window.c

/* Window creation, deletion and examination for GNU Emacs.
   Does not include redisplay.
   Copyright (C) 1985,86,87,93,94,95,96,97,1998 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include <config.h>
#include "lisp.h"
#include "buffer.h"
#include "frame.h"
#include "window.h"
#include "commands.h"
#include "indent.h"
#include "termchar.h"
#include "disptab.h"
#include "keyboard.h"
#include "blockinput.h"
#include "dispextern.h"
#ifdef HAVE_X_WINDOWS
#include "xterm.h"
#endif

Lisp_Object Qwindowp, Qwindow_live_p, Qwindow_configuration_p;

static struct window *decode_window P_ ((Lisp_Object));

static Lisp_Object select_window_1 P_ ((Lisp_Object, int));

/* This is the window in which the terminal's cursor should
   be left when nothing is being done with it.  This must
   always be a leaf window, and its buffer is selected by
   the top level editing loop at the end of each command.

   This value is always the same as
   FRAME_SELECTED_WINDOW (selected_frame).  */

Lisp_Object selected_window;

/* The minibuffer window of the selected frame.
   Note that you cannot test for minibufferness of an arbitrary window
   by comparing against this; but you can test for minibufferness of
   the selected window.  */
Lisp_Object minibuf_window;

/* Non-nil means it is the window for C-M-v to scroll
   when the minibuffer is selected.  */
Lisp_Object Vminibuf_scroll_window;

/* Non-nil means this is the buffer whose window C-M-v should scroll.  */
Lisp_Object Vother_window_scroll_buffer;

/* Non-nil means it's function to call to display temp buffers.  */
Lisp_Object Vtemp_buffer_show_function;

/* If a window gets smaller than either of these, it is removed. */
int window_min_height;
int window_min_width;

/* Nonzero implies Fdisplay_buffer should create windows. */
int pop_up_windows;

/* Nonzero implies make new frames for Fdisplay_buffer.  */
int pop_up_frames;

/* Non-nil means use this function instead of default */
Lisp_Object Vpop_up_frame_function;

/* Function to call to handle Fdisplay_buffer.  */
Lisp_Object Vdisplay_buffer_function;

/* List of buffer *names* for buffers that should have their own frames.  */
Lisp_Object Vspecial_display_buffer_names;

/* List of regexps for buffer names that should have their own frames.  */
Lisp_Object Vspecial_display_regexps;

/* Function to pop up a special frame.  */
Lisp_Object Vspecial_display_function;

/* List of buffer *names* for buffers to appear in selected window.  */
Lisp_Object Vsame_window_buffer_names;

/* List of regexps for buffer names to appear in selected window.  */
Lisp_Object Vsame_window_regexps;

/* Hook run at end of temp_output_buffer_show.  */
Lisp_Object Qtemp_buffer_show_hook;

/* Fdisplay_buffer always splits the largest window
   if that window is more than this high.  */
int split_height_threshold;

/* Number of lines of continuity in scrolling by screenfuls.  */
int next_screen_context_lines;

/* Incremented for each window created.  */
static int sequence_number;

/* Nonzero after init_window_once has finished.  */
static int window_initialized;

/* Hook to run when window config changes.  */
Lisp_Object Qwindow_configuration_change_hook;
Lisp_Object Vwindow_configuration_change_hook;

/* Nonzero means scroll commands try to put point
   at the same screen height as previously.  */
static int scroll_preserve_screen_position;

/* Nonzero means we can split a frame even if it is "unsplittable".  */
static int inhibit_frame_unsplittable;

#define min(a, b) ((a) < (b) ? (a) : (b))

extern int scroll_margin;

extern Lisp_Object Qwindow_scroll_functions, Vwindow_scroll_functions;

DEFUN ("windowp", Fwindowp, Swindowp, 1, 1, 0,
  "Returns t if OBJECT is a window.")
  (object)
     Lisp_Object object;
{
  return WINDOWP (object) ? Qt : Qnil;
}

DEFUN ("window-live-p", Fwindow_live_p, Swindow_live_p, 1, 1, 0,
  "Returns t if OBJECT is a window which is currently visible.")
     (object)
     Lisp_Object object;
{
  return (WINDOWP (object) && ! NILP (XWINDOW (object)->buffer) ? Qt : Qnil);
}

