window.c

/* Window creation, deletion and examination for GNU Emacs.
   Does not include redisplay.
   Copyright (C) 1985,86,87,93,94,95,96,97,1998,2000, 2001
   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 "keyboard.h"
#include "frame.h"
#include "window.h"
#include "commands.h"
#include "indent.h"
#include "termchar.h"
#include "disptab.h"
#include "dispextern.h"
#include "blockinput.h"
#include "intervals.h"

#ifdef HAVE_X_WINDOWS
#include "xterm.h"
#endif	/* HAVE_X_WINDOWS */
#ifdef WINDOWSNT
#include "w32term.h"
#endif
#ifdef MSDOS
#include "msdos.h"
#endif
#ifdef macintosh
#include "macterm.h"
#endif

#ifndef max
#define max(a, b) ((a) < (b) ? (b) : (a))
#endif

/* Values returned from coordinates_in_window.  */

enum window_part
{
  ON_NOTHING,
  ON_TEXT,
  ON_MODE_LINE,
  ON_VERTICAL_BORDER,
  ON_HEADER_LINE,
  ON_LEFT_FRINGE,
  ON_RIGHT_FRINGE
};


Lisp_Object Qwindowp, Qwindow_live_p, Qwindow_configuration_p;
Lisp_Object Qwindow_size_fixed, Qleft_fringe, Qright_fringe;
extern Lisp_Object Qheight, Qwidth;

static struct window *decode_window P_ ((Lisp_Object));
static Lisp_Object select_window_1 P_ ((Lisp_Object, int));
static int count_windows P_ ((struct window *));
static int get_leaf_windows P_ ((struct window *, struct window **, int));
static void window_scroll P_ ((Lisp_Object, int, int, int));
static void window_scroll_pixel_based P_ ((Lisp_Object, int, int, int));
static void window_scroll_line_based P_ ((Lisp_Object, int, int, int));
static int window_min_size_1 P_ ((struct window *, int));
static int window_min_size P_ ((struct window *, int, int, int *));
static void size_window P_ ((Lisp_Object, int, int, int));
static int freeze_window_start P_ ((struct window *, void *));
static int window_fixed_size_p P_ ((struct window *, int, int));
static void enlarge_window P_ ((Lisp_Object, int, int));
static Lisp_Object window_list P_ ((void));
static int add_window_to_list P_ ((struct window *, void *));
static int candidate_window_p P_ ((Lisp_Object, Lisp_Object, Lisp_Object,
				   Lisp_Object));
static Lisp_Object next_window P_ ((Lisp_Object, Lisp_Object,
				    Lisp_Object, int));
static void decode_next_window_args P_ ((Lisp_Object *, Lisp_Object *,
					 Lisp_Object *));
static int foreach_window_1 P_ ((struct window *,
				 int (* fn) (struct window *, void *),
				 void *));
static Lisp_Object window_list_1 P_ ((Lisp_Object, Lisp_Object, Lisp_Object));

/* The value of `window-size-fixed'.  */

int window_size_fixed;

/* 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;

/* A list of all windows for use by next_window and Fwindow_list.
   Functions creating or deleting windows should invalidate this cache
   by setting it to nil.  */

Lisp_Object Vwindow_list;

/* The mini-buffer window of the selected frame.
   Note that you cannot test for mini-bufferness of an arbitrary window
   by comparing against this; but you can test for mini-bufferness of
   the selected window.  */

Lisp_Object minibuf_window;

/* Non-nil means it is the window for C-M-v to scroll
   when the mini-buffer 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;

/* Nonzero means reuse existing frames for displaying buffers.  */

int display_buffer_reuse_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;

/* Non-nil means that Fdisplay_buffer should even the heights of windows.  */

Lisp_Object Veven_window_heights;

/* 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.  */

Lisp_Object Vscroll_preserve_screen_position;

#if 0 /* This isn't used anywhere.  */
/* Nonzero means we can split a frame even if it is "unsplittable".  */
static int inhibit_frame_unsplittable;
#endif /* 0 */

