cy].items, ci, entry);
        ctx->item = screen_write_get_citem();
}

/* Clear to end of line from cursor. */
void
screen_write_clearendofline(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen                   *s = ctx->s;
        struct grid_line                *gl;
        u_int                            sx = screen_size_x(s);
        struct screen_write_citem       *ci = ctx->item;

        if (s->cx == 0) {
                screen_write_clearline(ctx, bg);
                return;
        }

        gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
        if (s->cx > sx - 1 || (s->cx >= gl->cellsize && COLOUR_DEFAULT(bg)))
                return;

        grid_view_clear(s->grid, s->cx, s->cy, sx - s->cx, 1, bg);

        ci->x = s->cx;
        ci->used = sx - s->cx;
        ci->type = CLEAR;
        ci->bg = bg;
        screen_write_collect_insert(ctx, ci);
}

/* Clear to start of line from cursor. */
void
screen_write_clearstartofline(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen                    *s = ctx->s;
        u_int                            sx = screen_size_x(s);
        struct screen_write_citem       *ci = ctx->item;

        if (s->cx >= sx - 1) {
                screen_write_clearline(ctx, bg);
                return;
        }

        if (s->cx > sx - 1)
                grid_view_clear(s->grid, 0, s->cy, sx, 1, bg);
        else
                grid_view_clear(s->grid, 0, s->cy, s->cx + 1, 1, bg);

        ci->x = 0;
        ci->used = s->cx + 1;
        ci->type = CLEAR;
        ci->bg = bg;
        screen_write_collect_insert(ctx, ci);
}

/* Move cursor to px,py. */
void
screen_write_cursormove(struct screen_write_ctx *ctx, int px, int py,
    int origin)
{
        struct screen   *s = ctx->s;

        if (origin && py != -1 && (s->mode & MODE_ORIGIN)) {
                if ((u_int)py > s->rlower - s->rupper)
                        py = s->rlower;
                else
                        py += s->rupper;
        }

        if (px != -1 && (u_int)px > screen_size_x(s) - 1)
                px = screen_size_x(s) - 1;
        if (py != -1 && (u_int)py > screen_size_y(s) - 1)
                py = screen_size_y(s) - 1;

        log_debug("%s: from %u,%u to %u,%u", __func__, s->cx, s->cy, px, py);
        screen_write_set_cursor(ctx, px, py);
}

/* Reverse index (up with scroll). */
void
screen_write_reverseindex(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen   *s = ctx->s;
        struct tty_ctx   ttyctx;
        u_int            ry;

        if (s->cy != s->rupper) {
                if (s->cy > 0)
                        screen_write_set_cursor(ctx, -1, s->cy - 1);
                return;
        }

        grid_view_scroll_region_down(s->grid, s->rupper, s->rlower, bg);
        screen_write_collect_flush(ctx, 0, __func__);

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        ry = s->rlower + 1 - s->rupper;
        if (!screen_write_should_draw_lines(ctx, s->rupper, ry))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_reverseindex, &ttyctx);
                return;
        }

        screen_write_redraw_pane(ctx, &ttyctx);
}

/* Set scroll region. */
void
screen_write_scrollregion(struct screen_write_ctx *ctx, u_int rupper,
    u_int rlower)
{
        struct screen   *s = ctx->s;

        if (rupper > screen_size_y(s) - 1)
                rupper = screen_size_y(s) - 1;
        if (rlower > screen_size_y(s) - 1)
                rlower = screen_size_y(s) - 1;
        if (rupper >= rlower)   /* cannot be one line */
                return;

        screen_write_collect_flush(ctx, 0, __func__);

        /* Cursor moves to top-left. */
        screen_write_set_cursor(ctx, 0, 0);

        s->rupper = rupper;
        s->rlower = rlower;
}

/* Line feed. */
void
screen_write_linefeed(struct screen_write_ctx *ctx, int wrapped, u_int bg)
{
        struct screen           *s = ctx->s;
        struct grid             *gd = s->grid;
        struct grid_line        *gl;
        u_int                    rupper = s->rupper, rlower = s->rlower;

        gl = grid_get_line(gd, gd->hsize + s->cy);
        if (wrapped)
                gl->flags |= GRID_LINE_WRAPPED;

        log_debug("%s: at %u,%u (region %u-%u)", __func__, s->cx, s->cy,
            rupper, rlower);

        if (bg != ctx->bg) {
                screen_write_collect_flush(ctx, 1, __func__);
                ctx->bg = bg;
        }

        if (s->cy != s->rlower) {
                if (s->cy < screen_size_y(s) - 1)
                        screen_write_set_cursor(ctx, -1, s->cy + 1);
                return;
        }

        grid_view_scroll_region_up(gd, s->rupper, s->rlower, bg);
        screen_write_collect_scroll(ctx, bg);
        ctx->scrolled++;
}

/* Scroll up. */
void
screen_write_scrollup(struct screen_write_ctx *ctx, u_int lines, u_int bg)
{
        struct screen   *s = ctx->s;
        struct grid     *gd = s->grid;
        u_int            i;

        if (lines == 0)
                lines = 1;
        else if (lines > s->rlower - s->rupper + 1)
                lines = s->rlower - s->rupper + 1;

        if (bg != ctx->bg) {
                screen_write_collect_flush(ctx, 1, __func__);
                ctx->bg = bg;
        }

        for (i = 0; i < lines; i++) {
                grid_view_scroll_region_up(gd, s->rupper, s->rlower, bg);
                screen_write_collect_scroll(ctx, bg);
        }
        ctx->scrolled += lines;
}