Lisp_Object
make_window ()
{
  Lisp_Object val;
  register struct window *p;
  register struct Lisp_Vector *vec;
  int i;

  vec = allocate_vectorlike ((EMACS_INT) VECSIZE (struct window));
  for (i = 0; i < VECSIZE (struct window); i++)
    vec->contents[i] = Qnil;
  vec->size = VECSIZE (struct window);
  p = (struct window *)vec;
  XSETFASTINT (p->sequence_number, ++sequence_number);
  XSETFASTINT (p->left, 0);
  XSETFASTINT (p->top, 0);
  XSETFASTINT (p->height, 0);
  XSETFASTINT (p->width, 0);
  XSETFASTINT (p->hscroll, 0);
  XSETFASTINT (p->last_point, 0);
  XSETFASTINT (p->last_point_x, 0);
  XSETFASTINT (p->last_point_y, 0);
  p->start = Fmake_marker ();
  p->pointm = Fmake_marker ();
  XSETFASTINT (p->use_time, 0);
  p->frame = Qnil;
  p->display_table = Qnil;
  p->dedicated = Qnil;
  XSETWINDOW (val, p);
  return val;
}

DEFUN ("selected-window", Fselected_window, Sselected_window, 0, 0, 0,
  "Return the window that the cursor now appears in and commands apply to.")
  ()
{
  return selected_window;
}

DEFUN ("minibuffer-window", Fminibuffer_window, Sminibuffer_window, 0, 1, 0,
  "Return the window used now for minibuffers.\n\
If the optional argument FRAME is specified, return the minibuffer window\n\
used by that frame.")
  (frame)
    Lisp_Object frame;
{
  if (NILP (frame))
    XSETFRAME (frame, selected_frame);
  else
    CHECK_LIVE_FRAME (frame, 0);

  return FRAME_MINIBUF_WINDOW (XFRAME (frame));
}

DEFUN ("window-minibuffer-p", Fwindow_minibuffer_p, Swindow_minibuffer_p, 0, 1, 0,
  "Returns non-nil if WINDOW is a minibuffer window.")
  (window)
     Lisp_Object window;
{
  struct window *w = decode_window (window);
  return (MINI_WINDOW_P (w) ? Qt : Qnil);
}

DEFUN ("pos-visible-in-window-p", Fpos_visible_in_window_p,
  Spos_visible_in_window_p, 0, 2, 0,
  "Return t if position POS is currently on the frame in WINDOW.\n\
Returns nil if that position is scrolled vertically out of view.\n\
POS defaults to point; WINDOW, to the selected window.")
  (pos, window)
     Lisp_Object pos, window;
{
  register struct window *w;
  register int top;
  register int height;
  register int posint;
  register struct buffer *buf;
  struct position posval;
  int hscroll;

  if (NILP (pos))
    posint = PT;
  else
    {
      CHECK_NUMBER_COERCE_MARKER (pos, 0);
      posint = XINT (pos);
    }

  w = decode_window (window);
  top = marker_position (w->start);
  hscroll = XINT (w->hscroll);

  if (posint < top)
    return Qnil;

  height = XFASTINT (w->height) - ! MINI_WINDOW_P (w);

  buf = XBUFFER (w->buffer);
  if (XFASTINT (w->last_modified) >= BUF_MODIFF (buf)
      && XFASTINT (w->last_overlay_modified) >= BUF_OVERLAY_MODIFF (buf))
    {
      /* If frame is up to date,
	 use the info recorded about how much text fit on it. */
      if (posint < BUF_Z (buf) - XFASTINT (w->window_end_pos)
	  || (XFASTINT (w->window_end_vpos) < height))
	return Qt;
      return Qnil;
    }
  else
    {
      if (posint > BUF_ZV (buf))
	return Qnil;

      /* w->start can be out of range.  If it is, do something reasonable.  */
      if (top < BUF_BEGV (buf) || top > BUF_ZV (buf))
	return Qnil;

      /* If that info is not correct, calculate afresh */
      /* BUG FIX for the 7th arg (TOHPOS).

	 '0' is harmless, however, ' - (1 << (BITS_PER_SHORT - 1))' is
	 more appropriate here.  In case of HSCROLL > 0, this can avoid
	 needless calculation done until (HPOS == 0).