#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 WINDOW_LIVE_P (object) ? 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->min_hscroll, 0);
  p->orig_top = p->orig_height = Qnil;
  p->start = Fmake_marker ();
  p->pointm = Fmake_marker ();
  XSETFASTINT (p->use_time, 0);
  p->frame = Qnil;
  p->display_table = Qnil;
  p->dedicated = Qnil;
  p->pseudo_window_p = 0;
  bzero (&p->cursor, sizeof (p->cursor));
  bzero (&p->last_cursor, sizeof (p->last_cursor));
  bzero (&p->phys_cursor, sizeof (p->phys_cursor));
  p->desired_matrix = p->current_matrix = 0;
  p->phys_cursor_type = -1;
  p->must_be_updated_p = 0;
  XSETFASTINT (p->window_end_vpos, 0);
  XSETFASTINT (p->window_end_pos, 0);
  p->window_end_valid = Qnil;
  p->vscroll = 0;
  XSETWINDOW (val, p);
  XSETFASTINT (p->last_point, 0);
  p->frozen_window_start_p = 0;

  Vwindow_list = Qnil;
  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))
    frame = selected_frame;
  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, 3, 0,
  "Return t if position POS is currently on the frame in WINDOW.\n\
Return nil if that position is scrolled vertically out of view.\n\
If a character is only partially visible, nil is returned, unless the\n\
optional argument PARTIALLY is non-nil.\n\
POS defaults to point in WINDOW; WINDOW defaults to the selected window.")
  (pos, window, partially)
     Lisp_Object pos, window, partially;
{
  register struct window *w;
  register int posint;
  register struct buffer *buf;
  struct text_pos top;
  Lisp_Object in_window;
  int fully_p;

  w = decode_window (window);
  buf = XBUFFER (w->buffer);
  SET_TEXT_POS_FROM_MARKER (top, w->start);

  if (!NILP (pos))
    {
      CHECK_NUMBER_COERCE_MARKER (pos, 0);
      posint = XINT (pos);
    }
  else if (w == XWINDOW (selected_window))
    posint = PT;
  else
    posint = XMARKER (w->pointm)->charpos;

  /* If position is above window start, it's not visible.  */
  if (posint < CHARPOS (top))
    in_window = Qnil;
  else if (XFASTINT (w->last_modified) >= BUF_MODIFF (buf)
	   && XFASTINT (w->last_overlay_modified) >= BUF_OVERLAY_MODIFF (buf)
	   && posint < BUF_Z (buf) - XFASTINT (w->window_end_pos))
    {
      /* If frame is up-to-date, and POSINT is < window end pos, use
	 that info.  This doesn't work for POSINT == end pos, because
	 the window end pos is actually the position _after_ the last
	 char in the window.  */
      if (NILP (partially))
	{
	  pos_visible_p (w, posint, &fully_p, NILP (partially));
	  in_window = fully_p ? Qt : Qnil;
	}
      else
	in_window = Qt;
    }
  else if (posint > BUF_ZV (buf))
    in_window = Qnil;
  else if (CHARPOS (top) < BUF_BEGV (buf) || CHARPOS (top) > BUF_ZV (buf))
    /* If window start is out of range, do something reasonable.  */
    in_window = Qnil;
  else
    {
      if (pos_visible_p (w, posint, &fully_p, NILP (partially)))
	in_window = !NILP (partially) || fully_p ? Qt : Qnil;
      else
	in_window = Qnil;
    }

  return in_window;
}


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)
     Lisp_Object window, ncol;
{
  struct window *w = decode_window (window);
  int hscroll;

  CHECK_NUMBER (ncol, 1);
  hscroll = max (0, XINT (ncol));
  
  /* Prevent redisplay shortcuts when changing the hscroll.  */
  if (XINT (w->hscroll) != hscroll)
    XBUFFER (w->buffer)->prevent_redisplay_optimizations_p = 1;
  
  w->hscroll = make_number (hscroll);
  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.
   if it is on the window's top line, return 4;
   if it is in the bitmap area to the left/right of the window,
   return 5 or 6, and convert *X and *Y to window-relative corrdinates.

