/* $OpenBSD: layout.c,v 1.96 2026/07/15 13:02:33 nicm Exp $ */

/*
 * Copyright (c) 2009 Nicholas Marriott <nicholas.marriott@gmail.com>
 * Copyright (c) 2016 Stephen Kent <smkent@smkent.net>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

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

#include "tmux.h"

/*
 * The window layout is a tree of cells each of which can be one of: a
 * left-right container for a list of cells, a top-bottom container for a list
 * of cells, or a container for a window pane. 'Node' will be used to refer to
 * a cell which contains a list of cells, and 'leaf' to refer to a cell that
 * contains a window pane. A leaf is considered to be 'tiled' if it is to be
 * drawn as a part of the tiled layout. A 'neighbour' is a sibling that is also
 * tiled or a node that contains a tiled leaf in a subtree. A cell's 'split'
 * size refers to the side that is shortened when splitting it, determined by
 * the parent's type.
 *
 * Each window has a pointer to the root of its layout tree (containing its
 * panes), every pane has a pointer back to the cell containing it, and each
 * cell a pointer to its parent cell. Every cell has a position in the root
 * layout tree. This position is retained through cell state changes such as
 * floating or hiding.
 */

static u_int    layout_resize_check(struct window *, struct layout_cell *,
                    enum layout_type);
static int      layout_resize_pane_grow(struct window *, struct layout_cell *,
                    enum layout_type, int, int);
static int      layout_resize_pane_shrink(struct window *, struct layout_cell *,
                    enum layout_type, int);
static u_int    layout_new_pane_size(struct window *, u_int,
                    struct layout_cell *, enum layout_type, u_int, u_int,
                    u_int);
static int      layout_set_size_check(struct window *, struct layout_cell *,
                    enum layout_type, int);
static void     layout_resize_child_cells(struct window *,
                    struct layout_cell *);

/* Initializes cell geometry to sentinel values. */
static void
layout_geometry_init(struct layout_geometry *lg)
{
        lg->sx = UINT_MAX;
        lg->sy = UINT_MAX;
        lg->xoff = INT_MAX;
        lg->yoff = INT_MAX;
}

/* Create a new layout cell. */
struct layout_cell *
layout_create_cell(struct layout_cell *lcparent)
{
        struct layout_cell      *lc;

        lc = xcalloc(1, sizeof *lc);
        lc->type = LAYOUT_WINDOWPANE;
        lc->parent = lcparent;
        TAILQ_INIT(&lc->cells);

        layout_geometry_init(&lc->g);
        layout_geometry_init(&lc->fg);

        return (lc);
}

/* Free a layout cell. */
void
layout_free_cell(struct layout_cell *lc, int only_nodes)
{
        struct layout_cell      *lcchild, *lcnext;

        if (lc == NULL || (only_nodes && lc->type == LAYOUT_WINDOWPANE))
                return;

        switch (lc->type) {
        case LAYOUT_LEFTRIGHT:
        case LAYOUT_TOPBOTTOM:
                lcchild = TAILQ_FIRST(&lc->cells);
                while (lcchild != NULL) {
                        lcnext = TAILQ_NEXT(lcchild, entry);
                        if (!only_nodes || lcchild->type != LAYOUT_WINDOWPANE) {
                                TAILQ_REMOVE(&lc->cells, lcchild, entry);
                                layout_free_cell(lcchild, only_nodes);
                        }
                        lcchild = lcnext;
                }
                break;
        case LAYOUT_WINDOWPANE:
                if (lc->wp != NULL) {
                        lc->wp->layout_cell->parent = NULL;
                        lc->wp->layout_cell = NULL;
                }
                break;
        }

        free(lc);
}

/* Log a cell. */
void
layout_print_cell(struct layout_cell *lc, const char *hdr, u_int n)
{
        struct layout_cell      *lcchild;
        const char              *type;

        if (lc == NULL)
                return;

        switch (lc->type) {
        case LAYOUT_LEFTRIGHT:
                type = "LEFTRIGHT";
                break;
        case LAYOUT_TOPBOTTOM:
                type = "TOPBOTTOM";
                break;
        case LAYOUT_WINDOWPANE:
                type = "WINDOWPANE";
                break;
        default:
                type = "UNKNOWN";
                break;
        }
        log_debug("%s:%*s%p type %s [parent %p] wp=%p [%d,%d %ux%u]", hdr, n,
            " ", lc, type, lc->parent, lc->wp, lc->g.xoff, lc->g.yoff, lc->g.sx,
            lc->g.sy);
        switch (lc->type) {
        case LAYOUT_LEFTRIGHT:
        case LAYOUT_TOPBOTTOM:
                TAILQ_FOREACH(lcchild, &lc->cells, entry)
                        layout_print_cell(lcchild, hdr, n + 1);
                break;
        case LAYOUT_WINDOWPANE:
                break;
        }
}

/* Search for a cell by the border position. */
struct layout_cell *
layout_search_by_border(struct layout_cell *lc, u_int x, u_int y)
{
        struct layout_cell      *lcchild, *last = NULL;

        TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                if ((int)x >= lcchild->g.xoff &&
                    (int)x < lcchild->g.xoff + (int)lcchild->g.sx &&
                    (int)y >= lcchild->g.yoff &&
                    (int)y < lcchild->g.yoff + (int)lcchild->g.sy) {
                        /* Inside the cell - recurse. */
                        return (layout_search_by_border(lcchild, x, y));
                }

                if (last == NULL) {
                        last = lcchild;
                        continue;
                }

                switch (lc->type) {
                case LAYOUT_LEFTRIGHT:
                        if ((int)x < lcchild->g.xoff &&
                            (int)x >= last->g.xoff + (int)last->g.sx)
                                return (last);
                        break;
                case LAYOUT_TOPBOTTOM:
                        if ((int)y < lcchild->g.yoff &&
                            (int)y >= last->g.yoff + (int)last->g.sy)
                                return (last);
                        break;
                case LAYOUT_WINDOWPANE:
                        break;
                }

                last = lcchild;
        }

        return (NULL);
}

/* Set cell size. */
void
layout_set_size(struct layout_cell *lc, u_int sx, u_int sy, int xoff, int yoff)
{
        lc->g.sx = sx;
        lc->g.sy = sy;

        lc->g.xoff = xoff;
        lc->g.yoff = yoff;
}

/* Make a cell a leaf cell. */
void
layout_make_leaf(struct layout_cell *lc, struct window_pane *wp)
{
        lc->type = LAYOUT_WINDOWPANE;

        TAILQ_INIT(&lc->cells);

        wp->layout_cell = lc;
        lc->wp = wp;
}

/* Make a cell a node cell. */
void
layout_make_node(struct layout_cell *lc, enum layout_type type)
{
        if (type == LAYOUT_WINDOWPANE)
                fatalx("bad layout type");
        lc->type = type;

        TAILQ_INIT(&lc->cells);

        if (lc->wp != NULL)
                lc->wp->layout_cell = NULL;
        lc->wp = NULL;
}

/* Fix z-indexes. */
void
layout_fix_zindexes(struct window *w, struct layout_cell *lc)
{
        struct layout_cell      *lcchild;

        if (lc == NULL)
                return;

        switch (lc->type) {
        case LAYOUT_WINDOWPANE:
                TAILQ_INSERT_TAIL(&w->z_index, lc->wp, zentry);
                break;
        case LAYOUT_LEFTRIGHT:
        case LAYOUT_TOPBOTTOM:
                TAILQ_FOREACH(lcchild, &lc->cells, entry)
                        layout_fix_zindexes(w, lcchild);
                return;
        default:
                fatalx("bad layout type");
        }
}

int
layout_cell_is_tiled(struct layout_cell *lc)
{
        int     is_leaf = lc->type == LAYOUT_WINDOWPANE;
        int     is_floating = lc->flags & LAYOUT_CELL_FLOATING;

        return is_leaf && !is_floating;
}

static int
layout_cell_has_tiled_child(struct layout_cell *lc)
{
        struct layout_cell      *lcchild;

        if (lc->type == LAYOUT_WINDOWPANE)
                return (0);

        TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                if (layout_cell_is_tiled(lcchild) ||
                    layout_cell_has_tiled_child(lcchild))
                        return (1);
        }
        return (0);
}

static int
layout_cell_is_first_tiled(struct layout_cell *lc)
{
        struct layout_cell      *lcchild, *lcparent = lc->parent;

        if (lcparent == NULL)
                return (layout_cell_is_tiled(lc));

        TAILQ_FOREACH(lcchild, &lcparent->cells, entry) {
                if (layout_cell_is_tiled(lcchild) ||
                    layout_cell_has_tiled_child(lcchild))
                        break;
        }

        return (lcchild == lc);
}

static struct layout_cell *
layout_cell_get_first_tiled(struct layout_cell *lc)
{
        struct layout_cell      *lcchild, *lcchild2;

        if (layout_cell_is_tiled(lc))
                return (lc);
        if (lc->type == LAYOUT_WINDOWPANE)
                return (NULL);

        TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                if (layout_cell_is_tiled(lcchild))
                        return (lcchild);
                if (lcchild->type != LAYOUT_WINDOWPANE) {
                        lcchild2 = layout_cell_get_first_tiled(lcchild);
                        if (lcchild2 != NULL)
                                return (lcchild2);
                }
        }
        return (NULL);
}

/* Fix cell offsets for a child cell. */
static void
layout_fix_offsets1(struct layout_cell *lc)
{
        struct layout_cell      *lcchild;
        int                      xoff, yoff;

        if (lc->type == LAYOUT_LEFTRIGHT) {
                xoff = lc->g.xoff;
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        if (!layout_cell_is_tiled(lcchild) &&
                            !layout_cell_has_tiled_child(lcchild))
                                continue;
                        lcchild->g.xoff = xoff;
                        lcchild->g.yoff = lc->g.yoff;
                        if (lcchild->type != LAYOUT_WINDOWPANE)
                                layout_fix_offsets1(lcchild);
                        xoff += lcchild->g.sx + 1;
                }
        } else {
                yoff = lc->g.yoff;
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        if (!layout_cell_is_tiled(lcchild) &&
                            !layout_cell_has_tiled_child(lcchild))
                                continue;
                        lcchild->g.xoff = lc->g.xoff;
                        lcchild->g.yoff = yoff;
                        if (lcchild->type != LAYOUT_WINDOWPANE)
                                layout_fix_offsets1(lcchild);
                        yoff += lcchild->g.sy + 1;
                }
        }
}

/* Update cell offsets based on their sizes. */
void
layout_fix_offsets(struct window *w)
{
        struct layout_cell      *lc = w->layout_root;

        /* Root consists of a single floating cell */
        if (lc->flags & LAYOUT_CELL_FLOATING)
                return;

        lc->g.xoff = 0;
        lc->g.yoff = 0;

        layout_fix_offsets1(lc);
}

static int
layout_cell_is_last_tiled(struct layout_cell *lc)
{
        struct layout_cell      *lcchild, *lcparent = lc->parent;

        if (lcparent == NULL)
                return (layout_cell_is_tiled(lc));

        TAILQ_FOREACH_REVERSE(lcchild, &lcparent->cells, layout_cells, entry) {
                if (layout_cell_is_tiled(lcchild) ||
                    layout_cell_has_tiled_child(lcchild))
                        break;
        }

        return (lcchild == lc);
}

/* Is this a top cell? */
static int
layout_cell_is_top(struct layout_cell *root, struct layout_cell *lc)
{
        struct layout_cell      *next;

        while (lc != root) {
                next = lc->parent;
                if (next == NULL)
                        return (0);
                if (next->type == LAYOUT_TOPBOTTOM &&
                    !layout_cell_is_first_tiled(lc))
                        return (0);
                lc = next;
        }
        return (1);
}

/* Is this a bottom cell? */
static int
layout_cell_is_bottom(struct layout_cell *root, struct layout_cell *lc)
{
        struct layout_cell      *next;

        while (lc != root) {
                next = lc->parent;
                if (next == NULL)
                        return (0);
                if (next->type == LAYOUT_TOPBOTTOM &&
                    !layout_cell_is_last_tiled(lc))
                        return (0);
                lc = next;
        }
        return (1);
}

/*
 * Returns 1 if we need to add an extra line for the pane status line. This is
 * the case for the most upper or lower panes only.
 */
int
layout_add_horizontal_border(struct layout_cell *root, struct layout_cell *lc,
    int status)
{
        if (status == PANE_STATUS_TOP)
                return (layout_cell_is_top(root, lc));
        if (status == PANE_STATUS_BOTTOM)
                return (layout_cell_is_bottom(root, lc));
        return (0);
}

/* Update pane offsets and sizes based on their cells. */
void
layout_fix_panes(struct window *w, struct window_pane *skip)
{
        struct window_pane      *wp;
        struct layout_cell      *lc, *root = w->layout_root;
        int                      status, sb_w, sb_pad;
        int                      old_xoff, old_yoff, changed = 0;
        u_int                    sx, sy, old_sx, old_sy;

        TAILQ_FOREACH(wp, &w->panes, entry) {
                if ((lc = wp->layout_cell) == NULL || wp == skip)
                        continue;

                old_xoff = wp->xoff;
                old_yoff = wp->yoff;
                old_sx = wp->sx;
                old_sy = wp->sy;

                wp->xoff = lc->g.xoff;
                wp->yoff = lc->g.yoff;
                sx = lc->g.sx;
                sy = lc->g.sy;

                status = window_pane_get_pane_status(wp);
                if (!window_pane_is_floating(wp) &&
                    layout_add_horizontal_border(root, lc, status)) {
                        if (status == PANE_STATUS_TOP)
                                wp->yoff++;
                        if (sy > 1)
                                sy--;
                }

                if (window_pane_scrollbar_reserve(wp)) {
                        sb_w = wp->scrollbar_style.width;
                        sb_pad = wp->scrollbar_style.pad;
                        if (sb_w < 1)
                                sb_w = 1;
                        if (sb_pad < 0)
                                sb_pad = 0;
                        if (w->sb_pos == PANE_SCROLLBARS_LEFT) {
                                if ((int)sx - sb_w - sb_pad < PANE_MINIMUM) {
                                        wp->xoff = wp->xoff +
                                            (int)sx - PANE_MINIMUM;
                                        sx = PANE_MINIMUM;
                                } else {
                                        sx = sx - sb_w - sb_pad;
                                        wp->xoff = wp->xoff + sb_w + sb_pad;
                                }
                        } else /* sb_pos == PANE_SCROLLBARS_RIGHT */
                                if ((int)sx - sb_w - sb_pad < PANE_MINIMUM)
                                        sx = PANE_MINIMUM;
                                else
                                        sx = sx - sb_w - sb_pad;
                        wp->flags |= PANE_REDRAWSCROLLBAR;
                }

                window_pane_resize(wp, sx, sy);

                if (wp->xoff != old_xoff ||
                    wp->yoff != old_yoff ||
                    wp->sx != old_sx ||
                    wp->sy != old_sy)
                        changed = 1;
        }
        if (changed)
                redraw_invalidate_scene(w);
}

/* Count the number of available cells in a layout. */
u_int
layout_count_cells(struct layout_cell *lc)
{
        struct layout_cell      *lcchild;
        u_int                    count = 0;

        switch (lc->type) {
        case LAYOUT_WINDOWPANE:
                return (1);
        case LAYOUT_LEFTRIGHT:
        case LAYOUT_TOPBOTTOM:
                TAILQ_FOREACH(lcchild, &lc->cells, entry)
                        count += layout_count_cells(lcchild);
                return (count);
        default:
                fatalx("bad layout type");
        }
}