/* Scroll down. */
void
screen_write_scrolldown(struct screen_write_ctx *ctx, u_int lines, u_int bg)
{
        struct screen   *s = ctx->s;
        struct grid     *gd = s->grid;
        struct tty_ctx   ttyctx;
        u_int            i, ry;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        if (lines == 0)
                lines = 1;
        else if (lines > s->rlower - s->rupper + 1)
                lines = s->rlower - s->rupper + 1;

        for (i = 0; i < lines; i++)
                grid_view_scroll_region_down(gd, s->rupper, s->rlower, bg);

        screen_write_collect_flush(ctx, 0, __func__);
        ttyctx.n = lines;

        ry = s->rlower + 1 - s->rupper;
        if (!screen_write_should_draw_lines(ctx, s->rupper, ry))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED || ctx->wp == NULL) {
                tty_write(tty_cmd_scrolldown, &ttyctx);
                return;
        }

        screen_write_redraw_pane(ctx, &ttyctx);
}

/* Carriage return (cursor to start of line). */
void
screen_write_carriagereturn(struct screen_write_ctx *ctx)
{
        screen_write_set_cursor(ctx, 0, -1);
}

/* Clear to end of screen from cursor. */
void
screen_write_clearendofscreen(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen           *s = ctx->s;
        struct grid             *gd = s->grid;
        struct tty_ctx           ttyctx;
        u_int                    sx = screen_size_x(s), sy = screen_size_y(s);
        u_int                    y, i, xoff, yoff, ocx, ocy;
        struct visible_ranges   *r;
        struct visible_range    *ri;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        /* Scroll into history if it is enabled and clearing entire screen. */
        if (s->cx == 0 &&
            s->cy == 0 &&
            (gd->flags & GRID_HISTORY) &&
            ctx->wp != NULL &&
            options_get_number(ctx->wp->options, "scroll-on-clear"))
                grid_view_clear_history(gd, bg);
        else {
                if (s->cx <= sx - 1)
                        grid_view_clear(gd, s->cx, s->cy, sx - s->cx, 1, bg);
                grid_view_clear(gd, 0, s->cy + 1, sx, sy - (s->cy + 1), bg);
        }

        screen_write_collect_clear(ctx, s->cy + 1, sy - (s->cy + 1));
        screen_write_collect_flush(ctx, 0, __func__);

        if (!screen_write_should_draw_lines(ctx, s->cy, sy - s->cy))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED) {
                tty_write(tty_cmd_clearendofscreen, &ttyctx);
                return;
        }

        /* Can't just clear screen, must avoid floating windows. */
        ocx = s->cx;
        ocy = s->cy;
        if (ctx->wp != NULL) {
                xoff = ctx->wp->xoff;
                yoff = ctx->wp->yoff;
        } else {
                xoff = 0;
                yoff = 0;
        }

        /* First line (containing the cursor). */
        if (s->cx <= sx - 1) {
                r = window_visible_ranges(ctx->wp, xoff + s->cx, yoff + s->cy,
                    sx - s->cx, NULL);
                for (i = 0; i < r->used; i++) {
                        ri = &r->ranges[i];
                        if (ri->nx == 0)
                                continue;
                        screen_write_collect_insert_clear(ctx, ri->px - xoff,
                            ri->nx, bg);
                }
        }

        /* Below cursor to bottom. */
        for (y = s->cy + 1; y < sy; y++) {
                screen_write_set_cursor(ctx, 0, y);
                r = window_visible_ranges(ctx->wp, xoff, yoff + y, sx, NULL);
                for (i = 0; i < r->used; i++) {
                        ri = &r->ranges[i];
                        if (ri->nx == 0)
                                continue;
                        screen_write_collect_insert_clear(ctx, ri->px - xoff,
                            ri->nx, bg);
                }
        }
        screen_write_set_cursor(ctx, ocx, ocy);
}

/* Clear to start of screen. */
void
screen_write_clearstartofscreen(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen           *s = ctx->s;
        struct tty_ctx           ttyctx;
        u_int                    sx = screen_size_x(s);
        u_int                    y, i, xoff, yoff, ocx, ocy;
        struct visible_ranges   *r;
        struct visible_range    *ri;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        if (s->cy > 0)
                grid_view_clear(s->grid, 0, 0, sx, s->cy, bg);
        if (s->cx > sx - 1)
                grid_view_clear(s->grid, 0, s->cy, sx, 1, bg);
        else
                grid_view_clear(s->grid, 0, s->cy, s->cx + 1, 1, bg);

        screen_write_collect_clear(ctx, 0, s->cy);
        screen_write_collect_flush(ctx, 0, __func__);

        if (!screen_write_should_draw_lines(ctx, 0, s->cy + 1))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED) {
                tty_write(tty_cmd_clearstartofscreen, &ttyctx);
                return;
        }

        /* Can't just clear screen, must avoid floating windows. */
        ocx = s->cx;
        ocy = s->cy;
        if (ctx->wp != NULL) {
                xoff = ctx->wp->xoff;
                yoff = ctx->wp->yoff;
        } else {
                xoff = 0;
                yoff = 0;
        }

        /* Top to above the cursor. */
        for (y = 0; y < s->cy; y++) {
                screen_write_set_cursor(ctx, 0, y);
                r = window_visible_ranges(ctx->wp, xoff, yoff + y, sx, NULL);
                for (i = 0; i < r->used; i++) {
                        ri = &r->ranges[i];
                        if (ri->nx == 0)
                                continue;
                        screen_write_collect_insert_clear(ctx, ri->px - xoff,
                            ri->nx, bg);
                }
        }

        /* Last line (containing the cursor). */
        screen_write_set_cursor(ctx, 0, s->cy);
        r = window_visible_ranges(ctx->wp, xoff, yoff + ocy, s->cx + 1, NULL);
        for (i = 0; i < r->used; i++) {
                ri = &r->ranges[i];
                if (ri->nx == 0)
                        continue;
                screen_write_collect_insert_clear(ctx, ri->px - xoff, ri->nx,
                    bg);
        }
        screen_write_set_cursor(ctx, ocx, ocy);
}

/* Clear entire screen. */
void
screen_write_clearscreen(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen           *s = ctx->s;
        struct tty_ctx           ttyctx;
        u_int                    sx = screen_size_x(s), sy = screen_size_y(s);
        u_int                    y, i, xoff, yoff, ocx, ocy;
        struct visible_ranges   *r;
        struct visible_range    *ri;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        ttyctx.bg = bg;

