Merge branch 'obsd-master'

[tmux.git] / layout.c

/* $OpenBSD$ */

/*
 * 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 "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.
 *
 * 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.
 */

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 *);

struct layout_cell *
layout_create_cell(struct layout_cell *lcparent)
{
        struct layout_cell      *lc;

        lc = xmalloc(sizeof *lc);
        lc->type = LAYOUT_WINDOWPANE;
        lc->parent = lcparent;

        TAILQ_INIT(&lc->cells);

        lc->sx = UINT_MAX;
        lc->sy = UINT_MAX;

        lc->xoff = UINT_MAX;
        lc->yoff = UINT_MAX;

        lc->wp = NULL;

        return (lc);
}

void
layout_free_cell(struct layout_cell *lc)
{
        struct layout_cell      *lcchild;

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

        free(lc);
}

void
layout_print_cell(struct layout_cell *lc, const char *hdr, u_int n)
{
        struct layout_cell      *lcchild;
        const char              *type;

        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 [%u,%u %ux%u]", hdr, n,
            " ", lc, type, lc->parent, lc->wp, lc->xoff, lc->yoff, lc->sx,
            lc->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;
        }
}

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 (x >= lcchild->xoff && x < lcchild->xoff + lcchild->sx &&
                    y >= lcchild->yoff && y < lcchild->yoff + lcchild->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 (x < lcchild->xoff && x >= last->xoff + last->sx)
                                return (last);
                        break;
                case LAYOUT_TOPBOTTOM:
                        if (y < lcchild->yoff && y >= last->yoff + last->sy)
                                return (last);
                        break;
                case LAYOUT_WINDOWPANE:
                        break;
                }

                last = lcchild;
        }

        return (NULL);
}

void
layout_set_size(struct layout_cell *lc, u_int sx, u_int sy, u_int xoff,
    u_int yoff)
{
        lc->sx = sx;
        lc->sy = sy;

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

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;
}

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

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

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

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

        layout_fix_offsets1(lc);
}

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

        while (lc != w->layout_root) {
                next = lc->parent;
                if (next->type == LAYOUT_TOPBOTTOM &&
                    lc != TAILQ_FIRST(&next->cells))
                        return (0);
                lc = next;
        }
        return (1);
}

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

        while (lc != w->layout_root) {
                next = lc->parent;
                if (next->type == LAYOUT_TOPBOTTOM &&
                    lc != TAILQ_LAST(&next->cells, layout_cells))
                        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.
 */
static int
layout_add_horizontal_border(struct window *w, struct layout_cell *lc,
    int status)
{
        if (status == PANE_STATUS_TOP)
                return (layout_cell_is_top(w, lc));
        if (status == PANE_STATUS_BOTTOM)
                return (layout_cell_is_bottom(w, 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;
        int                      status, scrollbars, sb_pos, sb_w, sb_pad;
        u_int                    sx, sy;

        status = options_get_number(w->options, "pane-border-status");
        scrollbars = options_get_number(w->options, "pane-scrollbars");
        sb_pos = options_get_number(w->options, "pane-scrollbars-position");

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

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

                if (layout_add_horizontal_border(w, lc, status)) {
                        if (status == PANE_STATUS_TOP)
                                wp->yoff++;
                        sy--;
                }

                if (window_pane_show_scrollbar(wp, scrollbars)) {
                        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 (sb_pos == PANE_SCROLLBARS_LEFT) {
                                if ((int)sx - sb_w < 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);
        }
}

/* 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;

        switch (lc->type) {
        case LAYOUT_WINDOWPANE:
                return (1);
        case LAYOUT_LEFTRIGHT:
        case LAYOUT_TOPBOTTOM:
                count = 0;
                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;
        struct style            *sb_style = &w->active->scrollbar_style;
        u_int                    available, minimum;
        int                      status, scrollbars;

        status = options_get_number(w->options, "pane-border-status");
        scrollbars = options_get_number(w->options, "pane-scrollbars");

        if (lc->type == LAYOUT_WINDOWPANE) {
                /* Space available in this cell only. */
                if (type == LAYOUT_LEFTRIGHT) {
                        available = lc->sx;
                        if (scrollbars)
                                minimum = PANE_MINIMUM + sb_style->width +
                                    sb_style->pad;
                        else
                                minimum = PANE_MINIMUM;
                } else {
                        available = lc->sy;
                        if (layout_add_horizontal_border(w, 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;

        /* Adjust the cell size. */
        if (type == LAYOUT_LEFTRIGHT)
                lc->sx += change;
        else
                lc->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)
                        layout_resize_adjust(w, lcchild, type, change);
                return;
        }

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

/* 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, *lcparent;

        /*
         * If no parent, this is the last pane so window close is imminent and
         * there is no need to resize anything.
         */
        lcparent = lc->parent;
        if (lcparent == NULL) {
                layout_free_cell(lc);
                *lcroot = NULL;
                return;
        }

        /* Merge the space into the previous or next cell. */
        if (lc == TAILQ_FIRST(&lcparent->cells))
                lcother = TAILQ_NEXT(lc, entry);
        else
                lcother = TAILQ_PREV(lc, layout_cells, entry);
        if (lcother != NULL && lcparent->type == LAYOUT_LEFTRIGHT)
                layout_resize_adjust(w, lcother, lcparent->type, lc->sx + 1);
        else if (lcother != NULL)
                layout_resize_adjust(w, lcother, lcparent->type, lc->sy + 1);