   X and Y are frame relative pixel coordinates.  */

static enum window_part
coordinates_in_window (w, x, y)
     register struct window *w;
     register int *x, *y;
{
  /* Let's make this a global enum later, instead of using numbers
     everywhere.  */
  struct frame *f = XFRAME (WINDOW_FRAME (w));
  int left_x, right_x, top_y, bottom_y;
  int flags_area_width = FRAME_LEFT_FLAGS_AREA_WIDTH (f);
  enum window_part part;
  int ux = CANON_X_UNIT (f), uy = CANON_Y_UNIT (f);
  int x0 = XFASTINT (w->left) * ux;
  int x1 = x0 + XFASTINT (w->width) * ux;
  /* The width of the area where the vertical line can be dragged.
     (Between mode lines for instance.  */
  int grabbable_width = ux;

  if (*x < x0 || *x >= x1)
    return ON_NOTHING;
  
  /* In what's below, we subtract 1 when computing right_x because we
     want the rightmost pixel, which is given by left_pixel+width-1.  */
  if (w->pseudo_window_p)
    {
      left_x = 0;
      right_x = XFASTINT (w->width) * CANON_X_UNIT (f) - 1;
      top_y = WINDOW_DISPLAY_TOP_EDGE_PIXEL_Y (w);
      bottom_y = WINDOW_DISPLAY_BOTTOM_EDGE_PIXEL_Y (w);
    }
  else
    {
      left_x = (WINDOW_DISPLAY_LEFT_EDGE_PIXEL_X (w)
		- FRAME_INTERNAL_BORDER_WIDTH_SAFE (f));
      right_x = WINDOW_DISPLAY_RIGHT_EDGE_PIXEL_X (w) - 1;
      top_y = (WINDOW_DISPLAY_TOP_EDGE_PIXEL_Y (w)
	       - FRAME_INTERNAL_BORDER_WIDTH_SAFE (f));
      bottom_y = WINDOW_DISPLAY_BOTTOM_EDGE_PIXEL_Y (w);
    }

  /* On the mode line or header line?  If it's near the start of
     the mode or header line of window that's has a horizontal
     sibling, say it's on the vertical line.  That's to be able
     to resize windows horizontally in case we're using toolkit
     scroll bars.  */

  if (WINDOW_WANTS_MODELINE_P (w)
      && *y >= bottom_y - CURRENT_MODE_LINE_HEIGHT (w)
      && *y < bottom_y)
    {
      /* We're somewhere on the mode line.  We consider the place
	 between mode lines of horizontally adjacent mode lines
	 as the vertical border.    If scroll bars on the left,
	 return the right window.  */
      part = ON_MODE_LINE;
      
      if (FRAME_HAS_VERTICAL_SCROLL_BARS_ON_LEFT (f))
	{
	  if (abs (*x - x0) < grabbable_width)
	    part = ON_VERTICAL_BORDER;
	}
      else if (!WINDOW_RIGHTMOST_P (w) && abs (*x - x1) < grabbable_width)
	part = ON_VERTICAL_BORDER;
    }
  else if (WINDOW_WANTS_HEADER_LINE_P (w)
	   && *y < top_y + CURRENT_HEADER_LINE_HEIGHT (w)
	   && *y >= top_y)
    {
      part = ON_HEADER_LINE;
      
      if (FRAME_HAS_VERTICAL_SCROLL_BARS_ON_LEFT (f))
	{
	  if (abs (*x - x0) < grabbable_width)
	    part = ON_VERTICAL_BORDER;
	}
      else if (!WINDOW_RIGHTMOST_P (w) && abs (*x - x1) < grabbable_width)
	part = ON_VERTICAL_BORDER;
    }
  /* Outside anything interesting?  */
  else if (*y < top_y
	   || *y >= bottom_y
	   || *x < (left_x
		    - flags_area_width
		    - FRAME_LEFT_SCROLL_BAR_WIDTH (f) * ux)
	   || *x > (right_x
		    + flags_area_width
		    + FRAME_RIGHT_SCROLL_BAR_WIDTH (f) * ux))
    {
      part = ON_NOTHING;
    }
  else if (FRAME_WINDOW_P (f))
    {
      if (!w->pseudo_window_p
	  && !FRAME_HAS_VERTICAL_SCROLL_BARS (f)
	  && !WINDOW_RIGHTMOST_P (w)
	  && (abs (*x - right_x - flags_area_width) < grabbable_width))
	{
	  part = ON_VERTICAL_BORDER;
	}
      else if (*x < left_x || *x > right_x)
	{
	  /* Other lines than the mode line don't include flags areas and
	     scroll bars on the left.  */
      