        /* Scroll into history if it is enabled. */
        if ((s->grid->flags & GRID_HISTORY) &&
            ctx->wp != NULL &&
            options_get_number(ctx->wp->options, "scroll-on-clear"))
                grid_view_clear_history(s->grid, bg);
        else
                grid_view_clear(s->grid, 0, 0, sx, sy, bg);

        screen_write_collect_clear(ctx, 0, sy);

        if (!screen_write_should_draw_lines(ctx, 0, sy))
                return;
        if (~ttyctx.flags & TTY_CTX_PANE_OBSCURED) {
                tty_write(tty_cmd_clearscreen, &ttyctx);
                return;
        }

        /* Can't just clear screen, must avoid floating windows. */
        ocx = s->cx;
        ocy = s->cy;
        if (ctx->wp != NULL) {
                xoff = ctx->wp->xoff;
                yoff = ctx->wp->yoff;
        } else {
                xoff = 0;
                yoff = 0;
        }

        /* Clear every line. */
        for (y = 0; y < sy; y++) {
                screen_write_set_cursor(ctx, 0, y);
                r = window_visible_ranges(ctx->wp, xoff, yoff + y, sx, NULL);
                for (i = 0; i < r->used; i++) {
                        ri = &r->ranges[i];
                        if (ri->nx == 0)
                                continue;
                        screen_write_collect_insert_clear(ctx, ri->px - xoff,
                            ri->nx, bg);
                }
        }
        screen_write_set_cursor(ctx, ocx, ocy);
}

/* Clear entire history. */
void
screen_write_clearhistory(struct screen_write_ctx *ctx)
{
        grid_clear_history(ctx->s->grid);
}

/* Force a full redraw. */
void
screen_write_fullredraw(struct screen_write_ctx *ctx)
{
        struct tty_ctx   ttyctx;

        screen_write_collect_flush(ctx, 0, __func__);

        screen_write_initctx(ctx, &ttyctx, 1, 0);
        if (ttyctx.redraw_cb != NULL)
                ttyctx.redraw_cb(&ttyctx);
}

/* Trim collected items. */
static struct screen_write_citem *
screen_write_collect_trim(struct screen_write_ctx *ctx, u_int y, u_int x,
    u_int used, int *wrapped)
{
        struct screen_write_cline       *cl = &ctx->s->write_list[y];
        struct screen_write_citem       *ci, *ci2, *tmp, *before = NULL;
        u_int                            sx = x, ex = x + used - 1;
        u_int                            csx, cex;

        if (TAILQ_EMPTY(&cl->items))
                return (NULL);
        TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
                csx = ci->x;
                cex = ci->x + ci->used - 1;

                /* Item is entirely before. */
                if (cex < sx) {
                        log_debug("%s: %p %u-%u before %u-%u", __func__, ci,
                            csx, cex, sx, ex);
                        continue;
                }

                /* Item is entirely after. */
                if (csx > ex) {
                        log_debug("%s: %p %u-%u after %u-%u", __func__, ci,
                            csx, cex, sx, ex);
                        before = ci;
                        break;
                }

                /* Item is entirely inside. */
                if (csx >= sx && cex <= ex) {
                        log_debug("%s: %p %u-%u inside %u-%u", __func__, ci,
                            csx, cex, sx, ex);
                        TAILQ_REMOVE(&cl->items, ci, entry);
                        screen_write_free_citem(ci);
                        if (csx == 0 && ci->wrapped && wrapped != NULL)
                                *wrapped = 1;
                        continue;
                }

                /* Item under the start. */
                if (csx < sx && cex >= sx && cex <= ex) {
                        log_debug("%s: %p %u-%u start %u-%u", __func__, ci,
                            csx, cex, sx, ex);
                        ci->used = sx - csx;
                        log_debug("%s: %p now %u-%u", __func__, ci, ci->x,
                            ci->x + ci->used + 1);
                        continue;
                }

                /* Item covers the end. */
                if (cex > ex && csx >= sx && csx <= ex) {
                        log_debug("%s: %p %u-%u end %u-%u", __func__, ci,
                            csx, cex, sx, ex);
                        ci->x = ex + 1;
                        ci->used = cex - ex;
                        log_debug("%s: %p now %u-%u", __func__, ci, ci->x,
                            ci->x + ci->used + 1);
                        before = ci;
                        break;
                }

                /* Item must cover both sides. */
                log_debug("%s: %p %u-%u under %u-%u", __func__, ci,
                    csx, cex, sx, ex);
                ci2 = screen_write_get_citem();
                ci2->type = ci->type;
                ci2->bg = ci->bg;
                memcpy(&ci2->gc, &ci->gc, sizeof ci2->gc);
                TAILQ_INSERT_AFTER(&cl->items, ci, ci2, entry);

                ci->used = sx - csx;
                ci2->x = ex + 1;
                ci2->used = cex - ex;

                log_debug("%s: %p now %u-%u (%p) and %u-%u (%p)", __func__, ci,
                    ci->x, ci->x + ci->used - 1, ci, ci2->x,
                    ci2->x + ci2->used - 1, ci2);
                before = ci2;
                break;
        }
        return (before);
}

/* Clear collected lines. */
static void
screen_write_collect_clear(struct screen_write_ctx *ctx, u_int y, u_int n)
{
        struct screen_write_cline       *cl;
        u_int                            i;

        for (i = y; i < y + n; i++) {
                cl = &ctx->s->write_list[i];
                TAILQ_CONCAT(&screen_write_citem_freelist, &cl->items, entry);
        }
}