	 We want to determine if the position POSINT is in HEIGHT or
	 not.  We don't have to do calculation until (HPOS == 0).  We
	 can stop it when VPOS goes beyond HEIGHT.  */
      posval = *compute_motion (top, 0, (hscroll ? 1 - hscroll : 0), 0,
				posint, height, - (1 << (BITS_PER_SHORT - 1)),
				window_internal_width (w) - 1,
				hscroll, 0, w);

      return posval.vpos < height ? Qt : Qnil;
    }
}

static struct window *
decode_window (window)
     register Lisp_Object window;
{
  if (NILP (window))
    return XWINDOW (selected_window);

  CHECK_LIVE_WINDOW (window, 0);
  return XWINDOW (window);
}

DEFUN ("window-buffer", Fwindow_buffer, Swindow_buffer, 0, 1, 0,
  "Return the buffer that WINDOW is displaying.")
  (window)
     Lisp_Object window;
{
  return decode_window (window)->buffer;
}

DEFUN ("window-height", Fwindow_height, Swindow_height, 0, 1, 0,
  "Return the number of lines in WINDOW (including its mode line).")
  (window)
     Lisp_Object window;
{
  return decode_window (window)->height;
}

DEFUN ("window-width", Fwindow_width, Swindow_width, 0, 1, 0,
  "Return the number of display columns in WINDOW.\n\
This is the width that is usable columns available for text in WINDOW.\n\
If you want to find out how many columns WINDOW takes up,\n\
use  (let ((edges (window-edges))) (- (nth 2 edges) (nth 0 edges))).")
  (window)
     Lisp_Object window;
{
  return make_number (window_internal_width (decode_window (window)));
}

DEFUN ("window-hscroll", Fwindow_hscroll, Swindow_hscroll, 0, 1, 0,
  "Return the number of columns by which WINDOW is scrolled from left margin.")
  (window)
     Lisp_Object window;
{
  return decode_window (window)->hscroll;
}

DEFUN ("set-window-hscroll", Fset_window_hscroll, Sset_window_hscroll, 2, 2, 0,
  "Set number of columns WINDOW is scrolled from left margin to NCOL.\n\
NCOL should be zero or positive.")
  (window, ncol)
     register Lisp_Object window, ncol;
{
  register struct window *w;

  CHECK_NUMBER (ncol, 1);
  if (XINT (ncol) < 0) XSETFASTINT (ncol, 0);
  w = decode_window (window);
  if (XINT (w->hscroll) != XINT (ncol))
    XBUFFER (w->buffer)->clip_changed = 1; /* Prevent redisplay shortcuts */
  w->hscroll = ncol;
  return ncol;
}

DEFUN ("window-redisplay-end-trigger", Fwindow_redisplay_end_trigger,
       Swindow_redisplay_end_trigger, 0, 1, 0,
  "Return WINDOW's redisplay end trigger value.\n\
See `set-window-redisplay-end-trigger' for more information.")
  (window)
     Lisp_Object window;
{
  return decode_window (window)->redisplay_end_trigger;
}

DEFUN ("set-window-redisplay-end-trigger", Fset_window_redisplay_end_trigger,
       Sset_window_redisplay_end_trigger, 2, 2, 0,
  "Set WINDOW's redisplay end trigger value to VALUE.\n\
VALUE should be a buffer position (typically a marker) or nil.\n\
If it is a buffer position, then if redisplay in WINDOW reaches a position\n\
beyond VALUE, the functions in `redisplay-end-trigger-functions' are called\n\
with two arguments: WINDOW, and the end trigger value.\n\
Afterwards the end-trigger value is reset to nil.")
  (window, value)
     register Lisp_Object window, value;
{
  register struct window *w;

  w = decode_window (window);
  w->redisplay_end_trigger = value;
  return value;
}

DEFUN ("window-edges", Fwindow_edges, Swindow_edges, 0, 1, 0,
  "Return a list of the edge coordinates of WINDOW.\n\
\(LEFT TOP RIGHT BOTTOM), all relative to 0, 0 at top left corner of frame.\n\
RIGHT is one more than the rightmost column used by WINDOW,\n\
and BOTTOM is one more than the bottommost row used by WINDOW\n\
 and its mode-line.")
  (window)
     Lisp_Object window;
{
  register struct window *w = decode_window (window);

  return Fcons (w->left, Fcons (w->top,
           Fcons (make_number (WINDOW_RIGHT_EDGE (w)),
		  Fcons (make_number (XFASTINT (w->top)
				      + XFASTINT (w->height)),
			 Qnil))));
}