	  /* Convert X and Y to window-relative pixel coordinates.  */
	  *x -= left_x;
	  *y -= top_y;
	  part = *x < left_x ? ON_LEFT_FRINGE : ON_RIGHT_FRINGE;
	}
      else
	{
	  *x -= left_x;
	  *y -= top_y;
	  part = ON_TEXT;
	}
    }
  else
    {
      /* Need to say "*x > right_x" rather than >=, since on character
	 terminals, the vertical line's x coordinate is right_x.  */
      if (*x < left_x || *x > right_x)
	{
	  /* Other lines than the mode line don't include flags areas and
	     scroll bars on the left.  */
      
	  /* Convert X and Y to window-relative pixel coordinates.  */
	  *x -= left_x;
	  *y -= top_y;
	  part = *x < left_x ? ON_LEFT_FRINGE : ON_RIGHT_FRINGE;
	}
      /* Here, too, "*x > right_x" is because of character terminals.  */
      else if (!w->pseudo_window_p
	       && !WINDOW_RIGHTMOST_P (w)
	       && *x > right_x - ux)
	{
	  /* On the border on the right side of the window?  Assume that
	     this area begins at RIGHT_X minus a canonical char width.  */
	  part = ON_VERTICAL_BORDER;
	}
      else
	{
	  /* Convert X and Y to window-relative pixel coordinates.  */
	  *x -= left_x;
	  *y -= top_y;
	  part = ON_TEXT;
	}
    }

  return part;
}


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 in the top mode line of WINDOW, `header-line' is returned.\n\
If they are in the fringe to the left of the window,\n\
   `left-fringe' is returned, if they are in the area on the right of\n\
   the window, `right-fringe' 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;
{
  struct window *w;
  struct frame *f;
  int x, y;
  Lisp_Object lx, ly;

  CHECK_LIVE_WINDOW (window, 0);
  w = XWINDOW (window);
  f = XFRAME (w->frame);
  CHECK_CONS (coordinates, 1);
  lx = Fcar (coordinates);
  ly = Fcdr (coordinates);
  CHECK_NUMBER_OR_FLOAT (lx, 1);
  CHECK_NUMBER_OR_FLOAT (ly, 1);
  x = PIXEL_X_FROM_CANON_X (f, lx);
  y = PIXEL_Y_FROM_CANON_Y (f, ly);

  switch (coordinates_in_window (w, &x, &y))
    {
    case ON_NOTHING:
      return Qnil;

    case ON_TEXT:
      /* X and Y are now window relative pixel coordinates.  Convert
	 them to canonical char units before returning them.  */
      return Fcons (CANON_X_FROM_PIXEL_X (f, x), 
		    CANON_Y_FROM_PIXEL_Y (f, y));

    case ON_MODE_LINE:
      return Qmode_line;

    case ON_VERTICAL_BORDER:
      return Qvertical_line;

    case ON_HEADER_LINE:
      return Qheader_line;

    case ON_LEFT_FRINGE:
      return Qleft_fringe;
      
    case ON_RIGHT_FRINGE:
      return Qright_fringe;

    default:
      abort ();
    }
}


/* Callback for foreach_window, used in window_from_coordinates.
   Check if window W contains coordinates specified by USER_DATA which
   is actually a pointer to a struct check_window_data CW.