/* Scroll collected lines up. */
static void
screen_write_collect_scroll(struct screen_write_ctx *ctx, u_int bg)
{
        struct screen                   *s = ctx->s;
        struct screen_write_cline       *cl;
        u_int                            y;
        char                            *saved;
        struct screen_write_citem       *ci;

        log_debug("%s: at %u,%u (region %u-%u)", __func__, s->cx, s->cy,
            s->rupper, s->rlower);

        screen_write_collect_clear(ctx, s->rupper, 1);
        saved = ctx->s->write_list[s->rupper].data;
        for (y = s->rupper; y < s->rlower; y++) {
                cl = &ctx->s->write_list[y + 1];
                TAILQ_CONCAT(&ctx->s->write_list[y].items, &cl->items, entry);
                ctx->s->write_list[y].data = cl->data;
        }
        ctx->s->write_list[s->rlower].data = saved;

        ci = screen_write_get_citem();
        ci->x = 0;
        ci->used = screen_size_x(s);
        ci->type = CLEAR;
        ci->bg = bg;
        TAILQ_INSERT_TAIL(&ctx->s->write_list[s->rlower].items, ci, entry);
}

/* Flush collected scrolling. */
static int
screen_write_collect_flush_scrolled(struct screen_write_ctx *ctx)
{
        struct window_pane      *wp = ctx->wp;
        struct screen           *s = ctx->s;
        struct tty_ctx           ttyctx;

        screen_write_initctx(ctx, &ttyctx, 1, 1);
        if (ttyctx.flags & TTY_CTX_PANE_OBSCURED && wp != NULL) {
                screen_write_redraw_pane(ctx, &ttyctx);
                return 0;
        }
        if (wp != NULL && window_pane_scrollbar_overlay_visible(wp)) {
                wp->flags |= PANE_REDRAW;
                return 0;
        }

        log_debug("%s: scrolled %u (region %u-%u)", __func__, ctx->scrolled,
            s->rupper, s->rlower);
        if (ctx->scrolled > s->rlower - s->rupper + 1)
                ctx->scrolled = s->rlower - s->rupper + 1;

        if (wp != NULL && wp->yoff + wp->sy > wp->window->sy)
                ttyctx.orlower -= (wp->yoff + wp->sy - wp->window->sy);
        ttyctx.n = ctx->scrolled;
        ttyctx.bg = ctx->bg;
        tty_write(tty_cmd_scrollup, &ttyctx);

        if (wp != NULL)
                window_pane_scrollbar_redraw(wp);
        return 1;
}

/* Flush a collected line. */
static u_int
screen_write_collect_flush_line(struct screen_write_ctx *ctx, u_int y)
{
        struct window_pane              *wp = ctx->wp;
        struct screen                   *s = ctx->s;
        struct screen_write_citem       *ci, *tmp;
        struct screen_write_cline       *cl = &s->write_list[y];
        u_int                            last = UINT_MAX, items = 0, wsx, wsy;
        u_int                            w_length, i;
        int                              w_start, w_end, xoff, yoff, written;
        int                              r_start, r_end, c_start, c_end;
        struct tty_ctx                   ttyctx;
        struct visible_ranges           *r;
        struct visible_range            *ri;

        if (wp != NULL) {
                wsx = wp->window->sx;
                wsy = wp->window->sy;
                xoff = wp->xoff;
                yoff = wp->yoff;
        } else {
                wsx = screen_size_x(s);
                wsy = screen_size_y(s);
                xoff = 0;
                yoff = 0;
        }
        if (y + yoff >= wsy)
                return (0);

        r = window_visible_ranges(wp, 0, y + yoff, wsx, NULL);
        TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
                log_debug("collect list: x=%u (last %u), y=%u, used=%u", ci->x,
                    last, y, ci->used);
                if (last != UINT_MAX && ci->x <= last)
                        fatalx("collect list bad order: %u <= %u", ci->x, last);

                w_length = 0;
                written = 0;
                for (i = 0; i < r->used; i++) {
                        ri = &r->ranges[i];
                        if (ri->nx == 0)
                                continue;

                        r_start = ri->px;
                        r_end = ri->px + ri->nx;
                        c_start = ci->x;
                        c_end = ci->x + ci->used;

                        if (c_start + xoff >= r_end || c_end + xoff <= r_start)
                                continue;
                        if (r_start > c_start + xoff)
                                w_start = r_start - xoff;
                        else
                                w_start = c_start;
                        if (c_end + xoff > r_end)
                                w_end = r_end - xoff;
                        else
                                w_end = c_end;
                        if (w_end <= w_start)
                                continue;
                        w_length = w_end - w_start;
                        if (w_length <= 0)
                                continue;

                        screen_write_set_cursor(ctx, w_start, y);
                        if (ci->type == CLEAR) {
                                screen_write_initctx(ctx, &ttyctx, 1, 0);
                                ttyctx.bg = ci->bg;
                                ttyctx.n = w_length;
                                tty_write(tty_cmd_clearcharacter, &ttyctx);
                        } else {
                                screen_write_initctx(ctx, &ttyctx, 0, 0);
                                ttyctx.cell = &ci->gc;
                                if (ci->wrapped)
                                        ttyctx.flags |= TTY_CTX_WRAPPED;
                                ttyctx.data.data = cl->data + w_start;
                                ttyctx.data.size = w_length;
                                tty_write(tty_cmd_cells, &ttyctx);
                        }
                        items++;
                        written = 1;
                }
                if (written) {
                        last = ci->x;
                        TAILQ_REMOVE(&cl->items, ci, entry);
                        screen_write_free_citem(ci);
                }
        }
        return (items);
}

/* Flush collected lines. */
static void
screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
    const char *from)
{
        struct screen                   *s = ctx->s;
        struct window_pane              *wp = ctx->wp;
        u_int                            y, cx, cy, items = 0;
        struct screen_write_citem       *ci, *tmp;
        struct screen_write_cline       *cl;

        if (wp != NULL && (wp->flags & (PANE_REDRAW|PANE_DROP)))
                goto discard;
        if (s->mode & MODE_SYNC) {
                if (ctx->scrolled != 0) {
                        screen_write_should_draw_lines(ctx, s->rupper,
                            s->rlower + 1 - s->rupper);
                }
                for (y = 0; y < screen_size_y(s); y++) {
                        cl = &s->write_list[y];
                        if (!TAILQ_EMPTY(&cl->items))
                                screen_write_should_draw_line(ctx, y);
                }
                goto discard;
        }

        if (ctx->scrolled != 0) {
                if (!screen_write_collect_flush_scrolled(ctx))
                        goto discard;
                ctx->scrolled = 0;
        }
        ctx->bg = 8;

        if (scroll_only)
                return;

        cx = s->cx; cy = s->cy;
        for (y = 0; y < screen_size_y(s); y++)
                items += screen_write_collect_flush_line(ctx, y);
        s->cx = cx; s->cy = cy;

        log_debug("%s: flushed %u items (%s)", __func__, items, from);
        return;

discard:
        for (y = 0; y < screen_size_y(s); y++) {
                cl = &s->write_list[y];
                TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
                        TAILQ_REMOVE(&cl->items, ci, entry);
                        screen_write_free_citem(ci);
                }
        }
        ctx->scrolled = 0;
        ctx->bg = 8;
}