/* Calculate how much size is available to be removed from a cell. */
static u_int
layout_resize_check(struct window *w, struct layout_cell *lc,
    enum layout_type type)
{
        struct layout_cell      *lcchild, *root = w->layout_root;
        struct style            *sb_style = &w->active->scrollbar_style;
        u_int                    available, minimum;
        int                      status;

        status = window_get_pane_status(w);

        if (lc->type == LAYOUT_WINDOWPANE) {
                /* Space available in this cell only. */
                if (type == LAYOUT_LEFTRIGHT) {
                        available = lc->g.sx;
                        if (w->sb == PANE_SCROLLBARS_ALWAYS)
                                minimum = PANE_MINIMUM + sb_style->width +
                                    sb_style->pad;
                        else
                                minimum = PANE_MINIMUM;
                } else {
                        available = lc->g.sy;
                        if (layout_add_horizontal_border(root, lc, status))
                                minimum = PANE_MINIMUM + 1;
                        else
                                minimum = PANE_MINIMUM;
                }
                if (available > minimum)
                        available -= minimum;
                else
                        available = 0;
        } else if (lc->type == type) {
                /* Same type: total of available space in all child cells. */
                available = 0;
                TAILQ_FOREACH(lcchild, &lc->cells, entry)
                        available += layout_resize_check(w, lcchild, type);
        } else {
                /* Different type: minimum of available space in child cells. */
                minimum = UINT_MAX;
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        available = layout_resize_check(w, lcchild, type);
                        if (available < minimum)
                                minimum = available;
                }
                available = minimum;
        }

        return (available);
}

/*
 * Adjust cell size evenly, including altering its children. This function
 * expects the change to have already been bounded to the space available.
 */
void
layout_resize_adjust(struct window *w, struct layout_cell *lc,
    enum layout_type type, int change)
{
        struct layout_cell      *lcchild;
        int                      changed;

        /* Adjust the cell size. */
        if (type == LAYOUT_LEFTRIGHT)
                lc->g.sx += change;
        else
                lc->g.sy += change;

        /* If this is a leaf cell, that is all that is necessary. */
        if (type == LAYOUT_WINDOWPANE)
                return;

        /* Child cell runs in a different direction. */
        if (lc->type != type) {
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        if (!layout_cell_is_tiled(lcchild) &&
                            !layout_cell_has_tiled_child(lcchild))
                                continue;
                        layout_resize_adjust(w, lcchild, type, change);
                }
                return;
        }

        /*
         * If a node doesn't contain any tiled cells, there is nothing to do.
         */
        if (!layout_cell_has_tiled_child(lc))
                return;

        /*
         * Child cell runs in the same direction. Adjust each child equally
         * until no further change is possible.
         */
        while (change != 0) {
                changed = 0;
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        if (change == 0)
                                break;
                        if (!layout_cell_is_tiled(lcchild) &&
                            !layout_cell_has_tiled_child(lcchild))
                                continue;
                        if (change > 0) {
                                layout_resize_adjust(w, lcchild, type, 1);
                                change--;
                                changed = 1;
                                continue;
                        }
                        if (layout_resize_check(w, lcchild, type) > 0) {
                                layout_resize_adjust(w, lcchild, type, -1);
                                change++;
                                changed = 1;
                        }
                }
                if (!changed)
                        break;
        }
}

/* Resizes a cell to a specified size */
void
layout_resize_set_size(struct window *w, struct layout_cell *lc,
    enum layout_type type, u_int size)
{
        int     change;

        if (type == LAYOUT_LEFTRIGHT)
                change = size - lc->g.sx;
        else
                change = size - lc->g.sy;
        layout_resize_adjust(w, lc, type, change);
}

/* Find and return the nearest neighbour to a cell in a specific direction. */
static struct layout_cell *
layout_cell_get_neighbour_direction(struct layout_cell *lc, int direction)
{
        struct layout_cell      *lcn = lc;

        while (1) {
                if (direction)
                        lcn = TAILQ_NEXT(lcn, entry);
                else
                        lcn = TAILQ_PREV(lcn, layout_cells, entry);

                if (lcn == NULL ||
                    layout_cell_is_tiled(lcn) ||
                    layout_cell_has_tiled_child(lcn))
                        return (lcn);
        }
}

/*
 * Find and return the nearest neighbour. Prefers cells "after" the specified
 * cell. This behavior defines how cell dimensions are redistributed when a cell
 * is hidden/shown and floated/tiled.
 */
struct layout_cell *
layout_cell_get_neighbour(struct layout_cell *lc)
{
        struct layout_cell      *lcother, *lcparent = lc->parent;
        int                      direction = 1;

        if (lcparent == NULL)
                return (NULL);

        if (lc == TAILQ_LAST(&lcparent->cells, layout_cells))
                direction = !direction;

        lcother = layout_cell_get_neighbour_direction(lc, direction);
        if (lcother == NULL)
                lcother = layout_cell_get_neighbour_direction(lc, !direction);

        return (lcother);
}


/* Destroy a cell and redistribute the space. */
void
layout_destroy_cell(struct window *w, struct layout_cell *lc,
    struct layout_cell **lcroot)
{
        struct layout_cell      *lcother = NULL, *lcparent;
        int                      change;

        /* If no parent, this is the last pane in a window. */
        lcparent = lc->parent;
        if (lcparent == NULL) {
                if (lc->wp != NULL)
                        *lcroot = NULL;
                layout_free_cell(lc, 0);
                return;
        }

        if (!layout_cell_is_tiled(lc)) {
                TAILQ_REMOVE(&lcparent->cells, lc, entry);
                layout_free_cell(lc, 0);
                goto out;
        }

        lcother = layout_cell_get_neighbour(lc);
        if (lcother != NULL) {
                if (lcparent->type == LAYOUT_LEFTRIGHT)
                        change = lc->g.sx + 1;
                else
                        change = lc->g.sy + 1;
                layout_resize_adjust(w, lcother, lcparent->type, change);
        } else
                layout_remove_tile(w, lcparent);

        /* Remove this from the parent's list. */
        TAILQ_REMOVE(&lcparent->cells, lc, entry);
        layout_free_cell(lc, 0);

out:
        /*
         * If the parent now has one cell, remove the parent from the tree and
         * replace it by that cell.
         */
        lc = TAILQ_FIRST(&lcparent->cells);
        if (lc != NULL && TAILQ_NEXT(lc, entry) == NULL) {
                TAILQ_REMOVE(&lcparent->cells, lc, entry);

                lc->parent = lcparent->parent;
                if (lc->parent == NULL) {
                        if (layout_cell_is_tiled(lc)) {
                                lc->g.xoff = 0;
                                lc->g.yoff = 0;
                        }
                        *lcroot = lc;
                } else
                        TAILQ_REPLACE(&lc->parent->cells, lcparent, lc, entry);

                layout_free_cell(lcparent, 0);
        }
}

/* Initialize layout for pane. */
void
layout_init(struct window *w, struct window_pane *wp)
{
        struct layout_cell      *lc;

        lc = w->layout_root = layout_create_cell(NULL);
        layout_set_size(lc, w->sx, w->sy, 0, 0);
        layout_make_leaf(lc, wp);
        layout_fix_panes(w, NULL);
}

/* Free layout for pane. */
void
layout_free(struct window *w, int only_nodes)
{
        layout_free_cell(w->layout_root, only_nodes);
}

/* Resize the entire layout after window resize. */
void
layout_resize(struct window *w, u_int sx, u_int sy)
{
        struct layout_cell      *lc = w->layout_root;
        int                      xlimit, ylimit, xchange, ychange;