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

        /*
         * 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 (TAILQ_NEXT(lc, entry) == NULL) {
                TAILQ_REMOVE(&lcparent->cells, lc, entry);

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

                layout_free_cell(lcparent);
        }
}

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);
}

void
layout_free(struct window *w)
{
        layout_free_cell(w->layout_root);
}

/* 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.
         */
        xchange = sx - lc->sx;
        xlimit = layout_resize_check(w, lc, LAYOUT_LEFTRIGHT);
        if (xchange < 0 && xchange < -xlimit)
                xchange = -xlimit;
        if (xlimit == 0) {
                if (sx <= lc->sx)       /* lc->sx is minimum possible */
                        xchange = 0;
                else
                        xchange = sx - lc->sx;
        }
        if (xchange != 0)
                layout_resize_adjust(w, lc, LAYOUT_LEFTRIGHT, xchange);

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

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);
        notify_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, *lcparent;

        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;

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

        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 newly split 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->sx - available > min)
                        min = lc->sx - available;
                new_size = (lc->sx * size) / previous;
        } else {
                if (lc->sy - available > min)
                        min = lc->sy - available;
                new_size = (lc->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->sx;
                else
                        previous = lc->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                    previous, available, count, idx;

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

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

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

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

/*
 * 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;
        struct style            *sb_style = &wp->scrollbar_style;
        u_int                    sx, sy, xoff, yoff, size1, size2, minimum;
        u_int                    new_size, saved_size, resize_first = 0;
        int                      full_size = (flags & SPAWN_FULLSIZE), status;
        int                      scrollbars;

        /*
         * 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;
        status = options_get_number(wp->window->options, "pane-border-status");
        scrollbars = options_get_number(wp->window->options, "pane-scrollbars");

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

        /* Check there is enough space for the two new panes. */
        switch (type) {
        case LAYOUT_LEFTRIGHT:
                if (scrollbars) {
                        minimum = PANE_MINIMUM * 2 + sb_style->width +
                            sb_style->pad;
                } else
                        minimum = PANE_MINIMUM * 2 + 1;
                if (sx < minimum)
                        return (NULL);
                break;
        case LAYOUT_TOPBOTTOM:
                if (layout_add_horizontal_border(wp->window, lc, status))
                        minimum = PANE_MINIMUM * 2 + 2;
                else
                        minimum = PANE_MINIMUM * 2 + 1;
                if (sy < minimum)
                        return (NULL);
                break;
        default:
                fatalx("bad layout type");
        }

        /*
         * 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.
         */
        if (type == LAYOUT_LEFTRIGHT)
                saved_size = sx;
        else
                saved_size = sy;
        if (size < 0)
                size2 = ((saved_size + 1) / 2) - 1;
        else if (flags & SPAWN_BEFORE)
                size2 = saved_size - size - 1;
        else
                size2 = size;
        if (size2 < PANE_MINIMUM)
                size2 = PANE_MINIMUM;
        else if (size2 > saved_size - 2)
                size2 = saved_size - 2;
        size1 = saved_size - 1 - size2;

        /* 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->sx = new_size;
                        layout_resize_child_cells(wp->window, lc);
                        lc->sx = saved_size;
                } else if (lc->type == LAYOUT_TOPBOTTOM) {
                        lc->sy = new_size;
                        layout_resize_child_cells(wp->window, lc);
                        lc->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_create_cell(lc->parent);
                layout_make_node(lcparent, type);
                layout_set_size(lcparent, sx, sy, xoff, yoff);
                if (lc->parent == NULL)
                        wp->window->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);

                /* 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->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->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);
}

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

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

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

int
layout_spread_cell(struct window *w, struct layout_cell *parent)
{
        struct layout_cell      *lc;
        struct style            *sb_style = &w->active->scrollbar_style;
        u_int                    number, each, size, this;
        int                      change, changed, status, scrollbars;

        number = 0;
        TAILQ_FOREACH (lc, &parent->cells, entry)
                number++;
        if (number <= 1)
                return (0);
        status = options_get_number(w->options, "pane-border-status");
        scrollbars = options_get_number(w->options, "pane-scrollbars");

        if (parent->type == LAYOUT_LEFTRIGHT) {
                if (scrollbars)
                        size = parent->sx - sb_style->width + sb_style->pad;
                else
                        size = parent->sx;
        }
        else if (parent->type == LAYOUT_TOPBOTTOM) {
                if (layout_add_horizontal_border(w, parent, status))
                        size = parent->sy - 1;
                else
                        size = parent->sy;
        } else
                return (0);
        if (size < number - 1)
                return (0);
        each = (size - (number - 1)) / number;
        if (each == 0)
                return (0);

        changed = 0;
        TAILQ_FOREACH (lc, &parent->cells, entry) {
                if (TAILQ_NEXT(lc, entry) == NULL)
                        each = size - ((each + 1) * (number - 1));
                change = 0;
                if (parent->type == LAYOUT_LEFTRIGHT) {
                        change = each - (int)lc->sx;
                        layout_resize_adjust(w, lc, LAYOUT_LEFTRIGHT, change);
                } else if (parent->type == LAYOUT_TOPBOTTOM) {
                        if (layout_add_horizontal_border(w, lc, status))
                                this = each + 1;
                        else
                                this = each;
                        change = this - (int)lc->sy;
                        layout_resize_adjust(w, lc, LAYOUT_TOPBOTTOM, change);
                }
                if (change != 0)
                        changed = 1;
        }
        return (changed);
}

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);
}