/* Insert an item on current line. */
static void
screen_write_collect_insert(struct screen_write_ctx *ctx,
    struct screen_write_citem *ci)
{
        struct screen                   *s = ctx->s;
        struct screen_write_cline       *cl = &s->write_list[s->cy];
        struct screen_write_citem       *before;

        before = screen_write_collect_trim(ctx, s->cy, ci->x, ci->used,
            &ci->wrapped);
        if (before == NULL)
                TAILQ_INSERT_TAIL(&cl->items, ci, entry);
        else
                TAILQ_INSERT_BEFORE(before, ci, entry);
        ctx->item = screen_write_get_citem();
}

/* Insert a clear for part of a line. */
static void
screen_write_collect_insert_clear(struct screen_write_ctx *ctx, u_int px,
    u_int nx, u_int bg)
{
        struct screen_write_citem       *ci = ctx->item;

        if (nx != 0) {
                ci->x = px;
                ci->used = nx;
                ci->type = CLEAR;
                ci->bg = bg;
                screen_write_collect_insert(ctx, ci);
        }
}

/* Finish and store collected cells. */
void
screen_write_collect_end(struct screen_write_ctx *ctx)
{
        struct screen                   *s = ctx->s;
        struct screen_write_citem       *ci = ctx->item, *bci = NULL, *aci;
        struct screen_write_cline       *cl = &s->write_list[s->cy];
        struct grid_cell                 gc;
        u_int                            xx;

        if (ci->used == 0)
                return;

        ci->x = s->cx;
        screen_write_collect_insert(ctx, ci);

        log_debug("%s: %u %.*s (at %u,%u)", __func__, ci->used,
            (int)ci->used, cl->data + ci->x, s->cx, s->cy);

        if (s->cx != 0) {
                for (xx = s->cx; xx > 0; xx--) {
                        grid_view_get_cell(s->grid, xx, s->cy, &gc);
                        if (~gc.flags & GRID_FLAG_PADDING)
                                break;
                        grid_view_set_cell(s->grid, xx, s->cy,
                            &grid_default_cell);
                        log_debug("%s: padding erased (before) at %u (cx %u)",
                            __func__, xx, s->cx);
                }
                if (xx != s->cx) {
                        if (xx == 0)
                                grid_view_get_cell(s->grid, 0, s->cy, &gc);
                        if (gc.data.width > 1 ||
                            (gc.flags & GRID_FLAG_PADDING)) {
                                grid_view_set_cell(s->grid, xx, s->cy,
                                    &grid_default_cell);
                                log_debug("%s: padding erased (before) at %u "
                                    "(cx %u)", __func__, xx, s->cx);
                        }
                }
                if (xx != s->cx) {
                        bci = ctx->item;
                        bci->type = CLEAR;
                        bci->x = xx;
                        bci->bg = 8;
                        bci->used = s->cx - xx;
                        log_debug("%s: padding erased (before): from %u, "
                            "size %u", __func__, bci->x, bci->used);
                }
        }

        grid_view_set_cells(s->grid, s->cx, s->cy, &ci->gc, cl->data + ci->x,
            ci->used);
        if (bci != NULL)
                screen_write_collect_insert(ctx, bci);
        screen_write_set_cursor(ctx, s->cx + ci->used, -1);

        for (xx = s->cx; xx < screen_size_x(s); xx++) {
                grid_view_get_cell(s->grid, xx, s->cy, &gc);
                if (~gc.flags & GRID_FLAG_PADDING)
                        break;
                grid_view_set_cell(s->grid, xx, s->cy, &grid_default_cell);
                log_debug("%s: padding erased (after) at %u (cx %u)",
                    __func__, xx, s->cx);
        }
        if (xx != s->cx) {
                aci = ctx->item;
                aci->type = CLEAR;
                aci->x = s->cx;
                aci->bg = 8;
                aci->used = xx - s->cx;
                log_debug("%s: padding erased (after): from %u, size %u",
                    __func__, aci->x, aci->used);
                screen_write_collect_insert(ctx, aci);
        }
}

/* Write cell data, collecting if necessary. */
void
screen_write_collect_add(struct screen_write_ctx *ctx,
    const struct grid_cell *gc)
{
        struct screen                   *s = ctx->s;
        struct screen_write_citem       *ci;
        u_int                            sx = screen_size_x(s);
        int                              collect;

        /*
         * Don't need to check that the attributes and whatnot are still the
         * same - input_parse will end the collection when anything that isn't
         * a plain character is encountered.
         */

        collect = 1;
        if (gc->data.width != 1 || gc->data.size != 1 || *gc->data.data >= 0x7f)
                collect = 0;
        else if (gc->flags & GRID_FLAG_TAB)
                collect = 0;
        else if (gc->attr & GRID_ATTR_CHARSET)
                collect = 0;
        else if (~s->mode & MODE_WRAP)
                collect = 0;
        else if (s->mode & MODE_INSERT)
                collect = 0;
        else if (s->sel != NULL)
                collect = 0;
        if (!collect) {
                screen_write_collect_end(ctx);
                screen_write_collect_flush(ctx, 0, __func__);
                screen_write_cell(ctx, gc);
                return;
        }

        if (s->cx > sx - 1 || ctx->item->used > sx - 1 - s->cx)
                screen_write_collect_end(ctx);
        ci = ctx->item; /* may have changed */

        if (s->cx > sx - 1) {
                log_debug("%s: wrapped at %u,%u", __func__, s->cx, s->cy);
                ci->wrapped = 1;
                screen_write_linefeed(ctx, 1, 8);
                screen_write_set_cursor(ctx, 0, -1);
        }

        if (ci->used == 0)
                memcpy(&ci->gc, gc, sizeof ci->gc);
        if (ctx->s->write_list[s->cy].data == NULL)
                ctx->s->write_list[s->cy].data = xmalloc(screen_size_x(ctx->s));
        ctx->s->write_list[s->cy].data[s->cx + ci->used++] = gc->data.data[0];
}