        /*
         * Adjust horizontally. Do not attempt to reduce the layout lower than
         * the minimum (more than the amount returned by layout_resize_check).
         *
         * This can mean that the window size is smaller than the total layout
         * size: redrawing this is handled at a higher level, but it does leave
         * a problem with growing the window size here: if the current size is
         * < the minimum, growing proportionately by adding to each pane is
         * wrong as it would keep the layout size larger than the window size.
         * Instead, spread the difference between the minimum and the new size
         * out proportionately - this should leave the layout fitting the new
         * window size.
         */
        if (lc->type == LAYOUT_WINDOWPANE && (lc->flags & LAYOUT_CELL_FLOATING))
                return;
        xchange = sx - lc->g.sx;
        xlimit = layout_resize_check(w, lc, LAYOUT_LEFTRIGHT);
        if (xchange < 0 && xchange < -xlimit)
                xchange = -xlimit;
        if (xlimit == 0) {
                if (sx <= lc->g.sx)     /* lc->g.sx is minimum possible */
                        xchange = 0;
                else
                        xchange = sx - lc->g.sx;
        }
        if (xchange != 0)
                layout_resize_adjust(w, lc, LAYOUT_LEFTRIGHT, xchange);

        /* Adjust vertically in a similar fashion. */
        ychange = sy - lc->g.sy;
        ylimit = layout_resize_check(w, lc, LAYOUT_TOPBOTTOM);
        if (ychange < 0 && ychange < -ylimit)
                ychange = -ylimit;
        if (ylimit == 0) {
                if (sy <= lc->g.sy)     /* lc->g.sy is minimum possible */
                        ychange = 0;
                else
                        ychange = sy - lc->g.sy;
        }
        if (ychange != 0)
                layout_resize_adjust(w, lc, LAYOUT_TOPBOTTOM, ychange);

        /* Fix cell offsets. */
        layout_fix_offsets(w);
        layout_fix_panes(w, NULL);
}

/* Resize a pane to an absolute size. */
void
layout_resize_pane_to(struct window_pane *wp, enum layout_type type,
    u_int new_size)
{
        struct layout_cell     *lc, *lcparent;
        int                     change, size;

        lc = wp->layout_cell;

        /* Find next parent of the same type. */
        lcparent = lc->parent;
        while (lcparent != NULL && lcparent->type != type) {
                lc = lcparent;
                lcparent = lc->parent;
        }
        if (lcparent == NULL)
                return;

        /* Work out the size adjustment. */
        if (type == LAYOUT_LEFTRIGHT)
                size = lc->g.sx;
        else
                size = lc->g.sy;
        if (lc == TAILQ_LAST(&lcparent->cells, layout_cells))
                change = size - new_size;
        else
                change = new_size - size;

        /* Resize the pane. */
        layout_resize_pane(wp, type, change, 1);
}

/* Resize a floating pane to an absolute size. */
int
layout_resize_floating_pane_to(struct window_pane *wp, enum layout_type type,
    u_int size, char **cause)
{
        struct layout_cell      *lc = wp->layout_cell;

        if (~lc->flags & LAYOUT_CELL_FLOATING) {
                *cause = xstrdup("pane is not floating");
                return (-1);
        }

        if (window_pane_get_pane_lines(wp) != PANE_LINES_NONE &&
            size >= PANE_MINIMUM + 2)
                size -= 2;
        if (size < PANE_MINIMUM || size > PANE_MAXIMUM) {
                *cause = xstrdup("size is too big or too small");
                return (-1);
        }

        if (type == LAYOUT_TOPBOTTOM) {
                if (lc->g.sy == size)
                        return (0);
                lc->g.sy = size;
        } else {
                if (lc->g.sx == size)
                        return (0);
                lc->g.sx = size;
        }
        redraw_invalidate_scene(wp->window);
        return (0);
}

/* Resize a floating pane relative to its current size. */
int
layout_resize_floating_pane(struct window_pane *wp, enum layout_type type,
    int change, int opposite, char **cause)
{
        struct layout_cell      *lc = wp->layout_cell;
        u_int                    size;

        if (~lc->flags & LAYOUT_CELL_FLOATING) {
                *cause = xstrdup("pane is not floating");
                return (-1);
        }
        if (change == 0)
                return (0);

        if (type == LAYOUT_TOPBOTTOM) {
                size = lc->g.sy + change;
                if (size < PANE_MINIMUM || size > PANE_MAXIMUM) {
                        *cause = xstrdup("change is too big or too small");
                        return (-1);
                }
                lc->g.sy = size;
                if (opposite)
                        lc->g.yoff -= change;
        } else {
                size = lc->g.sx + change;
                if (size < PANE_MINIMUM || size > PANE_MAXIMUM) {
                        *cause = xstrdup("change is too big or too small");
                        return (-1);
                }
                lc->g.sx = size;
                if (opposite)
                        lc->g.xoff -= change;
        }
        redraw_invalidate_scene(wp->window);
        return (0);
}

/* Resize a layout cell. */
void
layout_resize_layout(struct window *w, struct layout_cell *lc,
    enum layout_type type, int change, int opposite)
{
        int     needed, size;

        /* Grow or shrink the cell. */
        needed = change;
        while (needed != 0) {
                if (change > 0) {
                        size = layout_resize_pane_grow(w, lc, type, needed,
                            opposite);
                        needed -= size;
                } else {
                        size = layout_resize_pane_shrink(w, lc, type, needed);
                        needed += size;
                }

                if (size == 0)  /* no more change possible */
                        break;
        }

        /* Fix cell offsets. */
        layout_fix_offsets(w);
        layout_fix_panes(w, NULL);
        events_fire_window("window-layout-changed", w);
}

/* Resize a single pane within the layout. */
void
layout_resize_pane(struct window_pane *wp, enum layout_type type, int change,
    int opposite)
{
        struct layout_cell      *lc = wp->layout_cell, *lcparent;

        /* Find next parent of the same type. */
        lcparent = lc->parent;
        while (lcparent != NULL && lcparent->type != type) {
                lc = lcparent;
                lcparent = lc->parent;
        }
        if (lcparent == NULL)
                return;

        /* If this is the last cell, move back one. */
        if (lc == TAILQ_LAST(&lcparent->cells, layout_cells)) {
                do
                        lc = TAILQ_PREV(lc, layout_cells, entry);
                while (lc->flags & LAYOUT_CELL_FLOATING);
        }

        layout_resize_layout(wp->window, lc, type, change, opposite);
}

/* Helper function to grow pane. */
static int
layout_resize_pane_grow(struct window *w, struct layout_cell *lc,
    enum layout_type type, int needed, int opposite)
{
        struct layout_cell      *lcadd, *lcremove;
        u_int                    size = 0;

        /* Growing. Always add to the current cell. */
        lcadd = lc;

        /* Look towards the tail for a suitable cell for reduction. */
        lcremove = TAILQ_NEXT(lc, entry);
        while (lcremove != NULL) {
                size = layout_resize_check(w, lcremove, type);
                if (size > 0)
                        break;
                lcremove = TAILQ_NEXT(lcremove, entry);
        }

        /* If none found, look towards the head. */
        if (opposite && lcremove == NULL) {
                lcremove = TAILQ_PREV(lc, layout_cells, entry);
                while (lcremove != NULL) {
                        size = layout_resize_check(w, lcremove, type);
                        if (size > 0)
                                break;
                        lcremove = TAILQ_PREV(lcremove, layout_cells, entry);
                }
        }
        if (lcremove == NULL)
                return (0);

        /* Change the cells. */
        if (size > (u_int) needed)
                size = needed;
        layout_resize_adjust(w, lcadd, type, size);
        layout_resize_adjust(w, lcremove, type, -size);
        return (size);
}

/* Helper function to shrink pane. */
static int
layout_resize_pane_shrink(struct window *w, struct layout_cell *lc,
    enum layout_type type, int needed)
{
        struct layout_cell      *lcadd, *lcremove;
        u_int                    size;