/* Test if the character at column *x, row *y is within window *w.
   If it is not, return 0;
   if it is in the window's text area,
      set *x and *y to its location relative to the upper left corner
         of the window, and
      return 1;
   if it is on the window's modeline, return 2;
   if it is on the border between the window and its right sibling,
      return 3.  */
static int
coordinates_in_window (w, x, y)
     register struct window *w;
     register int *x, *y;
{
  register int left = XINT (w->left);
  register int right_edge = WINDOW_RIGHT_EDGE (w);
  register int left_margin = WINDOW_LEFT_MARGIN (w);
  register int right_margin = WINDOW_RIGHT_MARGIN (w);
  register int window_height = XINT (w->height);
  register int top = XFASTINT (w->top);
  
  if (   *x < left || *x >= right_edge
      || *y < top  || *y >= top  + window_height)
    return 0;

  if (left_margin != left && *x < left_margin && *x >= left)
    return 3;
  
  if (right_margin != right_edge && *x >= right_margin && *x < right_edge)
    return 3;
  
  /* Is the character is the mode line?  */
  if (*y == top + window_height - 1
      && ! MINI_WINDOW_P (w))
    return 2;

  *x -= WINDOW_LEFT_MARGIN (w);
  *y -= top;
  return 1;
}

DEFUN ("coordinates-in-window-p", Fcoordinates_in_window_p,
  Scoordinates_in_window_p, 2, 2, 0,
  "Return non-nil if COORDINATES are in WINDOW.\n\
COORDINATES is a cons of the form (X . Y), X and Y being distances\n\
measured in characters from the upper-left corner of the frame.\n\
(0 .  0) denotes the character in the upper left corner of the\n\
frame.\n\
If COORDINATES are in the text portion of WINDOW,\n\
   the coordinates relative to the window are returned.\n\
If they are in the mode line of WINDOW, `mode-line' is returned.\n\
If they are on the border between WINDOW and its right sibling,\n\
   `vertical-line' is returned.")
  (coordinates, window)
     register Lisp_Object coordinates, window;
{
  int x, y;

  CHECK_LIVE_WINDOW (window, 0);
  CHECK_CONS (coordinates, 1);
  x = XINT (Fcar (coordinates));
  y = XINT (Fcdr (coordinates));

  switch (coordinates_in_window (XWINDOW (window), &x, &y))
    {
    case 0:			/* NOT in window at all. */
      return Qnil;

    case 1:			/* In text part of window. */
      return Fcons (make_number (x), make_number (y));

    case 2:			/* In mode line of window. */
      return Qmode_line;

    case 3:			/* On right border of window.  */
      return Qvertical_line;

    default:
      abort ();
    }
}

/* Find the window containing column x, row y, and return it as a
   Lisp_Object.  If x, y is on the window's modeline, set *part
   to 1; if it is on the separating line between the window and its
   right sibling, set it to 2; otherwise set it to 0.  If there is no
   window under x, y return nil and leave *part unmodified.  */
Lisp_Object
window_from_coordinates (frame, x, y, part)
     FRAME_PTR frame;
     int x, y;
     int *part;
{
  register Lisp_Object tem, first;

  tem = first = FRAME_SELECTED_WINDOW (frame);

  do
    {
      int found = coordinates_in_window (XWINDOW (tem), &x, &y);

      if (found)
	{
	  *part = found - 1;
	  return tem;
	}

      tem = Fnext_window (tem, Qt, Qlambda);
    }
  while (! EQ (tem, first));

  return Qnil;
}

DEFUN ("window-at", Fwindow_at, Swindow_at, 2, 3, 0,
  "Return window containing coordinates X and Y on FRAME.\n\
If omitted, FRAME defaults to the currently selected frame.\n\
The top left corner of the frame is considered to be row 0,\n\
column 0.")
  (x, y, frame)
      Lisp_Object x, y, frame;
{
  int part;

  if (NILP (frame))
    XSETFRAME (frame, selected_frame);
  else
    CHECK_LIVE_FRAME (frame, 2);
  CHECK_NUMBER (x, 0);
  CHECK_NUMBER (y, 1);

  return window_from_coordinates (XFRAME (frame),
				  XINT (x), XINT (y),
				  &part);
}

DEFUN ("window-point", Fwindow_point, Swindow_point, 0, 1, 0,
  "Return current value of point in WINDOW.\n\
For a nonselected window, this is the value point would have\n\
if that window were selected.\n\
\n\
Note that, when WINDOW is the selected window and its buffer\n\
is also currently selected, the value returned is the same as (point).\n\
It would be more strictly correct to return the `top-level' value\n\
of point, outside of any save-excursion forms.\n\
But that is hard to define.")
  (window)
     Lisp_Object window;
{
  register struct window *w = decode_window (window);

  if (w == XWINDOW (selected_window)
      && current_buffer == XBUFFER (w->buffer))
    return Fpoint ();
  return Fmarker_position (w->pointm);
}

DEFUN ("window-start", Fwindow_start, Swindow_start, 0, 1, 0,
  "Return position at which display currently starts in WINDOW.\n\
This is updated by redisplay or by calling `set-window-start'.")
  (window)
     Lisp_Object window;
{
  return Fmarker_position (decode_window (window)->start);
}

/* This is text temporarily removed from the doc string below.