   Check if window W contains coordinates *CW->x and *CW->y.  If it
   does, return W in *CW->window, as Lisp_Object, and return in
   *CW->part the part of the window under coordinates *X,*Y.  Return
   zero from this function to stop iterating over windows.  */

struct check_window_data
{
  Lisp_Object *window;
  int *x, *y, *part;
};

static int
check_window_containing (w, user_data)
     struct window *w;
     void *user_data;
{
  struct check_window_data *cw = (struct check_window_data *) user_data;
  enum window_part found;
  int continue_p = 1;

  found = coordinates_in_window (w, cw->x, cw->y);
  if (found != ON_NOTHING)
    {
      *cw->part = found - 1;
      XSETWINDOW (*cw->window, w);
      continue_p = 0;
    }
  
  return continue_p;
}


/* Find the window containing frame-relative pixel position X/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.  TOOL_BAR_P non-zero means detect tool-bar windows.

   This function was previously implemented with a loop cycling over
   windows with Fnext_window, and starting with the frame's selected
   window.  It turned out that this doesn't work with an
   implementation of next_window using Vwindow_list, because
   FRAME_SELECTED_WINDOW (F) is not always contained in the window
   tree of F when this function is called asynchronously from
   note_mouse_highlight.  The original loop didn't terminate in this
   case.  */

Lisp_Object
window_from_coordinates (f, x, y, part, tool_bar_p)
     struct frame *f;
     int x, y;
     int *part;
     int tool_bar_p;
{
  Lisp_Object window;
  struct check_window_data cw;

  window = Qnil;
  cw.window = &window, cw.x = &x, cw.y = &y; cw.part = part;
  foreach_window (f, check_window_containing, &cw);
  
  /* If not found above, see if it's in the tool bar window, if a tool
     bar exists.  */
  if (NILP (window)
      && tool_bar_p
      && WINDOWP (f->tool_bar_window)
      && XINT (XWINDOW (f->tool_bar_window)->height) > 0
      && (coordinates_in_window (XWINDOW (f->tool_bar_window), &x, &y)
	  != ON_NOTHING))
    {
      *part = 0;
      window = f->tool_bar_window;
    }

  return window;
}

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;
  struct frame *f;

  if (NILP (frame))
    frame = selected_frame;
  CHECK_LIVE_FRAME (frame, 2);
  f = XFRAME (frame);

  /* Check that arguments are integers or floats.  */
  CHECK_NUMBER_OR_FLOAT (x, 0);
  CHECK_NUMBER_OR_FLOAT (y, 1);

  return window_from_coordinates (f, 
				  PIXEL_X_FROM_CANON_X (f, x),
				  PIXEL_Y_FROM_CANON_Y (f, y),
				  &part, 0);
}

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 UPDATE 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))
    {
      struct text_pos startp;
      struct it it;
      struct buffer *old_buffer = NULL, *b = XBUFFER (buf);

      /* In case W->start is out of the range, use something
         reasonable.  This situation occured when loading a file with
         `-l' containing a call to `rmail' with subsequent other
         commands.  At the end, W->start happened to be BEG, while
         rmail had already narrowed the buffer.  */
      if (XMARKER (w->start)->charpos < BEGV)
	SET_TEXT_POS (startp, BEGV, BEGV_BYTE);
      else if (XMARKER (w->start)->charpos > ZV)
	SET_TEXT_POS (startp, ZV, ZV_BYTE);
      else
	SET_TEXT_POS_FROM_MARKER (startp, w->start);

      /* Cannot use Fvertical_motion because that function doesn't
	 cope with variable-height lines.  */
      if (b != current_buffer)
	{
	  old_buffer = current_buffer;
	  set_buffer_internal (b);
	}
      
      start_display (&it, w, startp);
      move_it_vertically (&it, window_box_height (w));
      move_it_past_eol (&it);
      value = make_number (IT_CHARPOS (it));
      
      if (old_buffer)
	set_buffer_internal (old_buffer);
    }
  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);

  /* We have to make sure that redisplay updates the window to show
     the new value of point.  */
  if (!EQ (window, selected_window))
    ++windows_or_buffers_changed;
  
  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++;