        /* Shrinking. Find cell to remove from by walking towards head. */
        lcremove = lc;
        do {
                size = layout_resize_check(w, lcremove, type);
                if (size != 0)
                        break;
                lcremove = TAILQ_PREV(lcremove, layout_cells, entry);
        } while (lcremove != NULL);
        if (lcremove == NULL)
                return (0);

        /* And add onto the next cell (from the original cell). */
        lcadd = TAILQ_NEXT(lc, entry);
        if (lcadd == NULL)
                return (0);

        /* Change the cells. */
        if (size > (u_int) -needed)
                size = -needed;
        layout_resize_adjust(w, lcadd, type, size);
        layout_resize_adjust(w, lcremove, type, -size);
        return (size);
}

/* Assign window pane to new cell. */
void
layout_assign_pane(struct layout_cell *lc, struct window_pane *wp,
    int do_not_resize)
{
        layout_make_leaf(lc, wp);
        if (do_not_resize)
                layout_fix_panes(wp->window, wp);
        else
                layout_fix_panes(wp->window, NULL);
}

/* Calculate the new pane size for resized parent. */
static u_int
layout_new_pane_size(struct window *w, u_int previous, struct layout_cell *lc,
    enum layout_type type, u_int size, u_int count_left, u_int size_left)
{
        u_int   new_size, min, max, available;

        /* If this is the last cell, it can take all of the remaining size. */
        if (count_left == 1)
                return (size_left);

        /* How much is available in this parent? */
        available = layout_resize_check(w, lc, type);

        /*
         * Work out the minimum size of this cell and the new size
         * proportionate to the previous size.
         */
        min = (PANE_MINIMUM + 1) * (count_left - 1);
        if (type == LAYOUT_LEFTRIGHT) {
                if (lc->g.sx - available > min)
                        min = lc->g.sx - available;
                new_size = (lc->g.sx * size) / previous;
        } else {
                if (lc->g.sy - available > min)
                        min = lc->g.sy - available;
                new_size = (lc->g.sy * size) / previous;
        }

        /* Check against the maximum and minimum size. */
        max = size_left - min;
        if (new_size > max)
                new_size = max;
        if (new_size < PANE_MINIMUM)
                new_size = PANE_MINIMUM;
        return (new_size);
}

/* Check if the cell and all its children can be resized to a specific size. */
static int
layout_set_size_check(struct window *w, struct layout_cell *lc,
    enum layout_type type, int size)
{
        struct layout_cell      *lcchild;
        u_int                    new_size, available, previous, count, idx;

        /* Cells with no children must just be bigger than minimum. */
        if (lc->type == LAYOUT_WINDOWPANE)
                return (size >= PANE_MINIMUM);
        available = size;

        /* Count number of children. */
        count = 0;
        TAILQ_FOREACH(lcchild, &lc->cells, entry)
                count++;

        /* Check new size will work for each child. */
        if (lc->type == type) {
                if (available < (count * 2) - 1)
                        return (0);

                if (type == LAYOUT_LEFTRIGHT)
                        previous = lc->g.sx;
                else
                        previous = lc->g.sy;

                idx = 0;
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        new_size = layout_new_pane_size(w, previous, lcchild,
                            type, size, count - idx, available);
                        if (idx == count - 1) {
                                if (new_size > available)
                                        return (0);
                                available -= new_size;
                        } else {
                                if (new_size + 1 > available)
                                        return (0);
                                available -= new_size + 1;
                        }
                        if (!layout_set_size_check(w, lcchild, type, new_size))
                                return (0);
                        idx++;
                }
        } else {
                TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                        if (lcchild->type == LAYOUT_WINDOWPANE)
                                continue;
                        if (!layout_set_size_check(w, lcchild, type, size))
                                return (0);
                }
        }

        return (1);
}

/* Resize all child cells to fit within the current cell. */
static void
layout_resize_child_cells(struct window *w, struct layout_cell *lc)
{
        struct layout_cell      *lcchild;
        u_int                    prev, available, count, idx;

        if (lc->type == LAYOUT_WINDOWPANE)
                return;

        /* What is the current size used? */
        count = 0;
        prev = 0;
        TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                if (!layout_cell_is_tiled(lcchild) &&
                    !layout_cell_has_tiled_child(lcchild))
                        continue;
                count++;
                if (lc->type == LAYOUT_LEFTRIGHT)
                        prev += lcchild->g.sx;
                else if (lc->type == LAYOUT_TOPBOTTOM)
                        prev += lcchild->g.sy;
        }
        prev += (count - 1);

        /* And how much is available? */
        available = 0;
        if (lc->type == LAYOUT_LEFTRIGHT)
                available = lc->g.sx;
        else if (lc->type == LAYOUT_TOPBOTTOM)
                available = lc->g.sy;

        /* Resize children into the new size. */
        idx = 0;
        TAILQ_FOREACH(lcchild, &lc->cells, entry) {
                if (!layout_cell_is_tiled(lcchild) &&
                    !layout_cell_has_tiled_child(lcchild))
                        continue;
                if (lc->type == LAYOUT_TOPBOTTOM) {
                        lcchild->g.sx = lc->g.sx;
                        lcchild->g.xoff = lc->g.xoff;
                } else {
                        lcchild->g.sx = layout_new_pane_size(w, prev, lcchild,
                            lc->type, lc->g.sx, count - idx, available);
                        available -= (lcchild->g.sx + 1);
                }
                if (lc->type == LAYOUT_LEFTRIGHT) {
                        lcchild->g.sy = lc->g.sy;
                        lcchild->g.yoff = lc->g.yoff;
                } else {
                        lcchild->g.sy = layout_new_pane_size(w, prev, lcchild,
                            lc->type, lc->g.sy, count - idx, available);
                        available -= (lcchild->g.sy + 1);
                }
                layout_resize_child_cells(w, lcchild);
                idx++;
        }
}

/*
 * Replaces the provided layout cell with a new node of the specified type and
 * inserts the cell into it. Used when creating new cells requires a different
 * layout type, or when the root layout is a window pane.
 */
struct layout_cell *
layout_replace_with_node(struct window *w, struct layout_cell *lc,
    enum layout_type type)
{
        struct layout_cell      *lcparent;

        lcparent = layout_create_cell(lc->parent);
        layout_make_node(lcparent, type);
        layout_set_size(lcparent, lc->g.sx, lc->g.sy, lc->g.xoff, lc->g.yoff);
        if (lc->parent == NULL)
                w->layout_root = lcparent;
        else
                TAILQ_REPLACE(&lc->parent->cells, lc, lcparent, entry);

        /* Insert the old cell. */
        lc->parent = lcparent;
        TAILQ_INSERT_HEAD(&lcparent->cells, lc, entry);

        return (lcparent);
}

/* Checks if there is enough space for two new panes. */
int
layout_split_check_space(struct window_pane *wp, struct layout_cell *lc,
   enum layout_type type)
{
        struct layout_cell      *root = wp->window->layout_root;
        struct style            *sb_style = &wp->scrollbar_style;
        u_int                    minimum, sx = lc->g.sx, sy = lc->g.sy;
        int                      status;

        if (lc->flags & LAYOUT_CELL_FLOATING)
                fatalx("floating cells cannot be split");

        status = window_get_pane_status(wp->window);

        switch (type) {
        case LAYOUT_LEFTRIGHT:
                if (wp->window->sb == PANE_SCROLLBARS_ALWAYS) {
                        minimum = PANE_MINIMUM * 2 + sb_style->width +
                            sb_style->pad;
                } else
                        minimum = PANE_MINIMUM * 2 + 1;
                if (sx < minimum)
                        return (0);
                break;
        case LAYOUT_TOPBOTTOM:
                if (layout_add_horizontal_border(root, lc, status))
                        minimum = PANE_MINIMUM * 2 + 2;
                else
                        minimum = PANE_MINIMUM * 2 + 1;
                if (sy < minimum)
                        return (0);
                break;
        default:
                fatalx("bad layout type");
        }

        return (1);
}

/* Calculates the new cell sizes when splitting a pane. */
void
layout_split_sizes(struct layout_cell *lc, int size, int before,
    enum layout_type type, u_int *size1, u_int *size2, u_int *saved_size)
{
        u_int   s1, s2, ss;
        u_int   sx = lc->g.sx, sy = lc->g.sy;

        if (type == LAYOUT_LEFTRIGHT)
                ss = sx;
        else
                ss = sy;
        if (size < 0)
                s2 = ((ss + 1) / 2) - 1;
        else if (before)
                s2 = ss - size - 1;
        else
                s2 = size;
        if (s2 < PANE_MINIMUM)
                s2 = PANE_MINIMUM;
        else if (s2 > ss - 2)
                s2 = ss - 2;
        s1 = ss - 1 - s2;