This function returns nil if the position is not currently known.\n\
That happens when redisplay is preempted and doesn't finish.\n\
If in that case you want to compute where the end of the window would\n\
have been if redisplay had finished, do this:\n\
    (save-excursion\n\
      (goto-char (window-start window))\n\
      (vertical-motion (1- (window-height window)) window)\n\
      (point))")  */

DEFUN ("window-end", Fwindow_end, Swindow_end, 0, 2, 0,
  "Return position at which display currently ends in WINDOW.\n\
This is updated by redisplay, when it runs to completion.\n\
Simply changing the buffer text or setting `window-start'\n\
does not update this value.\n\
If UP-TO-DATE is non-nil, compute the up-to-date position\n\
if it isn't already recorded.")
  (window, update)
     Lisp_Object window, update;
{
  Lisp_Object value;
  struct window *w = decode_window (window);
  Lisp_Object buf;

  buf = w->buffer;
  CHECK_BUFFER (buf, 0);

#if 0 /* This change broke some things.  We should make it later.  */
  /* If we don't know the end position, return nil.
     The user can compute it with vertical-motion if he wants to.
     It would be nicer to do it automatically,
     but that's so slow that it would probably bother people.  */
  if (NILP (w->window_end_valid))
    return Qnil;
#endif

  if (! NILP (update)
      && ! (! NILP (w->window_end_valid)
	    && XFASTINT (w->last_modified) >= MODIFF))
    {
      int opoint = PT, opoint_byte = PT_BYTE;
      TEMP_SET_PT_BOTH (XMARKER (w->start)->charpos,
			XMARKER (w->start)->bytepos);
      Fvertical_motion (make_number (window_internal_height (w)), Qnil);
      XSETINT (value, PT);
      TEMP_SET_PT_BOTH (opoint, opoint_byte);
    }
  else
    XSETINT (value,
	     BUF_Z (XBUFFER (buf)) - XFASTINT (w->window_end_pos));

  return value;
}

DEFUN ("set-window-point", Fset_window_point, Sset_window_point, 2, 2, 0,
  "Make point value in WINDOW be at position POS in WINDOW's buffer.")
  (window, pos)
     Lisp_Object window, pos;
{
  register struct window *w = decode_window (window);

  CHECK_NUMBER_COERCE_MARKER (pos, 1);
  if (w == XWINDOW (selected_window)
      && XBUFFER (w->buffer) == current_buffer)
    Fgoto_char (pos);
  else
    set_marker_restricted (w->pointm, pos, w->buffer);

  return pos;
}

DEFUN ("set-window-start", Fset_window_start, Sset_window_start, 2, 3, 0,
  "Make display in WINDOW start at position POS in WINDOW's buffer.\n\
Optional third arg NOFORCE non-nil inhibits next redisplay\n\
from overriding motion of point in order to display at this exact start.")
  (window, pos, noforce)
     Lisp_Object window, pos, noforce;
{
  register struct window *w = decode_window (window);

  CHECK_NUMBER_COERCE_MARKER (pos, 1);
  set_marker_restricted (w->start, pos, w->buffer);
  /* this is not right, but much easier than doing what is right. */
  w->start_at_line_beg = Qnil;
  if (NILP (noforce))
    w->force_start = Qt;
  w->update_mode_line = Qt;
  XSETFASTINT (w->last_modified, 0);
  XSETFASTINT (w->last_overlay_modified, 0);
  if (!EQ (window, selected_window))
    windows_or_buffers_changed++;
  return pos;
}

DEFUN ("window-dedicated-p", Fwindow_dedicated_p, Swindow_dedicated_p,
       1, 1, 0,
  "Return WINDOW's dedicated object, usually t or nil.\n\
See also `set-window-dedicated-p'.")
  (window)
     Lisp_Object window;
{
  return decode_window (window)->dedicated;
}