/* Write cell data. */
void
screen_write_cell(struct screen_write_ctx *ctx, const struct grid_cell *gc)
{
        struct screen           *s = ctx->s;
        struct window_pane      *wp = ctx->wp;
        struct grid             *gd = s->grid;
        const struct utf8_data  *ud = &gc->data;
        struct grid_line        *gl;
        struct grid_cell_entry  *gce;
        struct grid_cell         tmp_gc, now_gc;
        struct tty_ctx           ttyctx;
        u_int                    sx = screen_size_x(s), sy = screen_size_y(s);
        u_int                    width = ud->width, xx, not_wrap, i, n, vis;
        int                      selected, skip = 1, redraw = 0;
        int                      yoff = 0, xoff = 0;
        struct visible_ranges   *r;
        struct visible_range    *ri;

        /* Ignore padding cells. */
        if (gc->flags & GRID_FLAG_PADDING)
                return;

        /* Get the previous cell to check for combining. */
        if (screen_write_combine(ctx, gc) != 0)
                return;

        /* Flush any existing scrolling. */
        screen_write_collect_flush(ctx, 1, __func__);

        /* If this character doesn't fit, ignore it. */
        if ((~s->mode & MODE_WRAP) &&
            width > 1 &&
            (width > sx || (s->cx != sx && s->cx > sx - width)))
                return;

        /* If in insert mode, make space for the cells. */
        if (s->mode & MODE_INSERT) {
                grid_view_insert_cells(s->grid, s->cx, s->cy, width, 8);
                skip = 0;
        }

        /* Check this will fit on the current line and wrap if not. */
        if ((s->mode & MODE_WRAP) && s->cx > sx - width) {
                log_debug("%s: wrapped at %u,%u", __func__, s->cx, s->cy);
                screen_write_linefeed(ctx, 1, 8);
                screen_write_set_cursor(ctx, 0, -1);
                screen_write_collect_flush(ctx, 0, __func__);
        }

        /* Sanity check cursor position. */
        if (s->cx > sx - width || s->cy > sy - 1)
                return;
        screen_write_initctx(ctx, &ttyctx, 0, 0);

        /* Handle overwriting of UTF-8 characters. */
        gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
        if (gl->flags & GRID_LINE_EXTENDED) {
                grid_view_get_cell(gd, s->cx, s->cy, &now_gc);
                if (screen_write_overwrite(ctx, &now_gc, width)) {
                        redraw = 1;
                        skip = 0;
                }
        }

        /*
         * If the new character is UTF-8 wide, fill in padding cells. Have
         * already ensured there is enough room.
         */
        for (xx = s->cx + 1; xx < s->cx + width; xx++) {
                log_debug("%s: new padding at %u,%u", __func__, xx, s->cy);
                grid_view_set_padding(gd, xx, s->cy);
                skip = 0;
        }

        /* If no change, do not draw. */
        if (skip) {
                if (s->cx >= gl->cellsize)
                        skip = grid_cells_equal(gc, &grid_default_cell);
                else {
                        gce = &gl->celldata[s->cx];
                        if (gce->flags & GRID_FLAG_EXTENDED)
                                skip = 0;
                        else if (gc->flags != gce->flags)
                                skip = 0;
                        else if (gc->attr != gce->data.attr)
                                skip = 0;
                        else if (gc->fg != gce->data.fg)
                                skip = 0;
                        else if (gc->bg != gce->data.bg)
                                skip = 0;
                        else if (gc->data.width != 1)
                                skip = 0;
                        else if (gc->data.size != 1)
                                skip = 0;
                        else if (gce->data.data != gc->data.data[0])
                                skip = 0;
                }
        }

        /* Update the selected flag and set the cell. */
        selected = screen_check_selection(s, s->cx, s->cy);
        if (selected && (~gc->flags & GRID_FLAG_SELECTED)) {
                memcpy(&tmp_gc, gc, sizeof tmp_gc);
                tmp_gc.flags |= GRID_FLAG_SELECTED;
                grid_view_set_cell(gd, s->cx, s->cy, &tmp_gc);
        } else if (!selected && (gc->flags & GRID_FLAG_SELECTED)) {
                memcpy(&tmp_gc, gc, sizeof tmp_gc);
                tmp_gc.flags &= ~GRID_FLAG_SELECTED;
                grid_view_set_cell(gd, s->cx, s->cy, &tmp_gc);
        } else if (!skip)
                grid_view_set_cell(gd, s->cx, s->cy, gc);
        if (selected)
                skip = 0;

        /* Get visible ranges for the character before moving the cursor. */
        if (wp != NULL) {
                xoff = wp->xoff;
                yoff = wp->yoff;
        }
        r = window_visible_ranges(wp, xoff + s->cx, s->cy + yoff, width, NULL);

        /*
         * Move the cursor. If not wrapping, stick at the last character and
         * replace it.
         */
        not_wrap = !(s->mode & MODE_WRAP);
        if (s->cx <= sx - not_wrap - width)
                screen_write_set_cursor(ctx, s->cx + width, -1);
        else
                screen_write_set_cursor(ctx, sx - not_wrap, -1);

        /* Create space for character in insert mode. */
        if (s->mode & MODE_INSERT) {
                screen_write_collect_flush(ctx, 0, __func__);
                ttyctx.n = width;
                if (screen_write_should_draw_line(ctx, s->cy))
                        tty_write(tty_cmd_insertcharacter, &ttyctx);
        }