        *size1 = s1;
        *size2 = s2;
        *saved_size = ss;
}

/*
 * Split a pane into two. size is a hint, or -1 for default half/half
 * split. This must be followed by layout_assign_pane before much else happens!
 */
struct layout_cell *
layout_split_pane(struct window_pane *wp, enum layout_type type, int size,
    int flags)
{
        struct layout_cell      *lc, *lcparent, *lcnew, *lc1, *lc2;
        u_int                    sx, sy, xoff, yoff, size1, size2;
        u_int                    new_size, saved_size, resize_first = 0;
        int                      full_size = (flags & SPAWN_FULLSIZE);
        int                      before = (flags & SPAWN_BEFORE);

        /*
         * If full_size is specified, add a new cell at the top of the window
         * layout. Otherwise, split the cell for the current pane.
         */
        if (full_size)
                lc = wp->window->layout_root;
        else
                lc = wp->layout_cell;

        /* Copy the old cell size. */
        sx = lc->g.sx;
        sy = lc->g.sy;
        xoff = lc->g.xoff;
        yoff = lc->g.yoff;

        /* Check there is enough space for the two new panes. */
        if (!layout_split_check_space(wp, lc, type))
                return (NULL);

        /*
         * Calculate new cell sizes. size is the target size or -1 for middle
         * split, size1 is the size of the top/left and size2 the bottom/right.
         */
        layout_split_sizes(lc, size, before, type, &size1, &size2, &saved_size);

        /* Which size are we using? */
        if (flags & SPAWN_BEFORE)
                new_size = size2;
        else
                new_size = size1;

        /* Confirm there is enough space for full size pane. */
        if (full_size && !layout_set_size_check(wp->window, lc, type, new_size))
                return (NULL);

        if (lc->parent != NULL && lc->parent->type == type) {
                /*
                 * If the parent exists and is of the same type as the split,
                 * create a new cell and insert it after this one.
                 */
                lcparent = lc->parent;
                lcnew = layout_create_cell(lcparent);
                if (flags & SPAWN_BEFORE)
                        TAILQ_INSERT_BEFORE(lc, lcnew, entry);
                else
                        TAILQ_INSERT_AFTER(&lcparent->cells, lc, lcnew, entry);
        } else if (full_size && lc->parent == NULL && lc->type == type) {
                /*
                 * If the new full size pane is the same type as the root
                 * split, insert the new pane under the existing root cell
                 * instead of creating a new root cell. The existing layout
                 * must be resized before inserting the new cell.
                 */
                if (lc->type == LAYOUT_LEFTRIGHT) {
                        lc->g.sx = new_size;
                        layout_resize_child_cells(wp->window, lc);
                        lc->g.sx = saved_size;
                } else if (lc->type == LAYOUT_TOPBOTTOM) {
                        lc->g.sy = new_size;
                        layout_resize_child_cells(wp->window, lc);
                        lc->g.sy = saved_size;
                }
                resize_first = 1;

                /* Create the new cell. */
                lcnew = layout_create_cell(lc);
                size = saved_size - 1 - new_size;
                if (lc->type == LAYOUT_LEFTRIGHT)
                        layout_set_size(lcnew, size, sy, 0, 0);
                else if (lc->type == LAYOUT_TOPBOTTOM)
                        layout_set_size(lcnew, sx, size, 0, 0);
                if (flags & SPAWN_BEFORE)
                        TAILQ_INSERT_HEAD(&lc->cells, lcnew, entry);
                else
                        TAILQ_INSERT_TAIL(&lc->cells, lcnew, entry);
        } else {
                /*
                 * Otherwise create a new parent and insert it.
                 */

                /* Create and insert the replacement parent. */
                lcparent = layout_replace_with_node(wp->window, lc, type);

                /* Create the new child cell. */
                lcnew = layout_create_cell(lcparent);
                if (flags & SPAWN_BEFORE)
                        TAILQ_INSERT_HEAD(&lcparent->cells, lcnew, entry);
                else
                        TAILQ_INSERT_TAIL(&lcparent->cells, lcnew, entry);
        }
        if (flags & SPAWN_BEFORE) {
                lc1 = lcnew;
                lc2 = lc;
        } else {
                lc1 = lc;
                lc2 = lcnew;
        }

        /*
         * Set new cell sizes. size1 is the size of the top/left and size2 the
         * bottom/right.
         */
        if (!resize_first && type == LAYOUT_LEFTRIGHT) {
                layout_set_size(lc1, size1, sy, xoff, yoff);
                layout_set_size(lc2, size2, sy, xoff + lc1->g.sx + 1, yoff);
        } else if (!resize_first && type == LAYOUT_TOPBOTTOM) {
                layout_set_size(lc1, sx, size1, xoff, yoff);
                layout_set_size(lc2, sx, size2, xoff, yoff + lc1->g.sy + 1);
        }
        if (full_size) {
                if (!resize_first)
                        layout_resize_child_cells(wp->window, lc);
                layout_fix_offsets(wp->window);
        } else
                layout_make_leaf(lc, wp);

        return (lcnew);
}

/*
 * Creates a cell for a new floating pane. This must be followed by
 * layout_assign_pane before much else happens!
 */
struct layout_cell *
layout_floating_pane(struct window *w, struct window_pane *wp,
    struct layout_geometry *lg)
{
        struct layout_cell      *lc, *lcnew, *lcparent;

        if (wp == NULL)
                lc = w->layout_root;
        else
                lc = wp->layout_cell;
        lcparent = lc->parent;

        if (lcparent == NULL) {
                /*
                 * Adding a pane to a root that isn't a node. Must create and
                 * insert a new root.
                 */
                lcparent = layout_replace_with_node(w, lc, LAYOUT_TOPBOTTOM);
        }

        lcnew = layout_create_cell(lcparent);
        TAILQ_INSERT_AFTER(&lcparent->cells, lc, lcnew, entry);
        lcnew->flags |= LAYOUT_CELL_FLOATING;
        layout_set_size(lcnew, lg->sx, lg->sy, lg->xoff, lg->yoff);

        return (lcnew);
}

/* Destroy the cell associated with a pane. */
void
layout_close_pane(struct window_pane *wp)
{
        struct window   *w = wp->window;

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

        /* Remove the cell. */
        layout_destroy_cell(w, wp->layout_cell, &w->layout_root);
        wp->layout_cell = NULL;

        /* Fix pane offsets and sizes. */
        if (w->layout_root != NULL) {
                layout_fix_offsets(w);
                layout_fix_panes(w, NULL);
        }
        events_fire_window("window-layout-changed", w);
}