DEFUN ("set-window-dedicated-p", Fset_window_dedicated_p,
       Sset_window_dedicated_p, 2, 2, 0,
  "Control whether WINDOW is dedicated to the buffer it displays.\n\
If it is dedicated, Emacs will not automatically change\n\
which buffer appears in it.\n\
The second argument is the new value for the dedication flag;\n\
non-nil means yes.")
  (window, arg)
       Lisp_Object window, arg;
{
  register struct window *w = decode_window (window);

  if (NILP (arg))
    w->dedicated = Qnil;
  else
    w->dedicated = Qt;

  return w->dedicated;
}

DEFUN ("window-display-table", Fwindow_display_table, Swindow_display_table,
       0, 1, 0,
  "Return the display-table that WINDOW is using.")
  (window)
     Lisp_Object window;
{
  return decode_window (window)->display_table;
}

/* Get the display table for use currently on window W.
   This is either W's display table or W's buffer's display table.
   Ignore the specified tables if they are not valid;
   if no valid table is specified, return 0.  */

struct Lisp_Char_Table *
window_display_table (w)
     struct window *w;
{
  Lisp_Object tem;
  tem = w->display_table;
  if (DISP_TABLE_P (tem))
    return XCHAR_TABLE (tem);
  if (NILP (w->buffer))
    return 0;

  tem = XBUFFER (w->buffer)->display_table;
  if (DISP_TABLE_P (tem))
    return XCHAR_TABLE (tem);
  tem = Vstandard_display_table;
  if (DISP_TABLE_P (tem))
    return XCHAR_TABLE (tem);
  return 0;
}

DEFUN ("set-window-display-table", Fset_window_display_table, Sset_window_display_table, 2, 2, 0,
  "Set WINDOW's display-table to TABLE.")
  (window, table)
     register Lisp_Object window, table;
{
  register struct window *w;
  register Lisp_Object z;	/* Return value. */

  w = decode_window (window);
  w->display_table = table;
  return table;
}

/* Record info on buffer window w is displaying
   when it is about to cease to display that buffer.  */
static void
unshow_buffer (w)
     register struct window *w;
{
  Lisp_Object buf;
  struct buffer *b;

  buf = w->buffer;
  b = XBUFFER (buf);
  if (b != XMARKER (w->pointm)->buffer)
    abort ();

  if (w == XWINDOW (b->last_selected_window))
    b->last_selected_window = Qnil;

#if 0
  if (w == XWINDOW (selected_window)
      || ! EQ (buf, XWINDOW (selected_window)->buffer))
    /* Do this except when the selected window's buffer
       is being removed from some other window.  */
#endif
    /* last_window_start records the start position that this buffer
       had in the last window to be disconnected from it.
       Now that this statement is unconditional,
       it is possible for the buffer to be displayed in the
       selected window, while last_window_start reflects another
       window which was recently showing the same buffer.
       Some people might say that might be a good thing.  Let's see.  */
    b->last_window_start = marker_position (w->start);

  /* Point in the selected window's buffer
     is actually stored in that buffer, and the window's pointm isn't used.
     So don't clobber point in that buffer.  */
  if (! EQ (buf, XWINDOW (selected_window)->buffer))
    temp_set_point_both (b,
			 clip_to_bounds (BUF_BEGV (b),
					 XMARKER (w->pointm)->charpos,
					 BUF_ZV (b)),
			 clip_to_bounds (BUF_BEGV_BYTE (b),
					 marker_byte_position (w->pointm),
					 BUF_ZV_BYTE (b)));
}

/* Put replacement into the window structure in place of old. */
static void
replace_window (old, replacement)
     Lisp_Object old, replacement;
{
  register Lisp_Object tem;
  register struct window *o = XWINDOW (old), *p = XWINDOW (replacement);

  /* If OLD is its frame's root_window, then replacement is the new
     root_window for that frame.  */

  if (EQ (old, FRAME_ROOT_WINDOW (XFRAME (o->frame))))
    FRAME_ROOT_WINDOW (XFRAME (o->frame)) = replacement;

  p->left = o->left;
  p->top = o->top;
  p->width = o->width;
  p->height = o->height;

  p->next = tem = o->next;
  if (!NILP (tem))
    XWINDOW (tem)->prev = replacement;

  p->prev = tem = o->prev;
  if (!NILP (tem))
    XWINDOW (tem)->next = replacement;

  p->parent = tem = o->parent;
  if (!NILP (tem))
    {
      if (EQ (XWINDOW (tem)->vchild, old))
	XWINDOW (tem)->vchild = replacement;
      if (EQ (XWINDOW (tem)->hchild, old))
	XWINDOW (tem)->hchild = replacement;
    }