        /* If not writing, done now. */
        if (skip || !screen_write_should_draw_line(ctx, s->cy))
                return;

        /* Do a full line redraw if needed. */
        if (redraw && wp != NULL) {
                screen_write_redraw_line(ctx, &ttyctx, s->cy);
                return;
        }

        /* Work out the cell attributes. */
        if (selected)
                screen_select_cell(s, &tmp_gc, gc);
        else
                memcpy(&tmp_gc, gc, sizeof tmp_gc);
        ttyctx.cell = &tmp_gc;

        /* If the cell is fully visible, it can be written entirely. */
        for (i = 0, vis = 0; i < r->used; i++)
                vis += r->ranges[i].nx;
        if (vis >= width) {
                if (screen_write_should_draw_line(ctx, s->cy))
                        tty_write(tty_cmd_cell, &ttyctx);
                return;
        }

        /*
         * Otherwise this is a wide character or tab partly obscured. Write
         * spaces in the visible regions.
         */
        utf8_set(&tmp_gc.data, ' ');
        if (!screen_write_should_draw_line(ctx, s->cy))
                return;
        for (i = 0; i < r->used; i++) {
                ri = &r->ranges[i];
                if (ri->nx == 0)
                        continue;
                for (n = 0; n < ri->nx; n++) {
                        ttyctx.ocx = (int)ri->px - xoff + (int)n;
                        tty_write(tty_cmd_cell, &ttyctx);
                }
        }
}

/* Combine a UTF-8 zero-width character onto the previous if necessary. */
static int
screen_write_combine(struct screen_write_ctx *ctx, const struct grid_cell *gc)
{
        struct screen           *s = ctx->s;
        struct window_pane      *wp = ctx->wp;
        struct grid             *gd = s->grid;
        const struct utf8_data  *ud = &gc->data;
        struct options          *oo = global_options;
        u_int                    i, n, cx = s->cx, cy = s->cy, vis, yoff = 0;
        struct grid_cell         last;
        struct tty_ctx           ttyctx;
        int                      force_wide = 0, zero_width = 0;
        struct visible_ranges   *r;

        /* Ignore U+3164 HANGUL_FILLER entirely. */
        if (utf8_is_hangul_filler(ud))
                return (1);

        /*
         * Is this character which makes no sense without being combined? If
         * this is true then flag it here and discard the character (return 1)
         * if we cannot combine it.
         */
        if (utf8_is_zwj(ud))
                zero_width = 1;
        else if (utf8_is_vs(ud)) {
                zero_width = 1;
                if (options_get_number(oo, "variation-selector-always-wide"))
                        force_wide = 1;
        } else if (ud->width == 0)
                zero_width = 1;

        /* Cannot combine empty character or at left. */
        if (ud->size < 2 || cx == 0)
                return (zero_width);
        log_debug("%s: character %.*s at %u,%u (width %u)", __func__,
            (int)ud->size, ud->data, cx, cy, ud->width);

        /* Find the cell to combine with. */
        n = 1;
        grid_view_get_cell(gd, cx - n, cy, &last);
        if (cx != 1 && (last.flags & GRID_FLAG_PADDING)) {
                n = 2;
                grid_view_get_cell(gd, cx - n, cy, &last);
        }
        if (n != last.data.width || (last.flags & GRID_FLAG_PADDING))
                return (zero_width);

        /*
         * Check if we need to combine characters. This could be a Korean
         * Hangul Jamo character, zero width (set above), a modifier character
         * (with an existing Unicode character) or a previous ZWJ.
         */
        if (!zero_width) {
                switch (hanguljamo_check_state(&last.data, ud)) {
                case HANGULJAMO_STATE_NOT_COMPOSABLE:
                        return (1);
                case HANGULJAMO_STATE_CHOSEONG:
                        return (0);
                case HANGULJAMO_STATE_COMPOSABLE:
                        break;
                case HANGULJAMO_STATE_NOT_HANGULJAMO:
                        if (utf8_should_combine(&last.data, ud))
                                force_wide = 1;
                        else if (utf8_should_combine(ud, &last.data))
                                force_wide = 1;
                        else if (!utf8_has_zwj(&last.data))
                                return (0);
                        break;
                }
        }

        /* Check if this combined character would be too long. */
        if (last.data.size + ud->size > sizeof last.data.data)
                return (zero_width);

        /* Combining; flush any pending output. */
        screen_write_collect_flush(ctx, 0, __func__);

        log_debug("%s: %.*s -> %.*s at %u,%u (offset %u, width %u)", __func__,
            (int)ud->size, ud->data, (int)last.data.size, last.data.data,
            cx - n, cy, n, last.data.width);

        /* Append the data. */
        memcpy(last.data.data + last.data.size, ud->data, ud->size);
        last.data.size += ud->size;

        /* Force the width to 2 for modifiers and variation selector. */
        if (last.data.width == 1 && force_wide) {
                last.data.width = 2;
                n = 2;
                cx++;
        } else
                force_wide = 0;

        /* Set the new cell. */
        grid_view_set_cell(gd, cx - n, cy, &last);
        if (force_wide)
                grid_view_set_padding(gd, cx - 1, cy);

        /*
         * Check if all of this character is visible. No character will be
         * obscured in the middle, only on left or right, but there could be an
         * empty range in the visible ranges so we add them all up.
         */
        if (wp != NULL)
                yoff = wp->yoff;
        r = window_visible_ranges(wp, cx - n, cy + yoff, n, NULL);
        for (i = 0, vis = 0; i < r->used; i++)
                vis += r->ranges[i].nx;
        if (vis < n) {
                /*
                 * Part of this character is obscured. Return 1 and let
                 * screen_write_cell write a space.
                 */
                return (1);
        }