/* Spread out cells inside a parent cell. */
int
layout_spread_cell(struct window *w, struct layout_cell *parent)
{
        struct layout_cell      *lc, *root = w->layout_root;
        u_int                    number, each, size, this, remainder;
        int                      change, changed, status;

        number = 0;
        TAILQ_FOREACH (lc, &parent->cells, entry)
                if (layout_cell_is_tiled(lc))
                        number++;
        if (number <= 1)
                return (0);
        status = window_get_pane_status(w);

        if (parent->type == LAYOUT_LEFTRIGHT)
                size = parent->g.sx;
        else if (parent->type == LAYOUT_TOPBOTTOM) {
                if (layout_add_horizontal_border(root, parent, status))
                        size = parent->g.sy - 1;
                else
                        size = parent->g.sy;
        } else
                return (0);
        if (size < number - 1)
                return (0);
        each = (size - (number - 1)) / number;
        if (each == 0)
                return (0);

        /*
         * Remaining space after assigning that which can be evenly
         * distributed.
         */
        remainder = size - (number * (each + 1)) + 1;

        changed = 0;
        TAILQ_FOREACH (lc, &parent->cells, entry) {
                if (!layout_cell_is_tiled(lc))
                        continue;
                change = 0;
                if (parent->type == LAYOUT_LEFTRIGHT) {
                        change = each - (int)lc->g.sx;
                        if (remainder > 0) {
                                change++;
                                remainder--;
                        }
                        layout_resize_adjust(w, lc, LAYOUT_LEFTRIGHT, change);
                } else if (parent->type == LAYOUT_TOPBOTTOM) {
                        if (layout_add_horizontal_border(root, lc, status))
                                this = each + 1;
                        else
                                this = each;
                        if (remainder > 0) {
                                this++;
                                remainder--;
                        }
                        change = this - (int)lc->g.sy;
                        layout_resize_adjust(w, lc, LAYOUT_TOPBOTTOM, change);
                }
                if (change != 0)
                        changed = 1;
        }
        return (changed);
}

/* Spread out cells evenly. */
void
layout_spread_out(struct window_pane *wp)
{
        struct layout_cell      *parent;
        struct window           *w = wp->window;

        parent = wp->layout_cell->parent;
        if (parent == NULL)
                return;

        do {
                if (layout_spread_cell(w, parent)) {
                        layout_fix_offsets(w);
                        layout_fix_panes(w, NULL);
                        break;
                }
        } while ((parent = parent->parent) != NULL);
}

/* Get a new tiled cell. */
struct layout_cell *
layout_get_tiled_cell(struct cmdq_item *item, struct args *args,
    struct window *w, struct window_pane *wp, int flags, char **cause)
{
        struct layout_cell      *lc;
        enum layout_type         type = LAYOUT_TOPBOTTOM;
        u_int                    curval;
        int                      size = -1;
        char                    *error = NULL;

        if (window_pane_is_floating(wp)) {
                *cause = xstrdup("can't split a floating pane");
                return (NULL);
        }

        if (flags & SPAWN_HORIZONTAL)
                type = LAYOUT_LEFTRIGHT;

        if (args_has(args, 'l') || args_has(args, 'p')) {
                if (flags & SPAWN_FULLSIZE) {
                        if (type == LAYOUT_TOPBOTTOM)
                                curval = w->sy;
                        else
                                curval = w->sx;
                } else {
                        if (type == LAYOUT_TOPBOTTOM)
                                curval = wp->sy;
                        else
                                curval = wp->sx;
                }
        }

        if (args_has(args, 'l')) {
                size = args_percentage_and_expand(args, 'l', 0, INT_MAX, curval,
                    item, &error);
        } else if (args_has(args, 'p')) {
                size = args_strtonum_and_expand(args, 'p', 0, 100, item,
                    &error);
                if (error == NULL)
                        size = curval * size / 100;
        }
        if (error != NULL) {
                xasprintf(cause, "invalid tiled geometry %s", error);
                free(error);
                return (NULL);
        }

        window_push_zoom(wp->window, 1, (flags & SPAWN_ZOOM));
        lc = layout_split_pane(wp, type, size, flags);
        if (lc == NULL)
                *cause = xstrdup("no space for a new pane");

        return (lc);
}

struct layout_cell *
layout_get_floating_cell(struct cmdq_item *item, struct args *args,
    enum pane_lines lines, struct window *w, struct window_pane *wp, int flags,
    char **cause)
{
        struct layout_cell      *lcnew, *lc = wp->layout_cell;
        struct layout_geometry   fg;

        layout_geometry_init(&fg);
        if (flags & SPAWN_SPLIT) {
                if (layout_split_floating_cell(lc, w, &fg, lines, flags, cause)
                    != 0)
                        return (NULL);
        } else {
                if (layout_floating_args_parse(item, args, lines, w, &fg, cause)
                    != 0)
                        return (NULL);
        }

        if (flags & SPAWN_MODAL)
                window_push_modal_zoom(w);
        else
                window_push_zoom(wp->window, 1, (flags & SPAWN_ZOOM));
        lcnew = layout_floating_pane(w, wp, &fg);
        return (lcnew);
}

int
layout_floating_args_parse(struct cmdq_item *item, struct args *args,
    enum pane_lines lines, struct window *w, struct layout_geometry *lg,
    char **cause)
{
        int      sx, sy, ox, oy;
        char    *error = NULL;

        sx = lg->sx == UINT_MAX ? w->sx / 2 : lg->sx;
        sy = lg->sy == UINT_MAX ? w->sy / 4 : lg->sy;
        ox = lg->xoff;
        oy = lg->yoff;

        if (args_has(args, 'x')) {
                sx = args_percentage_and_expand(args, 'x', 0, PANE_MAXIMUM,
                    w->sx, item, &error);
                if (error != NULL) {
                        xasprintf(cause, "position %s", error);
                        free(error);
                        return (-1);
                }
                if (lines != PANE_LINES_NONE)
                        sx -= 2;
        }
        if (args_has(args, 'y')) {
                sy = args_percentage_and_expand(args, 'y', 0, PANE_MAXIMUM,
                    w->sy, item, &error);
                if (error != NULL) {
                        xasprintf(cause, "position %s", error);
                        free(error);
                        return (-1);
                }
                if (lines != PANE_LINES_NONE)
                        sy -= 2;
        }
        if (args_has(args, 'X')) {
                ox = args_percentage_and_expand(args, 'X', -sx, w->sx,
                    w->sx, item, &error);
                if (error != NULL) {
                        xasprintf(cause, "position %s", error);
                        free(error);
                        return (-1);
                }
        }
        if (args_has(args, 'Y')) {
                oy = args_percentage_and_expand(args, 'Y', -sy, w->sy,
                    w->sy, item, &error);
                if (error != NULL) {
                        xasprintf(cause, "position %s", error);
                        free(error);
                        return (-1);
                }
        }

        if (ox == INT_MAX) {
                if (w->last_new_pane_x == 0)
                        ox = 4;
                else {
                        ox = w->last_new_pane_x + 4;
                        if (w->last_new_pane_x > w->sx)
                                ox = 4;
                }
                w->last_new_pane_x = ox;
        } else if (args_has(args, 'X'))
                if (lines != PANE_LINES_NONE)
                        ox += 1;
        if (oy == INT_MAX) {
                if (w->last_new_pane_y == 0)
                        oy = 2;
                else {
                        oy = w->last_new_pane_y + 2;
                        if (w->last_new_pane_y > w->sy)
                                oy = 2;
                }
                w->last_new_pane_y = oy;
        } else if (args_has(args, 'Y'))
                if (lines != PANE_LINES_NONE)
                        oy += 1;

        if (sx < PANE_MINIMUM || sx > PANE_MAXIMUM) {
                *cause = xstrdup("invalid width");
                return (-1);
        }
        if (sy < PANE_MINIMUM || sy > PANE_MAXIMUM) {
                *cause = xstrdup("invalid height");
                return (-1);
        }

        lg->sx = sx;
        lg->sy = sy;
        lg->xoff = ox;
        lg->yoff = oy;
        return (0);
}

int
layout_split_floating_cell(struct layout_cell *lc, struct window *w,
    struct layout_geometry *out, enum pane_lines lines, int flags,
    char **cause)
{
        struct layout_geometry   old, new;
        int                      tborder = 1, bborder = w->sy - 1;
        int                      lborder = 3, rborder = w->sx - 3;
        int                      border = lines != PANE_LINES_NONE ? 1 : 0;
        int                      size, space;