/*** Here, if replacement is a vertical combination
and so is its new parent, we should make replacement's
children be children of that parent instead.  ***/
}

DEFUN ("delete-window", Fdelete_window, Sdelete_window, 0, 1, "",
  "Remove WINDOW from the display.  Default is selected window.")
  (window)
     register Lisp_Object window;
{
  delete_window (window);

  if (! NILP (Vwindow_configuration_change_hook)
      && ! NILP (Vrun_hooks))
    call1 (Vrun_hooks, Qwindow_configuration_change_hook);

  return Qnil;
}

void
delete_window (window)
     register Lisp_Object window;
{
  register Lisp_Object tem, parent, sib;
  register struct window *p;
  register struct window *par;

  /* Because this function is called by other C code on non-leaf
     windows, the CHECK_LIVE_WINDOW macro would choke inappropriately,
     so we can't decode_window here.  */
  if (NILP (window))
    window = selected_window;
  else
    CHECK_WINDOW (window, 0);
  p = XWINDOW (window);

  /* It's okay to delete an already-deleted window.  */
  if (NILP (p->buffer)
      && NILP (p->hchild)
      && NILP (p->vchild))
    return;

  parent = p->parent;
  if (NILP (parent))
    error ("Attempt to delete minibuffer or sole ordinary window");
  par = XWINDOW (parent);

  windows_or_buffers_changed++;
  FRAME_WINDOW_SIZES_CHANGED (XFRAME (WINDOW_FRAME (p))) = 1;

  /* Are we trying to delete any frame's selected window?  */
  {
    Lisp_Object frame, pwindow;

    /* See if the frame's selected window is either WINDOW
       or any subwindow of it, by finding all that window's parents
       and comparing each one with WINDOW.  */
    frame = WINDOW_FRAME (XWINDOW (window));
    pwindow = FRAME_SELECTED_WINDOW (XFRAME (frame));

    while (!NILP (pwindow))
      {
	if (EQ (window, pwindow))
	  break;
	pwindow = XWINDOW (pwindow)->parent;
      }

    if (EQ (window, pwindow))
      {
	Lisp_Object alternative;
	alternative = Fnext_window (window, Qlambda, Qnil);

	/* If we're about to delete the selected window on the
	   selected frame, then we should use Fselect_window to select
	   the new window.  On the other hand, if we're about to
	   delete the selected window on any other frame, we shouldn't do
	   anything but set the frame's selected_window slot.  */
	if (EQ (window, selected_window))
	  Fselect_window (alternative);
	else
	  FRAME_SELECTED_WINDOW (XFRAME (frame)) = alternative;
      }
  }

  tem = p->buffer;
  /* tem is null for dummy parent windows
     (which have inferiors but not any contents themselves) */
  if (!NILP (tem))
    {
      unshow_buffer (p);
      unchain_marker (p->pointm);
      unchain_marker (p->start);
    }

  tem = p->next;
  if (!NILP (tem))
    XWINDOW (tem)->prev = p->prev;

  tem = p->prev;
  if (!NILP (tem))
    XWINDOW (tem)->next = p->next;

  if (EQ (window, par->hchild))
    par->hchild = p->next;
  if (EQ (window, par->vchild))
    par->vchild = p->next;

  /* Find one of our siblings to give our space to.  */
  sib = p->prev;
  if (NILP (sib))
    {
      /* If p gives its space to its next sibling, that sibling needs
	 to have its top/left side pulled back to where p's is.
	 set_window_{height,width} will re-position the sibling's
	 children.  */
      sib = p->next;
      XWINDOW (sib)->top = p->top;
      XWINDOW (sib)->left = p->left;
    }

  /* Stretch that sibling.  */
  if (!NILP (par->vchild))
    set_window_height (sib,
		       XFASTINT (XWINDOW (sib)->height) + XFASTINT (p->height),
		       1);
  if (!NILP (par->hchild))
    set_window_width (sib,
		      XFASTINT (XWINDOW (sib)->width) + XFASTINT (p->width),
		      1);

  /* If parent now has only one child,
     put the child into the parent's place.  */
  tem = par->hchild;
  if (NILP (tem))
    tem = par->vchild;
  if (NILP (XWINDOW (tem)->next))
    replace_window (parent, tem);

  /* Since we may be deleting combination windows, we must make sure that
     not only p but all its children have been marked as deleted.  */
  if (! NILP (p->hchild))
    delete_all_subwindows (XWINDOW (p->hchild));
  else if (! NILP (p->vchild))
    delete_all_subwindows (XWINDOW (p->vchild));

  /* Mark this window as deleted.  */
  p->buffer = p->hchild = p->vchild = Qnil;
}


extern Lisp_Object next_frame (), prev_frame ();

/* This comment supplies the doc string for `next-window',
   for make-docfile to see.  We cannot put this in the real DEFUN
   due to limits in the Unix cpp.