        /*
         * Redraw the combined cell. If forcing the cell to width 2, reset the
         * cached cursor position in the tty, since we don't really know
         * whether the terminal thought the character was width 1 or width 2
         * and what it is going to do now.
         */
        screen_write_set_cursor(ctx, cx - n, cy);
        screen_write_initctx(ctx, &ttyctx, 0, 0);
        ttyctx.cell = &last;
        if (force_wide)
                ttyctx.flags |= TTY_CTX_CELL_INVALIDATE;
        if (screen_write_should_draw_line(ctx, cy))
                tty_write(tty_cmd_cell, &ttyctx);
        screen_write_set_cursor(ctx, cx, cy);

        return (1);
}

/*
 * UTF-8 wide characters are a bit of an annoyance. They take up more than one
 * cell on the screen, so following cells must not be drawn by marking them as
 * padding.
 *
 * So far, so good. The problem is, when overwriting a padding cell, or a UTF-8
 * character, it is necessary to also overwrite any other cells which covered
 * by the same character.
 */
static int
screen_write_overwrite(struct screen_write_ctx *ctx, struct grid_cell *gc,
    u_int width)
{
        struct screen           *s = ctx->s;
        struct grid             *gd = s->grid;
        struct grid_cell         tmp_gc;
        u_int                    xx;
        int                      done = 0;

        if (gc->flags & GRID_FLAG_PADDING) {
                /*
                 * A padding cell, so clear any following and leading padding
                 * cells back to the character. Don't overwrite the current
                 * cell as that happens later anyway.
                 */
                xx = s->cx + 1;
                while (--xx > 0) {
                        grid_view_get_cell(gd, xx, s->cy, &tmp_gc);
                        if (~tmp_gc.flags & GRID_FLAG_PADDING)
                                break;
                        log_debug("%s: padding at %u,%u", __func__, xx, s->cy);
                        grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
                }

                /* Overwrite the character at the start of this padding. */
                log_debug("%s: character at %u,%u", __func__, xx, s->cy);
                grid_view_set_cell(gd, xx, s->cy, &grid_default_cell);
                done = 1;
        }

        /*
         * Overwrite any padding cells that belong to any UTF-8 characters
         * we'll be overwriting with the current character.
         */
        if (width != 1 ||
            gc->data.width != 1 ||
            gc->flags & GRID_FLAG_PADDING) {
                xx = s->cx + width - 1;
                while (++xx < screen_size_x(s)) {
                        grid_view_get_cell(gd, xx, s->cy, &tmp_gc);
                        if (~tmp_gc.flags & GRID_FLAG_PADDING)
                                break;
                        log_debug("%s: overwrite at %u,%u", __func__, xx,
                            s->cy);
                        if (gc->flags & GRID_FLAG_TAB) {
                                memcpy(&tmp_gc, gc, sizeof tmp_gc);
                                memset(tmp_gc.data.data, 0,
                                    sizeof tmp_gc.data.data);
                                *tmp_gc.data.data = ' ';
                                tmp_gc.data.width = tmp_gc.data.size =
                                    tmp_gc.data.have = 1;
                                grid_view_set_cell(gd, xx, s->cy, &tmp_gc);
                        } else
                                grid_view_set_cell(gd, xx, s->cy,
                                    &grid_default_cell);
                        done = 1;
                }
        }

        return (done);
}

/* Set external clipboard. */
void
screen_write_setselection(struct screen_write_ctx *ctx, const char *clip,
    u_char *str, u_int len)
{
        struct tty_ctx  ttyctx;

        screen_write_initctx(ctx, &ttyctx, 0, 0);
        ttyctx.sel.clip = clip;
        ttyctx.sel.data = str;
        ttyctx.sel.size = len;

        tty_write(tty_cmd_setselection, &ttyctx);
}

/* Write unmodified string. */
void
screen_write_rawstring(struct screen_write_ctx *ctx, u_char *str, u_int len,
    int allow_invisible_panes)
{
        struct tty_ctx  ttyctx;

        screen_write_initctx(ctx, &ttyctx, 0, 0);
        if (allow_invisible_panes)
                ttyctx.flags |= TTY_CTX_INVISIBLE_PANES;
        ttyctx.data.data = str;
        ttyctx.data.size = len;

        tty_write(tty_cmd_rawstring, &ttyctx);
}

/* Turn alternate screen on. */
void
screen_write_alternateon(struct screen_write_ctx *ctx, struct grid_cell *gc,
    int cursor)
{
        struct tty_ctx                   ttyctx;
        struct window_pane              *wp = ctx->wp;

        if (wp != NULL && !options_get_number(wp->options, "alternate-screen"))
                return;

        screen_write_collect_flush(ctx, 0, __func__);
        if (!screen_alternate_on(ctx->s, gc, cursor))
                return;

        if (wp != NULL) {
                window_pane_clear_resizes(wp, NULL);
                if (event_initialized(&wp->resize_timer))
                        evtimer_del(&wp->resize_timer);
                layout_fix_panes(wp->window, NULL);
                if (!TAILQ_EMPTY(&wp->resize_queue)) {
                        window_pane_send_resize(wp, wp->sx, wp->sy);
                        window_pane_clear_resizes(wp, NULL);
                }
                server_redraw_window_borders(wp->window);
        }

        screen_write_initctx(ctx, &ttyctx, 1, 0);
        if (ttyctx.redraw_cb != NULL)
                ttyctx.redraw_cb(&ttyctx);
}

/* Turn alternate screen off. */
void
screen_write_alternateoff(struct screen_write_ctx *ctx, struct grid_cell *gc,
    int cursor)
{
        struct tty_ctx           ttyctx;
        struct window_pane      *wp = ctx->wp;

        if (wp != NULL && !options_get_number(wp->options, "alternate-screen"))
                return;

        screen_write_collect_flush(ctx, 0, __func__);
        if (!screen_alternate_off(ctx->s, gc, cursor))
                return;

        if (wp != NULL) {
                layout_fix_panes(wp->window, NULL);
                server_redraw_window_borders(wp->window);
        }

        screen_write_initctx(ctx, &ttyctx, 1, 0);
        if (ttyctx.redraw_cb != NULL)
                ttyctx.redraw_cb(&ttyctx);
}