        /* First, move the target cell in-bounds. */
        memcpy(&old, &lc->g, sizeof old);
        if (lborder > old.xoff - border)
                old.xoff = lborder + border;
        if (rborder < old.xoff + (int)old.sx + border)
                old.xoff = rborder - (int)old.sx - border;
        if (tborder > old.yoff - border)
                old.yoff = tborder + border;
        if (bborder < old.yoff + (int)old.sy + border)
                old.yoff = bborder - (int)old.sy - border;

        /* Move the new cell to its ideal position. */
        memcpy(&new, &old, sizeof new);
        if (flags & SPAWN_HORIZONTAL) {
                if (flags & SPAWN_BEFORE)
                        new.xoff -= old.sx + 2 * border;
                else
                        new.xoff += old.sx + 2 * border;
        } else {
                if (flags & SPAWN_BEFORE)
                        new.yoff -= old.sy + 2 * border;
                else
                        new.yoff += old.sy + 2 * border;
        }

        /*
         * The position of the new cell is checked to see if it is in bounds.
         * If it isn't, the availible space is split and equally given to both
         * cells. Only one border is check because the target cell is in bounds
         * already.
         */
        if (lborder > new.xoff - border) {
                /*
                 * The space for both panes is calculated. Since the offsets are
                 * associated to where pane contents start, we remove pane
                 * borders from the space. '1' is added in case the space is
                 * odd.
                 */
                space = old.xoff + old.sx - lborder - 3 * border + 1;
                size = space / 2;
                new.sx = size;
                old.sx = size;
                new.xoff = lborder + border;
                old.xoff = new.xoff + new.sx + 2 * border;
                /*
                 * If the original space was to be odd (now even), subtract 1
                 * from the rightmost cell
                 */
                if (space % 2 == 0)
                        old.sx -= 1;
        } else if (rborder < new.xoff + (int)new.sx + border) {
                space = rborder - old.xoff - 3 * border + 1;
                size = space / 2;
                new.sx = size;
                old.sx = size;
                new.xoff = old.xoff + old.sx + 2 * border;
                if (space % 2 == 0)
                        new.sx -= 1;
        } else if (tborder > new.yoff - border) {
                space = old.sy + old.yoff - tborder - 3 * border + 1;
                size = space / 2;
                new.sy = size;
                old.sy = size;
                new.yoff = tborder + border;
                old.yoff = new.yoff + new.sy + 2 * border;
                if (space % 2 == 0)
                        old.sy -= 1;
        } else if (bborder < new.yoff + (int)new.sy + border) {
                space = bborder - old.yoff - 3 * border + 1;
                size = space / 2;
                new.sy = size;
                old.sy = size;
                new.yoff = old.yoff + old.sy + 2 * border;
                if (space % 2 == 0)
                        new.sy -= 1;
        }

        /*
         * Expand the cell to occupy the whole availible space where it was
         * spawned.
         */
        if (flags & SPAWN_FULLSIZE) {
                if (flags & SPAWN_HORIZONTAL) {
                        new.yoff = tborder + border;
                        new.sy = bborder - tborder - 2 * border;
                        if (flags & SPAWN_BEFORE) {
                                new.xoff = lborder + border;
                                new.sx = old.xoff - new.xoff - 2 * border;
                        } else {
                                new.sx = rborder - new.xoff - border;
                        }
                } else {
                        new.xoff = lborder + border;
                        new.sx = rborder - lborder - 2 * border;
                        if (flags & SPAWN_BEFORE) {
                                new.yoff = tborder + border;
                                new.sy = old.yoff - new.yoff - 2 * border;
                        } else {
                                new.sy = bborder - new.yoff - border;
                        }
                }
        }

        if (new.sx < PANE_MINIMUM || new.sy < PANE_MINIMUM ||
            old.sx < PANE_MINIMUM || old.sy < PANE_MINIMUM) {
                *cause = xstrdup("no space for a new pane");
                return (-1);
        }

        layout_set_size(lc, old.sx, old.sy, old.xoff, old.yoff);
        memcpy(out, &new, sizeof *out);
        return (0);
}

/*
 * Removes a cell from the tiled layout by giving the cell's space to the
 * nearest neighbour.
 */
int
layout_remove_tile(struct window *w, struct layout_cell *lc)
{
        struct layout_cell      *lcneighbour, *lcparent;
        enum layout_type         type;
        int                      change;

        if (lc->flags & LAYOUT_CELL_FLOATING)
                return (-1);

        lcneighbour = layout_cell_get_neighbour(lc);
        if (lcneighbour == NULL) {
                if (lc->parent != NULL)
                        layout_remove_tile(w, lc->parent);
        } else if ((lcparent = lcneighbour->parent) != NULL) {
                type = lcparent->type;
                /*
                 * Adding the size of the layout cell plus its border to the
                 * neighbour.
                 */
                if (type == LAYOUT_TOPBOTTOM)
                        change = lc->g.sy + 1;
                else
                        change = lc->g.sx + 1;
                layout_resize_adjust(w, lcneighbour, type, change);
        }

        /*
         * Zeroing out the cell geometry until the cell is retiled unless this
         * is the top level node.
         */
        if (lc->parent != NULL)
                layout_set_size(lc, 0, 0, 0, 0);
        return (0);
}

/*
 * Inserts a cell back into the tiled layout by taking half the space from its
 * nearest neighbour.
 */
int
layout_insert_tile(struct window *w, struct layout_cell *lc)
{
        struct layout_cell      *lcneighbour, *lctiled, *lcparent;
        enum layout_type         type;
        u_int                    size1, size2, saved_size;

        if (lc == NULL)
                fatalx("layout cell cannot be null when tiling");

        if (layout_cell_is_tiled(lc))
                return (-1);

        lcparent = lc->parent;
        if (lcparent == NULL) {
                /* Only pane in the layout. */
                layout_set_size(lc, w->sx, w->sy, 0, 0);
                return (0);
        }

        type = lcparent->type;
        lcneighbour = layout_cell_get_neighbour(lc);
        if (lcneighbour == NULL) {
                /*
                 * This will become the only visible cell in the parent.
                 * Tile the parent, then set the child's 'split' size.
                 */
                layout_insert_tile(w, lcparent);
                if (type == LAYOUT_LEFTRIGHT)
                        size1 = lcparent->g.sx;
                else
                        size1 = lcparent->g.sy;
                layout_resize_set_size(w, lc, type, size1);
        } else {
                /*
                 * If the neighbour is a node, a tiled child in the subtree of
                 * the neighbour is needed to check for space.
                 */
                lctiled = layout_cell_get_first_tiled(lcneighbour);
                if (!layout_split_check_space(lctiled->wp, lcneighbour, type))
                        return (-1);
                layout_split_sizes(lcneighbour, -1, 0, type, &size1, &size2,
                    &saved_size);
                layout_resize_set_size(w, lc, type, size1);
                layout_resize_set_size(w, lcneighbour, type, size2);
        }

        /* Setting opposite of the 'split' size to that of the parent. */
        if (lcparent->type == LAYOUT_LEFTRIGHT) {
                size1 = lcparent->g.sy;
                type = LAYOUT_TOPBOTTOM;
        } else {
                size1 = lcparent->g.sx;
                type = LAYOUT_LEFTRIGHT;
        }
        layout_resize_set_size(w, lc, type, size1);

        return (0);
}