DEFUN ("next-window", Ffoo, Sfoo, 0, 3, 0,
  "Return next window after WINDOW in canonical ordering of windows.\n\
If omitted, WINDOW defaults to the selected window.\n\
\n\
Optional second arg MINIBUF t means count the minibuffer window even\n\
if not active.  MINIBUF nil or omitted means count the minibuffer iff\n\
it is active.  MINIBUF neither t nor nil means not to count the\n\
minibuffer even if it is active.\n\
\n\
Several frames may share a single minibuffer; if the minibuffer\n\
counts, all windows on all frames that share that minibuffer count\n\
too.  Therefore, `next-window' can be used to iterate through the\n\
set of windows even when the minibuffer is on another frame.  If the\n\
minibuffer does not count, only windows from WINDOW's frame count.\n\
\n\
Optional third arg ALL-FRAMES t means include windows on all frames.\n\
ALL-FRAMES nil or omitted means cycle within the frames as specified\n\
above.  ALL-FRAMES = `visible' means include windows on all visible frames.\n\
ALL-FRAMES = 0 means include windows on all visible and iconified frames.\n\
If ALL-FRAMES is a frame, restrict search to windows on that frame.\n\
Anything else means restrict to WINDOW's frame.\n\
\n\
If you use consistent values for MINIBUF and ALL-FRAMES, you can use\n\
`next-window' to iterate through the entire cycle of acceptable\n\
windows, eventually ending up back at the window you started with.\n\
`previous-window' traverses the same cycle, in the reverse order.")
  (window, minibuf, all_frames) */

DEFUN ("next-window", Fnext_window, Snext_window, 0, 3, 0,
       0)
  (window, minibuf, all_frames)
     register Lisp_Object window, minibuf, all_frames;
{
  register Lisp_Object tem;
  Lisp_Object start_window;

  if (NILP (window))
    window = selected_window;
  else
    CHECK_LIVE_WINDOW (window, 0);

  start_window = window;

  /* minibuf == nil may or may not include minibuffers.
     Decide if it does.  */
  if (NILP (minibuf))
    minibuf = (minibuf_level ? minibuf_window : Qlambda);
  else if (! EQ (minibuf, Qt))
    minibuf = Qlambda;
  /* Now minibuf can be t => count all minibuffer windows,
     lambda => count none of them,
     or a specific minibuffer window (the active one) to count.  */

  /* all_frames == nil doesn't specify which frames to include.  */
  if (NILP (all_frames))
    all_frames = (! EQ (minibuf, Qlambda)
		  ? (FRAME_MINIBUF_WINDOW
		     (XFRAME
		      (WINDOW_FRAME
		       (XWINDOW (window)))))
		  : Qnil);
  else if (EQ (all_frames, Qvisible))
    ;
  else if (XFASTINT (all_frames) == 0)
    ;
  else if (FRAMEP (all_frames) && ! EQ (all_frames, Fwindow_frame (window)))
    /* If all_frames is a frame and window arg isn't on that frame, just
       return the first window on the frame.  */
    return Fframe_first_window (all_frames);
  else if (! EQ (all_frames, Qt))
    all_frames = Qnil;
  /* Now all_frames is t meaning search all frames,
     nil meaning search just current frame,
     visible meaning search just visible frames,
     0 meaning search visible and iconified frames,
     or a window, meaning search the frame that window belongs to.  */

  /* Do this loop at least once, to get the next window, and perhaps
     again, if we hit the minibuffer and that is not acceptable.  */
  do
    {
      /* Find a window that actually has a next one.  This loop
	 climbs up the tree.  */
      while (tem = XWINDOW (window)->next, NILP (tem))
	if (tem = XWINDOW (window)->parent, !NILP (tem))
	  window = tem;
	else
	  {
	    /* We've reached the end of this frame.
	       Which other frames are acceptable?  */
	    tem = WINDOW_FRAME (XWINDOW (window));
	    if (! NILP (all_frames))